Structure of organic-inorganic hybrid low-melting glasses from Si NMR and ab initio molecular orbital calculations

The structure of organic-inorganic hybrid glass precursor Me₂Si(OPO(OH)₂)₂ and low-melting glasses SnO-Me₂SiO-P₂O₅ has been examined by ²⁹Si static and MAS NMR, respectively. The ²⁹Si MAS NMR spectra of SnO-Me₂SiO-P₂O₅ were deconvoluted into three Gaussian peaks, whose chemical shifts were located at −3.1, −10.2 and −18.1 ppm. Ab initio molecular orbital calculations have also been carried out for the clusters modeling the structure of precursor and glasses. From the calculations of ²⁹Si NMR shielding constants, the experimental chemical shifts at −10.2, −3.1 and −18.1 ppm were assigned to ²⁹Si atoms in P-O-Si(Me)₂-O-P network linkage, in P-O-Si(Me)₂-OH terminating structure and in P-O-Si(Me)₂-O-Si network linkage, respectively. Based on the area ratio of the assigned three peaks, the network structures around Si constructing SnO-Me₂SiO-P₂O₅ low-melting glasses were discussed in detail.