DFT study of structure, IR and Raman spectra of the first generation dendrimer built from cyclotriphosphazene core with terminal pyrazine groups

A phosphorus-containing dendrimer with pyrazine end groups that can be used for biological purposes has been synthesized. The vibrational spectra of the first generation dendrimer G 1 constructed from the cyclotriphosphazene core, six repeating units O C 6 H 4 –CH N N(CH 3 )–P(S) and twelve 4-oxyphenethylamidopyrazine end groups O C 6 H 4 –(CH 2 ) 2 –NH CO C 4 N 2 H 3 were registered. Analysis of the IR spectra of G 1 shows that the amide groups form an intermolecular hydrogen bond. Optimization of the structure and analysis of normal vibrations were carried out for dendrimer G 1 using the density functional theory (DFT). The six repeating units are arranged in a symmetric manner about the cyclophosphazene ring; each side of the ring contains three repeating units. It turned out that dendrimer G 1 is a double bowl with almost flat repeating units which represent the concave surface and a core as a bottom of the bowl. The assignment of bands in the vibrational spectra was carried out by analyzing the distribution of the potential energy. Amide groups show bands at 3393, 1675 cm −1 in the IR spectrum of G 1 . The line at 1577 cm −1 in the Raman spectrum is characteristic of repeating units.