1
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Hashemzadeh T, Christofferson AJ, White KF, Barnard PJ. Experimental and theoretical studies of pH-responsive iridium(III) complexes of azole and N-heterocyclic carbene ligands. Dalton Trans 2024; 53:8478-8493. [PMID: 38687288 DOI: 10.1039/d3dt03766e] [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
A series of nine luminescent iridium(III) complexes with pH-responsive imidazole and benzimidazole ligands have been prepared and characterized. The first series of complexes were of the form [Ir(ppy)2(N^N)]+ or [Ir(ppy)2(C^N)]+ (where ppy is 2-phenylpyridine and N^N is 2-(2-pyridyl)imidazole or 2-(2-pyridyl)benzimidazole and C^N represents a pyridyl-triazolylidene-based N-heterocyclic carbene ligand). For these complexes, the benzimidazole group was either unsubstituted or substituted with electron-withdrawing (Cl) or electron-donating (Me) groups. The second series of complexes were of the form [Ir(phbim)2(N^N)]+ or [Ir(phbim)2(C^N)]+ (where phbim is 2-phenylbenzimidazole and N^N is either 2,2'-bipyridine or 1,10-phenanthroline and C^N is either a pyridyl-imidazolylidene or pyridyl-triazolylidene N-heterocyclic carbene ligand). UV-visible and photoluminescence pH titration studies showed that changing the protonation state of these complexes results in significant changes in the photoluminescence emission properties. The pKa values of prepared complexes were estimated from the spectroscopic pH titration data and these values show that the nature of the pH-sensitive ligands (either main or ancillary ligands) resulted in a significant capacity to modulate the pKa values for these compounds with values ranging from 5.19-11.22. Theoretical investigations into the nature of the electronic transitions for the different protonation states of compounds were performed and the results were consistent with the experimental results.
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Affiliation(s)
- Tahmineh Hashemzadeh
- Department of Biochemistry and Chemistry, La Trobe Institute for Molecular Science, La Trobe University, Victoria, 3086, Australia.
| | - Andrew J Christofferson
- School of Science, STEM College, RMIT University, Melbourne, Victoria 3001, Australia
- ARC Centre of Excellence in Exciton Science, School of Science, RMIT University, Melbourne, Victoria 3001, Australia
| | - Keith F White
- Department of Biochemistry and Chemistry, La Trobe Institute for Molecular Science, La Trobe University, Victoria, 3086, Australia.
| | - Peter J Barnard
- Department of Biochemistry and Chemistry, La Trobe Institute for Molecular Science, La Trobe University, Victoria, 3086, Australia.
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2
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Goodwin MJ, Dickenson JC, Ripak A, Deetz AM, McCarthy JS, Meyer GJ, Troian-Gautier L. Factors that Impact Photochemical Cage Escape Yields. Chem Rev 2024. [PMID: 38743869 DOI: 10.1021/acs.chemrev.3c00930] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/16/2024]
Abstract
The utilization of visible light to mediate chemical reactions in fluid solutions has applications that range from solar fuel production to medicine and organic synthesis. These reactions are typically initiated by electron transfer between a photoexcited dye molecule (a photosensitizer) and a redox-active quencher to yield radical pairs that are intimately associated within a solvent cage. Many of these radicals undergo rapid thermodynamically favored "geminate" recombination and do not diffuse out of the solvent cage that surrounds them. Those that do escape the cage are useful reagents that may undergo subsequent reactions important to the above-mentioned applications. The cage escape process and the factors that determine the yields remain poorly understood despite decades of research motivated by their practical and fundamental importance. Herein, state-of-the-art research on light-induced electron transfer and cage escape that has appeared since the seminal 1972 review by J. P. Lorand entitled "The Cage Effect" is reviewed. This review also provides some background for those new to the field and discusses the cage escape process of both homolytic bond photodissociation and bimolecular light induced electron transfer reactions. The review concludes with some key goals and directions for future research that promise to elevate this very vibrant field to even greater heights.
