1
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Ghosh A, Yarranton JT, McCusker JK. Establishing the origin of Marcus-inverted-region behaviour in the excited-state dynamics of cobalt(III) polypyridyl complexes. Nat Chem 2024:10.1038/s41557-024-01564-3. [PMID: 38965436 DOI: 10.1038/s41557-024-01564-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2023] [Accepted: 05/24/2024] [Indexed: 07/06/2024]
Abstract
Growing interest in the use of first-row transition metal complexes in a number of applied contexts-including but not limited to photoredox catalysis and solar energy conversion-underscores the need for a detailed understanding of their photophysical properties. A recent focus on ligand-field photocatalysis using cobalt(III) polypyridyls in particular has unlocked unprecedented excited-state reactivities. Photophysical studies on Co(III) chromophores in general are relatively uncommon, and so here we carry out a systematic study of a series of Co(III) polypyridyl complexes in order to delineate their excited-state dynamics. Compounds with varying ligand-field strengths were prepared and studied using variable-temperature ultrafast transient absorption spectroscopy. Analysis of the data establishes that the ground-state recovery dynamics are operating in the Marcus inverted region, in stark contrast to what is typically observed in other first-row metal complexes. The analysis has further revealed the underlying reasons driving this excited-state behaviour, thereby enabling potential advancements in the targeted use of the Marcus inverted region for a variety of photolytic applications.
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Affiliation(s)
- Atanu Ghosh
- Department of Chemistry, Michigan State University, East Lansing, MI, USA
| | | | - James K McCusker
- Department of Chemistry, Michigan State University, East Lansing, MI, USA.
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2
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Sutcliffe E, Cagan DA, Hadt RG. Ultrafast Photophysics of Ni(I)-Bipyridine Halide Complexes: Spanning the Marcus Normal and Inverted Regimes. J Am Chem Soc 2024; 146:15506-15514. [PMID: 38776490 PMCID: PMC11157544 DOI: 10.1021/jacs.4c04091] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2024] [Revised: 05/09/2024] [Accepted: 05/13/2024] [Indexed: 05/25/2024]
Abstract
Owing to their light-harvesting properties, nickel-bipyridine (bpy) complexes have found wide use in metallaphotoredox cross-coupling reactions. Key to these transformations are Ni(I)-bpy halide intermediates that absorb a significant fraction of light at relevant cross-coupling reaction irradiation wavelengths. Herein, we report ultrafast transient absorption (TA) spectroscopy on a library of eight Ni(I)-bpy halide complexes, the first such characterization of any Ni(I) species. The TA data reveal the formation and decay of Ni(I)-to-bpy metal-to-ligand charge transfer (MLCT) excited states (10-30 ps) whose relaxation dynamics are well described by vibronic Marcus theory, spanning the normal and inverted regions as a result of simple changes to the bpy substituents. While these lifetimes are relatively long for MLCT excited states in first-row transition metal complexes, their duration precludes excited-state bimolecular reactivity in photoredox reactions. We also present a one-step method to generate an isolable, solid-state Ni(I)-bpy halide species, which decouples light-initiated reactivity from dark, thermal cycles in catalysis.
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Affiliation(s)
| | | | - Ryan G. Hadt
- Division of Chemistry and
Chemical Engineering, Arthur Amos Noyes Laboratory of Chemical Physics, California Institute of Technology, Pasadena, California 91125, United States
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3
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Athanasopoulos E, Conradie J. DFT study of the spectroscopic behaviour of different iron(II)-terpyridine derivatives with application in DSSCs. J Mol Graph Model 2024; 129:108753. [PMID: 38461758 DOI: 10.1016/j.jmgm.2024.108753] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2023] [Revised: 02/20/2024] [Accepted: 02/27/2024] [Indexed: 03/12/2024]
Abstract
Through a comprehensive computational analysis utilizing Density Functional Theory (DFT), we clarify the electronic structure and spectroscopic properties of modified iron(II)-terpyridine derivatives, with the aim of enhancing the efficiency of Dye-Sensitized Solar Cells (DSSCs). We optimized a series of nineteen iron(II)-terpyridine derivatives and related compounds in acetonitrile (MeCN) as the solvent using TDDFT, evaluating their potential as dyes for DSSCs. From the conducted computations on the optimized geometries of the nineteen [Fe(Ln)2]2+ complexes, containing substituted terpyridine and related ligands L1-L19, we determined the wavelengths (λ in nm), transition energy (E in eV), oscillator strength (f), type of transitions, excited state lifetime (τ), light harvesting efficiency (LHE), frontier orbital character and their energies (ELUMO/EHOMO), natural transition orbitals (NTOs), injection driving force of a dye (ΔGinject), and regeneration driving force of a dye (ΔGregenerate). Results show that the theoretically calculated values for assessing dye efficiency in a DSSC correlate with available experimental values. The UV-visible spectra of [Fe(Ln)2]2+ exhibited a peak above 500 nm (λmax) in the visible region, attributed to the ligand-to-metal charge transfer band (LMCT) in literature, and a significant absorbance peak at approximately 300 nm (λA,max) in the UV region. The M06-D3/CEP-121G method replicated all reported λmax and λA,max values with a mean absolute deviation (MAD) of 21 and 18 nm, respectively. Our findings underscore the connections between electronic modifications and absorption spectra, emphasizing their impact on the light-harvesting capabilities and overall performance of DSSCs. This research contributes to the advancement of fundamental principles governing the design and optimization of novel photovoltaic materials, facilitating the development of more efficient and sustainable solar energy technologies.
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Affiliation(s)
- Evangelia Athanasopoulos
- Department of Chemistry, University of the Free State, P.O. Box 339, Bloemfontein, 9300, South Africa
| | - Jeanet Conradie
- Department of Chemistry, University of the Free State, P.O. Box 339, Bloemfontein, 9300, South Africa.
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4
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Doeven EH, Connell TU, Sinha N, Wenger OS, Francis PS. Electrochemiluminescence of a First-Row d 6 Transition Metal Complex. Angew Chem Int Ed Engl 2024; 63:e202319047. [PMID: 38519420 DOI: 10.1002/anie.202319047] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2023] [Revised: 03/12/2024] [Accepted: 03/22/2024] [Indexed: 03/24/2024]
Abstract
We report the electrochemiluminescence (ECL) of a 3d6 Cr(0) complex ([Cr(LMes)3]; λem=735 nm) with comparable photophysical properties to those of ECL-active complexes of 4d6 or 5d6 precious metal ions. The electrochemical potentials of [Cr(LMes)3] are more negative than those of [Ir(ppy)3] and render the [Cr(LMes)3]* excited state inaccessible through conventional co-reactant ECL with tri-n-propylamine or oxalate. ECL can be obtained, however, through the annihilation route in which potentials sufficient to oxidise and reduce the luminophore are alternately applied. When combined with [Ir(ppy)3] (λem=520 nm), the annihilation ECL of [Cr(LMes)3] was greatly enhanced whereas that of [Ir(ppy)3] was diminished. Under appropriate conditions, the relative intensities of the two spectrally distinct emissions can be controlled through the applied potentials. From this starting point for ECL with 3d6 metal complexes, we discuss some directions for future development.
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Affiliation(s)
- Egan H Doeven
- Centre for Sustainable Bioproducts, Faculty of Science, Engineering and Built Environment, Deakin University Waurn Ponds, Victoria, 3216, Australia
| | - Timothy U Connell
- Centre for Sustainable Bioproducts, Faculty of Science, Engineering and Built Environment, Deakin University Waurn Ponds, Victoria, 3216, Australia
| | - Narayan Sinha
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056, Basel, Switzerland
- School of Chemical Sciences, Indian Institute of Technology (IIT) Mandi Kamand, Mandi, 175075, Himachal Pradesh, India
| | - Oliver S Wenger
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056, Basel, Switzerland
| | - Paul S Francis
- Centre for Sustainable Bioproducts, Faculty of Science, Engineering and Built Environment, Deakin University Waurn Ponds, Victoria, 3216, Australia
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5
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Maurer AB, Loague QR, Goodwin MJ, Meyer GJ. Impact of Diimine Ligand on Singlet-to-Triplet Charge Transfer Electroabsorption in Iron and Ruthenium Complexes. J Phys Chem A 2024. [PMID: 38683682 DOI: 10.1021/acs.jpca.3c08357] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/02/2024]
Abstract
The electroabsorption and absorption spectra of eight homoleptic complexes of the general form [M(LL)3]2+ where M = Ru, Fe, and LL = 1,10-phenanthroline (phen), 2,2'-bipyridine (bpy), and 4,4',-(R)2-bpy where R = -OCH3, -CF3, were quantified at 77 K in a butyronitrile glass. Intense metal-to-ligand charge transfer (MLCT) absorption bands were evident in the visible region. Electroabsorption spectra measured with applied electric fields >0.2 MV/cm were analyzed by the two-state Liptay model. Significant light-induced dipole moment changes of Δ μ ⇀ = 4-13 D were found consistent with a metal-to-ligand charge transfer (MLCT) excited state comprised an electron localized on a single diimine ligand, [MIII(LL-)(LL)2]*2+, in the initially formed Franck-Condon excited state. A low energy feature evident in the electroabsorption spectra was assigned to a direct singlet-to-triplet MLCT excited state. The identity of the diimine ligand had an unexpected and large impact on these transitions. Analysis relative to the higher energy absorption provides a comparison of spin-allowed and disallowed transitions for first- and second-row transition metal complexes. With the notable exception of [Fe(CF3bpy)3]2+, the change in dipole moment for the 3MLCT excited states was less than or equal to that of the 1MLCT excited states. The charge transfer distances for the iron complexes were generally larger than those for the Ru complexes, a behavior attributed to a smaller degree of iron-diimine coupling in the ground state. A striking result was the sensitivity of the extinction coefficient and spectral profile of the low energy electroabsorption assigned to the identity of the diimine ligand; data that suggests electronic coupling with ligand localized triplet states and high spin metal centered states must be considered when modeling the Franck-Condon excited state.
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Affiliation(s)
- Andrew B Maurer
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
| | - Quentin R Loague
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
| | - Matthew J Goodwin
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
| | - Gerald J Meyer
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
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6
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Wellauer J, Ziereisen F, Sinha N, Prescimone A, Velić A, Meyer F, Wenger OS. Iron(III) Carbene Complexes with Tunable Excited State Energies for Photoredox and Upconversion. J Am Chem Soc 2024; 146. [PMID: 38598280 PMCID: PMC11046485 DOI: 10.1021/jacs.4c00605] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2024] [Revised: 03/13/2024] [Accepted: 03/19/2024] [Indexed: 04/11/2024]
Abstract
Substituting precious elements in luminophores and photocatalysts by abundant first-row transition metals remains a significant challenge, and iron continues to be particularly attractive owing to its high natural abundance and low cost. Most iron complexes known to date face severe limitations due to undesirably efficient deactivation of luminescent and photoredox-active excited states. Two new iron(III) complexes with structurally simple chelate ligands enable straightforward tuning of ground and excited state properties, contrasting recent examples, in which chemical modification had a minor impact. Crude samples feature two luminescence bands strongly reminiscent of a recent iron(III) complex, in which this observation was attributed to dual luminescence, but in our case, there is clear-cut evidence that the higher-energy luminescence stems from an impurity and only the red photoluminescence from a doublet ligand-to-metal charge transfer (2LMCT) excited state is genuine. Photoinduced oxidative and reductive electron transfer reactions with methyl viologen and 10-methylphenothiazine occur with nearly diffusion-limited kinetics. Photocatalytic reactions not previously reported for this compound class, in particular the C-H arylation of diazonium salts and the aerobic hydroxylation of boronic acids, were achieved with low-energy red light excitation. Doublet-triplet energy transfer (DTET) from the luminescent 2LMCT state to an anthracene annihilator permits the proof of principle for triplet-triplet annihilation upconversion based on a molecular iron photosensitizer. These findings are relevant for the development of iron complexes featuring photophysical and photochemical properties competitive with noble-metal-based compounds.
