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Yuan H, Cheng B, Lei J, Jiang L, Han Z. Promoting photocatalytic CO 2 reduction with a molecular copper purpurin chromophore. Nat Commun 2021; 12:1835. [PMID: 33758178 PMCID: PMC7987958 DOI: 10.1038/s41467-021-21923-9] [Citation(s) in RCA: 41] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2020] [Accepted: 02/11/2021] [Indexed: 11/09/2022] Open
Abstract
CO2 reduction through artificial photosynthesis represents a prominent strategy toward the conversion of solar energy into fuels or useful chemical feedstocks. In such configuration, designing highly efficient chromophores comprising earth-abundant elements is essential for both light harvesting and electron transfer. Herein, we report that a copper purpurin complex bearing an additional redox-active center in natural organic chromophores is capable to shift the reduction potential 540 mV more negative than its organic dye component. When this copper photosensitizer is employed with an iron porphyrin as the catalyst and 1,3-dimethyl-2-phenyl-2,3-dihydro-1H-benzo[d]imidazole as the sacrificial reductant, the system achieves over 16100 turnover number of CO from CO2 with a 95% selectivity (CO vs H2) under visible-light irradiation, which is among the highest reported for a homogeneous noble metal-free system. This work may open up an effective approach for the rational design of highly efficient chromophores in artificial photosynthesis.
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Affiliation(s)
- Huiqing Yuan
- MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, School of Chemistry, Sun Yat-sen University, Guangzhou, 510275, China
| | - Banggui Cheng
- MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, School of Chemistry, Sun Yat-sen University, Guangzhou, 510275, China
| | - Jingxiang Lei
- MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, School of Chemistry, Sun Yat-sen University, Guangzhou, 510275, China
| | - Long Jiang
- MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, School of Chemistry, Sun Yat-sen University, Guangzhou, 510275, China
| | - Zhiji Han
- MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, School of Chemistry, Sun Yat-sen University, Guangzhou, 510275, China.
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Ansari MA, Mandal A, Paretzki A, Beyer K, Fiedler J, Kaim W, Lahiri GK. 1,5-Diamido-9,10-anthraquinone, a Centrosymmetric Redox-Active Bridge with Two Coupled β-Ketiminato Chelate Functions: Symmetric and Asymmetric Diruthenium Complexes. Inorg Chem 2016; 55:5655-70. [DOI: 10.1021/acs.inorgchem.6b00726] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Mohd. Asif Ansari
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
| | - Abhishek Mandal
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
| | - Alexa Paretzki
- Institut für Anorganische Chemie, Universität Stuttgart, Pfaffenwaldring 55, D-70550 Stuttgart, Germany
| | - Katharina Beyer
- Institut für Anorganische Chemie, Universität Stuttgart, Pfaffenwaldring 55, D-70550 Stuttgart, Germany
| | - Jan Fiedler
- J. Heyrovský Institute of Physical Chemistry, v.v.i., Academy of Sciences of the Czech Republic, Dolejškova 3, CZ-18223 Prague, Czech Republic
| | - Wolfgang Kaim
- Institut für Anorganische Chemie, Universität Stuttgart, Pfaffenwaldring 55, D-70550 Stuttgart, Germany
| | - Goutam Kumar Lahiri
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
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Mandal A, Hoque MA, Grupp A, Paretzki A, Kaim W, Lahiri GK. Analysis of Redox Series of Unsymmetrical 1,4-Diamido-9,10-anthraquinone-Bridged Diruthenium Compounds. Inorg Chem 2016; 55:2146-56. [DOI: 10.1021/acs.inorgchem.5b02541] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Abhishek Mandal
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai−400076, India
| | - Md Asmaul Hoque
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai−400076, India
| | - Anita Grupp
- Institut für Anorganische Chemie, Universität Stuttgart, Pfaffenwaldring 55, D-70550 Stuttgart, Germany
| | - Alexa Paretzki
- Institut für Anorganische Chemie, Universität Stuttgart, Pfaffenwaldring 55, D-70550 Stuttgart, Germany
