TRANSITION-METAL COMPLEXES OF TERPYRIDINE LIGANDS WITH HYDROQUINONE OR QUINONE SUBSTITUENTS

The new ligands 4'-(2,5-dimethoxyphenyl)-(L-1), 4'-(2,5-hydroxyphenyl) -(L-2) and 4'-(1,4-benzoquinonyl)-2,2': 6',2 ''-terpyridine (L-3) and, range of their transition-metal complexes have been prepared. The cry stal and molecular structures of L-1 and [CuL21][PF6](2) have been det ermined. Model reactions showed that the complexes [ML22](n+) can be d erivatized with suitable organic reagents, suggesting they may be inco rporated into multicomponent architectures using either ester or ether linkages. The chromophoric, magnetic and electrochemical properties o f the complexes vary with transition metal and 4' substituent. The hyd roquinonyl-substituted [ML22](2+) and the quinonyl-substituted [ML23]( 2+) complexes can be electrochemically interconverted in the presence of weak acid and switching between hydroquinonyl and quinonyl 4' subst ituents can significantly perturb physical properties of the bis(terpy ridyl) transition-metal centre(s).