IR spectroscopy investigation using DFT analysis on the structure of P1 phosphorus dendrimer built from octasubstituted metal-free phthalocyanine core

The IR spectra of P1 phosphorus dendrimer built from an octasubstituted metal-free phthalocyanine core have been recorded in the region 4000–400 cm−1. Besides the phthalocyanine core, P1 possess also eight C6H4–CHN–N(CH3)–P(S) arms and terminal P–Cl groups. The optimized molecular geometry, frequency and intensity of the IR bands have been calculated using density functional theory (DFT). The P1 molecules exist in a stable conformation with planar C6H4–CHN–N(CH3)– fragments and phthalocyanine core. The calculated geometrical parameters and harmonic vibrational frequencies are predicted in a good agreement with the experimental data. The experimental IR spectrum of P1 dendrimer was interpreted by means of potential energy distributions. Relying on DFT calculations a complete vibrational assignment is proposed. The difference IR spectra of molecules built from the thiophosphoryl, cyclotriphosphazene, and phthalocyanine cores with the same repeated units and terminal groups were studied in order to undermine the role of the core functionality on the dendrimer architecture.