| | - Wolfgang Kaim
- Institut für Anorganische Chemie, Universität Stuttgart, Pfaffenwaldring 55, D-70550 Stuttgart, Germany
| | - Goutam Kumar Lahiri
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai−400076, India
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Chegerev MG, Starikova AA, Piskunov AV, Cherkasov VK. Valence Tautomerism in Main‐Group Complexes? Computational Modeling of Si, Ge, Sn, and Pb Bischelates with
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‐Iminoquinone Ligands. Eur J Inorg Chem 2015. [DOI: 10.1002/ejic.201501155] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Maxim G. Chegerev
- G.A. Razuvaev Institute of Organometallic Chemistry, Russian Academy of Sciences, Laboratory of Organoelement Compounds, Tropinina Street 49, 603950 Nizhny Novgorod, Russian Federation http://www.iomc.ras.ru
| | - Alyona A. Starikova
- Institute of Physical and Organic Chemistry at Southern Federal University, Stachka Avenue 194/2, 344090 Rostov‐on‐Don, Russian Federation, http://www.ipoc.sfedu.ru/index.php
| | - Alexander V. Piskunov
- G.A. Razuvaev Institute of Organometallic Chemistry, Russian Academy of Sciences, Laboratory of Organoelement Compounds, Tropinina Street 49, 603950 Nizhny Novgorod, Russian Federation http://www.iomc.ras.ru
| | - Vladimir K. Cherkasov
- G.A. Razuvaev Institute of Organometallic Chemistry, Russian Academy of Sciences, Laboratory of Organoelement Compounds, Tropinina Street 49, 603950 Nizhny Novgorod, Russian Federation http://www.iomc.ras.ru
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Scattergood PA, Jesus P, Adams H, Delor M, Sazanovich IV, Burrows HD, Serpa C, Weinstein JA. Exploring excited states of Pt(II) diimine catecholates for photoinduced charge separation. Dalton Trans 2015; 44:11705-16. [PMID: 25683063 DOI: 10.1039/c4dt03466j] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The intense absorption in the red part of the visible range, and the presence of a lowest charge-transfer excited state, render Platinum(II) diimine catecholates potentially promising candidates for light-driven applications. Here, we test their potential as sensitisers in dye-sensitised solar cells and apply, for the first time, the sensitive method of photoacoustic calorimetry (PAC) to determine the efficiency of electron injection in the semiconductor from a photoexcited Pt(II) complex. Pt(II) catecholates containing 2,2′-bipyridine-4,4′-di-carboxylic acid (dcbpy) have been prepared from their parent iso-propyl ester derivatives, complexes of 2,2′-bipyridine-4,4′-di-C(O)OiPr, (COOiPr)2bpy, and their photophysical and electrochemical properties studied. Modifying diimine Pt(II) catecholates with carboxylic acid functionality has allowed for the anchoring of these complexes to thin film TiO2, where steric bulk of the complexes (3,5-di(t)Bu-catechol vs. catechol) has been found to significantly influence the extent of monolayer surface coverage. Dye-sensitised solar cells using Pt(dcbpy)((t)Bu2Cat), 1a, and Pt(dcbpy)(pCat), 2a, as sensitisers, have been assembled, and photovoltaic measurements performed. The observed low, 0.02–0.07%, device efficiency of such DSSCs is attributed at least in part to the short excited state lifetime of the sensitisers, inherent to this class of complexes. The lifetime of the charge-transfer ML/LLCT excited state in Pt((COO(I)Pr)2bpy)(3,5-di-(t)Bu-catechol) was determined as 250 ps by picosecond time-resolved infrared spectroscopy, TRIR. The measured increase in device efficiency for 2a over 1a is consistent with a similar increase in the quantum yield of charge separation (where the complex acts as a donor and the semiconductor as an acceptor) determined by PAC, and is also proportional to the increased surface loading achieved with 2a. It is concluded that the relative efficiency of devices sensitised with these particular Pt(II) species is governed by the degree of surface coverage. Overall, this work demonstrates the use of Pt(diimine)(catecholate) complexes as potential photosensitizers in solar cells, and the first application of photoacoustic calorimetry to Pt(II) complexes in general.
