THEORETICAL INVESTIGATION OF MODEL POLYMERS FOR EUMELANINS .1. FINITE AND INFINITE POLYMERS

We investigate the electronic structure of ideal ordered polymers of 5,6-indolequinone, in one or other redox form. These molecules are the most abundant constituents of eumelanin, the pigment appearing in human skin. Our study is carried out through Hückel π-electron theory, which allows us to follow the trends in electronic structure from a single monomer - the isolated molecules - to finite polymers of up to 10 units, and to infinite polymers. We have chosen different polymerization directions which produce semiconducting chains. The comparison between finite and infinite polymers is very useful and leads us to propose a model that accounts for some of the known properties of eumelanins. © 1990 American Institute of Physics.