Influence of atomic electronegativity on ESIPT behaviour for the BTDI and its derivatives: Theoretical exploration.

[Display omitted] • The strength of intramolecular hydrogen bonds in the excited state increases gradually as the electronegativity of the atom decreases. • The low atomic electronegativity can causes the red shift of absorption and fluorescence spectra. • As the atomic electronegativity decreases, the energy barrier of the excited state becomes lower, which helps to promote ESIPT. In this work, we theoretically explored the influence of atomic electronegativity on excited-state intramolecular proton transfer (ESIPT) behavior among novel fluorescent probes BTDI and its derivatives (BODI and BSeDI). A thorough examination of the optimized structural parameters and infrared vibrational spectra reveals an enhancement in intramolecular hydrogen bonding within BTDI and its derivatives upon light excitation. This finding is further reinforced by topological analysis and interaction region indicator scatter plots, which underscores the sensitivity of atomic electronegativity to variations in hydrogen bonding strength. With regards to absorption and fluorescence spectra, the decrease in atomic electronegativity leads to a pronounced redshift, primarily attributed to the narrowing of the energy gap. Additionally, an analysis of potential energy curves and the exploration of intrinsic reaction coordinate paths based on transition state structures afford a deeper understanding of the mechanism underlying ESIPT and being modulated through the manipulation of atomic electronegativity. We anticipate that this work on atomic electronegativity regulating ESIPT behavior will serve as a catalyst for novel fluorescent probes in the future, offering fresh perspectives and insights. [ABSTRACT FROM AUTHOR]