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Affiliation(s)
- Joël Wellauer
- Department
of Chemistry, University of Basel, St. Johanns-Ring 19, 4056 Basel, Switzerland
| | - Fabienne Ziereisen
- Department
of Chemistry, University of Basel, St. Johanns-Ring 19, 4056 Basel, Switzerland
| | - Narayan Sinha
- Department
of Chemistry, University of Basel, St. Johanns-Ring 19, 4056 Basel, Switzerland
| | - Alessandro Prescimone
- Department
of Chemistry, University of Basel, St. Johanns-Ring 19, 4056 Basel, Switzerland
| | - Ajdin Velić
- University
of Göttingen, Institute of Inorganic Chemistry, Tammannstraße 4, D-37077 Göttingen, Germany
| | - Franc Meyer
- University
of Göttingen, Institute of Inorganic Chemistry, Tammannstraße 4, D-37077 Göttingen, Germany
| | - Oliver S. Wenger
- Department
of Chemistry, University of Basel, St. Johanns-Ring 19, 4056 Basel, Switzerland
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7
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Zahn C, Pastore M, Lustres JLP, Gros PC, Haacke S, Heyne K. Femtosecond Infrared Spectroscopy Resolving the Multiplicity of High-Spin Crossover States in Transition Metal Iron Complexes. J Am Chem Soc 2024; 146:9347-9355. [PMID: 38520392 PMCID: PMC10995999 DOI: 10.1021/jacs.4c01637] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2024] [Revised: 03/09/2024] [Accepted: 03/11/2024] [Indexed: 03/25/2024]
Abstract
Tuning the photophysical properties of iron-based transition-metal complexes is crucial for their employment as photosensitizers in solar energy conversion. For the optimization of these new complexes, a detailed understanding of the excited-state deactivation paths is necessary. Here, we report femtosecond transient mid-IR spectroscopy data on a recently developed octahedral ligand-field enhancing [Fe(dqp)2]2+ (C1) complex with dqp = 2,6-diquinolylpyridine and prototypical [Fe(bpy)3]2+ (C0). By combining mid-IR spectroscopy with quantum chemical DFT calculations, we propose a method for disentangling the 5Q1 and 3T1 multiplicities of the long-lived metal-centered (MC) states, applicable to a variety of metal-organic iron complexes. Our results for C0 align well with the established assignment toward the 5Q1, validating our approach. For C1, we find that deactivation of the initially excited metal-to-ligand charge-transfer state leads to a population of a long-lived MC 5Q1 state. Analysis of transient changes in the mid-IR shows an ultrafast sub 200 fs rearrangement of ligand geometry for both complexes, accompanying the MLCT → MC deactivation. This confirms that the flexibility in the ligand sphere supports the stabilization of high spin states and plays a crucial role in the MLCT lifetime of metal-organic iron complexes.
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Affiliation(s)
- Clark Zahn
- Department
of Physics, Free University Berlin, Arnimallee 14, D-14195 Berlin, Germany
| | | | - J. Luis Perez Lustres
- Department
of Physics, Free University Berlin, Arnimallee 14, D-14195 Berlin, Germany
| | | | - Stefan Haacke
- Université
de Strasbourg—CNRS, IPCMS, 67034 Strasbourg, France
| | - Karsten Heyne
- Department
of Physics, Free University Berlin, Arnimallee 14, D-14195 Berlin, Germany
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8
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Kim D, Dang VQ, Teets TS. Improved transition metal photosensitizers to drive advances in photocatalysis. Chem Sci 2023; 15:77-94. [PMID: 38131090 PMCID: PMC10732135 DOI: 10.1039/d3sc04580c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2023] [Accepted: 11/22/2023] [Indexed: 12/23/2023] Open
Abstract
To function effectively in a photocatalytic application, a photosensitizer's light absorption, excited-state lifetime, and redox potentials, both in the ground state and excited state, are critically important. The absorption profile is particularly relevant to applications involving solar harvesting, whereas the redox potentials and excited-state lifetimes determine the thermodynamics, kinetics, and quantum yields of photoinduced redox processes. This perspective article focuses on synthetic inorganic and organometallic approaches to optimize these three characteristics of transition-metal based photosensitizers. We include our own work in these areas, which has focused extensively on exceptionally strong cyclometalated iridium photoreductants that enable challenging reductive photoredox transformations on organic substrates, and more recent work which has led to improved solar harvesting in charge-transfer copper(i) chromophores, an emerging class of earth-abundant compounds particularly relevant to solar-energy applications. We also extensively highlight many other complementary strategies for optimizing these parameters and highlight representative examples from the recent literature. It remains a significant challenge to simultaneously optimize all three of these parameters at once, since improvements in one often come at the detriment of the others. These inherent trade-offs and approaches to obviate or circumvent them are discussed throughout.
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Affiliation(s)
- Dooyoung Kim
- University of Houston, Department of Chemistry 3585 Cullen Blvd. Room 112 Houston TX 77204-5003 USA
| | - Vinh Q Dang
- University of Houston, Department of Chemistry 3585 Cullen Blvd. Room 112 Houston TX 77204-5003 USA
| | - Thomas S Teets
- University of Houston, Department of Chemistry 3585 Cullen Blvd. Room 112 Houston TX 77204-5003 USA
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9
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Lindh L, Pascher T, Persson S, Goriya Y, Wärnmark K, Uhlig J, Chábera P, Persson P, Yartsev A. Multifaceted Deactivation Dynamics of Fe(II) N-Heterocyclic Carbene Photosensitizers. J Phys Chem A 2023; 127:10210-10222. [PMID: 38000043 DOI: 10.1021/acs.jpca.3c06983] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2023]
Abstract
Excited state dynamics of three iron(II) carbene complexes that serve as prototype Earth-abundant photosensitizers were investigated by ultrafast optical spectroscopy. Significant differences in the dynamics between the investigated complexes down to femtosecond time scales are used to characterize fundamental differences in the depopulation of triplet metal-to-ligand charge-transfer (3MLCT) excited states in the presence of energetically accessible triplet metal-centered (3MC) states. Novel insights into the full deactivation cascades of the investigated complexes include evidence of the need to revise the deactivation model for a prominent iron carbene prototype complex, a refined understanding of complex 3MC dynamics, and a quantitative discrimination between activated and barrierless deactivation steps along the 3MLCT → 3MC → 1GS path. Overall, the study provides an improved understanding of photophysical limitations and opportunities for the use of iron(II)-based photosensitizers in photochemical applications.
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Affiliation(s)
- Linnea Lindh
- Division of Chemical Physics, Department of Chemistry, Lund University, Box 124, SE-22100 Lund, Sweden
- Division of Computational Chemistry, Department of Chemistry, Lund University, Box 124, SE-22100 Lund, Sweden
| | - Torbjörn Pascher
- Division of Chemical Physics, Department of Chemistry, Lund University, Box 124, SE-22100 Lund, Sweden
| | - Samuel Persson
- Center for Analysis and Synthesis (CAS), Department of Chemistry, Lund University, Box 124, SE-22100 Lund, Sweden
| | - Yogesh Goriya
- Center for Analysis and Synthesis (CAS), Department of Chemistry, Lund University, Box 124, SE-22100 Lund, Sweden
| | - Kenneth Wärnmark
- Center for Analysis and Synthesis (CAS), Department of Chemistry, Lund University, Box 124, SE-22100 Lund, Sweden
| | - Jens Uhlig
- Division of Chemical Physics, Department of Chemistry, Lund University, Box 124, SE-22100 Lund, Sweden
| | - Pavel Chábera
- Division of Chemical Physics, Department of Chemistry, Lund University, Box 124, SE-22100 Lund, Sweden
| | - Petter Persson
- Division of Computational Chemistry, Department of Chemistry, Lund University, Box 124, SE-22100 Lund, Sweden
| | - Arkady Yartsev
- Division of Chemical Physics, Department of Chemistry, Lund University, Box 124, SE-22100 Lund, Sweden
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10
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Lee A, Son M, Deegbey M, Woodhouse MD, Hart SM, Beissel HF, Cesana PT, Jakubikova E, McCusker JK, Schlau-Cohen GS. Observation of parallel intersystem crossing and charge transfer-state dynamics in [Fe(bpy) 3] 2+ from ultrafast 2D electronic spectroscopy. Chem Sci 2023; 14:13140-13150. [PMID: 38023502 PMCID: PMC10664481 DOI: 10.1039/d3sc02613b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2023] [Accepted: 10/29/2023] [Indexed: 12/01/2023] Open
Abstract
Transition metal-based charge-transfer complexes represent a broad class of inorganic compounds with diverse photochemical applications. Charge-transfer complexes based on earth-abundant elements have been of increasing interest, particularly the canonical [Fe(bpy)3]2+. Photoexcitation into the singlet metal-ligand charge transfer (1MLCT) state is followed by relaxation first to the ligand-field manifold and then to the ground state. While these dynamics have been well-studied, processes within the MLCT manifold that facilitate and/or compete with relaxation have been more elusive. We applied ultrafast two-dimensional electronic spectroscopy (2DES) to disentangle the dynamics immediately following MLCT excitation of this compound. First, dynamics ascribed to relaxation out of the initially formed 1MLCT state was found to correlate with the inertial response time of the solvent. Second, the additional dimension of the 2D spectra revealed a peak consistent with a ∼20 fs 1MLCT → 3MLCT intersystem crossing process. These two observations indicate that the complex simultaneously undergoes intersystem crossing and direct conversion to ligand-field state(s). Resolution of these parallel pathways in this prototypical earth-abundant complex highlights the ability of 2DES to deconvolve the otherwise obscured excited-state dynamics of charge-transfer complexes.
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Affiliation(s)
- Angela Lee
- Department of Chemistry, Massachusetts Institute of Technology Cambridge MA 02139 USA
| | - Minjung Son
- Department of Chemistry, Massachusetts Institute of Technology Cambridge MA 02139 USA
| | - Mawuli Deegbey
- Department of Chemistry, North Carolina State University Raleigh NC 27695 USA
| | - Matthew D Woodhouse
- Department of Chemistry, Michigan State University East Lansing MI 48824 USA
| | - Stephanie M Hart
- Department of Chemistry, Massachusetts Institute of Technology Cambridge MA 02139 USA
| | - Hayden F Beissel
- Department of Chemistry, Michigan State University East Lansing MI 48824 USA
| | - Paul T Cesana
- Department of Chemistry, Massachusetts Institute of Technology Cambridge MA 02139 USA
| | - Elena Jakubikova
- Department of Chemistry, North Carolina State University Raleigh NC 27695 USA
| | - James K McCusker
- Department of Chemistry, Michigan State University East Lansing MI 48824 USA
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11
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Kumaki F, Nagasaka M, Fukaya R, Okano Y, Yamashita S, Nozawa S, Adachi SI, Adachi JI. Operando time-resolved soft x-ray absorption spectroscopy for photoexcitation processes of metal complexes in solutions. J Chem Phys 2023; 158:104201. [PMID: 36922146 DOI: 10.1063/5.0129814] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/22/2023] Open
Abstract
Operando time-resolved soft x-ray absorption spectroscopy (TR-SXAS) is an effective method to reveal the photochemical processes of metal complexes in solutions. In this study, we have developed the TR-SXAS measurement system for observing various photochemical reactions in solutions by the combination of laser pump pulses with soft x-ray probe pulses from the synchrotron radiation. For the evaluation of the developed TR-SXAS system, we have measured nitrogen K-edge x-ray absorption spectroscopy (XAS) spectra of aqueous iron phenanthroline solutions during a photoinduced spin transition process. The decay process of the high spin state to the low spin state in the iron complex has been obtained from the ligand side by N K-edge XAS, and the time constant is close to that obtained from the central metal side by time-resolved Fe K-edge XAS in the previous studies.
