Localized intrinsic bond orbitals decode correlated charge migration dynamics

TL;DR

This paper introduces an extension of localized intrinsic bond orbitals (IBOs) to analyze and decode complex charge migration dynamics in molecules, providing a compact, chemically intuitive framework that enhances understanding and design of charge transfer processes.

Contribution

The work develops a novel IBO-based method to interpret correlated charge migration, linking quantum dynamics to chemical concepts like curly arrows and orbital interactions.

Findings

IBOs enable identification of key charge migration mechanisms

Different charge transfer pathways involve hyperconjugation and orbital coupling

The method can predict molecules with high charge migration efficiency

Abstract

For decades, scientists have studied the intricate charge migration dynamics, where after ionization a localized charge distribution ("hole") migrates across the molecule on a femtosecond timescale. This has the potential for controlling electrons in molecules, yet a comprehensive understanding of the many aspects of charge migration is still missing. In this work, we analyze charge migration using an extension of localized intrinsic bond orbitals (IBOs). These orbitals lead to a compact representation of the dynamics and map the complex, correlated many-electron charge migration to chemical concepts such as curly arrows and orbital-orbital interactions. By analyzing multiple challenging scenarios, we show how IBOs enable us to identify key mechanisms in charge migration. For example, we show that different mechanisms are responsible for converting a $\pi$-shaped hole to a $\sigma$-shaped hole and vice versa. We explain these in terms of hyperconjugation interactions and configurations that couple orbitals with different symmetries. We further demonstrate how IBOs can be used to find molecules with high charge migration efficiency. We carry out all simulations using an efficient set up of the time-dependent density matrix renormalization group (TDDMRG), correlating as many as 45 electrons in 50 orbitals. We believe that our results will be useful to design future experiments. The proposed IBO analysis is applicable to other types of real-time electron dynamics and spectroscopy.