Synthesis and properties of quinoxaline derivatives

Quoxaline and its derivatives can be used as acceptors in the design of fluorescent materials.Two analogues, 4,4-(2,3-diphenyl-quinoxalin-6,7-diyl)bis(N,N-diphenyl-phenylamine) (2TPA-DPQ) and 3,3-(2,3-diphenyl-quinoxalin-6,7-diyl)bis(9-phenyl-9H-carbazole) (2PC-DPQ) were designed and synthesized. 2TPA-DPQ and 2PC-DPQ possessed donor-acceptor structures, in which triphenylamine and N-phenyl carbazole acted as the electron donors while 2,3-diphenyl quinoxaline served as the electron acceptor, respectively. The molecular structures of the compounds were confirmed by NMR, mass spectrometry and single crystal XRD. Fluorescence emission and UV absorption spectra were used to study intramolecular charge transfer (ICT), piezofluorochromic, and sensing properties of two compounds. The results indicated that 2TPA-DPQ and 2PC-DPQ exhibited typical ICT characteristics with dipole moment gaps of 23.0 D and 21.4 D between the excited and ground state, respectively. 2PC-DPQ showed reversible piezofluorochromic property with a fluorescence spectrum change of 15 nm upon grinding and heating the solid sample. In contrast, 2TPA-DPQ demonstrate selective sensing property to Cu²⁺ ions and could be used as a fluorescent probe of Cu²⁺. The fluorescence of 2TPA-DPQ was completely quenched when the concentration of Cu²⁺ ions was 7 times or more than the concentration of 2TPA-DPQ.This study provides a reference for the design, synthesis and application of electron donor substituted quinoxaline derivatives.