Electrochemical and Spectroscopic Studies on the Oxidation of the cis-(Et2-dcbpy)2RuX2 Series of Photovoltaic Sensitizer Precursor Complexes (Et2-dcbpy = 2,2‘-Bipyridine-4,4‘-diethoxydicarboxylic Acid, X = Cl-, I-, NCS-, CN-)

Wolfbauer, Georg; Bond, Alan M.; MacFarlane, Douglas R.

doi:10.1021/ic990344u

Cited by 44 publications

(40 citation statements)

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“…[52] Also, when cis-L 2 Ru(NCS) 2 (L 2 ϭ diethyl 2,2Ј-bipyridyl-4,4Ј-dicarboxylate) is oxidised to Ru III , S is eliminated and the dicyanato complex is produced. [53] These workers noted that the reaction mechanism is complex, and postulated that extrusion of S occurs through a cyclic intermediate and rearrangement from N-to C-bound cyanide ion. Since SeCN Ϫ is coordinated to cobalamin in a bent fashion, an analogous cyclic intermediate appears to be feasible in the Se extrusion pathway.…”

Section: The Nature Of the Co III Ion In Cobalaminsmentioning

confidence: 99%

Probing the Nature of the Co^IIIIon in Cobalamins − Spectroscopic and Structural Investigations of the Reactions of Aquacobalamin (Vitamin B_12a) with Ambident Nucleophiles

et al. 2003

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The rate of substitution of the H2O β‐ligand in aquacobalamin (vitamin B12a) is surprisingly fast for CoIII. This may arise as a result of transfer of electron density to CoIII by the corrin, conferring on the metal atom a softer and more labile character, and would require electronic communication between the equatorial ligand and the axial coordination sites of the metal atom. We have substituted H2O in B12a with the ambidentate nucleophiles SCN−, SeCN−, NO2− and S2O32−, examined the UV/Vis spectra of the resultant complexes, crystallised them, and determined their structures by X‐ray diffraction methods. The UV/Vis spectra of these complexes, as well as those of H2OCbl+, SO3Cbl− and MeCbl, were fitted by Gaussian functions. The principal bands move to lower energy in response to an increase in donation of electron density from the axial ligand, demonstrating direct electronic communication between the axial and the equatorial ligands. In the solid state, the thiocyanato ligand in SCNCbl is coordinated through N, although 13C NMR spectroscopy shows that the complex exists as a mixture of two linkage isomers in solution. SeCN−, NO2− and S2O32− are coordinated through the softer available donor in each case (Se, N and S, respectively). There is a regular ground‐state trans effect such that as the donor power of the β‐ligand increases, the trans Co−Nax bond length increases. A survey of the structures available in the CSD shows that this preference for the softer donor atom in ambidentate nucleophiles is not unusual in CoIII complexes. The Co−N bond length in SCNCbl is marginally long for coordination to CoIII, but the axial bond lengths of the other complexes are as expected. Hence, whereas the corrin macrocycle clearly imparts lability on CoIII, presumably by transfer of electron density onto the metal atom, this is insufficient to have a major effect on the ground‐state structures of its complexes. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

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Section: The Nature Of the Co III Ion In Cobalaminsmentioning

confidence: 99%

Probing the Nature of the Co^IIIIon in Cobalamins − Spectroscopic and Structural Investigations of the Reactions of Aquacobalamin (Vitamin B_12a) with Ambident Nucleophiles

et al. 2003

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“…for 2,2′‐bipyridine‐4,4′‐dialkylcarboxylic acids and by Grätzel et al. for dcbpy upon exposure to temperatures of >200 °C . It was clear from these experiments that the reactivity of ligand 1 deviated significantly from that of dcbpy.…”

Section: Resultsmentioning

confidence: 78%

Tetracarboxylate Bis‐Bipyridine Ruthenium Dyes: Synthesis, Structural and Electronic Characterisation

et al. 2018

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The preparation of ruthenium complexes with novel 2,2′‐bipyridine (bpy) ligands bearing four carboxylic acid groups was investigated with a view to creating dyes containing more than two potential anchoring groups per bpy unit for attachment to a titania surface. Synthetic challenges are encountered upon using the 2,2′‐bipyridine‐3,3′,4,4′‐tetracarboxylic acid ligand because it readily decarboxylates. The use of the methyl esterified derivative (3) proved to be more successful for complex preparation, with a robust preparation of the [Ru(3)2Cl2] complex identified with diglyme as the solvent. This complex was further converted into the thiocyanato complex, [Ru(3)2(NCS)2], which could not be completely de‐esterified. X‐ray analysis of crystals obtained from a mixture of isomers for this complex provided data for the S,S‐ and N,S‐coordinated isomers; both showed a twisted arrangement of the pyridine rings in the 2,2′‐bipyridine‐3,3′,4,4′‐tetracarboxylic acid ligand, owing to steric hinderance. Conversely, the isosteric 2,2′‐bipyridine‐4,4′,5,5′‐tetracarboxylic acid ligand was easily converted into the desired [Ru(2)2(NCS)2] complex through a standard one‐pot procedure in N,N‐dimethylformamide solvent. All of the complexes presented herein exhibit a significant redshift for the metal to ligand charge‐transfer bands, relative to the benchmark ruthenium dye N719 and derivatives thereof. All complexes exhibit a quasi‐reversible process for the ruthenium(II/III) couple at approximately 0.4 V versus the ferrocene couple, comparable to analogous ruthenium dyes.