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Affiliation(s)
- Paul A Scattergood
- Department of Chemistry, University of Sheffield, Sheffield, S3 7HF, UK.
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Best J, Sazanovich IV, Adams H, Bennett RD, Davies ES, Meijer AJHM, Towrie M, Tikhomirov SA, Bouganov OV, Ward MD, Weinstein JA. Structure and ultrafast dynamics of the charge-transfer excited state and redox activity of the ground state of mono- and binuclear platinum(II) diimine catecholate and bis-catecholate complexes: a transient absorption, TRIR, DFT, and electrochemical study. Inorg Chem 2011; 49:10041-56. [PMID: 20873855 DOI: 10.1021/ic101344t] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
A series of mononuclear complexes of the type [Pt(Bu(2)cat)(4,4'-R(2)-bipy)] [where Bu(2)cat is the dianion of 3,5-(t)Bu(2)-catechol and R = H, (t)Bu, or C(O)NEt(2)] and analogous dinuclear complexes based on the "back-to-back" bis-catechol ligand 3,3',4,4'-tetrahydroxybiphenyl have been studied in detail in both their ground and excited states by a range of physical methods including electrochemistry, UV/vis/near-IR, IR, and electron paramagnetic resonance spectroelectrochemistry, and time-resolved IR (TRIR) and transient absorption (TA) spectroscopy. Density functional theory calculations have been performed to support these studies, which provide a detailed picture of the ground- and excited-state electronic structures, and excited-state dynamics, of these complexes. Notable observations include the following: (i) for the first time, the lowest-energy catecholate → bipyridine (bpy) ligand-to-ligand charge-transfer (LL'CT) excited states of these chromophores have been studied by TRIR spectroscopy, showing a range of transient bands associated with the bpy radical anion and semiquinone species, and back-electron-transfer occurring in hundreds of picoseconds; (ii) strong electronic coupling between the two catecholate units in the bridging ligand of the dinuclear complexes results in a delocalized, planar (class 3) "mixed-valence" catecholate(2-)/semiquinone(•-) state formed by one-electron oxidation of the bridging ligand; (iii) in the LL'CT excited state of the dinuclear complexes, the bridging ligand is symmetrical and delocalized, whereas the bpy radical anion is localized at one terminus of the complex. This study is the first example of an investigation of excited-state behavior in platinum(II) catecholate complexes, performed with the use of picosecond TRIR and femtosecond TA spectroscopy.
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Affiliation(s)
- Jonathan Best
- Department of Chemistry, University of Sheffield, Sheffield S3 7HF, UK
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Barry N, Furrer J, Therrien B. In- and Out-of-Cavity Interactions by Modulating the Size of Ruthenium Metallarectangles. Helv Chim Acta 2010. [DOI: 10.1002/hlca.200900422] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Synthesis and structural characterization of cadmium(II) complexes with chelating keto-hydroxy compounds: The X-ray molecular structure of [Cd2(nq)4(H2O)4]·3H2O (nqH=2-hydroxynaphthoquinone). Polyhedron 2009. [DOI: 10.1016/j.poly.2009.08.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Bhattacharya D, Sathiyendiran M, Luo TT, Chang CH, Cheng YH, Lin CY, Lee GH, Peng SM, Lu KL. Ground and Excited Electronic States of Quininone-Containing Re(I)-Based Rectangles: a Comprehensive Study of Their Preparation, Electrochemistry, and Photophysics. Inorg Chem 2009; 48:3731-42. [DOI: 10.1021/ic8024099] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Dibyendu Bhattacharya
