New side groups-tuned triphenylamine-based chromophores: Synthesis, morphology, photophysical properties and electronic structures

A new series of crossing symmetric triphenylamine-based chromophores with different side groups were synthesized. Their morphological structure, thermal stabilities and photo-physics were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), differential scanning calorimetry (DSC), thermogravimetric analyzer (TGA), UV–vis spectrophotometer and fluorescent photometer. The results indicated that these compounds emitted green fluorescence with a quantum yield ranging from 0.34 to 0.80 and a lifetime of 0.89 to 1.34 ns. Meanwhile, these compounds with crystal character or amorphous phase exhibited relatively high decomposition and glass transition temperatures. Their electrochemical behaviors and electronic structures were investigated in detail by cyclic voltammetry (CV), and further confirmed by theoretical calculation. The introduced side groups lowered the electron density of the conjugated system, resulting in a significant decrease of LUMO energy level. In a word, it suggested that the optical properties were regulated by the electronics structures with the different effect of the side groups on the LUMO.