The topology of the charge distribution of the silanol-thiophene van der Waals complex: ab initio and DFT study

This work reports a quantum-chemistry SCF-MO ab initio study of the topolog y of charge distribution of the silanol-thiophene van der Waals molecular c omplex, by using the Hatree-Fock method, perturbation theory at the second level MP2, and density functional theory at the BLYP level. The geometry of the isolated species and the corresponding complexes were fully optimized at each level of theory by using the standard STO/6-31+G(d,p) basis set. Cs symmetry was used for the molecular geometry of silanol and the complex, a nd C(2)v for thiophene. The geometric, electronic and vibrational results a re compared with previous calculations for the silanol-H2S molecular comple x. The nature of the chemical interactions that lead to the formation of th e silanol-thiophene complex is analyzed in terms of the topologic propertie s of the linear conformation. This model reproduces the experimental predic tion from the FT-IR adsorption spectra of thiophene in H-ZSM5 zeolites. (C) 2000 Published by Elsevier Science B.V.