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Reinhard ME, Sidhu BK, Lozada IB, Powers-Riggs N, Ortiz RJ, Lim H, Nickel R, Lierop JV, Alonso-Mori R, Chollet M, Gee LB, Kramer PL, Kroll T, Raj SL, van Driel TB, Cordones AA, Sokaras D, Herbert DE, Gaffney KJ. Time-Resolved X-ray Emission Spectroscopy and Synthetic High-Spin Model Complexes Resolve Ambiguities in Excited-State Assignments of Transition-Metal Chromophores: A Case Study of Fe-Amido Complexes. J Am Chem Soc 2024; 146:17908-17916. [PMID: 38889309 DOI: 10.1021/jacs.4c02748] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/20/2024]
Abstract
To fully harness the potential of abundant metal coordination complex photosensitizers, a detailed understanding of the molecular properties that dictate and control the electronic excited-state population dynamics initiated by light absorption is critical. In the absence of detectable luminescence, optical transient absorption (TA) spectroscopy is the most widely employed method for interpreting electron redistribution in such excited states, particularly for those with a charge-transfer character. The assignment of excited-state TA spectral features often relies on spectroelectrochemical measurements, where the transient absorption spectrum generated by a metal-to-ligand charge-transfer (MLCT) electronic excited state, for instance, can be approximated using steady-state spectra generated by electrochemical ligand reduction and metal oxidation and accounting for the loss of absorptions by the electronic ground state. However, the reliability of this approach can be clouded when multiple electronic configurations have similar optical signatures. Using a case study of Fe(II) complexes supported by benzannulated diarylamido ligands, we highlight an example of such an ambiguity and show how time-resolved X-ray emission spectroscopy (XES) measurements can reliably assign excited states from the perspective of the metal, particularly in conjunction with accurate synthetic models of ligand-field electronic excited states, leading to a reinterpretation of the long-lived excited state as a ligand-field metal-centered quintet state. A detailed analysis of the XES data on the long-lived excited state is presented, along with a discussion of the ultrafast dynamics following the photoexcitation of low-spin Fe(II)-Namido complexes using a high-spin ground-state analogue as a spectral model for the 5T2 excited state.
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Affiliation(s)
- Marco E Reinhard
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, United States
| | - Baldeep K Sidhu
- Department of Chemistry and the Manitoba Institute for Materials, University of Manitoba, 144 Dysart Rd, Winnipeg, Manitoba R3T 2N2, Canada
| | - Issiah B Lozada
- Department of Chemistry and the Manitoba Institute for Materials, University of Manitoba, 144 Dysart Rd, Winnipeg, Manitoba R3T 2N2, Canada
| | - Natalia Powers-Riggs
- Stanford PULSE Institute, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, United States
| | - Robert J Ortiz
- Department of Chemistry and the Manitoba Institute for Materials, University of Manitoba, 144 Dysart Rd, Winnipeg, Manitoba R3T 2N2, Canada
| | - Hyeongtaek Lim
- Stanford PULSE Institute, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, United States
| | - Rachel Nickel
- Department of Physics and Astronomy, University of Manitoba, 31A Sifton Rd, Winnipeg, Manitoba R3T 2N2, Canada
| | - Johan van Lierop
- Department of Physics and Astronomy, University of Manitoba, 31A Sifton Rd, Winnipeg, Manitoba R3T 2N2, Canada
| | - Roberto Alonso-Mori
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, United States
| | - Matthieu Chollet
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, United States
| | - Leland B Gee
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, United States
| | - Patrick L Kramer
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, United States
| | - Thomas Kroll
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, United States
| | - Sumana L Raj
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, United States
| | - Tim B van Driel
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, United States
| | - Amy A Cordones
- Stanford PULSE Institute, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, United States
| | - Dimosthenis Sokaras
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, 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 Rd, Winnipeg, Manitoba R3T 2N2, Canada
| | - Kelly J Gaffney
- Stanford PULSE Institute, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, United States
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2
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Guo M, Temperton R, D'Acunto G, Johansson N, Jones R, Handrup K, Ringelband S, Prakash O, Fan H, de Groot LHM, Hlynsson VF, Kaufhold S, Gordivska O, Velásquez González N, Wärnmark K, Schnadt J, Persson P, Uhlig J. Using Iron L-Edge and Nitrogen K-Edge X-ray Absorption Spectroscopy to Improve the Understanding of the Electronic Structure of Iron Carbene Complexes. Inorg Chem 2024. [PMID: 38934422 DOI: 10.1021/acs.inorgchem.4c01026] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/28/2024]
Abstract
Iron-centered N-heterocyclic carbene compounds have attracted much attention in recent years due to their long-lived excited states with charge transfer (CT) character. Understanding the orbital interactions between the metal and ligand orbitals is of great importance for the rational tuning of the transition metal compound properties, e.g., for future photovoltaic and photocatalytic applications. Here, we investigate a series of iron-centered N-heterocyclic carbene complexes with +2, + 3, and +4 oxidation states of the central iron ion using iron L-edge and nitrogen K-edge X-ray absorption spectroscopy (XAS). The experimental Fe L-edge XAS data were simulated and interpreted through restricted-active space (RAS) and multiplet calculations. The experimental N K-edge XAS is simulated and compared with time-dependent density functional theory (TDDFT) calculations. Through the combination of the complementary Fe L-edge and N K-edge XAS, direct probing of the complex interplay of the metal and ligand character orbitals was possible. The σ-donating and π-accepting capabilities of different ligands are compared, evaluated, and discussed. The results show how X-ray spectroscopy, together with advanced modeling, can be a powerful tool for understanding the complex interplay of metal and ligand.
