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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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2
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Malme JT, Clendening RA, Ash R, Curry T, Ren T, Vura-Weis J. Nanosecond Metal-to-Ligand Charge-Transfer State in an Fe(II) Chromophore: Lifetime Enhancement via Nested Potentials. J Am Chem Soc 2023; 145:6029-6034. [PMID: 36913625 DOI: 10.1021/jacs.2c13532] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/14/2023]
Abstract
Examples of Fe complexes with long-lived (≥1 ns) charge-transfer states are limited to pseudo-octahedral geometries with strong σ-donor chelates. Alternative strategies based on varying both coordination motifs and ligand donicity are highly desirable. Reported herein is an air-stable, tetragonal FeII complex, Fe(HMTI)(CN)2 (HMTI = 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradeca-1,3,8,10-tetraene), with a 1.25 ns metal-to-ligand charge-transfer (MLCT) lifetime. The structure has been determined, and the photophysical properties have been examined in a variety of solvents. The HMTI ligand is highly π-acidic due to low-lying π*(C═N), which enhances ΔFe via stabilizing t2g orbitals. The inflexible geometry of the macrocycle results in short Fe-N bonds, and density functional theory calculations show that this rigidity results in an unusual set of nested potential energy surfaces. Moreover, the lifetime and energy of the MLCT state depends strongly on the solvent environment. This dependence is caused by modulation of the axial ligand-field strength by Lewis acid-base interactions between the solvent and the cyano ligands. This work represents the first example of a long-lived charge transfer state in an FeII macrocyclic species.
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Affiliation(s)
- Justin T Malme
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Reese A Clendening
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, United States
| | - Ryan Ash
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Taylor Curry
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Tong Ren
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, United States
| | - Josh Vura-Weis
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
- Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
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3
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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: 26] [Impact Index Per Article: 26.0] [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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4
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Mrózek O, Mitra M, Hupp B, Belyaev A, Lüdtke N, Wagner D, Wang C, Wenger OS, Marian CM, Steffen A. An Air- and Moisture-stable Zinc(II) Carbene Dithiolate Dimer Showing Fast Thermally Activated Delayed Fluorescence and Dexter Energy Transfer Catalysis. Chemistry 2023; 29:e202203980. [PMID: 36637038 DOI: 10.1002/chem.202203980] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2022] [Revised: 01/06/2023] [Accepted: 01/09/2023] [Indexed: 01/14/2023]
Abstract
A dimeric ZnII carbene complex featuring bridging and chelating benzene-1,2-dithiolate ligands is highly stable towards air and water. The donor-Zn-acceptor structure leads to visible light emission in the solid state, solution and polymer matrices with λmax between 577-657 nm and, for zinc(II) complexes, unusually high radiative rate constants for triplet exciton decay of up to kr =1.5×105 s-1 at room temperature. Variable temperature and DFT/MRCI studies show that a small energy gap between the 1/3 LL/LMCT states of only 79 meV is responsible for efficient thermally activated delayed fluorescence (TADF). Time-resolved luminescence and transient absorption studies confirm the occurrence of long-lived, dominantly ligand-to-ligand charge transfer excited states in solution, allowing for application in Dexter energy transfer photocatalysis.
