Experimental and theoretical investigations of novel synthesized organo-silane compounds and modified mesoporous silica materials

In this study, the novel compounds (2,5-dimethoxy-methanimine propyltriethoxysilane; S1 and 3-ethoxy-salicylaldimine propyltriethoxysilane; S2) derived from aminopropyltriethoxysilane (APTES) were synthesized by a simple and facile approach in order to modify mesoporous silica (MS) surface. Characterization of S1 and S2 was experimentally performed by FTIR, 1H13C NMR spectroscopic methods and elemental analysis. The IR frequencies, 1H and 13C NMR chemical shift values for the optimized molecular geometries of S1 and S2 were calculated by using Density Functional Theory (DFT with B3LYP/6-311 + G (d, p) basis set), and the theoretical results were compared to the obtained experimental data. The experimental and theoretical results confirmed the proposed molecular structures of the synthesized S1 and S2 compounds. After that, the mesoporous silica material (MS) was synthesized according to the Stöber procedure, and characterized by the elemental analysis, and the experimental and theoretical IR spectra. The surface of MS was successfully functionalized with S1 and S2 to produce more selective and effective adsorbent materials, and the structures of functionalized MSs (S1-MS and S2-MS) were investigated with FTIR spectroscopy and elemental analysis. The theoretical optimized molecular geometries, IR frequencies and 1H13C NMR chemical shift values were calculated to execute the structural analysis of S1-MS and S2-MS. In addition, the calculations of the sum of electronic and thermal free energy (SETFE), dipole moment, the HOMO-LUMO energies, the molecular electrostatic potential (MEP), the solvent accessible surface (SAS) and atomic charge for the synthesized S1, S2, MS, S1-MS and S2-MS were accomplished by using DFT/B3LYP/6-311 + G (d, p) level of theory.