IR spectroscopy and DFT study of phosphorus-containing G2 generation dendrimer

The IR spectra of second generation dendrimer G2 has been recorded in the region 3500-350 cm−1. The optimised molecular geometry, frequency and intensity of IR bands of G2 have been computed using the density functional theory (DFT) methods. The geometrical parameters and harmonic frequencies, dipole moment, band intensities in the IR spectra of G2 are predicted in a reasonable agreement with experimental data. It was found that the molecule exists in a single stable conformation with planar OC6H4CHNN(CH3) fragments. All these observations suggest that steric congestion does not disturb the construction of dendrimers even for the highest generations, and that terminal groups are readily available for further reactions. Relying on DFT calculations a complete vibrational assignment is proposed for different parts of the studied dendrimer. IR spectroscopy combined with DFT computation provides unique detailed information about the structure of the technologically relevant materials, which could not be obtained before with any other technique.