Excited-state properties of functionalized corrole photosensitizers: Insights from ultrafast experiments and quantum mechanical calculations

Abstract

Corrole complex, as a new generation of porphyrin photosensitizer, shows promising applications in photodynamic therapy and optical imaging due to their unique structure and properties. However, lack of comprehensive understanding of the relationship between structure and property limits tailored preparation of demanding corroles. Here, we systematically investigate the excited-state properties of corrole complexes with diverse peripheral substitutions and central atom coordination through time-resolved fluorescence, femtosecond transient absorption spectra, and time-dependent density functional theory calculations. The results indicate that aromatic substituents affect frontier molecular orbitals, prompting intramolecular charge transfer. Coordination with main group P(V) and Ga(III) enhances macrocycle rigidity and symmetry, significantly boosting fluorescence emission rates and absorption efficiency of the Soret band, while improving intersystem crossing probabilities. Transition metal Mn(III) accelerates charge transfer from ligands to metal and shortens internal conversion and intersystem crossing times via d–pπ bonding interaction. This study establishes a foundational understanding for designing high-performance photosensitizers.