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Affiliation(s)
- Meiyuan Guo
- Division of Chemical Physics, Department of Chemistry, Lund University, 22100 Lund, Sweden
| | | | - Giulio D'Acunto
- Division of Synchrotron Radiation Research, Department of Physics, Lund University, 22100 Lund, Sweden
- NanoLund, Lund University, 22100 Lund, Sweden
- Department of Chemical Engineering, Stanford University, 94305 Stanford, California, United States
| | | | - Rosemary Jones
- Division of Synchrotron Radiation Research, Department of Physics, Lund University, 22100 Lund, Sweden
- NanoLund, Lund University, 22100 Lund, Sweden
| | | | - Sven Ringelband
- Division of Chemical Physics, Department of Chemistry, Lund University, 22100 Lund, Sweden
| | - Om Prakash
- Centre for Analysis and Synthesis (CAS), Department of Chemistry, Lund University, 22100 Lund, Sweden
| | - Hao Fan
- Centre for Analysis and Synthesis (CAS), Department of Chemistry, Lund University, 22100 Lund, Sweden
| | - Lisa H M de Groot
- Centre for Analysis and Synthesis (CAS), Department of Chemistry, Lund University, 22100 Lund, Sweden
| | - Valtýr Freyr Hlynsson
- Centre for Analysis and Synthesis (CAS), Department of Chemistry, Lund University, 22100 Lund, Sweden
| | - Simon Kaufhold
- Centre for Analysis and Synthesis (CAS), Department of Chemistry, Lund University, 22100 Lund, Sweden
| | - Olga Gordivska
- Centre for Analysis and Synthesis (CAS), Department of Chemistry, Lund University, 22100 Lund, Sweden
| | | | - Kenneth Wärnmark
- NanoLund, Lund University, 22100 Lund, Sweden
- Centre for Analysis and Synthesis (CAS), Department of Chemistry, Lund University, 22100 Lund, Sweden
| | - Joachim Schnadt
- MAX IV Laboratory, Lund University, 22100 Lund, Sweden
- Division of Synchrotron Radiation Research, Department of Physics, Lund University, 22100 Lund, Sweden
- NanoLund, Lund University, 22100 Lund, Sweden
| | - Petter Persson
- NanoLund, Lund University, 22100 Lund, Sweden
- Division of Computational Chemistry, Department of Chemistry, Lund University, 22100 Lund, Sweden
| | - Jens Uhlig
- Division of Chemical Physics, Department of Chemistry, Lund University, 22100 Lund, Sweden
- NanoLund, Lund University, 22100 Lund, Sweden
- LINXS Institute of Advanced Neutron and X-Ray Science, Lund University, 22370 Lund, Sweden
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3
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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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4
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Wegeberg C, Häussinger D, Kupfer S, Wenger OS. Controlling the Photophysical Properties of a Series of Isostructural d 6 Complexes Based on Cr 0, Mn I, and Fe II. J Am Chem Soc 2024; 146:4605-4619. [PMID: 38334415 PMCID: PMC10885143 DOI: 10.1021/jacs.3c11580] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/10/2024]
Abstract
Development of first-row transition metal complexes with similar luminescence and photoredox properties as widely used RuII polypyridines is attractive because metals from the first transition series are comparatively abundant and inexpensive. The weaker ligand field experienced by the valence d-electrons of first-row transition metals challenges the installation of the same types of metal-to-ligand charge transfer (MLCT) excited states as in precious metal complexes, due to rapid population of energetically lower-lying metal-centered (MC) states. In a family of isostructural tris(diisocyanide) complexes of the 3d6 metals Cr0, MnI, and FeII, the increasing