Charge transfer photochemistry of Ru(bpz)(3)(2+) with carboxylic acids andcarboxylate ions

RU(bpz)(3)(2+) (bpz = 2,2'-bipyrazine) has six peripheral uncoordinated nit rogen atoms potentially available for protonation in presence of acids. The emission from *Ru(bpz)(3)(2+) is efficiently quenched by organic acids and the observed quenching rate constants are explained in terms of proton tra nsfer from acids to *Ru(bpz)(3)(2+). The absorption and emission-intensity of Ru(bpz)(3)(2+) increases with increasing concentration of carboxylate io n suggesting the complex formation between the two reactants in the ground state. From these studies, the formation constant (K-f) have been evaluated by Benesi-Hildebrand method. The K-f values indicate that generally the io n pair association constants estimated from absorption and emission techniq ues are comparable and these values are sensitive to the structure of the c arboxylate ions. (C) 1999 Elsevier Science S.A. All rights reserved.