Molecular Structure, Quantum Coherence and Solvent Effects on the Ultrafast Electron Transport in BODIPY--C$_{60}$ Derivatives

TL;DR

This study investigates how molecular structure, solvent environment, and quantum coherence influence ultrafast electron transfer in BODIPY--C$_{60}$ derivatives, revealing the role of intermediate states and solvent effects on transfer rates.

Contribution

It introduces a computational approach combining DFT and a polarizable model to analyze solvent effects and intermediate states in ultrafast electron transfer in complex molecular systems.

Findings

Charge transfer stabilization varies with solvent polarity.

Molecular bridges create intermediate states affecting transfer pathways.

Solvent environment significantly influences electron transfer rates.

Abstract

Molecular systems containing donor-bridge-acceptor sites or molecular antennas constitute promising candidates for organic photovoltaic device implementation. Photo-induced electron transfer in multi-chromophore molecular systems is defined by a subtle interaction between the donor and the molecular bridge, and by the system-solvent coupling. Here, we address the computation of quantum properties such as population inversion and electron transfer in molecular photo-systems composed of fulleroisoxazoline, fulleropyrrolidine, BODIPY and Zn-porphyrin, as well as their system-solvent ultrafast dynamics. The molecular complexes are modelled as two- and three-site systems, and we use the density functional theory (DFT) for obtaining the site energies required in the construction of the open system diabatic Hamiltonians relevant to the computation of the electron transfer. The site energies and electronic couplings are calculated by using a continuous polarizable model that allow for the analysis of different solvent environments, and the site-to-site couplings are computed by means of the generalized Mulliken Hush method at the DFT level. We find that the stabilization energy of the charge transfer states exhibit a significant variation for a compound embedded in different polar environments, and thus the effect due to the solvent has been analyzed for the specific cases of Methanol, THF and Toluene. We show that the incorporation of a molecular bridge generates the creation of an intermediate state that plays a crucial role in the charge transfer process by defining $\Lambda$ or cascaded-type energy schemes; this affects the asymptotic value of the transfer rate and favors the cascaded-type configuration.