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Affiliation(s)
- Fumitoshi Kumaki
- Department of Materials Structure Science, School of High Energy Accelerator Science, SOKENDAI (The Graduate University for Advanced Studies), 1-1 Oho, Tsukuba, Ibaraki 305-0801, Japan
| | | | - Ryo Fukaya
- Department of Materials Structure Science, School of High Energy Accelerator Science, SOKENDAI (The Graduate University for Advanced Studies), 1-1 Oho, Tsukuba, Ibaraki 305-0801, Japan
| | - Yasuaki Okano
- Institute for Molecular Science, Myodaiji, Okazaki 444-8585, Japan
| | - Shohei Yamashita
- Department of Materials Structure Science, School of High Energy Accelerator Science, SOKENDAI (The Graduate University for Advanced Studies), 1-1 Oho, Tsukuba, Ibaraki 305-0801, Japan
| | - Shunsuke Nozawa
- Department of Materials Structure Science, School of High Energy Accelerator Science, SOKENDAI (The Graduate University for Advanced Studies), 1-1 Oho, Tsukuba, Ibaraki 305-0801, Japan
| | - Shin-Ichi Adachi
- Department of Materials Structure Science, School of High Energy Accelerator Science, SOKENDAI (The Graduate University for Advanced Studies), 1-1 Oho, Tsukuba, Ibaraki 305-0801, Japan
| | - Jun-Ichi Adachi
- Department of Materials Structure Science, School of High Energy Accelerator Science, SOKENDAI (The Graduate University for Advanced Studies), 1-1 Oho, Tsukuba, Ibaraki 305-0801, Japan
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12
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Sinha N, Wenger OS. Photoactive Metal-to-Ligand Charge Transfer Excited States in 3d 6 Complexes with Cr 0, Mn I, Fe II, and Co III. J Am Chem Soc 2023; 145:4903-4920. [PMID: 36808978 PMCID: PMC9999427 DOI: 10.1021/jacs.2c13432] [Citation(s) in RCA: 39] [Impact Index Per Article: 39.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/23/2023]
Abstract
Many coordination complexes and organometallic compounds with the 4d6 and 5d6 valence electron configurations have outstanding photophysical and photochemical properties, which stem from metal-to-ligand charge transfer (MLCT) excited states. This substance class makes extensive use of the most precious and least abundant metal elements, and consequently there has been a long-standing interest in first-row transition metal compounds with photoactive MLCT states. Semiprecious copper(I) with its completely filled 3d subshell is a relatively straightforward and well explored case, but in 3d6 complexes the partially filled d-orbitals lead to energetically low-lying metal-centered (MC) states that can cause undesirably fast MLCT excited state deactivation. Herein, we discuss recent advances made with isoelectronic Cr0, MnI, FeII, and CoIII compounds, for which long-lived MLCT states have become accessible over the past five years. Furthermore, we discuss possible future developments in the search for new first-row transition metal complexes with partially filled 3d subshells and photoactive MLCT states for next-generation applications in photophysics and photochemistry.
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Affiliation(s)
- Narayan Sinha
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056 Basel, Switzerland
| | - Oliver S Wenger
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056 Basel, Switzerland
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13
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Electronic structures and ligand effect on redox potential of iron and cobalt complexes: a computational insight. Struct Chem 2023. [DOI: 10.1007/s11224-022-02119-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/15/2023]
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14
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Zobel JP, Kruse A, Baig O, Lochbrunner S, Bokarev SI, Kühn O, González L, Bokareva OS. Can range-separated functionals be optimally tuned to predict spectra and excited state dynamics in photoactive iron complexes? Chem Sci 2023; 14:1491-1502. [PMID: 36794199 PMCID: PMC9906774 DOI: 10.1039/d2sc05839a] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2022] [Accepted: 12/27/2022] [Indexed: 01/14/2023] Open
Abstract
Density functional theory is an efficient computational tool to investigate photophysical and photochemical processes in transition metal complexes, giving invaluable assistance in interpreting spectroscopic and catalytic experiments. Optimally tuned range-separated functionals are particularly promising, as they were created to address some of the fundamental deficiencies present in approximate exchange-correlation functionals. In this paper, we scrutinize the selection of optimally tuned parameters and its influence on the excited state dynamics, using the example of the iron complex [Fe(cpmp)2]2+ with push-pull ligands. Various tuning strategies are contemplated based on pure self-consistent DFT protocols, as well as on the comparison with experimental spectra and multireference CASPT2 results. The two most promising sets of optimal parameters are then employed to carry out nonadiabatic surface-hopping dynamics simulations. Intriguingly, we find that the two sets lead to very different relaxation pathways and timescales. While the set of optimal parameters from one of the self-consistent DFT protocols predicts the formation of long-lived metal-to-ligand charge transfer triplet states, the set in better agreement with CASPT2 calculations leads to deactivation in the manifold of metal-centered states, in better agreement with the experimental reference data. These results showcase the complexity of iron-complex excited state landscapes and the difficulty of obtaining an unambiguous parametrization of long-range corrected functionals without experimental input.
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Affiliation(s)
- J. Patrick Zobel
- Institute of Theoretical Chemistry, Faculty of Chemistry, University of Vienna, Währingerstr. 191090 ViennaAustria
| | - Ayla Kruse
- Institute of Physics, University of Rostock, Albert-Einstein-Straße 23-24 18059 Rostock Germany .,Department of Life, Light and Matter, University of Rostock 18051 Rostock Germany
| | - Omar Baig
- Institute of Theoretical Chemistry, Faculty of Chemistry, University of Vienna, Währingerstr. 19 1090 Vienna Austria
| | - Stefan Lochbrunner
- Institute of Physics, University of Rostock, Albert-Einstein-Straße 23-24 18059 Rostock Germany .,Department of Life, Light and Matter, University of Rostock 18051 Rostock Germany
| | - Sergey I. Bokarev
- Institute of Physics, University of Rostock, Albert-Einstein-Straße 23-2418059 RostockGermany,Chemistry Department, Technical University of Munich, Lichtenbergstr. 4Garching 85748Germany
| | - Oliver Kühn
- Institute of Physics, University of Rostock, Albert-Einstein-Straße 23-24 18059 Rostock Germany
| | - Leticia González
- Institute of Theoretical Chemistry, Faculty of Chemistry, University of Vienna, Währingerstr. 19 1090 Vienna Austria
| | - Olga S. Bokareva
- Institute of Physics, University of Rostock, Albert-Einstein-Straße 23-2418059 RostockGermany,Institute of Physics, University of KasselHeinrich-Plett-Straße 4034132 KasselGermany
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15
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Ogawa T, Sinha N, Pfund B, Prescimone A, Wenger OS. Molecular Design Principles to Elongate the Metal-to-Ligand Charge Transfer Excited-State Lifetimes of Square-Planar Nickel(II) Complexes. J Am Chem Soc 2022; 144:21948-21960. [DOI: 10.1021/jacs.2c08838] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Affiliation(s)
- Tomohiro Ogawa
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056 Basel, Switzerland
| | - Narayan Sinha
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056 Basel, Switzerland
| | - Björn Pfund
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056 Basel, Switzerland
| | - Alessandro Prescimone
- Department of Chemistry, University of Basel, BPR 1096, Mattenstrasse 24a, 4058 Basel, Switzerland
| | - Oliver S. Wenger
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056 Basel, Switzerland
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16
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Pandey S, Mandal T, Mandal SK. Probing the strong electron-acceptor property of pyridine-appended 1,2,3-benzotriazole ligand in tris-homoleptic Ru(II) and Fe(II) complexes. Polyhedron 2022. [DOI: 10.1016/j.poly.2022.116109] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
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17
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Kübler J, Pfund B, Wenger OS. Zinc(II) Complexes with Triplet Charge-Transfer Excited States Enabling Energy-Transfer Catalysis, Photoinduced Electron Transfer, and Upconversion. JACS AU 2022; 2:2367-2380. [PMID: 36311829 PMCID: PMC9597861 DOI: 10.1021/jacsau.2c00442] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2022] [Revised: 09/22/2022] [Accepted: 09/22/2022] [Indexed: 05/28/2023]
Abstract
Many CuI complexes have luminescent triplet charge-transfer excited states with diverse applications in photophysics and photochemistry, but for isoelectronic ZnII compounds, this behavior is much less common, and they typically only show ligand-based fluorescence from singlet π-π* states. We report two closely related tetrahedral ZnII compounds, in which intersystem crossing occurs with appreciable quantum yields and leads to the population of triplet excited states with intraligand charge-transfer (ILCT) character. In addition to showing fluorescence from their initially excited 1ILCT states, these new compounds therefore undergo triplet-triplet energy transfer (TTET) from their 3ILCT states and consequently can act as sensitizers for photo-isomerization reactions and triplet-triplet annihilation upconversion from the blue to the ultraviolet spectral range. The photoactive 3ILCT state furthermore facilitates photoinduced electron transfer. Collectively, our findings demonstrate that mononuclear ZnII compounds with photophysical and photochemical properties reminiscent of well-known CuI complexes are accessible with suitable ligands and that they are potentially amenable to many different applications. Our insights seem relevant in the greater context of obtaining photoactive compounds based on abundant transition metals, complementing well-known precious-metal-based luminophores and photosensitizers.
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18
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Schmid L, Chábera P, Rüter I, Prescimone A, Meyer F, Yartsev A, Persson P, Wenger OS. Borylation in the Second Coordination Sphere of Fe II Cyanido Complexes and Its Impact on Their Electronic Structures and Excited-State Dynamics. Inorg Chem 2022; 61:15853-15863. [PMID: 36167335 PMCID: PMC9554916 DOI: 10.1021/acs.inorgchem.2c01667] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
Abstract
![]()
Second coordination sphere interactions
of cyanido complexes with hydrogen-bonding solvents and Lewis acids
are known to influence their electronic structures, whereby the non-labile
attachment of B(C6F5)3 resulted in
several particularly interesting new compounds lately. Here, we investigate
the effects of borylation on the properties of two FeII cyanido complexes in a systematic manner by comparing five different
compounds and using a range of experimental techniques. Electrochemical
measurements indicate that borylation entails a stabilization of the
FeII-based t2g-like orbitals by up to 1.65 eV,
and this finding was confirmed by Mössbauer spectroscopy. This
change in the electronic structure has a profound impact on the UV–vis
absorption properties of the borylated complexes compared to the non-borylated
ones, shifting their metal-to-ligand charge transfer (MLCT) absorption
bands over a wide range. Ultrafast UV–vis transient absorption
spectroscopy provides insight into how borylation affects the excited-state
dynamics. The lowest metal-centered (MC) excited states become shorter-lived
in the borylated complexes compared to their cyanido analogues by
a factor of ∼10, possibly due to changes in outer-sphere reorganization
energies associated with their decay to the electronic ground state
as a result of B(C6F5)3 attachment
at the cyanido N lone pair. Borylation
in the second coordination sphere of two well-known
FeII cyanido complexes leads to isocyanoborato complexes.
The effects of borylation on their electronic structure and photophysical
properties are thoroughly investigated with a range of experimental
techniques.
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Affiliation(s)
- Lucius Schmid
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056 Basel, Switzerland
| | - Pavel Chábera
- Department of Chemical Physics, Lund University, P.O. Box 12 4, 22100 Lund, Sweden
| | - Isabelle Rüter
- Institute of Inorganic Chemistry, University of Göttingen, Tammannstrasse 4, D-37077 Göttingen, Germany
| | - Alessandro Prescimone
- Department of Chemistry, University of Basel, BPR 1096, Mattenstrasse 24a, 4058 Basel, Switzerland
| | - Franc Meyer
- Institute of Inorganic Chemistry, University of Göttingen, Tammannstrasse 4, D-37077 Göttingen, Germany
| | - Arkady Yartsev
- Department of Chemical Physics, Lund University, P.O. Box 12 4, 22100 Lund, Sweden
| | - Petter Persson
- Theoretical Chemistry Division, Lund University, P.O. Box 124, 22100 Lund, Sweden
| | - Oliver S Wenger
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056 Basel, Switzerland
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19
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Holubowitch NE, Nguyen G. Dimerization of [Fe III(bpy) 3] 3+ in Aqueous Solutions: Elucidating a Mechanism Based on Historical Proposals, Electrochemical Data, and Computational Free Energy Analysis. Inorg Chem 2022; 61:9541-9556. [PMID: 35699660 DOI: 10.1021/acs.inorgchem.2c00640] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Iron(II) tris-bipyridine, [FeII(bpy)3]2+, is a historically significant organometallic coordination complex with attractive redox and photophysical properties. With respect to energy storage, it is a low-cost, high-redox potential complex and thus attractive for use as a catholyte in aqueous redox flow batteries. Despite these favorable characteristics, its oxidized Fe(III) form undergoes dimerization to form μ-O-[FeIII(bpy)2(H2O)]24+, leading to a dramatic ∼0.7 V decrease during battery discharge. To date, the energetics and complete mechanism of this slow, sequential electrochemical-chemical (EC) process, which includes electron transfer, nucleophilic attack, ligand cleavage, μ-oxo bond formation, and spin state transition, have not been elucidated. Using cyclic voltammetry, redox flow battery data, and density functional theory calculations guided by previously proposed mechanisms, we modeled more than 100 complexes and performed more than 50 geometry scans to resolve the key steps dictating these complex chemical processes. Quantitative free energy surfaces are developed to model the mechanism of dimerization accounting for the spins and identities of any possible Fe(II), Fe(III), or Fe(IV) intermediates. Electrochemical reduction of the dimer regenerates [FeII(bpy)3]2+ in an overall reversible process. Computational electrochemistry interrogates the influence of spin state, coordination environment, and molecular conformation at the electrode-electrolyte interface through a proposed stepwise dimer reduction process. Experimentally, we show that the considerable overpotential associated with this event can be catalytically mitigated with disparate materials, including platinum, copper hexacyanoferrate, and activated carbon. The findings are of fundamental and applied significance and could elevate [FeII(bpy)3]2+ and its derivatives to play a vital role in the burgeoning renewable energy economy.
