DFT study of structure, IR and Raman spectra of dendrimer with P=N-P=S linkages and its complexation with gold

The Fourier transform IR and Raman spectra of the zero generation dendrimer G(1) with two P=N-P=S linkages and four terminal aldehyde groups have been recorded. The optimized geometry of low energy isomer of G(1) have been calculated by density functional (DFT) method at the PBE/TZ2P level of theory. DFT is used for analyzing the properties of P=N-P=S linkages. DFT results for the structure of G(1) are in good agreement with X-ray diffraction measurements. A complete vibrational assignment is proposed for different parts of G(1). 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 G(1) is higher than that of sulfur atoms and of the dendron G(2). Thus P=N-P=S linkage has a high electron density on sulfur which allows the regiospecific complexation of gold, whereas the other P=S groups do not react this way. This explains why P=N bond in P=N-P=S linkage is much more stable than isolated P=N bonds, which are easily hydrolyzed. (C) 2014 Elsevier B.V. All rights reserved.