Effects of different halogen and chalcogen substitutions on the ESIPT process of benzoxazole derivatives: Theoretical research.

[Display omitted] • ESIPT properties of nine molecules are studied by DFT and TD-DFT methods. • The substitution of weak electronegative atoms can facilitate ESIPT reaction. • The substitution on oxazole ring has more conspicuous effect on ESIPT process and photophysical properties. • Both S and Se substituted derivatives are fluorescence quenched. 2-(2-carbomethoxy-3,4-dichloro-6-hydroxyphenyl)benzoxazole (DCl-O) has been extensively studied due to its excited-state intramolecular proton transfer (ESIPT) characteristics. To obtain molecules with better luminescence properties, eight derivatives were designed by using different atomic (S, Se and F, Cl) substitution for further study the influence of electronegativity on ESIPT properties. The ESIPT process and photophysical characters of DCl-O and derivatives were studied with theoretical methods. The analysis indicates that hydrogen bonds were strengthened upon photo-excitation. Moreover, the ESIPT reaction is more facile to proceed in derivatives with the weak electronegativity of substitution and the substitution of chalcogen has better effect than that of halogen. [ABSTRACT FROM AUTHOR]