Molecular Architecture and Solvent Effects on Photoinduced Dynamics in TPPS-PDI, (TPPS)2, and (PDI)2 Dimers: A...

Using optimally tuned screened range-separated hybrid (OT-SRSH) functionals combined with the polarizable continuum model (PCM) and nonadiabatic molecular dynamics (NAMD) simulations based on linear-response time-dependent density functional theory (LR-TDDFT), we explored how molecular architecture and solvent environment influence the excited-state characteristics and photoinduced relaxation processes of the tetra(4-sulfonatophenyl)porphyrin-perylene diimide (TPPS-PDI) heterodimer together with the corresponding (TPPS)2 and (PDI)2 homodimers in water and in the gas phase. Comparative analysis of these hetero- and homoaggregated systems demonstrates the combined influence of molecular architecture and environmental polarization on the balance between locally excited (LE) and charge-transfer (CT) states, as well as their impact on the ensuing photoinduced electron transfer (PET) and photoinduced energy transfer (PEnT) pathways. TPPS-PDI exhibits CT-mediated PET dynamics in both environments, whereas (TPPS)2 is dominated by PEnT. In contrast, (PDI)2 shows pronounced solvent-dependent behavior, with CT-dominated relaxation in water and PEnT-dominated LE-state relaxation in the gas phase. These findings demonstrate that both the aggregation pattern and the solvent environment play decisive roles in shaping excited-state relaxation pathways, providing molecular-level insight into the photoinduced dynamics of organic donor-acceptor assemblies and guidance for the rational design of photoactive materials.