- Institute of Chemistry, Academia Sinica, Taipei 115, Taiwan, Department of Applied Chemistry, National Chi Nan University, Nantou 545, Taiwan, and Department of Chemistry, National Taiwan University, Taipei 107, Taiwan
| | - Malaichamy Sathiyendiran
- Institute of Chemistry, Academia Sinica, Taipei 115, Taiwan, Department of Applied Chemistry, National Chi Nan University, Nantou 545, Taiwan, and Department of Chemistry, National Taiwan University, Taipei 107, Taiwan
| | - Tzuoo-Tsair Luo
- Institute of Chemistry, Academia Sinica, Taipei 115, Taiwan, Department of Applied Chemistry, National Chi Nan University, Nantou 545, Taiwan, and Department of Chemistry, National Taiwan University, Taipei 107, Taiwan
| | - Che-Hao Chang
- Institute of Chemistry, Academia Sinica, Taipei 115, Taiwan, Department of Applied Chemistry, National Chi Nan University, Nantou 545, Taiwan, and Department of Chemistry, National Taiwan University, Taipei 107, Taiwan
| | - Yu-Hsiang Cheng
- Institute of Chemistry, Academia Sinica, Taipei 115, Taiwan, Department of Applied Chemistry, National Chi Nan University, Nantou 545, Taiwan, and Department of Chemistry, National Taiwan University, Taipei 107, Taiwan
| | - Ching-Yao Lin
- Institute of Chemistry, Academia Sinica, Taipei 115, Taiwan, Department of Applied Chemistry, National Chi Nan University, Nantou 545, Taiwan, and Department of Chemistry, National Taiwan University, Taipei 107, Taiwan
| | - Gene-Hsiang Lee
- Institute of Chemistry, Academia Sinica, Taipei 115, Taiwan, Department of Applied Chemistry, National Chi Nan University, Nantou 545, Taiwan, and Department of Chemistry, National Taiwan University, Taipei 107, Taiwan
| | - Shie-Ming Peng
- Institute of Chemistry, Academia Sinica, Taipei 115, Taiwan, Department of Applied Chemistry, National Chi Nan University, Nantou 545, Taiwan, and Department of Chemistry, National Taiwan University, Taipei 107, Taiwan
| | - Kuang-Lieh Lu
- Institute of Chemistry, Academia Sinica, Taipei 115, Taiwan, Department of Applied Chemistry, National Chi Nan University, Nantou 545, Taiwan, and Department of Chemistry, National Taiwan University, Taipei 107, Taiwan
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Fedushkin IL, Maslova OV, Baranov EV, Shavyrin AS. Redox Isomerism in the Lanthanide Complex [(dpp-Bian)Yb(DME)(μ-Br)]2 (dpp-Bian = 1,2-Bis[(2,6-diisopropylphenyl)imino]acenaphthene). Inorg Chem 2009; 48:2355-7. [DOI: 10.1021/ic900022s] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Igor L. Fedushkin
- G. A. Razuvaev Institute of Organometallic Chemistry, Russian Academy of Sciences, Tropinina 49, 603950 Nizhny Novgorod, Russian Federation
| | - Olga V. Maslova
- G. A. Razuvaev Institute of Organometallic Chemistry, Russian Academy of Sciences, Tropinina 49, 603950 Nizhny Novgorod, Russian Federation
| | - Eugeny V. Baranov
- G. A. Razuvaev Institute of Organometallic Chemistry, Russian Academy of Sciences, Tropinina 49, 603950 Nizhny Novgorod, Russian Federation
| | - Andrei S. Shavyrin
- G. A. Razuvaev Institute of Organometallic Chemistry, Russian Academy of Sciences, Tropinina 49, 603950 Nizhny Novgorod, Russian Federation
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11
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Maji S, Sarkar B, Mobin SM, Fiedler J, Urbanos FA, Jimenez-Aparicio R, Kaim W, Lahiri GK. Valence-State Alternatives in Diastereoisomeric Complexes [(acac)2Ru(μ-QL)Ru(acac)2]n (QL2− = 1,4-Dioxido-9,10-anthraquinone,n = +2, +1, 0, −1, −2). Inorg Chem 2008; 47:5204-11. [DOI: 10.1021/ic800115q] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Somnath Maji
- Department of Chemistry, Indian Institute of Technology, Bombay, Powai, Mumbai-400076, India,
