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submitted on 13.03.2019 and posted on 13.03.2019by Gerard Riesco, Aleix Casademont, Lluís Blancafort
We have computed the vertical absorption of the
basic components of eumelanin, oligomers of 5,6-dihydroxyindole (DHI) and
5,6-dihydroxyindole-2-carboxylic acid (DHICA), at the TD-DFT level. Here we
present a preliminary report on the results for 73 DHI and 58 DHICA oligomers
that cover the structural and redox diversity found in eumelanin. We have
identified several structures that absorb at wave lengths above 800 nm, all of
which contain oxidized DHI units, ie
quinones or quinone methides. The transitions also have a pronounced charge
transfer character, which suggests that they may give rise to proton-coupled
electron transfer radiationless decay mechanisms that are important for the