Electronic Properties of Eumelanin Monomers and Dimmers

The melanin is a group of biological pigments commonly found in living beings, it can be classified in three groups: eumelanin human beings, pheomelanins in animals, and allomelanins in the vegetal kingdom. There is a special interest in the eumelanin because this biopolymer exhibits the typical properties of a semiconductor. Eumelanin is also responsible of the main cellular photoprotection mechanisms in the human beings. The exact structural pattern of eumelanin is not completely known yet, the planar molecules 5, 6-indolquinine and its reduced forms semiquinone and hydroquinone outline the greater part of the biological pigment. In this work the structural, electronic and optical properties of monomers in various charged states (0, -1) and dimmers of eumelanin in vacuum, are found for the neutral state of charge, by means of the Semiempirical methods MNDO, AM1, PM3 and ZINDO/S-CI