Effect of Noncovalent Interactions on the 31P Chemical Shift Tensor of Phosphine Oxides, Phosphinic, Phosphonic, and Phosphoric Acids, and Their Complexes with Lead(II)

Abstract

The effect of noncovalent interactions such as C–H···O and O–H···O hydrogen bonds and coordination to Pb2+ on the 31P NMR chemical shift tensor in the titled compounds has been studied experimentally and simulated theoretically using the density functional theory gauge-invariant atomic orbital (DFT-GIAO) approach. It has been shown that only in few cases the most suitable measure of these interactions is the isotropic 31P NMR chemical shift. In contrast, the analysis of the anisotropy and the principal components of the 31P NMR chemical shift tensor can be very useful to discriminate between different interactions and to characterize their properties. A great advantage is that these NMR parameters can be correctly simulated at relatively inexpensive levels of theory, namely, B3LYP/cc-pVDZ and B3LYP/6-311G**. Thus, a combination of 31P NMR and time-efficient calculations can be used to study the structural pattern in polycrystalline and noncrystalline materials. An illustrative result is the demonstration of the similarity of the unknown crystal structures of methylphosphonic acid, diphenyl hydrogen phosphate, and lead(II) methylphosphinate to the known crystal structures of tert-butylphosphonic acid, bis(4-chlorophenyl) hydrogen phosphate, and lead(II) vinylphosphonate, respectively. The scope of this approach is wide and covers the study of the local chemical structures in amorphous materials, at surfaces and interfaces.