Quantum dynamics of electron-transfer reactions: photoinduced intermolecular electron transfer in a porphyrin–quinone complex

Abstract

Photoinduced electron-transfer (ET) between a magnesium-porphyrin and benzoquinone in a model molecular complex is investigated employing ab initio multi-configuration electronicstructure calculations combined with quantum dynamical methods. The microscopic parameters controlling the electron-transfer process are obtained using a first-principles diabatization procedure. A model Hamiltonian which includes both linear and quadratic vibronic couplings of all nuclear degrees of freedom of the system is constructed. Quantum dynamical simulations of the ET process are performed employing the multilayer multiconfiguration time-dependent Hartree method. A detailed analysis of the ET dynamics for models of increasing complexity reveals that the dynamics is strongly influenced by resonances associated with vibronically active nuclear modes, leading to significant deviations from the results of classical ET theory.The comparison with results obtained with the simplified spin-boson model reveals the effects related to the Duschinsky rotation of normal modes.

Quantum Dynamics of Radiationless Electronic Transitions Including Normal Modes Displacements and Duschinsky Rotations: A Second-Order Cumulant Approach

“…[32][33][34] Second-order effects such as variations of vibrational frequencies and the directions of normal vibrations, are usually not included in most of the Hamiltonian models used in qunatum dynamics, though a number of works suggest that their effect can be quite relevant. [35][36][37][38][39][40] The coupling operator V AF is in general a function of the vibrational coordinates of the system, although it is quite common to assume its value constant, since electronic transitions take place in a restricted region of the nuclear coordinates. 41 Another approximation of V AF , widely used in the study of photoexcited decays where conical intersections play a major role, is the so called linear vibronic model 1,42,43 in which the coupling operator is a linear function of the nuclear coordinates.…”

Theoretical and experimental determination of the absorption and emission spectra of a prototypical indolenine-based squaraine dye

“…This approach has been recently applied to the simulation of spectral lineshapes of large molecules 58 as well as to the determination of electron-transfer rates with positive results. 18,19,53 …”

Photoinduced electron transfer processes in dye-semiconductor systems with different spacer groups

“…Considering, for example, electronically nonadiabatic dynamics, where the smallest (electronic) timescale is on the order of a femtosecond, the ML-MCTDH method can be applied efficiently for timescales of a few hundred femtoseconds up to about a picosecond. 105 For processes that take place on an even longer time scale, a rate (kinetic) description is often more appropriate. In this case, one may apply the ML-MCTDH method to calculate the reactive flux correlation function and then obtain the rate constant.…”