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Affiliation(s)
- Matthew J Goodwin
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
| | - John C Dickenson
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
| | - Alexia Ripak
- Université catholique de Louvain (UCLouvain), Institut de la Matière Condensée et des Nanosciences (IMCN), Molecular Chemistry, Materials and Catalysis (MOST), Place Louis Pasteur 1, bte L4.01.02, 1348 Louvain-la-Neuve, Belgium
| | - Alexander M Deetz
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
| | - Jackson S McCarthy
- 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
| | - Ludovic Troian-Gautier
- Université catholique de Louvain (UCLouvain), Institut de la Matière Condensée et des Nanosciences (IMCN), Molecular Chemistry, Materials and Catalysis (MOST), Place Louis Pasteur 1, bte L4.01.02, 1348 Louvain-la-Neuve, Belgium
- Wel Research Institute, Avenue Pasteur 6, 1300 Wavre, Belgium
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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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Jin T, Wagner D, Wenger OS. Luminescent and Photoredox-Active Molybdenum(0) Complexes Competitive with Isoelectronic Ruthenium(II) Polypyridines. Angew Chem Int Ed Engl 2024; 63:e202314475. [PMID: 37885363 DOI: 10.1002/anie.202314475] [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: 09/27/2023] [Revised: 10/25/2023] [Accepted: 10/25/2023] [Indexed: 10/28/2023]
Abstract
Ruthenium(II) complexes with chelating polypyridine ligands are among the most frequently investigated compounds in photophysics and photochemistry, owing to their favorable luminescence and photoredox properties. Equally good photoluminescence performance and attractive photocatalytic behavior is now achievable with isoelectronic molybdenum(0) complexes. The zero-valent oxidation state of molybdenum is stabilized by carbonyl or isocyanide ligands, and metal-to-ligand charge transfer (MLCT) excited states analogous to those in ruthenium(II) complexes can be established. Microsecond MLCT excited-state lifetimes and photoluminescence quantum yields up to 0.2 have been achieved in solution at room temperature, and the emission wavelength has become tunable over a large range. The molybdenum(0) complexes are stronger photoreductants than ruthenium(II) polypyridines and can therefore perform more challenging chemical reductions. The triplet nature of their luminescent MLCT states allows sensitization of photon upconversion via triplet-triplet annihilation, to convert low-energy input radiation into higher-energy output fluorescence. This review summarizes the current state of the art concerning luminescent molybdenum(0) complexes and highlights their application potential. Molybdenum is roughly 140 times more abundant and far cheaper than ruthenium, hence this research is relevant in the greater context of finding more sustainable alternatives to using precious and rare transition metals in photophysics and photochemistry.
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Affiliation(s)
- Tao Jin
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056, Basel, Switzerland
| | - Dorothee Wagner
- 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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5
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Losada IB, Persson P. Photoredox matching of earth-abundant photosensitizers with hydrogen evolving catalysts by first-principles predictions. J Chem Phys 2024; 160:074302. [PMID: 38375904 DOI: 10.1063/5.0174837] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2023] [Accepted: 01/09/2024] [Indexed: 02/21/2024] Open
Abstract
Photoredox properties of several earth-abundant light-harvesting transition metal complexes in combination with cobalt-based proton reduction catalysts have been investigated computationally to assess the fundamental viability of different photocatalytic systems of current experimental interest. Density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations using several GGA (BP86, BLYP), hybrid-GGA (B3LYP, B3LYP*), hybrid meta-GGA (M06, TPSSh), and range-separated hybrid (ωB97X, CAM-B3LYP) functionals were used to calculate relevant ground and excited state reduction potentials for photosensitizers, catalysts, and sacrificial electron donors. Linear energy correction factors for the DFT/TD-DFT results that provide the best agreement with available experimental reference results were determined in order to provide more accurate predictions. Among the selection of functionals, the B3LYP* and TPSSh sets of correction parameters were determined to give the best redox potentials and excited states energies, ΔEexc, with errors of ∼0.2 eV. Linear corrections for both reduction and oxidation processes significantly improve the predictions for all the redox pairs. In particular, for TPSSh and B3LYP*, the calculated errors decrease by more than 0.5 V against experimental values for catalyst reduction potentials, photosensitizer oxidation potentials, and electron donor oxidation potentials. Energy-corrected TPSSh results were finally used to predict the energetics of complete photocatalytic cycles for the light-driven activation of selected proton reduction cobalt catalysts. These predictions demonstrate the broader usefulness of the adopted approach to systematically predict full photocycle behavior for first-row transition metal photosensitizer-catalyst combinations more broadly.
