Conducting-polymer electrochemical switching as an easy means for control of the molecular properties of grafted transition metal complexes

Copper(II) 3',4'-bis(N,N'-oxamato)terthiophene has been synthesized and ele ctropolymerized. The copper(II)complex centers are not affected by the poly merization process, which involves coupling between C-alpha carbon atoms of the terthiophene units and leads to a new conjugated polymer consisting of polythiophene chains bearing bis(oxamato) -Cu-II groups regioregularly gra fted onto the polymer backbone. The polymer is stable with respect to polyt hiophene electroactivity, and no demetallation or modification of the Cu ox idation state occurs over a large potential range. In this material. the tw o moieties exhibit direct electronic interaction, which makes it possible t o use the conductive polymer backbone as a molecular wire or a nanocontact capable of inputting to the bis(oxamato) - Cull groups through the polythio phene-switching reaction. FTIR, XPS, and XAS spectroscopies have been used to study the effect of the state of the conducting polymer upon the propert ies of the copper(II) center (electron density, ligand field strength, size of cavity, force constants of some bonds). These properties can be control led to some extent by the potential applied to this device. From the point of view of the copper(II) center. this effect is similar to the grafting of substituents with various electronic properties.