Theoretical study of the structural,vibrational,and topologic,properties of the charge distribution of the molecular complexes between thiophene and bronsted acid sites of zeolites

摘要

The main interaction between thiophene and zeolites leads to the formation of a hydrogen bond between the S atom of thiphene and the OH group of zeolites,giving 1:1 stable molecular complexes.The present work reports a theoretical study about the structural,vibrational,and topoligic properties for the charge distribution of the molecular complexes between thiophene and a series of Bronsted acid sites of zeolites,modeled as the H_3SiOHAlH_3(B_1),(OH)_3Si(OH)Al(OH)_3(B_1OH),and H_3Bi(OH)Al(OH)_2OSiH_3(B_2)clusters.The studied properties were calculated at a Hartree-Fock level with the standard 6-31+G(d,p)basis set.Additionally,electron correlation effects for geometric and vibrational properties were evaluated at second-order M#PHI#ller-Plesset(MP2)and BLYP for B_1-thiophene complex,whereas the BLYP technique was employed for the complexes of thiophene with B_1OH and B_2 clusters.Symmetry restriction was considered for structure calculations,being C_(2v) for thiophene,C_s for zeolite clusters,and C_s linear conformationf or the complexes.It was found that these liear thiophene-zeolite complexes reproduce the tendencies in the experimental frequency shifts of the OH vibration mode from the adsorption of thiophene in ZSM5 zeolites.The topologic properties fo the complexes give a pattern for the interaction of thiophene-zeolite.The results are compared with previous ones from silnol-thiophene calculations.