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Affiliation(s)
- Iria Bolaño Losada
- Division of Computational Chemistry, 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
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6
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Mitra M, Mrózek O, Putscher M, Guhl J, Hupp B, Belyaev A, Marian CM, Steffen A. Structural Control of Highly Efficient Thermally Activated Delayed Fluorescence in Carbene Zinc(II) Dithiolates. Angew Chem Int Ed Engl 2024; 63:e202316300. [PMID: 38063260 DOI: 10.1002/anie.202316300] [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: 10/27/2023] [Indexed: 01/16/2024]
Abstract
Luminescent metal complexes based on earth abundant elements are a valuable target to substitute 4d/5d transition metal complexes as triplet emitters in advanced photonic applications. Whereas CuI complexes have been thoroughly investigated in the last two decades for this purpose, no structure-property-relationships for efficient luminescence involving triplet excited states from ZnII complexes are established. Herein, we report on the design of monomeric carbene zinc(II) dithiolates (CZT) featuring a donor-acceptor-motif that leads to highly efficient thermally activated delayed fluorescence (TADF) with for ZnII compounds unprecedented radiative rate constants kTADF =1.2×106 s-1 at 297 K. Our high-level DFT/MRCI calculations revealed that the relative orientation of the ligands involved in the ligand-to-ligand charge transfer (1/3 LLCT) states is paramount to control the TADF process. Specifically, a dihedral angle of 36-40° leads to very efficient reverse intersystem-crossing (rISC) on the order of 109 s-1 due to spin-orbit coupling (SOC) mediated by the sulfur atoms in combination with a small ΔES1-T1 of ca. 56 meV.
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Affiliation(s)
- Mousree Mitra
- Faculty of Chemistry and Chemical Biology, TU Dortmund University, Otto-Hahn-Str. 6, 44227, Dortmund, Germany
| | - Ondřej Mrózek
- Faculty of Chemistry and Chemical Biology, TU Dortmund University, Otto-Hahn-Str. 6, 44227, Dortmund, Germany
| | - Markus Putscher
- Institute of Theoretical and Computational Chemistry, Faculty of Mathematics and Natural Sciences, Heinrich Heine University Düsseldorf, Universitätsstr. 1, 40225, Düsseldorf, Germany
| | - Jasper Guhl
- Institute of Theoretical and Computational Chemistry, Faculty of Mathematics and Natural Sciences, Heinrich Heine University Düsseldorf, Universitätsstr. 1, 40225, Düsseldorf, Germany
| | - Benjamin Hupp
- Faculty of Chemistry and Chemical Biology, TU Dortmund University, Otto-Hahn-Str. 6, 44227, Dortmund, Germany
| | - Andrey Belyaev
- Faculty of Chemistry and Chemical Biology, TU Dortmund University, Otto-Hahn-Str. 6, 44227, Dortmund, Germany
| | - Christel M Marian
- Institute of Theoretical and Computational Chemistry, Faculty of Mathematics and Natural Sciences, Heinrich Heine University Düsseldorf, Universitätsstr. 1, 40225, Düsseldorf, Germany
| | - Andreas Steffen
- Faculty of Chemistry and Chemical Biology, TU Dortmund University, Otto-Hahn-Str. 6, 44227, Dortmund, Germany
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7
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Ye Y, Garrido-Barros P, Wellauer J, Cruz CM, Lescouëzec R, Wenger OS, Herrera JM, Jiménez JR. Luminescence and Excited-State Reactivity in a Heteroleptic Tricyanido Fe(III) Complex. J Am Chem Soc 2024; 146:954-960. [PMID: 38156951 PMCID: PMC10786067 DOI: 10.1021/jacs.3c11517] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2023] [Revised: 12/07/2023] [Accepted: 12/08/2023] [Indexed: 01/03/2024]
Abstract
