4,4,4"-tricarboxy-2,2 :6,2,-terpyridin

The photostability and photoelectrochemical behavior of a red sensitive Os(II) complex, [(tct)Os(CN)3] (tct = 4,4/,4"-tricarboxy-2,2/ 6, 2"-terpyridine), was investigated by Argazzi et al. The complex is stable to photosolvation in acetonitrile and methanol and, when used in DSSCs, exhibits efficient photocurrent generation at wavelengths in excess of 900 nm, comparable to the well studied [(tct)Ru(SCN)3] complex [121]. 

The interesting feature of these complexes is a broad MLCT absorption bands in the visible region. The most intense MLCT transition maxima of complexes 1, 2, and 3 are at 500, 535, and 620 nm, respectively. The 120 nm red shift of 3 compared to 1 is the result of an increase in the energy of the metal t2g orbitals caused by introducing nonchro-mophoric ligands and a slight decrease in the LUMO of the 4,4, 4"-tricarboxy-2,2 6, 2"-terpyridine. The electrochemical data are consistent with the above assignments [22, 39, 40). 

Ghosh S, Chaitanya GK, Bhanuprakash K, Nazeeruddin MK, Gratzel M, Yella RP (2006) Electronic structures and absorption spectra of linkage isomers of trithiocyanato (4,4 ,4 -tricarboxy-2,2 6,2 -terpyridine)mthenium(ll) complexes a DFT Study. Inorg Chem 45(19) 7600-7611... 

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