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Affiliation(s)
- Ondřej Mrózek
- Department of Chemistry and Chemical Biology, TU Dortmund University, Otto-Hahn-Str. 6, 44227, Dortmund, Germany
| | - Mousree Mitra
- Department of Chemistry and Chemical Biology, TU Dortmund University, Otto-Hahn-Str. 6, 44227, Dortmund, Germany
| | - Bejamin Hupp
- Department of Chemistry and Chemical Biology, TU Dortmund University, Otto-Hahn-Str. 6, 44227, Dortmund, Germany
| | - Andrey Belyaev
- Department of Chemistry and Chemical Biology, TU Dortmund University, Otto-Hahn-Str. 6, 44227, Dortmund, Germany
| | - Nora Lüdtke
- Institute of Theoretical and Computational Chemistry, Heinrich Heine University Düsseldorf, 40225, Düsseldorf, Germany
| | - Dorothee Wagner
- Department of Chemistry, University of Basel, 4056, Basel, Switzerland
| | - Cui Wang
- Department of Chemistry, University of Basel, 4056, Basel, Switzerland
| | - Oliver S Wenger
- Department of Chemistry, University of Basel, 4056, Basel, Switzerland
| | - Christel M Marian
- Institute of Theoretical and Computational Chemistry, Heinrich Heine University Düsseldorf, 40225, Düsseldorf, Germany
| | - Andreas Steffen
- Department of Chemistry and Chemical Biology, TU Dortmund University, Otto-Hahn-Str. 6, 44227, Dortmund, Germany
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5
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Curtin GM, Jakubikova E. Extended π-Conjugated Ligands Tune Excited-State Energies of Iron(II) Polypyridine Dyes. Inorg Chem 2022; 61:18850-18860. [DOI: 10.1021/acs.inorgchem.2c02362] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Affiliation(s)
- Gregory M. Curtin
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695, United States
| | - Elena Jakubikova
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695, United States
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6
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Forde A, Lystrom L, Sun W, Kilin D, Kilina S. Improving Near-Infrared Emission of meso-Aryldipyrrin Indium(III) Complexes via Annulation Bridging: Excited-State Dynamics. J Phys Chem Lett 2022; 13:9210-9220. [PMID: 36170557 DOI: 10.1021/acs.jpclett.2c02115] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Using non-adiabatic dynamics and Redfield theory, we predicted the optical spectra, radiative and nonradiative decay rates, and photoluminescence quantum yields (PLQYs) for In(III) dipyrrin-based complexes (i) with electron-withdrawing (EW) or electron-donating (ED) substituents on the meso-phenyl group and (ii) upon fusing the pyrrin and phenyl rings via saturated or unsaturated bridging to increase structural rigidity. The ED groups lead to a primary π,π* character with a minor intraligand charge transfer (ILCT) contribution to the emissive state, while EW groups increase the ILCT contribution and red-shift the luminescence to ∼1.5 eV. Saturated annulation enhances the PLQYs for complexes with primary π,π* character compared to those of the non-annulated and unsaturated-annulated complexes, while both unsaturated and saturated annulation decrease the PLQYs for complexes with primary ILCT character. We found that PLQY improvement goes beyond a simple concept of structural rigidity. In contrast, the charge transfer character of excitonic states is a key parameter for engineering the NIR emission of In(III) dipyrrin complexes.
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Affiliation(s)
- Aaron Forde
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108, United States
- Materials and Nanotechnology Program, North Dakota State University, Fargo, North Dakota 58108, United States
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
- Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Levi Lystrom
- Shock and Detonation Physics, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Wenfang Sun
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108, United States
| | - Dmitri Kilin
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108, United States
| | - Svetlana Kilina
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108, United States
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7
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Magra K, Francés‐Monerris A, Cebrián C, Monari A, Haacke S, Gros PC. Bidentate Pyridyl‐NHC Ligands: Synthesis, Ground and Excited State Properties of Their Iron(II) Complexes and the Role of the fac/mer Isomerism. Eur J Inorg Chem 2021. [DOI: 10.1002/ejic.202100818] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- Kévin Magra
- Université de Lorraine, CNRS, L2CM 57000 Metz France
| | | | | | - Antonio Monari
- Université de Lorraine, CNRS, LPCT 54000 Nancy France
- Université de de Paris and CNRS, Itodys 75006 Paris France
| | - Stefan Haacke
- Université de Strasbourg, CNRS, IPCMS 67000 Strasbourg France
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8
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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: 17] [Impact Index Per Article: 5.7] [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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9
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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: 100] [Impact Index Per Article: 33.3] [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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