effective nuclear charge and ligand field strength allow us to control the energetic order between the 3MLCT and 3MC states, whereas pyrene decoration of the isocyanide ligand framework provides control over intraligand (ILPyr) states. The chromium(0) complex shows red 3MLCT phosphorescence because all other excited states are higher in energy. In the manganese(I) complex, a microsecond-lived dark 3ILPyr state, reminiscent of the types of electronic states encountered in many polyaromatic hydrocarbon compounds, is the lowest and becomes photoactive. In the iron(II) complex, the lowest MLCT state has shifted to so much higher energy that 1ILPyr fluorescence occurs, in parallel to other excited-state deactivation pathways. Our combined synthetic-spectroscopic-theoretical study provides unprecedented insights into how effective nuclear charge, ligand field strength, and ligand π-conjugation affect the energetic order between MLCT and ligand-based excited states, and under what circumstances these individual states become luminescent and exploitable in photochemistry. Such insights are the key to further developments of luminescent and photoredox-active first-row transition metal complexes.
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Affiliation(s)
- Christina Wegeberg
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056 Basel, Switzerland
| | - Daniel Häussinger
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056 Basel, Switzerland
| | - Stephan Kupfer
- Institute of Physical Chemistry, Friedrich Schiller University Jena, Helmholtzweg 4, 07743 Jena, Germany
| | - Oliver S Wenger
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056 Basel, Switzerland
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Hernández‐Castillo D, Nau REP, Schmid M, Tschierlei S, Rau S, González L. Mehrere Triplett-Metall-zentrierte Jahn-Teller-Isomere bestimmen die temperaturabhängigen Lumineszenzlebensdauern in [Ru(bpy) 3] 2. ANGEWANDTE CHEMIE (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2023; 135:e202308803. [PMID: 38529088 PMCID: PMC10962581 DOI: 10.1002/ange.202308803] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/22/2023] [Indexed: 03/27/2024]
Abstract
AbstractEin genaues Verständnis der Faktoren, welche die Lumineszenzlebensdauer von Übergangsmetallverbindungen bestimmen, ist für Anwendungen in der Photokatalyse und der photodynamischen Therapie von entscheidender Bedeutung. Die im Falle von [Ru(bpy)3]2+ (bpy=2,2’‐Bipyridin) allgemein akzeptierte Theorie besagt, dass die Emissionslebensdauer durch Optimierung der Energiebarriere zwischen dem emittierenden Triplett‐Zustand des Metall‐Liganden‐Ladungstransfers (3MLCT) und dem thermisch aktivierten Triplett‐Zustand des Metall‐Zentrums (3MC), oder der Energielücke zwischen beiden Zuständen gesteuert werden kann. Hier zeigen wir, dass dies nicht allgemeingültig ist. Darüber hinaus demonstrieren wir, dass die Betrachtung eines einzelnen Relaxationspfades, der vom energetisch niedrigsten Minimum aus bestimmt wird, zu falschen Vorhersagen der temperaturabhängigen Emissionslebensdauer führt. Stattdessen erhalten wir eine ausgezeichnete Übereinstimmung mit den experimentellen temperaturabhängigen Lebensdauern, wenn ein erweitertes kinetisches Modell herangezogen wird, welches alle Pfade im Zusammenhang mit mehreren Jahn–Teller‐Isomeren und ihren effektiven Reaktionsbarrieren beinhaltet. Diese Konzepte sind für das Design weiterer lumineszierender Übergangsmetallkomplexe mit individuell angepassten Emissionslebensdauern auf der Grundlage theoretischer Vorhersagen unerlässlich.
