Symmetry Breaking and Solvent Effects Regulated Photoinduced Dynamics in the PDI Dimer Linked via the Imide N-Position: A Nonadiabatic Dynamics Simulation.

Herein, we have employed a combination of the optimally tuned screened range-separated hybrid (OT-SRSH) functional, the polarizable continuum model (PCM), and nonadiabatic molecular dynamics (NAMD) simulations based on linear-response time-dependent density functional theory (LR-TDDFT) to investigate the photoinduced dynamics of PDI dimer systems connected through imide N atoms consisting of either different or identical monomers (denoted as DPDI-1 and DPDI-2, respectively). DPDI-1, composed of distinct PDI monomers, exhibits symmetry breaking, while DPDI-2, formed by identical monomers, maintains a symmetric configuration. Our simulations analyze the excited-state dynamics of these dimers in the gas phase and dichloromethane. The results reveal that symmetry breaking and solvent effects significantly influence the excited-state dynamics of such systems. Specifically, in the gas phase, symmetry-breaking DPDI-1 exhibits photoinduced energy transfer (PEnT), whereas symmetric DPDI-2 shows no electron or hole transfer. Moreover, the polar solvent dichloromethane not only reduces the excited-state energies of both structures but also significantly alters the dynamics of DPDI-1, causing it to undergo a photoinduced hole transfer (PHT)-dominated process, while DPDI-2 exhibits no charge transfer. Our present work not only agrees well with previous experimental findings but also further reveals the microscopic mechanisms of photoinduced dynamics in N-imide-linked PDI dimers driven by symmetry breaking. These insights provide a theoretical foundation for designing and optimizing novel symmetry-breaking PDI dimers to enhance the performance of optoelectronic devices.