Distinct roles of subphthalocyanine in the ultrafast photodynamics of three donor–acceptor conjugates directly linked by a single B-N bond revealed by nonadiabatic dynamics simulations

Abstract

Herein, we investigate the photodynamics of three donor–acceptor subphthalocyanine (SubPc)-based conjugates, namely SubPc-PDI, PTZ-SubPc, and PTZ-SubPcF, by leveraging the synergy of linear-response time-dependent density functional theory (LR-TDDFT) for static electronic structure analysis and nonadiabatic molecular dynamics (NAMD) simulations. Based on the obtained results, the distinct roles of SubPc in different conjugates are confirmed. In SubPc-PDI, the SubPc fragment acts as an electron donor, whereas in PTZ-SubPc and PTZ-SubPcF, it functions as an electron acceptor. Consequently, the photodynamics of these conjugates vary upon excitation around the lowest absorption band of SubPc. In the case of SubPc-PDI, energy transfer from SubPc to PDI occurs on an ultrafast timescale, completing within 500 fs. In contrast, hole transfer from SubPc/SubPcF is observed in the PTZ-SubPc/SubPcF conjugates. Furthermore, the introduction of fluorine substitution notably lowers the energy of charge transfer states in PTZ-SubPc conjugates, thereby enhancing charge transfer efficiency. The findings of our current study strongly align with previous experimental results and provide a more comprehensive understanding of the photoinduced dynamics in SubPc-based donor–acceptor systems. Additionally, the methodologies employed in this work prove effective for investigating the photodynamics of these systems, offering valuable insights for analyzing complex photodynamic behaviors in diverse organic donor–acceptor systems.