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Affiliation(s)
- David Hernández‐Castillo
- Institute of Theoretical ChemistryFaculty of ChemistryUniversity of ViennaWähringer Str. 171090ViennaAustria
- Doctoral School in Chemistry (DoSChem)University of ViennaWähringer Straße 421090ViennaAustria
| | - Roland E. P. Nau
- Institute of Inorganic Chemistry IUlm UniversityAlbert-Einstein-Allee 1189081UlmGermany
| | - Marie‐Ann Schmid
- Technische Universität BraunschweigDepartment of Energy Conversion, Institute of Physical and Theoretical ChemistryRebenring 3138106BraunschweigGermany
| | - Stefanie Tschierlei
- Technische Universität BraunschweigDepartment of Energy Conversion, Institute of Physical and Theoretical ChemistryRebenring 3138106BraunschweigGermany
| | - Sven Rau
- Institute of Inorganic Chemistry IUlm UniversityAlbert-Einstein-Allee 1189081UlmGermany
| | - Leticia González
- Institute of Theoretical ChemistryFaculty of ChemistryUniversity of ViennaWähringer Str. 171090ViennaAustria
- Vienna Research Platform Accelerating Photoreaction DiscoveryUniversity of ViennaWähringer Straße 171090ViennaAustria
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6
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Hernández‐Castillo D, Nau REP, Schmid M, Tschierlei S, Rau S, González L. Multiple Triplet Metal-Centered Jahn-Teller Isomers Determine Temperature-Dependent Luminescence Lifetimes in [Ru(bpy) 3 ] 2. Angew Chem Int Ed Engl 2023; 62:e202308803. [PMID: 37433755 PMCID: PMC10962642 DOI: 10.1002/anie.202308803] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2023] [Revised: 07/11/2023] [Accepted: 07/11/2023] [Indexed: 07/13/2023]
Abstract
Understanding the factors that determine the luminescence lifetime of transition metal compounds is key for applications in photocatalysis and photodynamic therapy. Here we show that for[ Ru ( bpy ) 3 ] 2 + ${[{\rm{Ru}}({\rm{bpy}})_{\rm{3}} ]^{{\rm{2 + }}} }$ (bpy = 2,2'-bipyridine), the generally accepted idea that emission lifetimes can be controlled optimizing the energy barrier from the emissive triplet metal-to-ligand charge-transfer (3 MLCT) state to the thermally-activated triplet metal-centered (3 MC) state or the energy gap between both states is a misconception. Further, we demonstrate that considering a single relaxation pathway determined from the minimum that is lowest in energy leads to wrong temperature-dependent emission lifetimes predictions. Instead, we obtain excellent agreement with experimental temperature-dependent lifetimes when an extended kinetic model that includes all the pathways related to multiple Jahn-Teller isomers and their effective reaction barriers is employed. These concepts are essential to correctly design other luminescent transition metal complexes with tailored emission lifetimes based on theoretical predictions.
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Affiliation(s)
- David Hernández‐Castillo
- Institute of Theoretical ChemistryFaculty of ChemistryUniversity of ViennaWähringer Str. 171090ViennaAustria
- Doctoral School in Chemistry (DoSChem)University of ViennaWähringer Straße 421090ViennaAustria
| | - Roland E. P. Nau
- Institute of Inorganic Chemistry IUlm UniversityAlbert-Einstein-Allee 1189081UlmGermany
| | - Marie‐Ann Schmid
- Technische Universität BraunschweigDepartment of Energy Conversion, Institute of Physical and Theoretical ChemistryRebenring 3138106BraunschweigGermany
| | - Stefanie Tschierlei
- Technische Universität BraunschweigDepartment of Energy Conversion, Institute of Physical and Theoretical ChemistryRebenring 3138106BraunschweigGermany
| | - Sven Rau
- Institute of Inorganic Chemistry IUlm UniversityAlbert-Einstein-Allee 1189081UlmGermany
| | - Leticia González
- Institute of Theoretical ChemistryFaculty of ChemistryUniversity of ViennaWähringer Str. 171090ViennaAustria
- Vienna Research Platform Accelerating Photoreaction DiscoveryUniversity of ViennaWähringer Straße 171090ViennaAustria
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7
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Johnson CE, Schwarz J, Deegbey M, Prakash O, Sharma K, Huang P, Ericsson T, Häggström L, Bendix J, Gupta AK, Jakubikova E, Wärnmark K, Lomoth R. Ferrous and ferric complexes with cyclometalating N-heterocyclic carbene ligands: a case of dual emission revisited. Chem Sci 2023; 14:10129-10139. [PMID: 37772113 PMCID: PMC10530338 DOI: 10.1039/d3sc02806b] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2023] [Accepted: 08/27/2023] [Indexed: 09/30/2023] Open