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Affiliation(s)
- Nicolas E Holubowitch
- Texas A&M University-Corpus Christi, 6300 Ocean Drive, Corpus Christi, Texas 78412, United States
| | - Giang Nguyen
- Texas A&M University-Corpus Christi, 6300 Ocean Drive, Corpus Christi, Texas 78412, United States
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20
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Yarranton JT, McCusker JK. Ligand-Field Spectroscopy of Co(III) Complexes and the Development of a Spectrochemical Series for Low-Spin d 6 Charge-Transfer Chromophores. J Am Chem Soc 2022; 144:12488-12500. [PMID: 35749670 DOI: 10.1021/jacs.2c04945] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
A study of a series of six-coordinate Co(III) complexes has been carried out to quantify spectroscopic parameters for a range of ligands that are commonly employed to realize strong charge-transfer absorptions in low-spin, d6 systems. Identification of any three ligand-field transitions allows for the determination of the splitting parameter (10 Dq) as well as the Racah B and C parameters for a given compound. The data revealed a relatively small spread in the magnitude of 10 Dq, ranging from ca. 23 000 cm-1 in the case of [Co(pyrro-bpy)3]3+ (where pyrro-bpy is 4,4'-dipyrrolidinyl-2,2'-bipyridine) to ca. 26 000 cm-1 for [Co(terpy)2]3+ (where terpy is 2,2':6',2″-terpyridine). Significantly, trends across the series suggest that polypyridyl ligands behave as net π-donors when interacting with Co(III), in contrast to the net π-accepting character they exhibit when bound to second- and third-row metals. The influence of strong σ donation associated with carbene-based ligands was evident from the data acquired for [Co(BMeImPy)2]3+ (where BMeImPy is 3,3'-(pyridine-2,6-diyl)bis(1-methyl-1H-3-imidazolium)), where a 10 Dq value of ca. 30 000 cm-1 was determined. Spectroscopic data were also analyzed for [Fe(bpy)3]2+ using the results on [Co(bpy)3]3+ as a reference point. A value for 10 Dq of 21 000 cm-1 was estimated, indicating a reduction in the ligand-field strength of ca. 3000 cm-1 upon replacing Co(III) with Fe(II). We suggest that this approach of taking advantage of the blueshift of the charge-transfer feature in Co(III) complexes to reveal otherwise obscured ligand-field bands can be a useful tool for the development of new ligand systems to expand the photofunctionality of first-row transition-metal-based chromophores.
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Affiliation(s)
- Jonathan T Yarranton
- Department of Chemistry, Michigan State University, 578 South Shaw Lane, East Lansing, Michigan 48824, United States
| | - James K McCusker
- Department of Chemistry, Michigan State University, 578 South Shaw Lane, East Lansing, Michigan 48824, United States
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21
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Sinha N, Pfund B, Wegeberg C, Prescimone A, Wenger OS. Cobalt(III) Carbene Complex with an Electronic Excited-State Structure Similar to Cyclometalated Iridium(III) Compounds. J Am Chem Soc 2022; 144:9859-9873. [PMID: 35623627 PMCID: PMC9490849 DOI: 10.1021/jacs.2c02592] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
![]()
Many organometallic
iridium(III) complexes have photoactive excited
states with mixed metal-to-ligand and intraligand charge transfer
(MLCT/ILCT) character, which form the basis for numerous applications
in photophysics and photochemistry. Cobalt(III) complexes with analogous
MLCT excited-state properties seem to be unknown yet, despite the
fact that iridium(III) and cobalt(III) can adopt identical low-spin
d6 valence electron configurations due to their close chemical
relationship. Using a rigid tridentate chelate ligand (LCNC), in which a central amido π-donor is flanked by two σ-donating
N-heterocyclic carbene subunits, we obtained a robust homoleptic complex
[Co(LCNC)2](PF6), featuring a photoactive
excited state with substantial MLCT character. Compared to the vast
majority of isoelectronic iron(II) complexes, the MLCT state of [Co(LCNC)2](PF6) is long-lived because it
does not deactivate as efficiently into lower-lying metal-centered
excited states; furthermore, it engages directly in photoinduced electron
transfer reactions. The comparison with [Fe(LCNC)2](PF6), as well as structural, electrochemical, and UV–vis
transient absorption studies, provides insight into new ligand design
principles for first-row transition-metal complexes with photophysical
and photochemical properties reminiscent of those known from the platinum
group metals.
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Affiliation(s)
- Narayan Sinha
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056 Basel, Switzerland
| | - Björn Pfund
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056 Basel, Switzerland
| | - Christina Wegeberg
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056 Basel, Switzerland
| | - Alessandro Prescimone
- Department of Chemistry, University of Basel, BPR 1096, Mattenstrasse 24a, 4058 Basel, Switzerland
| | - Oliver S Wenger
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056 Basel, Switzerland
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22
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Chiral control of spin-crossover dynamics in Fe(II) complexes. Nat Chem 2022; 14:739-745. [PMID: 35618767 DOI: 10.1038/s41557-022-00933-0] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2021] [Accepted: 03/14/2022] [Indexed: 11/08/2022]
Abstract
Iron-based spin-crossover complexes hold tremendous promise as multifunctional switches in molecular devices. However, real-world technological applications require the excited high-spin state to be kinetically stable-a feature that has been achieved only at cryogenic temperatures. Here we demonstrate high-spin-state trapping by controlling the chiral configuration of the prototypical iron(II)tris(4,4'-dimethyl-2,2'-bipyridine) in solution, associated for stereocontrol with the enantiopure Δ- or Λ-enantiomer of tris(3,4,5,6-tetrachlorobenzene-1,2-diolato-κ2O1,O2)phosphorus(V) (P(O2C6Cl4)3- or TRISPHAT) anions. We characterize the high-spin-state relaxation using broadband ultrafast circular dichroism spectroscopy in the deep ultraviolet in combination with transient absorption and anisotropy measurements. We find that the high-spin-state decay is accompanied by ultrafast changes of its optical activity, reflecting the coupling to a symmetry-breaking torsional twisting mode, contrary to the commonly assumed picture. The diastereoselective ion pairing suppresses the vibrational population of the identified reaction coordinate, thereby achieving a fourfold increase of the high-spin-state lifetime. More generally, our results motivate the synthetic control of the torsional modes of iron(II) complexes as a complementary route to manipulate their spin-crossover dynamics.
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23
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Abstract
In molecular photochemistry, charge-transfer emission is well understood and widely exploited. In contrast, luminescent metal-centered transitions only came into focus in recent years. This gave rise to strongly phosphorescent CrIII complexes with a d3 electronic configuration featuring luminescent metal-centered excited states which are characterized by the flip of a single spin. These so-called spin-flip emitters possess unique properties and require different design strategies than traditional charge-transfer phosphors. In this review, we give a brief introduction to ligand field theory as a framework to understand this phenomenon and outline prerequisites for efficient spin-flip emission including ligand field strength, symmetry, intersystem crossing and common deactivation pathways using CrIII complexes as instructive examples. The recent progress and associated challenges of tuning the energies of emissive excited states and of emerging applications of the unique photophysical properties of spin-flip emitters are discussed. Finally, we summarize the current state-of-the-art and challenges of spin-flip emitters beyond CrIII with d2, d3, d4 and d8 electronic configuration, where we mainly cover pseudooctahedral molecular complexes of V, Mo, W, Mn, Re and Ni, and highlight possible future research opportunities.
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24
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Cebrían C, Pastore M, Monari A, Assfeld X, Gros PC, Haacke S. Ultrafast Spectroscopy of Fe(II) Complexes Designed for Solar Energy Conversion: Current Status and Open Questions. Chemphyschem 2022; 23:e202100659. [DOI: 10.1002/cphc.202100659] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2021] [Revised: 01/22/2022] [Indexed: 11/11/2022]
Affiliation(s)
| | | | | | | | | | - Stefan Haacke
- University of Strasbourg: Universite de Strasbourg IPCMS 23, rue du Loess 67034 Strasbourg FRANCE
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25
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Sold S, Mummaneni BC, Michenfelder NC, Peng Y, Powell AK, Unterreiner AN, Lefkidis G, Hübner W. Experimental and Theoretical Study of the Ultrafast Dynamics of a Ni 2 Dy 2 -Compound in DMF After UV/Vis Photoexcitation. ChemistryOpen 2021; 11:e202100153. [PMID: 34931474 PMCID: PMC9059312 DOI: 10.1002/open.202100153] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2021] [Revised: 11/04/2021] [Indexed: 01/30/2023] Open
Abstract
We present a combined experimental and theoretical study of the ultrafast transient absorption spectroscopy results of a {Ni2Dy2}‐compound in DMF, which can be considered as a prototypic molecule for single molecule magnets. We apply state‐of‐the‐art ab initio quantum chemistry to quantitatively describe the optical properties of an inorganic complex system comprising ten atoms to form the chromophoric unit, which is further stabilized by surrounding ligands. Two different basis sets are used for the calculations to specifically identify two dominant peaks in the ground state. Furthermore, we theoretically propagate the compound's correlated many‐body wavefunction under the influence of a laser pulse as well as relaxation processes and compare against the time‐resolved absorption spectra. The experimental data can be described with a time constant of several hundreds of femtoseconds attributed to vibrational relaxation and trapping into states localized within the band gap. A second time constant is ascribed to the excited state while trap states show lifetimes on a longer timescale. The theoretical propagation is performed with the density‐matrix formalism and the Lindblad superoperator, which couples the system to a thermal bath, allowing us to extract relaxation times from first principles.
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Affiliation(s)
- S Sold
- Department of Physics and Research Center OPTIMAS, Technische Universität Kaiserslautern, P.O. Box 3049, 67653, Kaiserslautern, Germany
| | - B C Mummaneni
- Department of Physics and Research Center OPTIMAS, Technische Universität Kaiserslautern, P.O. Box 3049, 67653, Kaiserslautern, Germany
| | - N C Michenfelder
- Institute of Physical Chemistry, Karlsruhe Institute of Technology, Fritz-Haber-Weg 2, 76131, Karlsruhe, Germany
| | - Y Peng
- Institute of Inorganic Chemistry, Karlsruhe Institute of Technology, Engesserstrasse 15, 76131, Karlsruhe, Germany.,Institute of Nanotechnology, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344, Eggenstein-Leopoldshafen, Germany
| | - A K Powell
- Institute of Inorganic Chemistry, Karlsruhe Institute of Technology, Engesserstrasse 15, 76131, Karlsruhe, Germany.,Institute of Nanotechnology, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344, Eggenstein-Leopoldshafen, Germany
| | - A-N Unterreiner
- Institute of Physical Chemistry, Karlsruhe Institute of Technology, Fritz-Haber-Weg 2, 76131, Karlsruhe, Germany
| | - G Lefkidis
- Department of Physics and Research Center OPTIMAS, Technische Universität Kaiserslautern, P.O. Box 3049, 67653, Kaiserslautern, Germany.,School of Mechanics, Civil Engineering and Architecture, Northwestern Polytechnical University, Xi'an, 710072, China
| | - W Hübner
- Department of Physics and Research Center OPTIMAS, Technische Universität Kaiserslautern, P.O. Box 3049, 67653, Kaiserslautern, Germany
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26
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Larsen CB, Braun JD, Lozada IB, Kunnus K, Biasin E, Kolodziej C, Burda C, Cordones AA, Gaffney KJ, Herbert DE. Reduction of Electron Repulsion in Highly Covalent Fe-Amido Complexes Counteracts the Impact of a Weak Ligand Field on Excited-State Ordering. J Am Chem Soc 2021; 143:20645-20656. [PMID: 34851636 DOI: 10.1021/jacs.1c06429] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The ability to access panchromatic absorption and long-lived charge-transfer (CT) excited states is critical to the pursuit of abundant-metal molecular photosensitizers. Fe(II) complexes supported by benzannulated diarylamido ligands have been reported to broadly absorb visible light with nanosecond CT excited state lifetimes, but as amido donors exert a weak ligand field, this defies conventional photosensitizer design principles. Here, we report an aerobically stable Fe(II) complex of a phenanthridine/quinoline diarylamido ligand, Fe(ClL)2, with panchromatic absorption and a 3 ns excited-state lifetime. Using X-ray absorption spectroscopy (XAS) and resonant inelastic X-ray scattering (RIXS) at the Fe L-edge and N K-edge, we experimentally validate the strong Fe-Namido orbital mixing in Fe(ClL)2 responsible for the panchromatic absorption and demonstrate a previously unreported competition between ligand-field strength and metal-ligand (Fe-Namido) covalency that stabilizes the 3CT state over the lowest energy triplet metal-centered (3MC) state in the ground-state geometry. Single-crystal X-ray diffraction (XRD) and density functional theory (DFT) suggest that formation of this CT state depopulates an orbital with Fe-Namido antibonding character, causing metal-ligand bonds to contract and accentuating the geometric differences between CT and MC excited states. These effects diminish the driving force for electron transfer to metal-centered excited states and increase the intramolecular reorganization energy, critical properties for extending the lifetime of CT excited states. These findings highlight metal-ligand covalency as a novel design principle for elongating excited state lifetimes in abundant metal photosensitizers.
