Synthesis and spectral properties of fluorene substituted cyclic and polymeric phosphazenes

Abstract

Two new fluorene chromophores were prepared by the Suzuki cross-coupling reactions of 9,9-dimethylfluorene-2-boronic acid pinacol ester with bromophenol or 3,5-dibromophenol, respectively. The cyclic compounds were obtained by the reactions of chromophores with hexachlorocyclotriphosphazene (N3P3Cl6). For the comparison of spectral properties of cyclic compounds, the poly(bis-fluorenyl)phosphazene was also prepared from nucleophilic displacement reactions of chromophore with polydichlorophosphazene (Cl2PN)n. The synthesized compounds were characterized by standard spectroscopic methods (MALDI-TOF mass spectrometry, gel permeation chromatography for poly(bis-fluorenyl)phosphazene, FT-IR, 1H, 13C and 31P NMR spectroscopy) and their structure was confirmed by elemental analysis. The spectral properties were analysised by UV–Vis and fluorescence spectroscopy, thermogravimetric analysis, differential scanning calorimetry and cyclic voltammetry.