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

Abstract

The ruthenium complexes trans-[Ru(dcbpyH 2) 2(Cl) 2] ( 1), trans-[Ru(dcbpyH 2) 2(NCS) 2] ( 2), were synthesized and characterized by UV–Vis absorption, emission, IR, and NMR spectroscopy. The absorption and emission maxima 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 luminescence consisting of a single band with a maximum at 870 nm, in DMF solution at 298 K. The red shift of the MLCT absorption of the trans-chloro complex 1 (662 nm) is even more pronounced than that of the trans-complex 2 and shows the onset of weak and broad emission signals above 900 nm. The proton 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 13C NMR spectrum of the trans-isomer is characterized by a relatively simple pattern of resonances from the four equivalent pyridine rings. The enhanced red response of the trans-complex 2 renders it an attractive candidate as a panchromatic charge transfer sensitizer in mesoporous oxide solar cells.