Novel syntheses of the bipyridine ligand 1, dcHb (dcHb = 4,4′-dicarboxy-2,2′-bipyridine), by anionic oxidation of 4,4′-dimethyl-2′,2-bipyridine (dmb) using molecular oxygen (4 atm), and of the sensitizer precursor 4, tris(4,4′-diethoxycarbonyl-2,2′-bipyridine)ruthenium(II) bis(triflate), from a chloride-free Ru(II) precursor 3b, RuII(DMSO)4(triflate)2-n(EtOH)n (n = 0-2, DMSO = dimethyl sulfoxide, triflate = OSO2CF3) are reported. The anionic sensitizer Ru(dcb)3 4- (5) was shown to bind to vesicles of lecithin when these were made positively charged by cationic bipyridinium electron acceptors. With cetylmethylviologen (CMV2+) as quencher, the time-resolved decay of the Ru(dcb)3 4- emission followed a model for diffusion-controlled quenching in two dimensions. However, the diffusion coefficient obtained from a fit to the data was very small, (6 ± 2) x 10-11 m2 s-1, comparable to values for amphiphiles in bilayers, even though Ru(dcb)3 4- diffuses in the water region at the vesicle surface. The quantum yield of primary charge separation was 0.06 ± 0.02, which is significant, if not high, despite the large elecrostatic attraction between the reactants. Attempts were made to increase the charge separation yield by the use of a monocationic acceptor. Possible extensions of the system are discussed, such as charge separation across the vesicle membrane and the covalent linking of a donor to the sensitizer.
|Number of pages||11|
|Journal||Journal of Physical Chemistry B|
|Publication status||Published - Sep 18 1997|
ASJC Scopus subject areas
- Physical and Theoretical Chemistry