First-principles study of photoinduced electron-transfer dynamics in a Mg–porphyrin–quinone complex

Abstract

The photoinduced electron-transfer process between a magnesium-porphyrin and a quinone in a model complex has been studied by means of quantum dynamical methods. The microscopic parameters controlling the electrontransfer process have been obtained using ab initio electronic structure calculations. A quantum dynamical simulation for a reduced dimensionality model, including only the totally symmetric vibrational degrees of freedom of the quinone molecule, shows that the electron-transfer is fast, taking place in a few hundreds of femtoseconds, in agreement with experimental results for similar systems.

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

“…These results extend our previous work for lower-dimensionality models. [17] The analysis of models of increasing complexity and dimensionality shows that most of the vibronic activity during the ET reaction is associated with the nuclear motion in the benzoquinone moiety, mainly due to large changes of its molecular The present work opens the way for several extensions. Particularly interesting will be the study of ET reactions coupled to water oxidation processes as proposed, e.g.…”

“…Extending previous work on the basis of reduced dimensionality models of the ET complex, [17] we provide in this paper a detailed analysis of the dynamics of ET and its dependence on the driving force, employing the multilayer multiconfiguration time-dependent Hartree (ML-MCTDH) method. Using this approach, it is possible to provide an accurate treatment of the dynamics of the ET process including all 135 intramolecular vibrational degrees of freedom of the system.…”

“…In previous work, we have developed a model Hamiltonian to describe the photoinduced ET reaction in this system, which takes into account both the effects of the displacement of the equilibrium geometries and the variation of the normal modes upon ET (Duschinsky effect). [17] The structure of the complex is shown in figure 1. [17,18] The overall system has C s symmetry and the minimum atom-atom distance is about 4.5Å, whereas the center-to-center distance of the two rings is about 6.5Å.…”

“…[17] The structure of the complex is shown in figure 1. [17,18] The overall system has C s symmetry and the minimum atom-atom distance is about 4.5Å, whereas the center-to-center distance of the two rings is about 6.5Å. The motivation for this choice is to allow an easy extension of the present calculations to the more complex case of ET reactions coupled to water oxidation processes as described by Sobolewski and Domcke, [18] which will be the subject of future research.…”

Elementary electron transfer reactions: from basic concepts to recent computational advances

“…Model systems with different spectral densities and coupling parameters were solved numerically 108,114,115 ; quantum dynamics of heterogeneous ET between organic dyes (alizarin and coumarin derivatives) and semiconductors (TiO 2 ) were studied by using electronic structure calculations to obtain a microscopic Hamiltonian [17][18][19]22,116 ; full quantum dynamics of ET in model biochemical systems comprised of a porphyrin-quinone redox pair has also been recently studied including more than 130 vibrational degrees of freedom, with a full ab initio microscopic Hamiltonian. 117,118 The ML-MCTDH techniques is a quite impressive methodology for studying quantum dynamical problems, but it requires a careful attention in choosing how nuclear degrees of freedom are grouped to form a single particle and in testing the convergence of the SPFs basis for each layer.…”