Issue 12, 2019

Non-radiative decay of an eumelanin monomer: to be or not to be planar

Abstract

In order to understand the photoprotection process in eumelanin, it is imperative to understand the photoprocesses in its monomers. Eumelanin is a polymeric structure made of di-hydroxyindole (DHI) as the basic motif. There have been studies on the ground and low-lying excited state potential energy surfaces (PESs) and a few of the important modes have been identified in the eumelanin monomer. However, to properly depict the fate of a molecule after an initial photoexcitation, it is important to look at the dynamical picture and in this work, we have studied the excited state dynamics of a eumelanin monomer. We observe that there are planar OH elongation modes that can be important for the de-excitation mechanism. There are also non-planar modes that distort the phenyl ring of the DHI molecule. In the excited state dynamics, it is the non-planar modes that are more relevant to the non-radiative deactivation process of the monomer. We further notice that due to the non-planarity in the molecules along the deactivation path, the excited states involved in the processes are mixed ππ* and πσ* in nature. Furthermore, it is noticed that this deactivation process occurs well below a ps timescale.

Graphical abstract: Non-radiative decay of an eumelanin monomer: to be or not to be planar

Supplementary files

Article information

Article type
Paper
Submitted
14 Sun 2019
Accepted
21 Yan 2019
First published
11 Kul 2019

Phys. Chem. Chem. Phys., 2019,21, 6635-6642

Non-radiative decay of an eumelanin monomer: to be or not to be planar

P. Ghosh and D. Ghosh, Phys. Chem. Chem. Phys., 2019, 21, 6635 DOI: 10.1039/C9CP00246D

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