Département de chimie moléculaire

The tridentate 2-tert-butyl-4-methoxy-6-(quinolin-8-ylazo)phenol ligand HL was synthesized and structurally characterized. Its redox activity was studied by electrochem. measurements and DFT calcns. Oxidn. of HL (irreversible process) affords primarily a hydrogen bonded phenoxyl radical, whereas its redn. affords an iminosemiquinonate radical species. The reaction of two equiv. of HL with Zn(OAc)2 affords the Zn complex Zn(L)2, which was structurally characterized. Its oxidn. is easier than that of HL and is reversible. The EPR spectrum of [Zn(L)(L·)]+ shows an unresolved (S = 1/2) signal at g = 2.005, while [Zn(L·)]2+ exhibits spin triplet resonances (|D| = 0.0118 cm-1 and E/D = 0). The extra delocalization of spin d. on the azo group contributes to a lowering of the D value relative to those of Schiff base derivs. The temp. dependence of the EPR signal and DFT calcns. reveal an excited state for the spin triplet and a weak exchange coupling const. J = -2.73 cm-1. [on SciFinder(R)]