- Institut für Anorganische Chemie, Universität Stuttgart, Pfaffenwaldring 55, D-70550 Stuttgart, Germany,
- J. Heyrovský Institute of Physical Chemistry, v.v.i., Academy of Sciences of the Czech Republic, Dolejškova 3, CZ-18223 Prague, Czech Republic,
- Departamento de Quimica Inorganica, Facultad de Ciencias Quimicas, Universidad Complutenses, Ciudad Universitaria, E-28040 Madrid, Spain
| | - Biprajit Sarkar
- Department of Chemistry, Indian Institute of Technology, Bombay, Powai, Mumbai-400076, India,
- Institut für Anorganische Chemie, Universität Stuttgart, Pfaffenwaldring 55, D-70550 Stuttgart, Germany,
- J. Heyrovský Institute of Physical Chemistry, v.v.i., Academy of Sciences of the Czech Republic, Dolejškova 3, CZ-18223 Prague, Czech Republic,
- Departamento de Quimica Inorganica, Facultad de Ciencias Quimicas, Universidad Complutenses, Ciudad Universitaria, E-28040 Madrid, Spain
| | - Shaikh M. Mobin
- Department of Chemistry, Indian Institute of Technology, Bombay, Powai, Mumbai-400076, India,
- Institut für Anorganische Chemie, Universität Stuttgart, Pfaffenwaldring 55, D-70550 Stuttgart, Germany,
- J. Heyrovský Institute of Physical Chemistry, v.v.i., Academy of Sciences of the Czech Republic, Dolejškova 3, CZ-18223 Prague, Czech Republic,
- Departamento de Quimica Inorganica, Facultad de Ciencias Quimicas, Universidad Complutenses, Ciudad Universitaria, E-28040 Madrid, Spain
| | - Jan Fiedler
- Department of Chemistry, Indian Institute of Technology, Bombay, Powai, Mumbai-400076, India,
- Institut für Anorganische Chemie, Universität Stuttgart, Pfaffenwaldring 55, D-70550 Stuttgart, Germany,
- J. Heyrovský Institute of Physical Chemistry, v.v.i., Academy of Sciences of the Czech Republic, Dolejškova 3, CZ-18223 Prague, Czech Republic,
- Departamento de Quimica Inorganica, Facultad de Ciencias Quimicas, Universidad Complutenses, Ciudad Universitaria, E-28040 Madrid, Spain
| | - Francisco A. Urbanos
- Department of Chemistry, Indian Institute of Technology, Bombay, Powai, Mumbai-400076, India,
- Institut für Anorganische Chemie, Universität Stuttgart, Pfaffenwaldring 55, D-70550 Stuttgart, Germany,
- J. Heyrovský Institute of Physical Chemistry, v.v.i., Academy of Sciences of the Czech Republic, Dolejškova 3, CZ-18223 Prague, Czech Republic,
- Departamento de Quimica Inorganica, Facultad de Ciencias Quimicas, Universidad Complutenses, Ciudad Universitaria, E-28040 Madrid, Spain
| | - Reyes Jimenez-Aparicio
- Department of Chemistry, Indian Institute of Technology, Bombay, Powai, Mumbai-400076, India,
- Institut für Anorganische Chemie, Universität Stuttgart, Pfaffenwaldring 55, D-70550 Stuttgart, Germany,
- J. Heyrovský Institute of Physical Chemistry, v.v.i., Academy of Sciences of the Czech Republic, Dolejškova 3, CZ-18223 Prague, Czech Republic,
- Departamento de Quimica Inorganica, Facultad de Ciencias Quimicas, Universidad Complutenses, Ciudad Universitaria, E-28040 Madrid, Spain
| | - Wolfgang Kaim
- Department of Chemistry, Indian Institute of Technology, Bombay, Powai, Mumbai-400076, India,
- Institut für Anorganische Chemie, Universität Stuttgart, Pfaffenwaldring 55, D-70550 Stuttgart, Germany,
- J. Heyrovský Institute of Physical Chemistry, v.v.i., Academy of Sciences of the Czech Republic, Dolejškova 3, CZ-18223 Prague, Czech Republic,
- Departamento de Quimica Inorganica, Facultad de Ciencias Quimicas, Universidad Complutenses, Ciudad Universitaria, E-28040 Madrid, Spain
| | - Goutam Kumar Lahiri
- Department of Chemistry, Indian Institute of Technology, Bombay, Powai, Mumbai-400076, India,
- Institut für Anorganische Chemie, Universität Stuttgart, Pfaffenwaldring 55, D-70550 Stuttgart, Germany,
