Quantum Dynamics in an Explicit Solvent Environment: A Photochemical Bond Cleavage Treated with a Combined QD/MD Approach

Abstract

In quantum chemistry methods to describe environmental effects on different levels of complexity are available in the common program packages. Electrostatic effects of a solvent for example can be included in an implicit or explicit way. For chemical reactions with large structural changes additional mechanical effects come into play. Their treatment within a quantum dynamical context is a major challenge, especially when excited states are involved. Recently, we introduced a method that realizes an implicit description. Here, we present an approach combining quantum dynamics and molecular dynamics. It explicitly incorporates the solvent environment, whereby the electrostatic as well as the dynamic effects are captured. This new method is demonstrated for the ultrafast photoinduced bond cleavage of diphenylmethylphosphonium ions (Ph2CH-PPh3(+)), a common precursor to generate reactive carbocations in solution.

Molecular Dynamics Simulations of the Initial-State Predict Product Distributions of Dediazoniation of Aryldiazonium in Binary Solvents

“…Probably, calculations of reactive trajectories (as in ref 13) will be necessary if we want to deeply understand the assumption of equal probabilities.…”

Theoretical Quantum Control of Fluctuating Molecular Energy Levels in Complex Chemical Environments

“…The theoretical approach in the present study uses a combined quantum dynamical (QD) treatment of the chemical reactant with a classical time evolution according to molecular dynamics (MD) of solvent molecules (QD/MD procedure) . The model coordinate uses the intrinsic reaction coordinate (IRC) of the methyl transfer in the gas phase depicted in Figure .…”

“…Effects which are described by this formalism are for example the dephasing influence of the environment on the molecular system, how this affects quantum control and whether this can be overcome by pulse shaping . Another approach uses the time‐dependent Schrödinger equation (TDSE) to simulate the time evolution of the molecular quantum system, represented by the Hamiltonian, and explicitly includes solvent molecules in the computation of molecular properties . With respect to quantum control, this approach has been used to describe selective vibrational excitation of the carboxy‐hemoglobin carbonyl mode within its protein environment, and for vibrational initiation of a methyl transfer reaction in a tetrahydrofurane (THF) solution .…”

Molecular features in complex environment: Cooperative team players during excited state bond cleavage

“…Recently, we developed two different approaches with increasing complexity to calculate the solvent potential ${\widehat{V}}_{\text{solv}}$. The first method includes the solvent effects in a continuum-like fashion, 18 the second treats the solvent environment explicitly 19 . We will give a brief overview of both methods in the following.…”

“…The second method, the QD/MD approach, combines QD calculations with molecular dynamics (MD) simulations of the solvent environment 19 . Randomly selected snapshots from the MD trajectories give an averaged picture of the atomistic solvent surrounding of the reactant.…”