Harnessing sunlight via photosensitizing molecules is key for novel optical applications and solar-to-chemical energy conversion. Exploiting abundant metals such as iron is attractive but becomes challenging due to typically fast nonradiative relaxation processes. In this work, we report on the luminescence and excited-state reactivity of the heteroleptic [FeIII(pzTp)(CN)3]- complex (pzTp = tetrakis(pyrazolyl)borate), which incorporates a σ-donating trispyrazolyl chelate ligand and three monodentate σ-donating and π-accepting cyanide ligands. Contrary to the nonemissive [Fe(CN)6]3-, a broad emission band centered at 600 nm at room temperature has been recorded for the heteroleptic analogue attributed to the radiative deactivation from a 2LMCT excited state with a luminescence quantum yield of 0.02% and a lifetime of 80 ps in chloroform at room temperature. Bimolecular reactivity of the 2LMCT excited state was successfully applied to different alcohol photo-oxidation, identifying a cyanide-H bonding as a key reaction intermediate. Finally, this research demonstrated the exciting potential of [Fe(pzTp)(CN)3]- as a photo-oxidant, paving the way for further exploration and development of emissive Fe-based photosensitizers competent for photochemical transformations.
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Affiliation(s)
- Yating Ye
- Departamento
de Química Inorgánica, Facultad de Ciencias, Universidad de Granada and Unidad de Excelencia en
Química (UEQ), Avenida Fuente Nueva s/n, 18071, Granada, Spain
| | - Pablo Garrido-Barros
- Departamento
de Química Inorgánica, Facultad de Ciencias, Universidad de Granada and Unidad de Excelencia en
Química (UEQ), Avenida Fuente Nueva s/n, 18071, Granada, Spain
| | - Joël Wellauer
- Department
of Chemistry, University of Basel, St. Johanns-Ring 19, 4056, Basel, Switzerland
| | - Carlos M. Cruz
- Departamento
de Química Orgánica, Facultad de Ciencias, Universidad de Granada and Unidad de Excelencia en
Química (UEQ), Avenida Fuente Nueva s/n, 18071, Granada, Spain
| | - Rodrigue Lescouëzec
- Institut
Parisien de Chimie Moléculaire, CNRS, UMR 8232, Sorbonne Université, F-75252 Paris Cedex
5, France
| | - Oliver S. Wenger
- Department
of Chemistry, University of Basel, St. Johanns-Ring 19, 4056, Basel, Switzerland
| | - Juan Manuel Herrera
- Departamento
de Química Inorgánica, Facultad de Ciencias, Universidad de Granada and Unidad de Excelencia en
Química (UEQ), Avenida Fuente Nueva s/n, 18071, Granada, Spain
| | - Juan-Ramón Jiménez
- Departamento
de Química Inorgánica, Facultad de Ciencias, Universidad de Granada and Unidad de Excelencia en
Química (UEQ), Avenida Fuente Nueva s/n, 18071, Granada, Spain
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8
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Alowakennu MM, Ghosh A, McCusker JK. Direct Evidence for Excited Ligand Field State-based Oxidative Photoredox Chemistry of a Cobalt(III) Polypyridyl Photosensitizer. J Am Chem Soc 2023; 145:20786-20791. [PMID: 37703518 DOI: 10.1021/jacs.3c09374] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/15/2023]
Abstract
Increasing interest in sustainable chemistry coupled with the quest to explore new reactivity has spurred research on first-row transition metal complexes for potential applications in a variety of settings. One of the more active areas of research is photoredox catalysis, where the synthetically tunable nature of their electronic structures provides a rich palette of options for tailoring their reactivity to a desired chemical transformation. Understanding the mechanism of excited-state reactivity is critical for the informed development of next-generation catalysts, which in turn requires information concerning the propensity