Excimer Intermediates en Route to Long-Lived Charge-Transfer States in Single-Stranded Adenine DNA as Revealed by Nonadiabatic Dynamics

• Published in: The journal of physical chemistry letters 2020-09, Vol.11 (18), p.7483-7488
• Main Authors: Ibele, Lea M, Sánchez-Murcia, Pedro A, Mai, Sebastian, Nogueira, Juan J, González, Leticia
• Format: Article
• Language: English
• Subjects: Adenine - chemistry; DNA, Single-Stranded - chemistry; Letter; Molecular Dynamics Simulation; Physical Insights into Light Interacting with Matter; Quantum Theory
• ISSN: 1948-7185; 1948-7185
• DOI: 10.1021/acs.jpclett.0c02193

The ultrafast time evolution of a single-stranded adenine DNA is studied using a hybrid multiscale quantum mechanics/molecular mechanics (QM/MM) scheme coupled to nonadiabatic surface hopping dynamics. As a model, we use (dA)20 where a stacked adenine tetramer is treated quantum chemically. The dynamical simulations combined with on-the-fly quantitative wave function analysis evidence the nature of the long-lived electronically excited states formed upon absorption of UV light. After a rapid decrease of the initially excited excitons, relaxation to monomer-like states and excimers occurs within 100 fs. The former monomeric states then relax into additional excimer states en route to forming stabilized charge-transfer states on a longer timescale of hundreds of femtoseconds. The different electronic-state characters is reflected on the spatial separation between the adenines: excimers and charge-transfer states show a much smaller spatial separation than the monomer-like states and the initially formed excitons.