Photo-induced non-adiabatic dynamics of Carotenoids: a systematic investigation of small model systems towards the biological molecule

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Carotenoids are central building blocks of natural photo-active pigment proteins. Their molecular structure is dominated by a conjugated polyene chain and they possess passive as well as active biological functions. In plant and bacterial light harvesting complexes, carotenoids act as protecting pigments by quenching reactive singlet and triplet states thereby preventing the generation of harmful singlet oxygen. However, until today the mechanistic details of these biological functions, even the energetic order as well as decisive properties of the relevant electronic states are yet highly debated. Within this project we aim at closing this knowledge gap.In a systematic theoretical study of the electronic structure and the nuclear dynamics we first aim at investigating medium long polyenes quantum mechanically before we turn to longer ones. Besides the linear polyenes with increasing number of conjugated double bonds, we plan to systematically study also the influence of their methyl substitution on the photochemical processes. Thereby, important insights will be gained into the photochemistry of polyenes themselves, however, with the help of these results quantum chemical methods will be developed further to open a viable way to the quantitative description of the electronic structure of carotenoids and the semi-classical simulation of their excited state dynamics.Our outlined systematic project will, in the long run, lead to a fundamental understanding of the photochemistry of the biologically utterly important Carotenoids and eventually close the existing knowledge gap.