of their electronic excited states to engage in the desired electron or energy transfer processes. Herein we provide direct evidence of the highly oxidizing nature of the lowest-energy ligand-field (LF) excited state of a first-row d6-low-spin Co(III) photosensitizer [Co(4,4'-Br2bpy)3]3+ (where 4,4'-Br2bpy is 4,4'-dibromo-2,2'-bipyridine). The redox potential associated with the LF excited state of the Co(III) complex was bracketed by performing bimolecular quenching studies by using a series of simple organic electron donors. Time-resolved absorption spectroscopy confirmed a dynamic quenching process attributed to reductive quenching of the lowest-energy ligand-field excited state of the Co(III) chromophore. Analysis of the Stern-Volmer plots for each chromophore-quencher pair revealed a limiting value of Ered* ∼ 1.25 V vs Fc/Fc+ for the metal-centered excited state, which is significantly stronger than that of more commonly employed transition metal-based photoredox agents such as [Ru(bpy)3]2+ (Ered* = 0.32 V vs Fc/Fc+) and [Ir(ppy)2(bpy)]+ (Ered* = 0.27 V vs Fc/Fc+). These results suggest that this class of chromophores could find utility in applications requiring the activation of oxidatively resistant organic substrates for photoredox catalysis.
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Affiliation(s)
- Micheal M Alowakennu
- Department of Chemistry, Michigan State University, 578 South Shaw Lane, East Lansing, Michigan 48824, United States
| | - Atanu Ghosh
- 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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9
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Kitzmann WR, Bertrams MS, Boden P, Fischer AC, Klauer R, Sutter J, Naumann R, Förster C, Niedner-Schatteburg G, Bings NH, Hunger J, Kerzig C, Heinze K. Stable Molybdenum(0) Carbonyl Complex for Upconversion and Photoredox Catalysis. J Am Chem Soc 2023. [PMID: 37478053 DOI: 10.1021/jacs.3c03832] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/23/2023]
Abstract
Photoactive complexes with earth-abundant metals have attracted increasing interest in the recent years fueled by the promise of sustainable photochemistry. However, sophisticated ligands with complicated syntheses are oftentimes required to enable photoactivity with nonprecious metals. Here, we combine a cheap metal with simple ligands to easily access a photoactive complex. Specifically, we synthesize the molybdenum(0) carbonyl complex Mo(CO)3(tpe) featuring the tripodal ligand 1,1,1-tris(pyrid-2-yl)ethane (tpe) in two steps with a high overall yield. The complex shows intense deep-red phosphorescence with excited state lifetimes of several hundred nanoseconds. Time-resolved infrared spectroscopy and laser flash photolysis reveal a triplet metal-to-ligand charge-transfer (3MLCT) state as the lowest excited state. Temperature-dependent luminescence complemented by density functional theory (DFT) calculations suggest thermal deactivation of the 3MLCT state via higher lying metal-centered states in analogy to the well-known photophysics of [Ru(bpy)3]2+. Importantly, we found that the title compound is very photostable due to the lack of labilized Mo-CO bonds (as caused by trans-coordinated CO) in the facial configuration of the ligands. Finally, we show the versatility of the molybdenum(0) complex in two applications: (1) green-to-blue photon upconversion via a triplet-triplet annihilation mechanism and (2) photoredox catalysis for a green-light-driven dehalogenation reaction. Overall, our results establish tripodal carbonyl complexes as a promising design strategy to access stable photoactive complexes of nonprecious metals avoiding tedious multistep syntheses.