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Affiliation(s)
- Christopher B Larsen
- Stanford PULSE Institute, SLAC National Accelerator Laboratory, Stanford University, 2575 Sand Hill Road, Menlo Park, California 94025, United States
| | - Jason D Braun
- Department of Chemistry and the Manitoba Institute for Materials, University of Manitoba, 144 Dysart Road, Winnipeg, MB R3T 2N2, Canada
| | - Issiah B Lozada
- Department of Chemistry and the Manitoba Institute for Materials, University of Manitoba, 144 Dysart Road, Winnipeg, MB R3T 2N2, Canada
| | - Kristjan Kunnus
- Stanford PULSE Institute, SLAC National Accelerator Laboratory, Stanford University, 2575 Sand Hill Road, Menlo Park, California 94025, United States
| | - Elisa Biasin
- Stanford PULSE Institute, SLAC National Accelerator Laboratory, Stanford University, 2575 Sand Hill Road, Menlo Park, California 94025, United States
| | - Charles Kolodziej
- Department of Chemistry, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, Ohio 44106, United States
| | - Clemens Burda
- Department of Chemistry, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, Ohio 44106, United States
| | - Amy A Cordones
- Stanford PULSE Institute, SLAC National Accelerator Laboratory, Stanford University, 2575 Sand Hill Road, Menlo Park, California 94025, United States
| | - Kelly J Gaffney
- Stanford PULSE Institute, SLAC National Accelerator Laboratory, Stanford University, 2575 Sand Hill Road, Menlo Park, California 94025, United States
| | - David E Herbert
- Department of Chemistry and the Manitoba Institute for Materials, University of Manitoba, 144 Dysart Road, Winnipeg, MB R3T 2N2, Canada
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27
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Ahoulou S, Vilà N, Pillet S, Carteret C, Schaniel D, Walcarius A. Multi-stimuli Photo and Redox-active Nanostructured Mesoporous Silica Films on Transparent Electrodes. Chemphyschem 2021; 22:2464-2477. [PMID: 34708493 DOI: 10.1002/cphc.202100608] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2021] [Revised: 09/24/2021] [Indexed: 11/12/2022]
Abstract
Silica matrices hosting transition metal guest complexes may offer remarkable platforms for the development of advanced functional devices. We report here the elaboration of ordered and vertically oriented mesoporous silica thin films containing covalently attached tris(bipyridine)iron derivatives using a combination of electrochemically assisted self-assembly (EASA) method and Huisgen cycloaddition reaction. Such a versatile approach is primarily used to bind nitrogen-based chelating ligands such as (4-[(2-propyn-1-yloxy)]4'-methyl-2,2'-bypiridine, bpy') inside the nanochannels. Further derivatization of the bpy'-functionalized silica thin films is then achieved via a subsequent in-situ complexation step to generate [Fe(bpy)2 (bpy')]2+ inside the mesopore channels. After giving spectroscopic evidences for the presence of such complexes in the functionalized film, electrochemistry is used to transform the confined diamagnetic (S=0) F e L S b p y 2 b p y ' 2 + species to paramagnetic (S=1/2) oxidized F e L S b p y 2 b p y ' 3 + species in a reversible way, while blue light irradiation (λ=470 nm) enables populating the short-lived paramagnetic (S=2) F e H S b p y 2 b p y ' 2 + excited state. [Fe(bpy)2 (bpy')]2+ -functionalized ordered films are therefore both electro- and photo-active through the manipulation of the oxidation state and spin state of the confined complexes, paving the way for their integration in optoelectronic devices.
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Affiliation(s)
- Samuel Ahoulou
- Université de Lorraine, CNRS, LCPME UMR 7564, 54000, Nancy, France.,Université de Lorraine, CRM2 UMR 7036, 54000, Nancy, France
| | - Neus Vilà
- Université de Lorraine, CNRS, LCPME UMR 7564, 54000, Nancy, France
| | | | - Cédric Carteret
- Université de Lorraine, CNRS, LCPME UMR 7564, 54000, Nancy, France
| | | | - Alain Walcarius
- Université de Lorraine, CNRS, LCPME UMR 7564, 54000, Nancy, France
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28
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Wegeberg C, Wenger OS. Luminescent First-Row Transition Metal Complexes. JACS AU 2021; 1:1860-1876. [PMID: 34841405 PMCID: PMC8611671 DOI: 10.1021/jacsau.1c00353] [Citation(s) in RCA: 101] [Impact Index Per Article: 33.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/13/2021] [Indexed: 05/25/2023]
Abstract
Precious and rare elements have traditionally dominated inorganic photophysics and photochemistry, but now we are witnessing a paradigm shift toward cheaper and more abundant metals. Even though emissive complexes based on selected first-row transition metals have long been known, recent conceptual breakthroughs revealed that a much broader range of elements in different oxidation states are useable for this purpose. Coordination compounds of V, Cr, Mn, Fe, Co, Ni, and Cu now show electronically excited states with unexpected reactivity and photoluminescence behavior. Aside from providing a compact survey of the recent conceptual key advances in this dynamic field, our Perspective identifies the main design strategies that enabled the discovery of fundamentally new types of 3d-metal-based luminophores and photosensitizers operating in solution at room temperature.
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29
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Muñoz-García AB, Benesperi I, Boschloo G, Concepcion JJ, Delcamp JH, Gibson EA, Meyer GJ, Pavone M, Pettersson H, Hagfeldt A, Freitag M. Dye-sensitized solar cells strike back. Chem Soc Rev 2021; 50:12450-12550. [PMID: 34590638 PMCID: PMC8591630 DOI: 10.1039/d0cs01336f] [Citation(s) in RCA: 94] [Impact Index Per Article: 31.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2021] [Indexed: 12/28/2022]
Abstract
Dye-sensitized solar cells (DSCs) are celebrating their 30th birthday and they are attracting a wealth of research efforts aimed at unleashing their full potential. In recent years, DSCs and dye-sensitized photoelectrochemical cells (DSPECs) have experienced a renaissance as the best technology for several niche applications that take advantage of DSCs' unique combination of properties: at low cost, they are composed of non-toxic materials, are colorful, transparent, and very efficient in low light conditions. This review summarizes the advancements in the field over the last decade, encompassing all aspects of the DSC technology: theoretical studies, characterization techniques, materials, applications as solar cells and as drivers for the synthesis of solar fuels, and commercialization efforts from various companies.
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Affiliation(s)
- Ana Belén Muñoz-García
- Department of Physics "Ettore Pancini", University of Naples Federico II, 80126 Naples, Italy
| | - Iacopo Benesperi
- School of Natural and Environmental Science, Newcastle University, Bedson Building, NE1 7RU Newcastle upon Tyne, UK.
| | - Gerrit Boschloo
- Department of Chemistry, Ångström Laboratory, Uppsala University, P.O. Box 523, 751 20 Uppsala, Sweden.
| | - Javier J Concepcion
- Chemistry Division, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - Jared H Delcamp
- Department of Chemistry and Biochemistry, University of Mississippi, University, MS 38677, USA
| | - Elizabeth A Gibson
- School of Natural and Environmental Science, Newcastle University, Bedson Building, NE1 7RU Newcastle upon Tyne, UK.
| | - Gerald J Meyer
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
| | - Michele Pavone
- Department of Chemical Sciences, University of Naples Federico II, 80126 Naples, Italy
| | | | - Anders Hagfeldt
- Department of Chemistry, Ångström Laboratory, Uppsala University, P.O. Box 523, 751 20 Uppsala, Sweden.
- University Management and Management Council, Vice Chancellor, Uppsala University, Segerstedthuset, 752 37 Uppsala, Sweden
| | - Marina Freitag
- School of Natural and Environmental Science, Newcastle University, Bedson Building, NE1 7RU Newcastle upon Tyne, UK.
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30
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Herr P, Kerzig C, Larsen CB, Häussinger D, Wenger OS. Manganese(I) complexes with metal-to-ligand charge transfer luminescence and photoreactivity. Nat Chem 2021; 13:956-962. [PMID: 34341527 DOI: 10.1038/s41557-021-00744-9] [Citation(s) in RCA: 70] [Impact Index Per Article: 23.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2020] [Accepted: 06/04/2021] [Indexed: 11/09/2022]
Abstract
Precious metal complexes with the d6 valence electron configuration often exhibit luminescent metal-to-ligand charge transfer (MLCT) excited states, which form the basis for many applications in lighting, sensing, solar cells and synthetic photochemistry. Iron(II) has received much attention as a possible Earth-abundant alternative, but to date no iron(II) complex has been reported to show MLCT emission upon continuous-wave excitation. Manganese(I) has the same electron configuration as that of iron(II), but until now has typically been overlooked in the search for cheap MLCT luminophores. Here we report that isocyanide chelate ligands give access to air-stable manganese(I) complexes that exhibit MLCT luminescence in solution at room temperature. These compounds were successfully used as photosensitizers for energy- and electron-transfer reactions and were shown to promote the photoisomerization of trans-stilbene. The observable electron transfer photoreactivity occurred from the emissive MLCT state, whereas the triplet energy transfer photoreactivity originated from a ligand-centred 3π-π* state.
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Affiliation(s)
- Patrick Herr
- Department of Chemistry, University of Basel, Basel, Switzerland
| | - Christoph Kerzig
- Department of Chemistry, University of Basel, Basel, Switzerland
| | | | | | - Oliver S Wenger
- Department of Chemistry, University of Basel, Basel, Switzerland.
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31
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Paulus BC, Nielsen KC, Tichnell CR, Carey MC, McCusker JK. A Modular Approach to Light Capture and Synthetic Tuning of the Excited-State Properties of Fe(II)-Based Chromophores. J Am Chem Soc 2021; 143:8086-8098. [PMID: 34014077 DOI: 10.1021/jacs.1c02451] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The development of chromophores based on earth-abundant transition metals whose photophysical properties are dominated by their charge-transfer excited states has inspired considerable research over the past decade. One challenge associated with this effort is satisfying the dual requirements of a strong ligand field and chemical tunability of the compound's absorptive cross-section. Herein we explore one possible approach using a heteroleptic compositional motif that combines both of these attributes into a single compound. With the parent complex [Fe(phen)3]2+ (1; where phen is 1,10-phenanthroline) as the starting material, replacement of one of the phen ligands for two cyanides to obtain Fe(phen)2(CN)2 (2) allows for conversion to [Fe(phen)2(C4H10N4)]2+ (3), a six-coordinate Fe(II) complex whose coordination sphere consists of two chelating polypyridyl ligands and one bidentate carbene-based donor. Ground-state absorption spectra of all three compounds exhibit 1A1 → 1MLCT transition(s) associated with the phen ligands that are relatively insensitive to the identity of the third counterligand(s). Ultrafast time-resolved electronic absorption measurements revealed lifetimes for the MLCT excited states of compounds 1 and 2 of 180 ± 30 and 250 ± 90 fs, respectively, values that are typical for iron(II)-based polypyridyl complexes. The corresponding kinetics for compound 3 were substantially slower at 7.4 ± 0.9 ps; the spectral evolution associated with these dynamics confirms that these kinetics are tracking the MLCT excited state and, more importantly, are coupled to ground-state recovery from this excited state. The data are interpreted in terms of a modulation of the relative energies of the MLCT and ligand-field states across the series, leading to a systematic destabilization of metal-localized ligand-field excited states such that the low-energy portions of the charge-transfer and ligand-field manifolds are at or near an energetic inversion point in compound 3. We believe these results illustrate the potential for a modular, orthogonal approach to chromophore design in which part of the coordination sphere can be targeted for light absorption while another can be used to tune electronic-state energetics.
