Electrochemistry and electrogenerated chemiluminescence of benzoxazole derivatives in nonaqueous media

Abstract

Benzoxazole derivatives, an important type of heterocyclic compounds, have attracted significant interest in photonics and electronics since they are highly efficient luminophores with high photo-stability. The electrochemistry and electrogenerated chemiluminescence (ECL) of benzoxazole derivatives were reported and the substituent effects on the electrochemical and ECL properties of benzoxazole derivatives were investigated in an acetonitrile:benzene (v:v=1:1) solvent for the first time. The studied derivatives contain a 2-biphenyl benzoxazole moiety with the substituents (–CH3, –Cl, and –NO2 groups) at the 5-position of the benzoxazole ring and the alkoxy chains (CnH2n+1, n=2–10) at the 4′-position of the biphenyl ring. The electrochemical and ECL behavior of benzoxazole derivatives were found to be dependent on the nature of the substituents at the 5-position of the benzoxazole ring but independent on the alkoxy chain length at 4′-position of biphenyl moiety. Under ion annihilation conditions, 5B–H (2-(4′-pentyloxy-biphenyl-4-yl)-benzoxazole), 5B–Me (2-(4′-pentyloxy- biphenyl-4-yl)-5-methylbenzoxazole), and 5B–Cl (2-(4′-pentyloxy-biphenyl-4-yl)-5-chlorobenzoxazole), display high ECL blue emission (ECL efficiencies are 0.51, 0.54, and 0.78 for 5B–H, 5B–Me, and 5B–Cl, respectively), while 5B-NO2 (2-(4′-pentyloxy-biphenyl-4-yl)-5-nitrobenzoxazole) does low ECL emission. In the presence of benzoyl peroxide, four derivatives exhibit strong ECL blue emissions. The results provide important electrochemical and ECL information of benzoxazole derivatives as well as their structure–properties relationships for future research.