Fine-tuning of blue-emitting pyrazoline using phenyl and thiophene terminal group substituents

Two pyrazoline (PYR) materials with phenyl and thiophene terminal group substituents (PPYR and TPYR, respectively) were synthesized, and their optical properties were examined. Variation of the terminal group allowed manipulation of the physicochemical properties of PYR based on differences in the intracharge transfer of the molecules. The peak maxima of the absorption/emission spectra PPYR and TPYR differed, occurring at 348/439 and 366/446 nm, respectively. The difference in the optical properties was due to greater electron transfer of the thiophene group compared with the phenyl group, which led to an increase in the intracharge transfer of the thiophene-containing molecule. These results demonstrate that the physicochemical properties of PYR materials can be tuned by modification with suitable substituents.