  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
