Raman spectroscopy studies of phosphorus dendrimers with phenoxy and deuterophenoxy terminal groups

Abstract

The FT-IR and FT–Raman measurements of 6 generations of phosphorus dendrimers G′ci built from cyclotriphosphazene core with phenoxy and deuterophenoxy terminal groups have been performed. Spectra of dendrimers depends on the ratio of end groups and repeated units. This ratio tends to be r–1 (r – functionality of repeated unit), and becomes constant, when the generation number is above 3. Experimental Raman spectra of generations of dendrimers are very closely similar in accordance with the theory. Structural optimization and normal mode analysis were obtained for G′c1 by the density functional theory (DFT). Calculations have shown that each OC6H4CHNN(CH3) moiety is flat and six repeating units are located above and below the nearly flat cyclotriphosphazene ring. Optimized geometric bond length and angles obtained by DFT show good agreement with the experiment. The phenoxy terminal groups are characterized by the well-defined line at 1008cm−1 in the experimental Raman spectrum of G′c1-H and by line at 968cm−1 in the Raman spectrum of G′c1-D. The medium-intensity line in the Raman spectra of G′c1-H and G′c1-D at 1576cm−1 refer to the repeating units vibrations.