Abstract
Iron N-heterocyclic carbene (FeNHC) complexes with long-lived charge transfer states are emerging as a promising class of photoactive materials. We have synthesized [FeII(ImP)2] (ImP = bis(2,6-bis(3-methylimidazol-2-ylidene-1-yl)phenylene)) that combines carbene ligands with cyclometalation for additionally improved ligand field strength. The 9 ps lifetime of its 3MLCT (metal-to-ligand charge transfer) state however reveals no benefit from cyclometalation compared to Fe(ii) complexes with NHC/pyridine or pure NHC ligand sets. In acetonitrile solution, the Fe(ii) complex forms a photoproduct that features emission characteristics (450 nm, 5.1 ns) that were previously attributed to a higher (2MLCT) state of its Fe(iii) analogue [FeIII(ImP)2]+, which led to a claim of dual (MLCT and LMCT) emission. Revisiting the photophysics of [FeIII(ImP)2]+, we confirmed however that higher (2MLCT) states of [FeIII(ImP)2]+ are short-lived (<10 ps) and therefore, in contrast to the previous interpretation, cannot give rise to emission on the nanosecond timescale. Accordingly, pristine [FeIII(ImP)2]+ prepared by us only shows red emission from its lower 2LMCT state (740 nm, 240 ps). The long-lived, higher energy emission previously reported for [FeIII(ImP)2]+ is instead attributed to an impurity, most probably a photoproduct of the Fe(ii) precursor. The previously reported emission quenching on the nanosecond time scale hence does not support any excited state reactivity of [FeIII(ImP)2]+ itself.
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Affiliation(s)
- Catherine Ellen Johnson
- Department of Chemistry -Ångström Laboratory, Uppsala University Box 523 SE-75120 Uppsala Sweden
| | - Jesper Schwarz
- Centre for Analysis and Synthesis, Department of Chemistry, Lund University Box 124 SE-22100 Lund Sweden
| | - Mawuli Deegbey
- Department of Chemistry, North Carolina State University Raleigh North Carolina 27695 USA
| | - Om Prakash
- Centre for Analysis and Synthesis, Department of Chemistry, Lund University Box 124 SE-22100 Lund Sweden
| | - Kumkum Sharma
- Centre for Analysis and Synthesis, Department of Chemistry, Lund University Box 124 SE-22100 Lund Sweden
| | - Ping Huang
- Department of Chemistry -Ångström Laboratory, Uppsala University Box 523 SE-75120 Uppsala Sweden
| | - Tore Ericsson
- Department of Physics - Ångström Laboratory, Uppsala University Box 523 SE-751 20 Uppsala Sweden
| | - Lennart Häggström
- Department of Physics - Ångström Laboratory, Uppsala University Box 523 SE-751 20 Uppsala Sweden
| | - Jesper Bendix
- Department of Chemistry, University of Copenhagen Universitetsparken 5 DK-2100 Copenhagen Denmark
| | - Arvind Kumar Gupta
- Centre for Analysis and Synthesis, Department of Chemistry, Lund University Box 124 SE-22100 Lund Sweden
| | - Elena Jakubikova
- Department of Chemistry, North Carolina State University Raleigh North Carolina 27695 USA
| | - Kenneth Wärnmark
- Centre for Analysis and Synthesis, Department of Chemistry, Lund University Box 124 SE-22100 Lund Sweden
| | - Reiner Lomoth
- Department of Chemistry -Ångström Laboratory, Uppsala University Box 523 SE-75120 Uppsala Sweden
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8
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Iuchi S, Koga N. Ultrafast Electronic Relaxation in Aqueous [Fe(bpy) 3] 2+: A Surface Hopping Study. J Phys Chem Lett 2023; 14:4225-4232. [PMID: 37126354 DOI: 10.1021/acs.jpclett.3c00686] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Trajectory surface hopping simulations are performed to better understand the electronic relaxation dynamics of [Fe(bpy)3]2+ in aqueous solution. Specifically, the ultrafast relaxation from the photoexcited singlet metal-to-ligand charge-transfer (MLCT) to the metastable quintet metal-centered (MC) states is simulated through the surface hopping method, where the MLCT and MC states of [Fe(bpy)3]2+ in aqueous solution are computed by using a model electronic Hamiltonian developed previously. As a result, most of the trajectories are interpreted to show the sequential relaxation pathways via the triplet MC states, though some are the direct pathway from MLCT to the quintet MC states. Even though the triplet MC states are involved in the relaxation, the population transfer to the singlet MC ground state is very small, and the population of the quintet MC states reaches more than ∼96%, reasonably consistent with the unity quantum efficiency discussed experimentally.
