DFT study of structure, IR and Raman spectra of dendrimer with P[dbnd]N[sbnd]P[dbnd]S linkages and its complexation with gold

Abstract

The Fourier transform IR and Raman spectra of the zero generation dendrimer G1 with two PNPS linkages and four terminal aldehyde groups have been recorded. The optimized geometry of low energy isomer of G1 have been calculated by density functional (DFT) method at the PBE/TZ2P level of theory. DFT is used for analyzing the properties of PNPS linkages. DFT results for the structure of G1 are in good agreement with X-ray diffraction measurements. A complete vibrational assignment is proposed for different parts of G1. The global and local reactivity descriptors have been used to characterize the reactivity pattern of the core function and terminal group. Natural bond orbital (NBO) analysis has been applied to comparative study of charge delocalization. Our study reveals that the softness and electrophilicity of sulfur atom in the core of the dendrimer G1 is higher than that of sulfur atoms and of the dendron G2. Thus PNPS linkage has a high electron density on sulfur which allows the regiospecific complexation of gold, whereas the other PS groups do not react this way. This explains why PN bond in PNPS linkage is much more stable than isolated PN bonds, which are easily hydrolyzed.