- J. Heyrovský Institute of Physical Chemistry, v.v.i., Academy of Sciences of the Czech Republic, Dolejškova 3, CZ-18223 Prague, Czech Republic,
- Departamento de Quimica Inorganica, Facultad de Ciencias Quimicas, Universidad Complutenses, Ciudad Universitaria, E-28040 Madrid, Spain
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Ruthenium-azoimine-chloranilates Synthesis, Spectra and Electrochemistry of Ruthenium(II)-1-alkyl-2-(arylazo)imidazole-chloranilate Complexes. TRANSIT METAL CHEM 2005. [DOI: 10.1007/s11243-005-6225-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Jasimuddin S, Byabartta P, Sinha C, Mostafa G, Lu TH. First example of ruthenium–azoimine–chloranilates: synthesis, structure, spectra and electrochemistry of ruthenium(II) 1-alkyl-2-(arylazo)imidazole chloranilates, and correlation of electronic properties with ZINDO calculation. Inorganica Chim Acta 2004. [DOI: 10.1016/j.ica.2003.11.040] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Meacham AP, Druce KL, Bell ZR, Ward MD, Keister JB, Lever ABP. Mono- and Dinuclear Ruthenium Carbonyl Complexes with Redox-Active Dioxolene Ligands: Electrochemical and Spectroscopic Studies and the Properties of the Mixed-Valence Complexes. Inorg Chem 2003; 42:7887-96. [PMID: 14632505 DOI: 10.1021/ic034579o] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The mononuclear complex [Ru(PPh(3))(2)(CO)(2)(L(1))] (1; H(2)L(1) = 7,8-dihydroxy-6-methoxycoumarin) and the dinuclear complexes [[Ru(PPh(3))(2)(CO)(2)](2)(L(2))][PF(6)] [[2][PF(6)]; H(3)L(2) = 9-phenyl-2,3,7-trihydroxy-6-fluorone] and [[Ru(PBu(3))(2)(CO)(2)](2)(L(3))] (3; H(4)L(3) = 1,2,3,5,6,7-hexahydroxyanthracene-9,10-dione) have been prepared; all complexes contain one or two trans,cis-[Ru(PR(3))(2)(CO)(2)] units, each connected to a chelating dioxolene-type ligand. In all cases the dioxolene ligands exhibit reversible redox activity, and accordingly the complexes were studied by electrochemistry and UV/vis/NIR, IR, and EPR spectroscopy in their accessible oxidation states. Oxidation of 1 to [1](+) generates a ligand-centered semiquinone radical with some metal character as shown by the IR and EPR spectra. Dinuclear complexes [2](+) and 3 show two reversible ligand-centered couples (one associated with each dioxolene terminus) which are separated by 690 and 440 mV, respectively. This indicates that the mixed-valence species [2](2+) has greater degree of electronic delocalization between the ligand termini than does [3](+), an observation which was supported by IR, EPR, and UV/vis/NIR spectroelectrochemistry. Both [2](2+) and [3](+) have a solution EPR spectrum consistent with full delocalization of the unpaired electron between the ligand termini on the EPR time scale (a quintet arising from equal coupling to all four (31)P nuclei); [3](+) is localized on the faster IR time scale (four CO vibrations rather than two, indicative of inequivalent [Ru(CO)(2)] units) whereas [2](2+) is fully delocalized (two CO vibrations). UV/vis/NIR spectroelectrochemistry revealed the presence of a narrow, low-energy (2695 nm) transition for [3](+) associated with the catecholate --> semiquinone intervalence transition. The narrowness and solvent-independence of this transition (characteristic of class III mixed-valence character) coupled with evidence for inequivalent [Ru(CO)(2)] termini in the mixed-valence state (characteristic of class II character) place this complex at the class II-III borderline, in contrast to [2](2+) which is clearly class III.
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Affiliation(s)
- Andrew P Meacham
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, UK
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