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Affiliation(s)
- Winald R Kitzmann
- Department of Chemistry, Johannes Gutenberg University Mainz, Duesbergweg 10-14, 55128 Mainz, Germany
| | - Maria-Sophie Bertrams
- Department of Chemistry, Johannes Gutenberg University Mainz, Duesbergweg 10-14, 55128 Mainz, Germany
| | - Pit Boden
- Department of Chemistry and State Research Center OPTIMAS, RPTU Kaiserslautern, Erwin-Schrödinger-Straße 52, 67663 Kaiserslautern-Landau, Germany
| | - Alexander C Fischer
- Department of Chemistry, Johannes Gutenberg University Mainz, Duesbergweg 10-14, 55128 Mainz, Germany
| | - René Klauer
- Department of Chemistry, Johannes Gutenberg University Mainz, Duesbergweg 10-14, 55128 Mainz, Germany
| | - Johannes Sutter
- Max-Planck-Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Robert Naumann
- Department of Chemistry, Johannes Gutenberg University Mainz, Duesbergweg 10-14, 55128 Mainz, Germany
| | - Christoph Förster
- Department of Chemistry, Johannes Gutenberg University Mainz, Duesbergweg 10-14, 55128 Mainz, Germany
| | - Gereon Niedner-Schatteburg
- Department of Chemistry and State Research Center OPTIMAS, RPTU Kaiserslautern, Erwin-Schrödinger-Straße 52, 67663 Kaiserslautern-Landau, Germany
| | - Nicolas H Bings
- Department of Chemistry, Johannes Gutenberg University Mainz, Duesbergweg 10-14, 55128 Mainz, Germany
| | - Johannes Hunger
- Max-Planck-Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Christoph Kerzig
- Department of Chemistry, Johannes Gutenberg University Mainz, Duesbergweg 10-14, 55128 Mainz, Germany
| | - Katja Heinze
- Department of Chemistry, Johannes Gutenberg University Mainz, Duesbergweg 10-14, 55128 Mainz, Germany
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10
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Barth AT, Fajardo J, Sattler W, Winkler JR, Gray HB. Electronic Structures and Photoredox Chemistry of Tungsten(0) Arylisocyanides. Acc Chem Res 2023. [PMID: 37384787 DOI: 10.1021/acs.accounts.3c00184] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/01/2023]
Abstract
ConspectusThe high energy barriers associated with the reaction chemistry of inert substrates can be overcome by employing redox-active photocatalysts. Research in this area has grown exponentially over the past decade, as transition metal photosensitizers have been shown to mediate challenging organic transformations. Critical for the advancement of photoredox catalysis is the discovery, development, and study of complexes based on earth-abundant metals that can replace and/or complement established noble-metal-based photosensitizers.Recent work has focused on redox-active complexes of 3d metals, as photosensitizers containing these metals most likely would be scalable. Although low lying spin doublet ("spin flip") excited states of chromium(III) and metal-to-ligand charge transfer (MLCT) excited states of copper(I) have relatively long lifetimes, the electronic excited states of many other 3d metal complexes fall on dissociative potential energy surfaces, owing to the population of highly energetic σ-antibonding orbitals. Indeed, we and other investigators have shown that low lying spin singlet and triplet excited states of robust closed-shell metal complexes are too short-lived at room temperature to engage in bimolecular reactions in solutions. In principle, this problem could be overcome by designing and constructing 3d metal complexes containing strong field π-acceptor ligands, where thermally equilibrated MLCT or intraligand charge transfer excited states might fall well below the upper surfaces of dissociative 3d-3d states. Notably, such design elements have been exploited by investigators in very recent work on redox-active iron(II) systems. Another approach, one we have actively pursued, is to design and construct closed-shell complexes of earth-abundant 5d metals containing very strong π-acceptor ligands, where vertical excitation of 5d-5d excited states at the