Effects of ligand topology on the properties of dinuclear ruthenium complexes of bis-semiquinone bridging ligands

Barthram, Anita M.; Cleary, Rosemary L.; Jeffery, John C.; Couchman, Samantha M.; Ward, Michael D.

doi:10.1016/s0020-1693(97)05883-0

Cited by 17 publications

(12 citation statements)

References 15 publications

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“…In the complexes where the metal ion is redox active with delocalisable dp-orbitals and/or p-acidic co-ligands having vacant p * -orbitals can participate with additional charge transitions: 3b 1 (catecho lato) fi dp (metal) [17], 3b 1 (catecholato) fi p * (co-ligand) [26]. Usually these transitions appear in the longer wavelength region (>700 nm) and are highly intense in nature (e$10 4 ) [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][20][21][22][23][24]. In [Ru(R-aai-R¢) 2 (CA)], Ru(II) is not a pacceptor system (d 6 ) but the Ru(R-aai-R¢) 2 -fragment is a potent system to receive p-electrons.…”

Section: Spectra and Bondingmentioning

confidence: 99%

“…A common feature of the metal-RQ chemistry is the delocalization of active electrons beween the metal and the quinonoid ligand. Thus transition metals are good candidates to stabilize different redox states of the quinonoid system [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. This is mainly due to the closer energy of quinonoid based ligands to those of metal based dporbitals and recently much effort has been devoted to the study of the electrochemical and spectroscopic properties of ruthenium complexes.…”

Section: Introductionmentioning

confidence: 99%

“…This is mainly due to the closer energy of quinonoid based ligands to those of metal based dporbitals and recently much effort has been devoted to the study of the electrochemical and spectroscopic properties of ruthenium complexes. The presence of p-acidic coligands like CO, [4] pyridines (R-Py), a-diimines (bpy, phen, tpy), [5][6][7][8][9][10][11][12][13][14][15] PPh 3 , [2,3,16] and 2-(arylazo)pyridines [17] efficiently control the energy of metal dp levels. As a result of this, the electron delocalisation between ruthenium and RQ is perturbed in the mixed ligand complexes.…”

Section: Introductionmentioning

confidence: 99%

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Ruthenium-azoimine-chloranilates Synthesis, Spectra and Electrochemistry of Ruthenium(II)-1-alkyl-2-(arylazo)imidazole-chloranilate Complexes

Byabartta¹

2005

Transition Met Chem

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Ag + -assisted dechlorination of blue cis-trans-cis Ru(R-aai-R¢) 2 Cl 2 followed by the reaction with chloranilic acid (H 2 CA) in the presence of Et 3 N, gives a neutral mononuclear violet complex [Ru(R-aai-R¢) 2 (CA)]. [R-aai-R¢=p-R-C 6 H 4 AN@NAC 3 H 2 ANN, abbreviated as an N,N¢ chelator where N(imidazole) and N(azo) represent N and N¢, respectively; R = H (a), OMe (b), NO 2 (c) and R¢= Me (4), Et(5), Bz (6)]. All the complexes exhibit strong intense MLCT transitions in the visible region and weak broad bands at higher wavelength (>700 nm). Visible transitions (580-595 nm) show a negative solvatochromic effect. The cyclic voltammograms show two quasireversible to irreversible couples positive to SCE and are due to CA ) /CA 2) (1.2-1.35 V) and Ru(III)/Ru(II) (1.6-1.8 V) redox processes. Three couples, negative to SCE, are assigned to CA 2) /CA 3) ()0.2 to )0.3 V), and azo reductions ()0.5 to )0.7, )0.8 to )0.9 V) of the chelated R-aai-R¢.

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Section: Spectra and Bondingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Ruthenium-azoimine-chloranilates Synthesis, Spectra and Electrochemistry of Ruthenium(II)-1-alkyl-2-(arylazo)imidazole-chloranilate Complexes

Byabartta¹

2005

Transition Met Chem

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“…This has resulted in † Royal Society of Chemistry Sir Edward Frankland fellow for 2000/ 2001. a series of polynuclear complexes displaying exceptionally rich electrochemical and spectroscopic behaviour. [13][14][15][16][17] The relevant ligands as shown above. Our interest in these is twofold.…”

Section: Introductionmentioning

confidence: 99%

Polynuclear osmium–dioxolene complexes: comparison of electrochemical and spectroelectrochemical properties with those of their ruthenium analogues

Barthram

Reeves

Jeffery

et al. 2000

J. Chem. Soc., Dalton Trans.

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“…Catechol ligands, members of the dioxolene family, have been extensively utilised within the coordination chemistry of various metal ions such as Ru(II), [1][2][3][4][5][6][7][8] Os(II) 4,9,10 and Re(I). [11][12][13] The most attractive feature of catechol ligands is their rich electrochemistry, with facile and reversible oxidation to semiquinone and quinone forms, together with the strong interplay between catechol and metal-based orbitals frequently resulting in transition metal complexes which display 'non-innocent' behaviour.…”

Section: Introductionmentioning

confidence: 99%

Exploring excited states of Pt(ii) diimine catecholates for photoinduced charge separation

et al. 2015

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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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Effects of ligand topology on the properties of dinuclear ruthenium complexes of bis-semiquinone bridging ligands

Cited by 17 publications

References 15 publications

Ruthenium-azoimine-chloranilates Synthesis, Spectra and Electrochemistry of Ruthenium(II)-1-alkyl-2-(arylazo)imidazole-chloranilate Complexes

Ruthenium-azoimine-chloranilates Synthesis, Spectra and Electrochemistry of Ruthenium(II)-1-alkyl-2-(arylazo)imidazole-chloranilate Complexes

Polynuclear osmium–dioxolene complexes: comparison of electrochemical and spectroelectrochemical properties with those of their ruthenium analogues

Exploring excited states of Pt(ii) diimine catecholates for photoinduced charge separation

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