Synthesis and Spectroscopic Properties of Cyclotriphosphazenes Containing 6-(4-Hydroxyphenyl)-2,2′-bipyridine Side Groups

Two novel cyclotriphosphazene derivatives containing 6-(4-hydroxyphenyl)-2,2′-bipyridine (hopbp) side groups, N3P3 (dobp)2 (hopbp)2 (1) and N3P3 (dobp) (hopbp)4 (2) (dobp = 2,2′-dioxybiphenyl), were synthesized and characterized. These compounds display strong fluorescent emission both in solution and in solid state. Their absorption and emission spectra are sensitive to proton: the addition of HBF4 to the methanol and dichloromethane solution (9:1, volume ratio) of compound 1 led to a red-shift from 350 to 460 nm for the emission spectrum, and the process was also characterized by isosbestic points of absorption spectra at 267, 287 and 313 nm.