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

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.