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

类胡萝卜素是天然光活性色素蛋白的核心组成部分。它们的分子结构以共轭多烯链为主，具有主动和被动的生物学功能。在植物和细菌的光收集复合体中，类胡萝卜素通过猝灭活性单线态和三重态来保护色素，从而防止产生有害的单线态氧。然而，直到今天，这些生物功能的机械细节，甚至相关电子状态的能量秩序和决定性特性仍然存在高度争议。在这个项目中，我们的目标是缩小这一知识差距。在电子结构和核动力学的系统理论研究中，我们首先以量子力学的方式研究中长多烯，然后再转向长多烯。除了共轭双键数量增加的线性多烯外，我们还计划系统地研究它们的甲基取代对光化学过程的影响。因此，将获得对多烯本身光化学的重要见解，然而，在这些结果的帮助下，量子化学方法将进一步发展，为类胡萝卜素电子结构的定量描述和其激发态动力学的半经典模拟开辟一条可行的途径。从长远来看，我们概述的系统项目将导致对生物学上非常重要的类胡萝卜素的光化学的基本理解，并最终缩小现有的知识差距。

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.