Ruthenium sensitizers of the type trans-[Ru(L(1))(X)(2)], trans-[Ru(L(2))(X)(2)], trans-[Ru(L(3))(X)(2)], and trans-[Ru(L(4))(X)(2)] (where L(1) = 6,6'-bis(1-H-benzimidazol-2-yl)-4,4'-bis(methoxycarbonyl)-2,2'-bipyridine, L(2) = 4,4' "-bis(tert-butyl)-4',4' '-bis[p-(methoxycarbonyl)phenyl]-2,2':6',2' ':6' ',2' "-quaterpyridine, L(3) = 4',4' '-bis[3,4-(dimethoxy)phenyl]-2,2':6',2' ':6' ',2' "-quaterpyridine, and L(4) = 4',4' '-diethoxycarbonyl-2,2':6',2' ':6' ',2' "-quaterpyridine; X = Cl(-), NCS(-)) were synthesized and characterized by CV, NMR, and UV-vis absorption and emission spectroscopy. The trans-dichloro and dithiocyanate complexes show MLCT transitions in the entire visible and near-IR region. The lowest energy metal-to-ligand charge-transfer transition band of the trans-dichloro complexes is around 14 300 cm(-1) in DMF solution, and these complexes show weak and broad emission signals with onset at above 10 500 cm(-1). The absorption and emission maxima of the trans-dithiocyanate complexes are blue-shifted compared to those of its trans-dichloro analogues because of the strong pi acceptor property of the NCS(-) compared to the Cl(-). The electronic spectra of trans-[Ru(L)(X)(2)] complexes were calculated by INDO/S and compared with the experimental data. The extent of mixing between metal 4d and ligand pi orbitals is discussed. Extensive pi-back-donation is observed. The panchromatic response of these novel complexes renders them as suitable sensitizers for solar energy conversion applications based on titanium dioxide mesoporous electrodes. Preliminary results using the trans-[Ru(L(4))(NCS)(2)] complex show 75% incident photon-to-current efficiencies (IPCE), yielding 18 mA/cm(2) current density under standard AM 1.5 sunlight.

The Living Daylight: Ruthenium‐based chromophores are employed as building blocks for a photo‐active complex bearing a known water‐oxidation catalytic system [(Terpy)2(MnIII‐μ‐(O2)‐MnIV)]. Its activation by visible light has been studied by EPR spectroscopy.

In an effort to bring out efficient thiocyanate-free dyes for dye sensitized solar cells (DSSC) we have designed, synthesized and characterized four novel cyclometalated ruthenium(II) dyes (M1 to M4) with superior photochemical properties. All dyes contain terpyridyl ligands (TPY) with carboxylic acids as anchoring groups and cyclometalated ligand (TPY-C) with substituents for fine tuning the electronic properties. We obtain a broad absorption band which extends up to 725 nm due to metal to ligand charge transfer (MLCT) when donating groups are used, which slightly blue-shifts when a withdrawing group is used. In addition to the CT, small HOMO-LUMO gaps are obtained from electrochemical measurements which indicate characteristics of an ideal sensitizer. All four dyes were used as sensitizers for DSSC and photoelectrochemical measurements were carried out. Reasonably good efficiency (7.1%) has been achieved for . We have carried out periodic-DFT studies of these dyes adsorbed on the (TiO2)38 cluster. They revealed that, in bidentate bridging mode the dyes preferably bind with the help of two carboxylic groups onto the TiO2. To the best of our knowledge we are the first to do DFT studies of thiocyanate free cyclometalated ruthenium(ii) dyes tethered to TiO2.

Dimethyl azulene-l,2-dicarboxylates are reduced with a 4 5 molar excess of DIBAH in Et20/hexane at 0" to yield the corresponding 2-(hydroxymethyl)-l-methylazulenes which can be further reduced to 1,2-dimethylazulenes on treatment with Et,SiH in TFA at 60" (cf the Table).