DFT study of IR and Raman spectra of phosphotrihydrazone dendrimer with terminal phenolic groups

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FT Raman and infrared spectra of phosphotrihydrazone (S)P[N(CH3)NCHC6H4OH]3 (G0) were recorded. This compound is a zero generation phosphorus dendrimer with terminal phenolic groups. Optimal geometry and vibrational frequencies were calculated for G0 using the density functional theory (DFT). The molecule studied has C3 symmetry. In the molecule G0, each C6H4CHNN(CH3)P arm is flat. Optimized geometric parameters correspond to experimental data. The core of the dendrimer manifests itself as a band at 647 cm−1 in the Raman spectrum of G0 related to PS stretching. Phenolic end functions exhibit a well-defined band at 3374 cm−1 in the experimental IR spectrum of G0. The observed frequency of the OH stretching vibrations of the phenolic groups is lower than the theoretical value due to the intermolecular OH⋯O hydrogen bond. This hydrogen bond is also responsible for the higher intensity of this band in the experimental IR spectrum compared with the theoretical value. DFT calculations suggest full assignment of normal modes. Global and local descriptors characterize the reactivity of the core and end groups.