DFT study of Raman spectra of hexakis(4-N′(-di(4-oxyphenethylamino)-(thio)phosphonyl)-N′-methyl-diazobenzene)cyclotriphosphazene

• The FT-Raman spectrum of dendrimer was studied.
• The structural optimization and normal mode analysis were performed.
• Dendrimer molecule has a concave lens structure.
• The Raman spectrum of dendrimer was calculated and interpreted.

The FT-Raman spectrum of the hexakis(4-N′(-di(4-oxyphenethylamino)-(thio)phosphonyl)-N′-methyl-diazobenzene)cyclotriphosphazene which is the first generation dendrimer G1 built from the cyclotriphosphazene core, six arms OC6H4CHNN(CH3)P(S) and twelve 4-oxyphenethylamino terminal groups OC6H4(CH2)2NH2G1 has been recorded. The structural optimization and normal mode analysis were performed for model compound C, consisting of cyclotriphosphazene core, one arm OC6H4CHNN(CH3)P(S) and two 4-oxyphenethylamino terminal groups OC6H4(CH2)2NH2 on the basis of the density functional theory (DFT) at the PBE/TZ2P level. The calculated geometrical parameters and harmonic vibrational frequencies are predicted in good agreement with the experimental data. It was found that G1 has a concave lens structure with planar OC6H4CHNN(CH3)P(S) fragments and slightly non-planar cyclotriphosphazene core. The 4-oxyphenethylamino groups attached to different arms show significant deviations from a symmetrical arrangement relative to the local planes of repeating units. The experimental Raman spectra of G1 dendron was interpreted by means of potential energy distribution. Relying on DFT calculations, as well as on experimental information, a spectral interpretation was proposed.

Theoretical curve for model C (1) and experimental (2) Raman spectra of G1 in the region 1800–400 cm−1.Figure optionsDownload as PowerPoint slide