Synthesis and photophysical properties of trans-dithiocyanato bis(4,4 '-dicarboxylic acid-2,2 '-bipyridine) ruthenium(II) charge transfer sensitizer

The ruthenium complexes trans-[Ru(dcbpyH(2))(2)(Cl)(2)] (1), trans-[Ru(dcbp yH(2))(2)(NCS)(2)] (2), were synthesized and characterized by UV-Vis absorp tion, emission, TR, and NMR spectroscopy. The absorption and emission maxim s of the trans complexes are red-shifted when compared to the cis analogs. The low energy MLCT maximum of complex 2 shows at 582 nm and exhibits a lum inescence consisting of a single band with a maximum at 870 nm, in DMF solu tion at 298 K. The red shift of the MLCT absorption of the trans-chloro com plex 1 (662 nm) is even more pronounced than that of the trans-complex 2 an d shows the onset of weak and broad emission signals above 900 nm. The prot on NMR spectra of the trans-isomers show only three peaks corresponding to the two dcbpy ligands in which all the pyridine rings are equivalent. The C -13 NMR spectrum of the trans-isomer is characterized by a relatively simpl e pattern of resonances from the four equivalent pyridine rings. The enhanc ed red response of the trans-complex 2 renders it an attractive candidate a s a panchromatic charge transfer sensitizer in mesoporous oxide solar cells . (C) 1999 Elsevier Science S.A. All rights reserved.