Physical and Theoretical Chemistry

Biography

Biography: Valérie Brenner

Abstract

Following UV absorption, many biomolecular systems are endowed with mechanisms of excited-states deactivation that ensure their photochemical stability. One of the major goals of our research is to investigate conformer-selective dynamics of biologically relevant molecular systems by an original innovative computational strategy in order to document the basic physical phenomena controlling the lifetime of excited states, highlighting the link between electronic dynamics and structure. This innovative multi-step computational strategy allows to both characterize the first excited states of bio-relevant systems and model efficiently their potential energy surfaces, using, first, nonadiabatic dynamics simulations based on time-dependent density functional theory (NA-TDDFT) to provide hints about the critical motions that drive the deactivation, which will then be investigated at a better level with two families of methods: i) the standard approximate coupled cluster singles and doubles method (CC2) and ii) and multireference (MR) methods. Developed on small capped peptide models and always backed up by key conformation selective gas phase experiments carried out in our team at several timescales,^1,2 this innovative strategy is now applied to monohydrated capped peptides as well as capped dipeptides. We will present here the last results obtained on these systems. In addition, benchmark of the CC2 method on a set of model peptide chains (structure, energetic and vibrational frequencies of the first ππ* exited state)^3,4 as well as assessment of the CC2 method validity from comparison with MR methods⁵ will be also reported.

Figure: Illustration of a deactivation mechanism: Time dependence of the potential energy of the ground (blue) and four lowest excited states of NAPA-H2O along a selected nonadiabatic trajectory.