Intramolecular Vibrations in Excitation Energy Transfer: Insights from Real-Time Path Integral Calculations

Abstract

Excitation energy transfer (EET) is fundamental to many processes in chemical and biological systems and carries significant implications for the design of materials suitable for efficient solar energy harvest and transport. This review discusses the role of intramolecular vibrations on the dynamics of EET in nonbonded molecular aggregates of bacteriochlorophyll, a perylene bisimide, and a model system, based on insights obtained from fully quantum mechanical real-time path integral results for a Frenkel exciton Hamiltonian that includes all vibrational modes of each molecular unit at finite temperature. Generic trends, as well as features specific to the vibrational characteristics of the molecules, are identified. Weak exciton-vibration (EV) interaction leads to compact, near-Gaussian densities on each electronic state, whose peak follows primarily a classical trajectory on a torus, while noncompact densities and nonlinear peak evolution are observed with strong EV coupling. Interaction with many intramolecular modes and increasing aggregate size smear, shift, and damp these dynamical features. Expected final online publication date for the Annual Review of Physical Chemistry, Volume 73 is April 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Vibronic Resonance Along Effective Modes Mediates Selective Energy Transfer in Excitonically Coupled Aggregates

“…The interference of vibronic couplings along multiple modes implies that vibrational motions along orthogonal effective modes can simultaneously drive the vibronic probability density evolution between electronic states. This is similar to the case of indirect coupling between independent vibrational modes discussed by Makri and co-workers 9 . This will be recalled in Section III C.…”

“…Path integral 9 and effective modes schemes 10,11 can in principal treat all intramolecular Franck-Condon (FC) vibrational modes of the system on the same footing to provide numerically exact microscopic view of quantum decoherence even for molecular aggregates. While calculations of population transfer rates including the full multidimensional vibrational subspace are now feasible, calculations of spectroscopic signatures of four-wave mixing spectroscopies, which scale as fourth power of the number of basis states may be too expensive still.…”

Synthetic Control of Exciton Dynamics in Bioinspired Cofacial Porphyrin Dimers

“… 6 − 9 The diverse roles of individual and collective vibrations in excitation energy transfer were recently identified and illustrated through fully quantum mechanical, all-mode path integral calculations in small and large molecular aggregates. 10 As a first step toward creating guidelines for functional synthetic structures, model systems are needed to explore the influence of molecular topology and symmetry on electronic mixing and vibronic coupling. 11 − 13 Studies of natural systems show that rapid coherent transport occurs when the electronic coupling and the reorganization energy are of similar magnitude.…”

“…The aim of this experimental–theoretical study is to examine the interplay among structure, exciton delocalization, reorganization energy and vibronic effects on exciton transport and dynamics, , with the goal of developing strategies to exploit these parameters to control energy transfer and transport. For synthetic coherent transport systems, the optimal values of, and relations among, a number of key electronic and vibrational parameters need to be established. − The diverse roles of individual and collective vibrations in excitation energy transfer were recently identified and illustrated through fully quantum mechanical, all-mode path integral calculations in small and large molecular aggregates . As a first step toward creating guidelines for functional synthetic structures, model systems are needed to explore the influence of molecular topology and symmetry on electronic mixing and vibronic coupling. − Studies of natural systems show that rapid coherent transport occurs when the electronic coupling and the reorganization energy are of similar magnitude. , For moderate interpigment electronic couplings (100–200 cm –1 ), the reorganization energy should be in the 100–200 cm –1 range to achieve coherent transport.…”

Coherent excitation energy transfer in model photosynthetic reaction center: Effects of non-Markovian quantum environment

“…Unlike the light-harvesting systems, which have been theoretically intensively studied, [10][11][12][13][14][15][16][17][18][19] dynamics of the EET/ET processes in the reaction center is relatively rarely explored. So far theoretical studies on EET/ET in the photosynthetic reaction center are mainly based on some approximate methods, such as the Redfield equation, 4,20 polaron master equation, 21 and Pauli master equation.…”