Study of three-dimensional configurations of organic/inorganic hybrid nanostructural blocks:: A quantum chemical investigation for cage structure of (γ-glycidoxypropyl)silsesquioxanes

(gamma-Glycidoxypropyl)silsesquioxanes (GSSO) were prepared from the hydrolytic condensation of (gamma-glycidoxypropyl)trimethoxysilane (GPMS) in the presence of an acid catalyst (HCOOH). The proposed GSSO structures were characterized with FTIR and NMR (H-1, C-13 and Si-29), and were assigned by UV-MALDI-TOF MS along with the molecular mass increase after the opening of the epoxy rings. The large organic group connected to silicon was simplified for the quantum chemical calculation (QCC), and the correlation of the calculated total energies (E-T) before and after simplification was analyzed by multiple linear regression, verifying no significant influence on the final conclusions of the research of structural formulas. The geometric parameters (Si-O bond length and Si-O-Si, O-Si-O bond angle) and E-T of the simplified GSSO were calculated by QCC to determine the relative stability of various SSO structures. The structural geometry (m-silicon ring) and the fraction of intramolecular cycles W were also employed to qualitatively determine the relative stability. The results of the calculation showed that almost all of the cage structures had a lower E-T than the isomeric ladder structures; therefore, most GSSO molecular structures are of the cage type. (c) 2007 Elsevier B.V. All rights reserved.