2 research outputs found
Fine Tuning of Retinal Photoinduced Decay in Solution
Single methylation
at position C<sub>10</sub> of the all-trans
retinal protonated Schiff base switches its excited-state decay in
methanol from a slower picosecond into an ultrafast, protein-like
subpicosecond process. QM/MM modeling in conjunction with on-the-fly
excited-state dynamics provides fundamental understanding of the fine-tuning
mechanics that “catalyzes” the photoinduced decay of
solvated retinals. Methylation alters the interplay between the ionic
S<sub>1</sub> and covalent S<sub>2</sub> states, reducing the excited-state
lifetime by favoring the formation of a S<sub>1</sub> transient fluorescent
state with fully inverted bond lengths that accounts for the recorded
transient spectroscopy and from which a space-saving conical intersection
seam is quickly (<1 ps) reached. Minimal and apparently innocent
chemical modifications thus affect the characteristic intramolecular
charge-transfer of the S<sub>1</sub> state as well as the interaction
with the covalent S<sub>2</sub> excited state, eventually providing
the high tunability of retinal photophysics and photochemistry and
delivering a new concept for the rational design of retinal-based
photoactive molecular devices
Newton-X platform: new software developments for surface hopping and nuclear ensembles
Newton-X is an open-source computational platform to perform nonadiabatic molecular dynamics based on surface hopping and spectrum simulations using the nuclear ensemble approach. Both are among the most common methodologies in computational chemistry for photophysical and photochemical investigations. This paper describes the main features of these methods and how they are implemented in Newton-X. It emphasizes the newest developments, including zero-point-energy leakage correction, dynamics on complex-valued potential energy surfaces, dynamics induced by incoherent light, dynamics based on machine-learning potentials, exciton dynamics of multiple chromophores, and supervised and unsupervised machine learning techniques. Newton-X is interfaced with several third-party quantum-chemistry programs, spanning a broad spectrum of electronic structure methods