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Affiliation(s)
- Bryan C Paulus
- Department of Chemistry, Michigan State University 578 South Shaw Lane, East Lansing, Michigan 48824, United States
| | - Karl C Nielsen
- Department of Chemistry, Michigan State University 578 South Shaw Lane, East Lansing, Michigan 48824, United States
| | - Christopher R Tichnell
- Department of Chemistry, Michigan State University 578 South Shaw Lane, East Lansing, Michigan 48824, United States
| | - Monica C Carey
- Department of Chemistry, Michigan State University 578 South Shaw Lane, East Lansing, Michigan 48824, United States
| | - James K McCusker
- Department of Chemistry, Michigan State University 578 South Shaw Lane, East Lansing, Michigan 48824, United States
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32
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Vittardi SB, Magar RT, Schrage BR, Ziegler CJ, Jakubikova E, Rack JJ. Evidence for a lowest energy 3MLCT excited state in [Fe(tpy)(CN) 3] . Chem Commun (Camb) 2021; 57:4658-4661. [PMID: 33977987 DOI: 10.1039/d1cc01090e] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Transient absorption data of [FeII(tpy)(CN)3]- reveals spectroscopic signatures indicative of 3MLCT with a ∼10 ps kinetic component. These data are supported by DFT and TD-DFT calculations, which show that excited state ordering is responsive to the number of cyanide ligands on the complex.
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Affiliation(s)
- Sebastian B Vittardi
- Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, NM 87131, USA.
| | - Rajani Thapa Magar
- Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, NM 87131, USA.
| | - Briana R Schrage
- Department of Chemistry, North Carolina State University, Raleigh, NC 27695, USA
| | | | - Elena Jakubikova
- Knight Chemical Laboratory, Department of Chemistry, University of Akron, Akron, OH, USA.
| | - Jeffrey J Rack
- Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, NM 87131, USA.
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33
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Lauenstein R, Mader SL, Derondeau H, Esezobor OZ, Block M, Römer AJ, Jandl C, Riedle E, Kaila VRI, Hauer J, Thyrhaug E, Hess CR. The central role of the metal ion for photoactivity: Zn- vs. Ni-Mabiq. Chem Sci 2021; 12:7521-7532. [PMID: 34163843 PMCID: PMC8171322 DOI: 10.1039/d0sc06096h] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Photoredox catalysts are integral components of artificial photosystems, and have recently emerged as powerful tools for catalysing numerous organic reactions. However, the development of inexpensive and efficient earth-abundant photoredox catalysts remains a challenge. We here present the photochemical and photophysical properties of a Ni–Mabiq catalyst ([NiII(Mabiq)]OTf (1); Mabiq = 2-4:6-8-bis(3,3,4,4-tetramethyldihydropyrrolo)-10-15-(2,2-biquinazolino)-[15]-1,3,5,8,10,14-hexaene1,3,7,9,11,14-N6)—and of a Zn-containing analogue ([ZnII(Mabiq)OTf] (2))—using steady state and time resolved optical spectroscopy, time-dependent density functional theory (TDDFT) calculations, and reactivity studies. The Ni and Zn complexes exhibit similar absorption spectra, but markedly different photochemical properties. These differences arise because the excited states of 2 are ligand-localized, whereas metal-centered states account for the photoactivity of 1. The distinct properties of the Ni and Zn complexes are manifest in their behavior in the photo-driven aza-Henry reaction and oxidative coupling of methoxybenzylamine. The development of earth-abundant photoredox catalysts remains a challenge. Studies of Ni- and Zn-Mabiq complexes demonstrate how the coordinating metal ion influences the photochemistry, photodynamics and reactivity of photocatalysts.![]()
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Affiliation(s)
- Raphael Lauenstein
- Department of Chemistry and Catalysis Research Center, Technical University of Munich Lichtenbergstr. 4, 85747 Garching Germany
| | - Sophie L Mader
- Department of Chemistry, Technical University of Munich Lichtenbergstr. 4, 85747 Garching Germany
| | - Henrieta Derondeau
- Lehrstuhl für BioMolekulare Optik, Fakultät für Physik, Ludwig-Maximilians-Universität München Oettingenstr. 67 80538 Munich Germany
| | - Oaikhena Z Esezobor
- Department of Chemistry and Catalysis Research Center, Technical University of Munich Lichtenbergstr. 4, 85747 Garching Germany
| | - Matthias Block
- Lehrstuhl für BioMolekulare Optik, Fakultät für Physik, Ludwig-Maximilians-Universität München Oettingenstr. 67 80538 Munich Germany
| | - Armin J Römer
- Department of Chemistry, Technical University of Munich Lichtenbergstr. 4, 85747 Garching Germany
| | - Christian Jandl
- Department of Chemistry and Catalysis Research Center, Technical University of Munich Lichtenbergstr. 4, 85747 Garching Germany
| | - Eberhard Riedle
- Lehrstuhl für BioMolekulare Optik, Fakultät für Physik, Ludwig-Maximilians-Universität München Oettingenstr. 67 80538 Munich Germany
| | - Ville R I Kaila
- Department of Chemistry, Technical University of Munich Lichtenbergstr. 4, 85747 Garching Germany
| | - Jürgen Hauer
- Department of Chemistry and Catalysis Research Center, Technical University of Munich Lichtenbergstr. 4, 85747 Garching Germany
| | - Erling Thyrhaug
- Department of Chemistry and Catalysis Research Center, Technical University of Munich Lichtenbergstr. 4, 85747 Garching Germany
| | - Corinna R Hess
- Department of Chemistry and Catalysis Research Center, Technical University of Munich Lichtenbergstr. 4, 85747 Garching Germany
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34
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Zhong Y, Feng Q, Wang X, Yang L, Korovich AG, Madsen LA, Tong R. Photocatalyst-independent photoredox ring-opening polymerization of O-carboxyanhydrides: stereocontrol and mechanism. Chem Sci 2021; 12:3702-3712. [PMID: 34163644 PMCID: PMC8179436 DOI: 10.1039/d0sc05550f] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2020] [Accepted: 01/18/2021] [Indexed: 11/21/2022] Open
Abstract
Photoredox ring-opening polymerization of O-carboxyanhydrides allows for the synthesis of polyesters with precisely controlled molecular weights, molecular weight distributions, and tacticities. While powerful, obviating the use of precious metal-based photocatalysts would be attractive from the perspective of simplifying the protocol. Herein, we report the Co and Zn catalysts that are activated by external light to mediate efficient ring-opening polymerization of O-carboxyanhydrides, without the use of exogenous precious metal-based photocatalysts. Our methods allow for the synthesis of isotactic polyesters with high molecular weights (>200 kDa) and narrow molecular weight distributions (M w/M n < 1.1). Mechanistic studies indicate that light activates the oxidative status of a CoIII intermediate that is generated from the regioselective ring-opening of the O-carboxyanhydride. We also demonstrate that the use of Zn or Hf complexes together with Co can allow for stereoselective photoredox ring-opening polymerizations of multiple racemic O-carboxyanhydrides to synthesize syndiotactic and stereoblock copolymers, which vary widely in their glass transition temperatures.
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Affiliation(s)
- Yongliang Zhong
- Department of Chemical Engineering, Virginia Polytechnic Institute and State University 635 Prices Fork Road, Blacksburg Virginia 24061 USA
| | - Quanyou Feng
- Department of Chemical Engineering, Virginia Polytechnic Institute and State University 635 Prices Fork Road, Blacksburg Virginia 24061 USA
- Key Laboratory for Organic Electronics and Information Displays, Jiangsu Key Laboratory for Biosensors, Institute of Advanced Materials, Jiangsu National Synergetic Innovation Center for Advanced Materials, Nanjing University of Posts and Telecommunications 9 Wenyuan Road Nanjing 210023 China
| | - Xiaoqian Wang
- Department of Chemical Engineering, Virginia Polytechnic Institute and State University 635 Prices Fork Road, Blacksburg Virginia 24061 USA
| | - Lei Yang
- Key Laboratory for Organic Electronics and Information Displays, Jiangsu Key Laboratory for Biosensors, Institute of Advanced Materials, Jiangsu National Synergetic Innovation Center for Advanced Materials, Nanjing University of Posts and Telecommunications 9 Wenyuan Road Nanjing 210023 China
| | - Andrew G Korovich
- Department of Chemistry, Virginia Polytechnic Institute and State University 1040 Drillfield Drive, Blacksburg Virginia 24061 USA
| | - Louis A Madsen
- Department of Chemistry, Virginia Polytechnic Institute and State University 1040 Drillfield Drive, Blacksburg Virginia 24061 USA
| | - Rong Tong
- Department of Chemical Engineering, Virginia Polytechnic Institute and State University 635 Prices Fork Road, Blacksburg Virginia 24061 USA
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35
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Abstract
Coordination compounds, characterized by fascinating and tunable electronic properties, are capable of binding easily to proteins, polymers, wires and DNA. Upon irradiation, these molecular systems develop functions finding applications in solar cells, photocatalysis, luminescent and conformational probes, electron transfer triggers and diagnostic or therapeutic tools. The control of these functions is activated by the light wavelength, the metal/ligand cooperation and the environment within the first picoseconds (ps). After a brief summary of the theoretical background, this perspective reviews case studies, from 1st row to 3rd row transition metal complexes, that illustrate how spin-orbit, vibronic coupling and quantum effects drive the photophysics of this class of molecules at the early stage of the photoinduced elementary processes within the fs-ps time scale range.
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Affiliation(s)
- Chantal Daniel
- Laboratoire de Chimie Quantique, Université de Strasbourg, CNRS UMR7177, Institut Le Bel, 4 Rue Blaise Pascal, 67000 Strasbourg, France.
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36
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Sárosiné Szemes D, Keszthelyi T, Papp M, Varga L, Vankó G. Quantum-chemistry-aided ligand engineering for potential molecular switches: changing barriers to tune excited state lifetimes. Chem Commun (Camb) 2020; 56:11831-11834. [PMID: 33021253 DOI: 10.1039/d0cc04467a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Substitution of terpyridine at the 4' position with electron withdrawing and donating groups is used to tune the quintet lifetime of its iron(ii) complex. DFT calculations suggest that the energy barrier between the quintet and singlet states can be altered significantly upon substitution, inducing a large variation of the lifetime of the photoexcited quintet state. This prediction was experimentally verified by transient optical absorption spectroscopy and good agreement with the trend expected from the calculations was found. This demonstrates that the potential energy landscape can indeed be rationally tailored by relevant modifications based on DFT predictions. This result should pave the way to advancing efficient theory-based ligand engineering of functional molecules to a wide range of applications.
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37
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Zobel JP, Bokareva OS, Zimmer P, Wölper C, Bauer M, González L. Intersystem Crossing and Triplet Dynamics in an Iron(II) N-Heterocyclic Carbene Photosensitizer. Inorg Chem 2020; 59:14666-14678. [PMID: 32869981 PMCID: PMC7581298 DOI: 10.1021/acs.inorgchem.0c02147] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
![]()
The electronic excited
states of the iron(II) complex [FeII(tpy)(pyz-NHC)]2+ [tpy = 2,2′:6′,2″-terpyridine; pyz-NHC
= 1,1′-bis(2,6-diisopropylphenyl)pyrazinyldiimidazolium-2,2′-diylidene]
and their relaxation pathways have been theoretically investigated.
