Theoretical study of atomic electronegativity effects on the excited-state behavior of fluorescent compounds of citrinin

The present work focuses on the light-induced behavior of citrinin derivatives in relation to atomic electronegativity. A detailed theoretical study on the photophysical properties and excited-state behavior of fluorescent compounds of citrinin (Cit-O, Cit-S, and Cit-Se, with different atomic electronegativity) has been conducted, and the effect of electronegativity on the proton transfer in this system has been explained. First, the relevant hydrogen bond parameters and infrared vibrational spectra of the optimized geometrical configurations have been insightfully investigated. It is elucidated that the hydrogen bond is strengthened after photoexcitation, and it provides a driving force for excited-state intramolecular proton transfer (ESIPT). In addition, the frontier molecular orbitals were analyzed, and the intramolecular charge transfer process in all Cit systems, the phenomenon of charge redistribution, facilitates the ESIPT reaction. By constructing potential energy surfaces for different transfer paths, the atomic electronegativity impact on the ESIPT dynamical behavior of the Cit system was determined. This work clarifies the mechanism of the intramolecular proton transfer process in the excited state of citrinin molecules and complements the theoretical study of the atomic electronegativity-regulated citrinin system, which provides a corresponding theoretical basis for the design and synthesis of new luminescence-adjustable citrinin systems.