ground state geometry would require energies far above minima in the potential surfaces of MLCT excited states. As this requirement is met by tungsten(0) arylisocyanides, these complexes have been the focus of our work aimed at the development of robust redox-active photosensitizers.In the following Account, we review recent work on homoleptic tungsten(0) arylisocyanides. Originally reported by our group 45 years ago, W(CNAr)6 complexes have exceptionally large one- and two-photon absorption cross-sections. One- or two-photon excitation produces relatively long-lived (hundreds of nanoseconds to microsecond) MLCT excited states in high yields. These MLCT excited states, which are very strong reductants with E°(W+/*W0) = -2.2 to -3.0 V vs Fc[+/0], mediate photocatalysis of organic reactions with both visible and near-infrared (NIR) light. Here, we highlight design principles that led to the development of three generations of W(CNAr)6 photosensitizers; and we discuss likely steps in the mechanism of a prototypal W(CNAr)6-catalyzed base-promoted homolytic aromatic substitution reaction. Among the many potential applications of these very bright luminophores, two-photon imaging and two-photon-initiated polymerization are ones we plan to pursue.
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Affiliation(s)
- Alexandra T Barth
- Beckman Institute, California Institute of Technology, Pasadena, California 91125, United States
| | - Javier Fajardo
- Beckman Institute, California Institute of Technology, Pasadena, California 91125, United States
| | - Wesley Sattler
- Beckman Institute, California Institute of Technology, Pasadena, California 91125, United States
| | - Jay R Winkler
- Beckman Institute, California Institute of Technology, Pasadena, California 91125, United States
| | - Harry B Gray
- Beckman Institute, California Institute of Technology, Pasadena, California 91125, United States
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11
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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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12
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Cheng Y, Yang Q, He J, Zou W, Liao K, Chang X, Zou C, Lu W. The energy gap law for NIR-phosphorescent Cr(III) complexes. Dalton Trans 2023; 52:2561-2565. [PMID: 36354370 DOI: 10.1039/d2dt02872g] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A series of homoleptic Cr(III) complexes containing substituted anionic 1,3-bis(pyridin-2-ylimino)isoindolin-2-ide ligands are phosphorescent with λmax in the 777-970 nm range in degassed fluid solutions. The energy gap law has been successfully applied to the doublet excited states of Cr(III) complexes.
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Affiliation(s)
- Yang Cheng
- Department of Chemistry, Southern University of Science and Technology, Shenzhen, Guangdong 518055, P. R. China.
| | - Qingqing Yang
- Department of Chemistry, Southern University of Science and Technology, Shenzhen, Guangdong 518055, P. R. China.
| | - Jiang He
- Department of Chemistry, Southern University of Science and Technology, Shenzhen, Guangdong 518055, P. R. China.
| | - Wenjie Zou
- Department of Chemistry, Southern University of Science and Technology, Shenzhen, Guangdong 518055, P. R. China.
| | - Keyu Liao
- Department of Chemistry, Southern University of Science and Technology, Shenzhen, Guangdong 518055, P. R. China.
| | - Xiaoyong Chang
- Department of Chemistry, Southern University of Science and Technology, Shenzhen, Guangdong 518055, P. R. China.
| | - Chao Zou
- Department of Chemistry, Southern University of Science and Technology, Shenzhen, Guangdong 518055, P. R. China. .,Functional Coordination Material Group-Frontier Research Center, Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, P. R. China.
| | - Wei Lu
- Department of Chemistry, Southern University of Science and Technology, Shenzhen, Guangdong 518055, P. R. China.