To this purpose, trajectory surface-hopping simulations within a linear
vibronic coupling model including a 244-dimensional potential energy
surface (PES) with 20 singlet and 20 triplet coupled states have been
used. The simulations show that, after excitation to the lowest-energy
absorption band of predominant metal-to-ligand charge-transfer character
involving the tpy ligand, almost 80% of the population undergoes intersystem
crossing to the triplet manifold in about 50 fs, while the remaining
20% decays through internal conversion to the electronic ground state
in about 300 fs. The population transferred to the triplet states
is found to deactivate into two different regions of the PESs, one
where the static dipole moment is small and shows increased metal-centered
character and another with a large static dipole moment, where the
electron density is transferred from the tpy to pyz-NHC ligand. Coherent
oscillations of 400 fs are observed between these two sets of triplet
populations, until the mixture equilibrates to a ratio of 60:40. Finally,
the importance of selecting suitable normal modes is highlighted—a
choice that can be far from straightforward in transition-metal complexes
with hundreds of degrees of freedom. Trajectory
surface-hopping simulations with a linear vibronic coupling model
reveal the competition of major intersystem crossing versus minor
internal conversion dynamics in an iron(II) N-heterocyclic carbene
dye. The triplet population bifurcates into two regions of the potential
energy surfaces, characterized by small and large static dipole moments
due to different electronic character and showing coherent oscillations
of 400 fs until both triplet populations coexist in a mixture of 60:40.
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Affiliation(s)
- J Patrick Zobel
- Institute of Theoretical Chemistry, Faculty of Chemistry, University of Vienna, Währingerstraße 19, 1090 Vienna, Austria
| | - Olga S Bokareva
- Institute of Physics, Rostock University, Albert Einstein Straße 23-24, 18059 Rostock, Germany
| | - Peter Zimmer
- Faculty of Science, Chemistry Department and Center for Sustainable Systems Design (CSSD), Paderborn University, Warburger Straße 100, 33098 Paderborn, Germany
| | - Christoph Wölper
- Department for X-Ray Diffraction, Inorganic Chemistry, University of Duisburg-Essen, Universitätsstraße 7, D-45117 Essen, Germany
| | - Matthias Bauer
- Faculty of Science, Chemistry Department and Center for Sustainable Systems Design (CSSD), Paderborn University, Warburger Straße 100, 33098 Paderborn, Germany
| | - Leticia González
- Institute of Theoretical Chemistry, Faculty of Chemistry, University of Vienna, Währingerstraße 19, 1090 Vienna, Austria.,Vienna Research Platform on Accelerating Photoreaction Discovery, University of Vienna, Währingerstr. 19, 1090 Vienna, Austria
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38
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Hu K, Sampaio RN, Schneider J, Troian-Gautier L, Meyer GJ. Perspectives on Dye Sensitization of Nanocrystalline Mesoporous Thin Films. J Am Chem Soc 2020; 142:16099-16116. [DOI: 10.1021/jacs.0c04886] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Ke Hu
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, United States
| | - Renato N. Sampaio
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, United States
| | - Jenny Schneider
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, United States
| | - Ludovic Troian-Gautier
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, United States
| | - Gerald J. Meyer
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, United States
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39
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Iglesias S, Gamonal A, Abudulimu A, Picón A, Carrasco E, Écija D, Liu C, Luer L, Zhang X, Costa JS, Moonshiram D. Tracking the Light-Induced Excited-State Dynamics and Structural Configurations of an Extraordinarily Long-Lived Metastable State at Room Temperature. Chemistry 2020; 26:10801-10810. [PMID: 32452581 DOI: 10.1002/chem.202001393] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2020] [Revised: 05/22/2020] [Indexed: 11/11/2022]
Abstract
Time-resolved X-ray (Tr-XAS) and optical transient absorption (OTA) spectroscopy on the pico-microsecond timescale coupled with density functional theory calculations are applied to study the light-induced spin crossover processes of a Fe-based macrocyclic complex in solution. Tr-XAS analysis after light illumination shows the formation of a seven-coordinated high-spin quintet metastable state, which relaxes to a six-coordinated high-spin configuration before decaying to the ground state. Kinetic analysis of the macrocyclic complex reveals an unprecedented long-lived decay lifetime of approximately 42.6 μs. Comparative studies with a non-macrocyclic counterpart illustrate a significantly shortened approximately 568-fold decay lifetime of about 75 ns, and highlight the importance of the ligand arrangement in stabilizing the reactivity of the excited state. Lastly, OTA analysis shows the seven-coordinated high-spin state to be formed within approximately 6.2 ps. These findings provide a complete understanding of the spin crossover reaction and relaxation pathways of the macrocyclic complex, and reveal the importance of a flexible coordination environment for their rational design.
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Affiliation(s)
- Sirma Iglesias
- Instituto Madrileño de Estudios Avanzados en, Nanociencia (IMDEA Nanociencia), Calle Faraday 9, 28049, Madrid, Spain
| | - Arturo Gamonal
- Instituto Madrileño de Estudios Avanzados en, Nanociencia (IMDEA Nanociencia), Calle Faraday 9, 28049, Madrid, Spain
| | - Abasi Abudulimu
- Instituto Madrileño de Estudios Avanzados en, Nanociencia (IMDEA Nanociencia), Calle Faraday 9, 28049, Madrid, Spain
| | - Antonio Picón
- Departamento de Química, Universidad Autónoma de Madrid, 28049, Madrid, Spain
| | - Esther Carrasco
- Instituto Madrileño de Estudios Avanzados en, Nanociencia (IMDEA Nanociencia), Calle Faraday 9, 28049, Madrid, Spain
| | - David Écija
- Instituto Madrileño de Estudios Avanzados en, Nanociencia (IMDEA Nanociencia), Calle Faraday 9, 28049, Madrid, Spain
| | - Cunming Liu
- X-ray Science Division, Argonne National Laboratory, 9700 S. Cass Avenue, Lemont, IL, 60439, USA
| | - Larry Luer
- Instituto Madrileño de Estudios Avanzados en, Nanociencia (IMDEA Nanociencia), Calle Faraday 9, 28049, Madrid, Spain.,Institute of Materials for Electronics and Energy Technology (i-MEET), Friedrich-Alexander University Erlangen-Nürnberg, Martensstraße 7, 91058, Erlangen, Germany
| | - Xiaoyi Zhang
- X-ray Science Division, Argonne National Laboratory, 9700 S. Cass Avenue, Lemont, IL, 60439, USA
| | - José Sánchez Costa
- Instituto Madrileño de Estudios Avanzados en, Nanociencia (IMDEA Nanociencia), Calle Faraday 9, 28049, Madrid, Spain
| | - Dooshaye Moonshiram
- Instituto Madrileño de Estudios Avanzados en, Nanociencia (IMDEA Nanociencia), Calle Faraday 9, 28049, Madrid, Spain
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40
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Tang Z, Chang XY, Wan Q, Wang J, Ma C, Law KC, Liu Y, Che CM. Bis(tridentate) Iron(II) Complexes with a Cyclometalating Unit: Photophysical Property Enhancement with Combinatorial Strong Ligand Field Effect. Organometallics 2020. [DOI: 10.1021/acs.organomet.0c00149] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Affiliation(s)
- Zhou Tang
- Department of Chemistry, Southern University of Science and Technology, Shenzhen, Guangdong 518055, People’s Republic of China
- Department of Chemistry and State Key Laboratory of Synthetic Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, People’s Republic of China
| | - Xiao-Yong Chang
- Department of Chemistry, Southern University of Science and Technology, Shenzhen, Guangdong 518055, People’s Republic of China
| | - Qingyun Wan
- Department of Chemistry and State Key Laboratory of Synthetic Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, People’s Republic of China
| | - Jian Wang
- Department of Chemistry, Southern University of Science and Technology, Shenzhen, Guangdong 518055, People’s Republic of China
| | - Chensheng Ma
- College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen, Guangdong 518055, People’s Republic of China
| | - Kwok-Chung Law
- Department of Chemistry and State Key Laboratory of Synthetic Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, People’s Republic of China
| | - Yungen Liu
- Department of Chemistry, Southern University of Science and Technology, Shenzhen, Guangdong 518055, People’s Republic of China
| | - Chi-Ming Che
- Department of Chemistry, Southern University of Science and Technology, Shenzhen, Guangdong 518055, People’s Republic of China
- Department of Chemistry and State Key Laboratory of Synthetic Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, People’s Republic of China
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41
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Miller JN, McCusker JK. Outer-sphere effects on ligand-field excited-state dynamics: solvent dependence of high-spin to low-spin conversion in [Fe(bpy) 3] 2. Chem Sci 2020; 11:5191-5204. [PMID: 34122975 PMCID: PMC8159330 DOI: 10.1039/d0sc01506g] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2020] [Accepted: 05/01/2020] [Indexed: 11/21/2022] Open
Abstract
In condensed phase chemistry, the solvent can have a significant impact on everything from yield to product distribution to mechanism. With regard to photo-induced processes, solvent effects have been well-documented for charge-transfer states wherein the redistribution of charge subsequent to light absorption couples intramolecular dynamics to the local environment of the chromophore. Ligand-field excited states are expected to be largely insensitive to such perturbations given that their electronic rearrangements are localized on the metal center and are therefore insulated from so-called outer-sphere effects by the ligands themselves. In contrast to this expectation, we document herein a nearly two-fold variation in the time constant associated with the 5T2 → 1A1 high-spin to low-spin relaxation process of tris(2,2'-bipyridine)iron(ii) ([Fe(bpy)3]2+) across a range of different solvents. Likely origins for this solvent dependence, including relevant solvent properties, ion pairing, and changes in solvation energy, were considered and assessed by studying [Fe(bpy)3]2+ and related derivatives via ultrafast time-resolved absorption spectroscopy and computational analyses. It was concluded that the effect is most likely associated with the volume change of the chromophore arising from the interconfigurational nature of the 5T2 → 1A1 relaxation process, resulting in changes to the solvent-solvent and/or solvent-solute interactions of the primary solvation shell sufficient to alter the overall reorganization energy of the system and influencing the kinetics of ground-state recovery.
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Affiliation(s)
- Jennifer N Miller
- Department of Chemistry, Michigan State University 578 South Shaw Lane East Lansing Michigan 48824 USA
| | - James K McCusker
- Department of Chemistry, Michigan State University 578 South Shaw Lane East Lansing Michigan 48824 USA
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42
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Päpcke A, Friedrich A, Lochbrunner S. Revealing the initial steps in homogeneous photocatalysis by time-resolved spectroscopy. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 32:153001. [PMID: 31801126 DOI: 10.1088/1361-648x/ab5ed1] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Photocatalysis attracts currently intense research since it can provide efficient routes for generating solar fuels and allows to apply sunlight for an environmentally friendly synthesis of valuable chemical compounds. Accordingly, in future photocatalysis may contribute significantly to a sustainable economy. However, up to now photocatalysis has made it only into some niche applications. The reasons are manifold including too low yields, insufficient stability, and scarce availability of the precious metals and rare earths used in most cases. The design of better systems is the goal of many research activities. They call for a detailed knowledge of the individual steps and the microscopic mechanisms. Time-resolved spectroscopy is a powerful tool to improve our understanding of the individual steps of a photocatalytic process and of the efficiencies and losses associated with them. This allows to address specific weaknesses of the components of a photocatalytic system and to pursue a rational design of the corresponding compounds. In this review an overview is given about what insights can be gained by time-resolved spectroscopy referring mostly to our own results while it has to be stressed that many other groups are also highly successfully working in this area. We restrict ourselves to homogeneous systems which are often easier to analyze and focus on the primary steps occurring after optical excitation. This includes intramolecular relaxation and intersystem crossing in the photosensitizer as well as the first electron transfer step resulting from the interaction of the sensitizer with other components of the system. Ultrafast pump-probe spectroscopy turns out to be particularly helpful in analyzing new photosensitizers based on abundant metals, i.e. copper and iron. These sensitizers can suffer from short lifetimes of the metal-to-ligand charge transfer states which are typically involved in the intermolecular charge transfer processes. The latter are investigated on the pico- to microsecond timescale by quenching experiments making use of a streak camera and by pump-probe spectroscopy applying a YAG-laser system for excitation. The experiments with the streak camera allow to discriminate between oxidative and reductive pathways and to determine the corresponding bimolecular quenching rates which are compared to their diffusion limit to obtain a measure for the quenching efficiency. By applying transient absorption spectroscopy, it is furthermore possible to observe appearing charge transfer products and to determine their concentrations. In this way the efficiency of the electron transfer itself can be deduced and the relevance of lossy quenching events can be estimated.