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Affiliation(s)
- Satoru Iuchi
- Graduate School of Informatics, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan
| | - Nobuaki Koga
- Graduate School of Informatics, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan
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9
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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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10
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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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11
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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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12
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Moll J, Naumann R, Sorge L, Förster C, Gessner N, Burkhardt L, Ugur N, Nuernberger P, Seidel W, Ramanan C, Bauer M, Heinze K. Pseudo-Octahedral Iron(II) Complexes with Near-Degenerate Charge Transfer and Ligand Field States at the Franck-Condon Geometry. Chemistry 2022; 28:e202201858. [PMID: 35862259 DOI: 10.1002/chem.202201858] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2022] [Indexed: 01/07/2023]
Abstract
Increasing the metal-to-ligand charge transfer (MLCT) excited state lifetime of polypyridine iron(II) complexes can be achieved by lowering the ligand's π* orbital energy and by increasing the ligand field splitting. In the homo- and heteroleptic complexes [Fe(cpmp)2 ]2+ (12+ ) and [Fe(cpmp)(ddpd)]2+ (22+ ) with the tridentate ligands 6,2''-carboxypyridyl-2,2'-methylamine-pyridyl-pyridine (cpmp) and N,N'-dimethyl-N,N'-di-pyridin-2-ylpyridine-2,6-diamine (ddpd) two or one dipyridyl ketone moieties provide low energy π* acceptor orbitals. A good metal-ligand orbital overlap to increase the ligand field splitting is achieved by optimizing the octahedricity through CO and NMe units between the coordinating pyridines which enable the formation of six-membered chelate rings. The push-pull ligand cpmp provides intra-ligand and ligand-to-ligand charge transfer (ILCT, LL'CT) excited states in addition to MLCT excited states. Ground and excited state properties of 12+ and 22+ were accessed by X-ray diffraction analyses, resonance Raman spectroscopy, (spectro)electrochemistry, EPR spectroscopy, X-ray emission spectroscopy, static and time-resolved IR and UV/Vis/NIR absorption spectroscopy as well as quantum chemical calculations.
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Affiliation(s)
- Johannes Moll
- Department of Chemistry, Johannes Gutenberg University of Mainz, Duesbergweg 10-14, 55128, Mainz, Germany
| | - Robert Naumann
- Department of Chemistry, Johannes Gutenberg University of Mainz, Duesbergweg 10-14, 55128, Mainz, Germany
| | - Lukas Sorge
- Department of Chemistry, Johannes Gutenberg University of Mainz, Duesbergweg 10-14, 55128, Mainz, Germany
| | - Christoph Förster
- Department of Chemistry, Johannes Gutenberg University of Mainz, Duesbergweg 10-14, 55128, Mainz, Germany
| | - Niklas Gessner
- Institut für Physikalische und Theoretische Chemie, Universität Regensburg, Universitätsstraße 31, 93053, Regensburg, Germany
| | - Lukas Burkhardt
- Department of Chemistry, University of Paderborn, Warburger Str. 100, 33098, Paderborn, Germany
| | - Naz Ugur
- Max-Planck-Institute for Polymer Research, Mainz, Germany
| | - Patrick Nuernberger
- Institut für Physikalische und Theoretische Chemie, Universität Regensburg, Universitätsstraße 31, 93053, Regensburg, Germany
| | - Wolfram Seidel
- Institute of Chemistry, University of Rostock, Albert-Einstein-Straße 3a, 18059, Rostock, Germany
| | - Charusheela Ramanan
- Max-Planck-Institute for Polymer Research, Mainz, Germany
- Department of Physics and Astronomy, Vrije Universiteit Amsterdam, Amsterdam, Netherlands
| | - Matthias Bauer
- Department of Chemistry, University of Paderborn, Warburger Str. 100, 33098, Paderborn, Germany
| | - Katja Heinze
- Department of Chemistry, Johannes Gutenberg University of Mainz, Duesbergweg 10-14, 55128, Mainz, Germany
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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
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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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