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13
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Cheng Y, He J, Zou W, Chang X, Yang Q, Lu W. Circularly polarized near-infrared phosphorescence of chiral chromium(III) complexes. Chem Commun (Camb) 2023; 59:1781-1784. [PMID: 36723000 DOI: 10.1039/d2cc06548g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Homoleptic Cr(III) complexes containing anionic tridentate 1,8-(bisoxazolyl)carbazolide ligands are phosphorescent in deaerated solutions with peak maxima in the range of 813-845 nm. The ligand carbon-centred chirality has been transferred to the helical chirality of the complexes and hence induced circularly polarized NIR-emissions with dissymmetry factor in the scale of 2.0 × 10-3.
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Affiliation(s)
- Yang Cheng
- Department of Chemistry, Southern University of Science and Technology, Shenzhen, Guangdong 518055, P. R. China.
| | - Jiang He
- Department of Chemistry, Southern University of Science and Technology, Shenzhen, Guangdong 518055, P. R. China.
| | - Wenjie Zou
- Department of Chemistry, Southern University of Science and Technology, Shenzhen, Guangdong 518055, P. R. China.
| | - Xiaoyong Chang
- Department of Chemistry, Southern University of Science and Technology, Shenzhen, Guangdong 518055, P. R. China.
| | - Qingqing Yang
- Department of Chemistry, Southern University of Science and Technology, Shenzhen, Guangdong 518055, P. R. China.
| | - Wei Lu
- Department of Chemistry, Southern University of Science and Technology, Shenzhen, Guangdong 518055, P. R. China.
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14
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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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15
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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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16
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Ossinger S, Prescimone A, Häussinger D, Wenger OS. Manganese(I) Complex with Monodentate Arylisocyanide Ligands Shows Photodissociation Instead of Luminescence. Inorg Chem 2022; 61:10533-10547. [PMID: 35768069 PMCID: PMC9377510 DOI: 10.1021/acs.inorgchem.2c01438] [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: 11/29/2022]
Abstract
![]()
Recently reported
manganese(I) complexes with chelating arylisocyanide
ligands exhibit luminescent metal-to-ligand charge-transfer (MLCT)
excited states, similar to ruthenium(II) polypyridine complexes with
the same d6 valence electron configuration used for many
different applications in photophysics and photochemistry. However,
chelating arylisocyanide ligands require substantial synthetic effort,
and therefore it seemed attractive to explore the possibility of using
more readily accessible monodentate arylisocyanides instead. Here,
we synthesized the new Mn(I) complex [Mn(CNdippPhOMe2)6]PF6 with the known ligand CNdippPhOMe2 = 4-(3,5-dimethoxyphenyl)-2,6-diisopropylphenylisocyanide. This
complex was investigated by NMR spectroscopy, single-crystal structure
analysis, high-resolution electrospray ionization mass spectrometry
(HR-ESI-MS) measurements, IR spectroscopy supported by density functional
theory (DFT) calculations, cyclic voltammetry, and time-resolved as
well as steady-state UV–vis absorption spectroscopy. The key
finding is that the new Mn(I) complex is nonluminescent and instead
undergoes arylisocyanide ligand loss during continuous visible laser
irradiation into ligand-centered and charge-transfer absorption bands,
presumably owed to the population of dissociative d–d excited
states. Thus, it seems that chelating bi- or tridentate binding motifs
are essential for obtaining emissive MLCT excited states in manganese(I)
arylisocyanides. Our work contributes to understanding the basic properties
of photoactive first-row transition metal complexes and could help
advance the search for alternatives to precious metal-based luminophores,
photocatalysts, and sensors. We
report the synthesis, characterization, and X-ray crystal
structure of an octahedral manganese(I) complex with six monodentate
arylisocyanide ligands that undergoes photoinduced ligand loss.
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Affiliation(s)
- Sascha Ossinger
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056 Basel, Switzerland
| | - Alessandro Prescimone
- Department of Chemistry, University of Basel, Mattenstrasse 24a, 4058 Basel, Switzerland
| | - Daniel Häussinger
- 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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