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Affiliation(s)
- Ayla Päpcke
- Institute for Physics and Department of Life, Light and Matter, University of Rostock, 18051 Rostock, Germany
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43
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Maurer AB, Meyer GJ. Stark Spectroscopic Evidence that a Spin Change Accompanies Light Absorption in Transition Metal Polypyridyl Complexes. J Am Chem Soc 2020; 142:6847-6851. [DOI: 10.1021/jacs.9b13602] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Andrew B. Maurer
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
| | - Gerald J. Meyer
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
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44
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Excited-State Relaxation in Luminescent Molybdenum(0) Complexes with Isocyanide Chelate Ligands. INORGANICS 2020. [DOI: 10.3390/inorganics8020014] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Diisocyanide ligands with a m-terphenyl backbone provide access to Mo0 complexes exhibiting the same type of metal-to-ligand charge transfer (MLCT) luminescence as the well-known class of isoelectronic RuII polypyridines. The luminescence quantum yields and lifetimes of the homoleptic tris(diisocyanide) Mo0 complexes depend strongly on whether methyl- or tert-butyl substituents are placed in α-position to the isocyanide groups. The bulkier tert-butyl substituents lead to a molecular structure in which the three individual diisocyanides ligated to one Mo0 center are interlocked more strongly into one another than the ligands with the sterically less demanding methyl substituents. This rigidification limits the distortion of the complex in the emissive excited-state, causing a decrease of the nonradiative relaxation rate by one order of magnitude. Compared to RuII polypyridines, the molecular distortions in the luminescent 3MLCT state relative to the electronic ground state seem to be smaller in the Mo0 complexes, presumably due to delocalization of the MLCT-excited electron over greater portions of the ligands. Temperature-dependent studies indicate that thermally activated nonradiative relaxation via metal-centered excited states is more significant in these homoleptic Mo0 tris(diisocyanide) complexes than in [Ru(2,2′-bipyridine)3]2+.
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Herr P, Glaser F, Büldt LA, Larsen CB, Wenger OS. Long-Lived, Strongly Emissive, and Highly Reducing Excited States in Mo(0) Complexes with Chelating Isocyanides. J Am Chem Soc 2019; 141:14394-14402. [PMID: 31464429 DOI: 10.1021/jacs.9b07373] [Citation(s) in RCA: 64] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Newly discovered tris(diisocyanide)molybdenum(0) complexes are Earth-abundant isoelectronic analogues of the well-known class of [Ru(α-diimine)3]2+ compounds with long-lived 3MLCT (metal-to-ligand charge transfer) excited states that lead to rich photophysics and photochemistry. Depending on ligand design, luminescence quantum yields up to 0.20 and microsecond excited state lifetimes are achieved in solution at room temperature, both significantly better than those for [Ru(2,2'-bipyridine)3]2+. The excited Mo(0) complexes can induce chemical reactions that are thermodynamically too demanding for common precious metal-based photosensitizers, including the widely employed fac-[Ir(2-phenylpyridine)3] complex, as demonstrated on a series of light-driven aryl-aryl coupling reactions. The most robust Mo(0) complex exhibits stable photoluminescence and remains photoactive after continuous irradiation exceeding 2 months. Our comprehensive optical spectroscopic and photochemical study shows that Mo(0) complexes with diisocyanide chelate ligands constitute a new family of luminophores and photosensitizers, which is complementary to precious metal-based 4d6 and 5d6 complexes and represents an alternative to nonemissive Fe(II) compounds. This is relevant in the greater context of sustainable photophysics and photochemistry, as well as for possible applications in lighting, sensing, and catalysis.
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Affiliation(s)
- Patrick Herr
- Department of Chemistry , University of Basel , St. Johanns-Ring 19 , 4056 Basel , Switzerland
| | - Felix Glaser
- Department of Chemistry , University of Basel , St. Johanns-Ring 19 , 4056 Basel , Switzerland
| | - Laura A Büldt
- Department of Chemistry , University of Basel , St. Johanns-Ring 19 , 4056 Basel , Switzerland
| | - Christopher B Larsen
- Department of Chemistry , University of Basel , St. Johanns-Ring 19 , 4056 Basel , Switzerland
| | - Oliver S Wenger
- Department of Chemistry , University of Basel , St. Johanns-Ring 19 , 4056 Basel , Switzerland
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46
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Karges J, Blacque O, Goldner P, Chao H, Gasser G. Towards Long Wavelength Absorbing Photodynamic Therapy Photosensitizers via the Extension of a [Ru(bipy)
3
]
2+
Core. Eur J Inorg Chem 2019. [DOI: 10.1002/ejic.201900569] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Johannes Karges
- Institute of Chemistry for Life and Health Sciences, Laboratory for Inorganic Chemical Biology Chimie ParisTech, PSL University, CNRS 75005 Paris France
| | - Olivier Blacque
- Department of Chemistry University of Zurich Winterthurerstrasse 190 8057, Zurich Switzerland
| | - Philippe Goldner
- Institut de Recherche de Chimie Paris Chimie ParisTech, PSL University, CNRS 75005 Paris France
| | - Hui Chao
- MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, School of Chemistry Sun Yat‐sen University 510275 Guangzhou People's Republic of China
| | - Gilles Gasser
- Institute of Chemistry for Life and Health Sciences, Laboratory for Inorganic Chemical Biology Chimie ParisTech, PSL University, CNRS 75005 Paris France
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Britz A, Gawelda W, Assefa TA, Jamula LL, Yarranton JT, Galler A, Khakhulin D, Diez M, Harder M, Doumy G, March AM, Bajnóczi É, Németh Z, Pápai M, Rozsályi E, Sárosiné Szemes D, Cho H, Mukherjee S, Liu C, Kim TK, Schoenlein RW, Southworth SH, Young L, Jakubikova E, Huse N, Vankó G, Bressler C, McCusker JK. Using Ultrafast X-ray Spectroscopy To Address Questions in Ligand-Field Theory: The Excited State Spin and Structure of [Fe(dcpp)2]2+. Inorg Chem 2019; 58:9341-9350. [DOI: 10.1021/acs.inorgchem.9b01063] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- Alexander Britz
- European XFEL, Holzkoppel 4, 22869 Schenefeld, Germany
- The Hamburg Centre for Ultrafast Imaging, Luruper Chaussee 149, 22761 Hamburg, Germany
| | - Wojciech Gawelda
- European XFEL, Holzkoppel 4, 22869 Schenefeld, Germany
- Faculty of Physics, Adam Mickiewicz University, Umultowska 85, 61-614 Poznań, Poland
| | - Tadesse A. Assefa
- European XFEL, Holzkoppel 4, 22869 Schenefeld, Germany
- Institute of Laser Physics, University of Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany
| | - Lindsey L. Jamula
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, United States
| | - Jonathan T. Yarranton
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, United States
| | | | - Dmitry Khakhulin
- European XFEL, Holzkoppel 4, 22869 Schenefeld, Germany
- The Hamburg Centre for Ultrafast Imaging, Luruper Chaussee 149, 22761 Hamburg, Germany
| | - Michael Diez
- European XFEL, Holzkoppel 4, 22869 Schenefeld, Germany
- The Hamburg Centre for Ultrafast Imaging, Luruper Chaussee 149, 22761 Hamburg, Germany
| | - Manuel Harder
- Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, 22607 Hamburg, Germany
| | - Gilles Doumy
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Anne Marie March
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Éva Bajnóczi
- Wigner Research Centre for Physics, Hungarian Academy Sciences, H-1525 Budapest, Hungary
| | - Zoltán Németh
- Wigner Research Centre for Physics, Hungarian Academy Sciences, H-1525 Budapest, Hungary
| | - Mátyás Pápai
- Wigner Research Centre for Physics, Hungarian Academy Sciences, H-1525 Budapest, Hungary
- Department of Chemistry, Technical University of Denmark, DK-2800, Kongens Lyngby, Denmark
| | - Emese Rozsályi
- Wigner Research Centre for Physics, Hungarian Academy Sciences, H-1525 Budapest, Hungary
| | | | - Hana Cho
- Center for Analytical Chemistry, Division of Chemical and Medical Metrology, Korea Research Institute of Standards and Science, Daejeon 34113, Republic of Korea
| | - Sriparna Mukherjee
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695, United States
| | - Chang Liu
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695, United States
| | - Tae Kyu Kim
- Department of Chemistry and Chemistry Institute of Functional Materials, Pusan National University, Busan 46241, Republic of Korea
| | - Robert W. Schoenlein
- Ultrafast X-ray Science Laboratory, Lawrence Berkeley National Laboratory, Berkeley, United States
| | - Stephen H. Southworth
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Linda Young
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
- Department of Physics and The James Franck Institute, The University of Chicago, Chicago, Illinois 60637, United States
| | - Elena Jakubikova
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695, United States
| | - Nils Huse
- Center for Free-Electron Laser Science, University of Hamburg, 22607 Hamburg, Germany
- Max Planck Institute for the Structure and Dynamics of Matter, 22761 Hamburg, Germany
| | - György Vankó
- Wigner Research Centre for Physics, Hungarian Academy Sciences, H-1525 Budapest, Hungary
| | - Christian Bressler
- European XFEL, Holzkoppel 4, 22869 Schenefeld, Germany
- The Hamburg Centre for Ultrafast Imaging, Luruper Chaussee 149, 22761 Hamburg, Germany
| | - James K. McCusker
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, United States
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Ferrari L, Satta M, Palma A, Di Mario L, Catone D, O'Keeffe P, Zema N, Prosperi T, Turchini S. A Fast Transient Absorption Study of Co(AcAc) 3. Front Chem 2019; 7:348. [PMID: 31165061 PMCID: PMC6536591 DOI: 10.3389/fchem.2019.00348] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2019] [Accepted: 04/29/2019] [Indexed: 01/20/2023] Open
Abstract
The study of transition metal coordination complexes has played a key role in establishing quantum chemistry concepts such as that of ligand field theory. Furthermore, the study of the dynamics of their excited states is of primary importance in determining the de-excitation path of electrons to tailor the electronic properties required for important technological applications. This work focuses on femtosecond transient absorption spectroscopy of Cobalt tris(acetylacetonate) (Co(AcAc)3) in solution. The fast transient absorption spectroscopy has been employed to study the excited state dynamics after optical excitation. Density functional theory coupled with the polarizable continuum model has been used to characterize the geometries and the electronic states of the solvated ion. The excited states have been calculated using the time dependent density functional theory formalism. The time resolved dynamics of the ligand to metal charge transfer excitation revealed a biphasic behavior with an ultrafast rise time of 0.07 ± 0.04 ps and a decay time of 1.5 ± 0.3 ps, while the ligand field excitations dynamics is characterized by a rise time of 0.07 ± 0.04 ps and a decay time of 1.8 ± 0.3 ps. Time dependent density functional theory calculations of the spin-orbit coupling suggest that the ultrafast rise time can be related to the intersystem crossing from the originally photoexcited state. The picosecond decay is faster than that of similar cobalt coordination complexes and is mainly assigned to internal conversion within the triplet state manifold. The lack of detectable long living states (>5 ps) suggests that non-radiative decay plays an important role in the dynamics of these molecules.
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Affiliation(s)
- Luisa Ferrari
- CNR-ISM, Division of Ultrafast Processes in Materials (FLASHit), Area della Ricerca di Roma Tor Vergata, Rome, Italy
| | - Mauro Satta
- CNR-ISMN, Chemistry Department, Università di Roma Sapienza, Rome, Italy
| | - Amedeo Palma
- CNR-ISMN, Area della Ricerca di Roma 1 - Montelibretti, Rome, Italy
| | - Lorenzo Di Mario
- CNR-ISM, Division of Ultrafast Processes in Materials (FLASHit), Area della Ricerca di Roma Tor Vergata, Rome, Italy
| | - Daniele Catone
- CNR-ISM, Division of Ultrafast Processes in Materials (FLASHit), Area della Ricerca di Roma Tor Vergata, Rome, Italy
| | - Patrick O'Keeffe
- CNR-ISM, Division of Ultrafast Processes in Materials (FLASHit), Area della Ricerca di Roma 1 - Montelibretti, Rome, Italy
| | - Nicola Zema
- CNR-ISM, Division of Ultrafast Processes in Materials (FLASHit), Area della Ricerca di Roma Tor Vergata, Rome, Italy
| | - Tommaso Prosperi
- CNR-ISM, Division of Ultrafast Processes in Materials (FLASHit), Area della Ricerca di Roma Tor Vergata, Rome, Italy
| | - Stefano Turchini
- CNR-ISM, Division of Ultrafast Processes in Materials (FLASHit), Area della Ricerca di Roma Tor Vergata, Rome, Italy
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