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“…6). For cis-Ru II X 2 (4,4 0 -(CO 2 Et) 2 -2,2 0 -bpy) 2 (X = Cl À or NCS À ) in acetonitrile, a slightly larger difference (290 mV) is observed [31]. These observations clearly indicate that Cl À is the stronger electron donor, rendering the Ru II centre more electron rich and therefore destabilising the HOMO.…”

Section: Electrochemistrymentioning

confidence: 91%

Ruthenium(II) dichloro or dithiocyanato complexes with 4,4′:2′,2″:4″,4‴-quaterpyridinium ligands: Towards photosensitisers with enhanced low-energy absorption properties

Blackburn¹,

Coe²,

Helliwell³

et al. 2013

Polyhedron

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a b s t r a c tFourteen new complexes of the form cis-[Ru II X 2 (R 2 qpy 2+ ) 2 ] 4+ (R 2 qpy 2+ = a 4,4 0 :2 0 ,2 00 :4 00 ,4 000 -quaterpyridinium ligand, X = Cl À or NCS À ) have been prepared and isolated as their PF 6 À salts. Characterisation involved various techniques including 1 H NMR spectroscopy and +electrospray or MALDI mass spectrometry. The UV-Vis spectra display intense intraligand p ? p ⁄ absorptions, and also metal-to-ligand charge-transfer (MLCT) bands with two resolved maxima in the visible region. Red-shifts in the MLCT bands occur as the electron-withdrawing strength of the pyridinium groups increases, while replacing Cl À with NCS À causes blue-shifts. Cyclic voltammograms show quasi-reversible or reversible Ru III/II oxidation waves, and several ligand-based reductions that are irreversible. The variations in the redox potentials correlate with changes in the MLCT energies. A single-crystal X-ray structure has been obtained for a protonated form of a proligand salt, [(4-(CO 2 H)Ph) 2 qpyH 3+ ][HSO 4 ] 3 Á3H 2 O. Time-dependent density functional theory calculations give adequate correlations with the experimental UV-Vis spectra for the two carboxylic acidfunctionalised complexes in DMSO. Despite their attractive electronic absorption spectra, these dyes are relatively inefficient photosensitisers on electrodes coated with TiO 2 or ZnO. These observations are attributed primarily to weak electronic coupling with the surfaces, since the DFT-derived LUMOs include no electron density near the carboxylic acid anchors.

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Electrochemical and Spectroscopic Studies on the Oxidation of the cis-(Et₂-dcbpy)₂RuX₂ Series of Photovoltaic Sensitizer Precursor Complexes (Et₂-dcbpy = 2,2‘-Bipyridine-4,4‘-diethoxydicarboxylic Acid, X = Cl^-, I^-, NCS^-, CN^-)

Cited by 44 publications

References 53 publications

Probing the Nature of the Co^IIIIon in Cobalamins − Spectroscopic and Structural Investigations of the Reactions of Aquacobalamin (Vitamin B_12a) with Ambident Nucleophiles

Probing the Nature of the Co^IIIIon in Cobalamins − Spectroscopic and Structural Investigations of the Reactions of Aquacobalamin (Vitamin B_12a) with Ambident Nucleophiles

Tetracarboxylate Bis‐Bipyridine Ruthenium Dyes: Synthesis, Structural and Electronic Characterisation

Ruthenium(II) dichloro or dithiocyanato complexes with 4,4′:2′,2″:4″,4‴-quaterpyridinium ligands: Towards photosensitisers with enhanced low-energy absorption properties

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Electrochemical and Spectroscopic Studies on the Oxidation of the cis-(Et2-dcbpy)2RuX2 Series of Photovoltaic Sensitizer Precursor Complexes (Et2-dcbpy = 2,2‘-Bipyridine-4,4‘-diethoxydicarboxylic Acid, X = Cl-, I-, NCS-, CN-)

Cited by 44 publications

References 53 publications

Probing the Nature of the CoIIIIon in Cobalamins − Spectroscopic and Structural Investigations of the Reactions of Aquacobalamin (Vitamin B12a) with Ambident Nucleophiles

Probing the Nature of the CoIIIIon in Cobalamins − Spectroscopic and Structural Investigations of the Reactions of Aquacobalamin (Vitamin B12a) with Ambident Nucleophiles

Tetracarboxylate Bis‐Bipyridine Ruthenium Dyes: Synthesis, Structural and Electronic Characterisation

Ruthenium(II) dichloro or dithiocyanato complexes with 4,4′:2′,2″:4″,4‴-quaterpyridinium ligands: Towards photosensitisers with enhanced low-energy absorption properties

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Electrochemical and Spectroscopic Studies on the Oxidation of the cis-(Et₂-dcbpy)₂RuX₂ Series of Photovoltaic Sensitizer Precursor Complexes (Et₂-dcbpy = 2,2‘-Bipyridine-4,4‘-diethoxydicarboxylic Acid, X = Cl^-, I^-, NCS^-, CN^-)

Probing the Nature of the Co^IIIIon in Cobalamins − Spectroscopic and Structural Investigations of the Reactions of Aquacobalamin (Vitamin B_12a) with Ambident Nucleophiles

Probing the Nature of the Co^IIIIon in Cobalamins − Spectroscopic and Structural Investigations of the Reactions of Aquacobalamin (Vitamin B_12a) with Ambident Nucleophiles