Synthesis, thermal and photophysical properties of phenoxy-substituted dendrimeric cyclic phosphazenes

In the present study, we describe the synthesis of a hydroxyl substituted bridged phenoxycyclotriphosphazene (5), [N3P3(OPh)5OPhO(OPh)5N3P3OPhOH], as a side group and its use for preparation of dendrimeric cyclic phosphazenes. For this purposes, compound 5 is synthesised in five steps from the reactions of cyclotriphosphazene with phenol derivatives. The dendrimeric compounds 6 and 7 have been prepared by the reactions of compound 5 with hexachlorocyclotriphosphazene, N3P3Cl6, or octachlorocyclotetraphosphazene, N4P4Cl8, respectively. Newly synthesized compounds have been fully characterized by elemental analysis, MALDI-TOF mass spectrometry, FT-IR, 1H, 13C and 31P NMR spectroscopy. The thermal stability and fluorescence spectral properties of dendrimeric compounds 6 and 7 are investigated and compared with that of the previously reported cyclic compounds (I–II). Fluorescence quantum yields and lifetimes of dendrimeric compounds and their quenching behaviour by 1,4-benzoquinone are studied in dichloromethane.