Synthesis and properties of [Pt(4-CO2CH3-py)2(mnt)]: comparison of pyridyl and bipyridyl-based dyes for solar cellsElectronic supplementary information (ESI) available: Fig. S1, CV of 1b; Fig. S2, CV of 2b; Fig. S3 and Table S1, OTTLE of 1b; Fig. S4 and Table S2, OTTLE of 2b; Fig. S5, EPR spectrum and simulation of 1b1−; Table S3, EPR simulation parameters for 1b1−; Fig. S6, EPR spectrum and simulation of 2b2−; Table S4, calculated atom contributions to frontier orbitals of 3band Table S5, TDDFT calculated selected transitions for 3b. CCDC reference number 694836. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/b811943k

The dye complexes [Pt(4-CO2R-py)2(mnt)] (R = H (3a), CH3(3b)) and the precursor complexes [Pt(4-CO2R-py)2Cl2] (2a, 2b) (py = pyridyl) were synthesised, characterised by electrochemical, spectroscopic, spectroelectrochemical (UV-vis-nIR and in situEPR) and hybrid DFT computational methods and attached to a TiO2substrate to determine charge recombination kinetics. The results were compared to the bipyridyl analogues [Pt{X,X′-(CO2R)-2,2′-bipyridyl}(mnt)], (X= 3 or 4). The electronic characteristics of the bis-pyridyl complex were found to be different to the bipyridyl complexes making the former harder to reduce, shifting the lowest-energy absorption band to higher energy and showing separate degenerate LUMO orbitals on the two pyridine rings. The latter point determines that the di-reduced pyridyl complex remains EPR active, unlike the bipyridyl analogue. Complex 3aattached to nanocrystalline TiO2shows a long charge recombination lifetime in comparison with the analogous complex with the ubiquitous 4,4′-(CO2H)2-bipyridyl ligand, suggesting that pyridyl complexes may possess some advantage over bipyridyl complexes in dye-sensitised solar cells. [ABSTRACT FROM AUTHOR]