Electronic Energy Transfer in Polarizable Heterogeneous Environments: A Systematic Investigation of Different Quantum Chemical Approaches

Abstract

Theoretical prediction of transport and optical properties of protein-pigment complexes is of significant importance when aiming at understanding the structure-function relationship in such systems. Electronic energy transfer (EET) couplings represent a key property in this respect since such couplings provide important insight into the strength of interaction between photoactive pigments in protein-pigment complexes. Recently, attention has been payed to how the environment modifies or even controls the electronic couplings. To enable such theoretical predictions, a fully polarizable embedding model has been suggested (Curutchet, C., et al. J. Chem. Theory Comput., 2009, 5, 1838-1848). In this work, we further develop this computational model by extending it with an ab initio derived polarizable force field including higher-order multipole moments. We use this extended model to systematically examine three different ways of obtaining EET couplings in a heterogeneous medium ranging from use of the exact transition density to a point-dipole approximation. Several interesting observations are made, for example, the explicit use of transition densities in the calculation of the electronic couplings, and also when including the explicit environment contribution, can be replaced by a much simpler transition point charge description without comprising the quality of the model predictions.

Excitation Dynamics in Hetero‐bichromophoric Calixarene Systems

“…In this sense,m ore refined treatments werer ecently proposed. [65][66][67][68] Finally,a sa nticipated at the beginningo fthis section, Fçrster theory is expected to be partially inadequate to describe the photophysicso f the systemsu nder investigation due to the strength of the couplings between the local excitations and the couplings between these states and additional CT states. Full quantum-dynamicala pproaches based on wavepacket propagation are expected to offer am ore complete picture, but they are challenging and their application is postponed to future work.…”

How Static Disorder Mimics Decoherence in Anisotropy Pump–Probe Experiments on Purple-Bacteria Light Harvesting Complexes

“…52,53 Improvements in the couplings can be made using such methods as frozen density embedding, 54,55 or by using higher-order multipole moments. 53 Kenny et al investigated the accuracy of different methods for calculating the couplings, but found that given the size of the errors arising from uncertainties in crystallographic atomic coordinates, more computationally expensive methods for calculating the couplings are 'rarely justified'. 56 The parameters E j and µ j were computed using linear-response time-dependent density functional theory (TDDFT) as implemented in the Turbomole package.…”

EXAT: EXcitonic analysis tool

“…[20] Since then the exciton model has been applied to systems of increasing complexity and in particular it has been successfully used to predict the CD spectra of proteins, [21][22][23][24] pigmentprotein complexes, [25][26][27] and nucleic acids. [28][29][30][31] In most applications, quantum mechanical (QM) methods have been used to determine the fundamental quantities of the exciton model, with various approaches for the calculation of exciton couplings, [21,23,[32][33][34][35][36][37][38][39][40] and possibly extending the model to charge-transfer (CT) states. [41] The QM version of the exciton model is particularly interesting as, in principle, it is parameterfree; however, the quality of the results strongly depends on the level of QM theory adopted to describe the subunits and their interactions.…”