Solvent Effects on Ultrafast Charge Transfer Population: Insights from the Quantum Dynamics of Guanine‐Cytosine in Chloroform

Abstract

We study the ultrafast photoactivated dynamics of the hydrogen bonded dimer Guanine‐Cytosine in chloroform solution, focusing on the population of the Guanine→Cytosine charge transfer state (GC‐CT), an important elementary process for the photophysics and photochemistry of nucleic acids. We integrate a quantum dynamics propagation scheme, based on a linear vibronic model parameterized through time dependent density functional theory calculations, with four different solvation models, either implicit or explicit. On average, after 50 fs, 30∼40 % of the bright excited state population has been transferred to GC‐CT. This process is thus fast and effective, especially when transferring from the Guanine bright excited states, in line with the available experimental studies. Independent of the adopted solvation model, the population of GC‐CT is however disfavoured in solution with respect to the gas phase. We show that dynamical solvation effects are responsible for this puzzling result and assess the different chemical‐physical effects modulating the population of CT states on the ultrafast time‐scale. We also propose some simple analyses to predict how solvent can affect the population transfer between bright and CT states, showing that the effect of the solute/solvent electrostatic interactions on the energy of the CT state can provide a rather reliable indication of its possible population.

Effect of the Thermal Fluctuations of the Photophysics of GC and CG DNA Steps: A Computational Dynamical Study

“…Furthermore, for an example snapshot at 2000 ns that shows significant oscillations, we compute and plot the off diagonal elements of the density matrix ρ LE , CT ( t ) = Tr { | CT ⟩ ⟨ LE | ρ̂ false( t false) } for a more direct measure of the coherence, as shown in Figure S19. We noticed similar behavior for the population of a CT state in a GC Watson–Crick pair in ref . These coherences are essentially washed-out when the populations are averaged over a number of simulations.…”

Quantum-Classical Protocol for Efficient Characterization of Absorption Lineshape and Fluorescence Quenching upon Aggregation: The Case of Zinc Phthalocyanine Dyes

“…The latter path, in fact, additionally extends the capability of the Ad-MD|gLVC protocol, introducing the possibility to treat multichromophore systems, with possible intra-site internal conversions, while taking into account inter-state coupling and inter-molecular structural distortion effects. A similar extension was already employed to study the formation of CT states in guanine–cytosine in explicit solvent models …”

“…A similar extension was already employed to study the formation of CT states in guanine−cytosine in explicit solvent models. 49 2.…”

The dynamical temporal behaviors of guanine–cytosine coherent charge transfer

“…Recently, Green et al calculated the dynamics of G-C for different excited states and found a rapid population transfer at S 4 . 36 It is worth noting that the absorption peak in Fig. 1(b) comes from the fourth excited state (S 4 ), which corresponds to the strongest oscillator strength ( f = 0.0959) in Table S3 (ESI †).…”