Non-radiative relaxation mechanisms of electronically excited phenylalanine in model peptides

Mališ, Momir (2015) Non-radiative relaxation mechanisms of electronically excited phenylalanine in model peptides. Doctoral thesis, Faculty of Science > Department of Chemistry.

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Abstract

A systematic study of the non-radiative deactivation mechanisms of the three photoexcited N-acetylphenylalanylamide conformers was conducted in order to disclose the experimentally observed conformational dependent lifetime of phenyl vibrationless 1ππ* excited state. The all-atom trajectory surface hopping non-adiabatic molecular dynamics simulations, based on linear response time dependent density functional theory, were utilized for blind screening of relaxation pathways and revealed a number of excitation transfer mechanisms from 1ππ* to the 1nπ* excited states localized on each of the two amide groups. Possible pathways were further refined by obtaining conical intersection barrier energies from corresponding reaction paths constructed at the coupled cluster (CC2) level of theory. Finally, from semiclassical consideration of conical intersection accessibility with only the nuclear zero point vibrational energy and from the increased rigidity of the second amide group towards distorsion upon its methylation, it was concluded that the classically accessible part of conical intersection seam for population transfer to the 1nπ* state of the second amide group is the largest for the conformer with the shortest 1ππ* state lifetime.

Item Type: Thesis (Doctoral thesis)
Keywords: CC2, Conical intersection seam, Non-adiabatic molecular dynamics, Non-radiative deactivation, Peptide, Phenylalanine, TDDFT
Supervisor: Došlić, Nađa
Date: 2015
Number of Pages: 182
Subjects: NATURAL SCIENCES > Chemistry
Divisions: Faculty of Science > Department of Chemistry
Depositing User: Branka Maravic
Date Deposited: 15 Jun 2015 15:58
Last Modified: 15 Jun 2015 15:58
URI: http://digre.pmf.unizg.hr/id/eprint/4049

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