STUDIES ON THE SOLVENT EFFECTS ON THE CHARGE-TRANSFER COMPLEXES BETWEEN BENZOQUINONE AND 2,2'-BIPYRIDINE AND 1,10-PHENANTHROLINE

Complex formation between benzoquinone (Q) and the aromatic heterocycl ic donors like 2,2'-bipyridine (bipy.) and 1,10-phenanthroline (phen.) were studied in different aliphatic and aromatic solvents. Benzoquino ne forms strong CT complexes with these ligands as apparent from the a ssociation constants of the complexes in different solvents. The compa rable values of both the Q-bipy. and Q-phen. complexes suggest that th e complexes are similar in nature. Since the acceptor is the same, the differences in Gibbs energy changes for Q-bipy. and Q-phen. complexes reflect the differences of the Gibbs energy values of the complexes a nd the donors. The difference in Gibbs energy values arises from the g reater resonance stabilization of phen. compared to bipy. and the chan ge from trans form of bipy. to cis form to make the Q-bipy. complex co planar. As excpected, the effect of the solvents has been found to be marginal but the effect appears to be similar for both the complexes.