Sharif Digital Repository

In this study, drastic influence of the intramolecular cation-π interaction on the basicity of selected amines has been considered. The optimized minimum energy geometries of different studied amines and their protonated structures were determined by using DFT calculations at the B3LYP/6-311++G(d,p) level of theory. Geometry optimizations indicate that the most stable structures of protonated amines are stabilized by intramolecular cation-π interaction. The proton affinity (PA) of selected amines is controlled by the strength of intramolecular cation-π interaction of ammonium with aromatic ring. These cation-π interactions strongly influence the basicity of amines. Natural bond orbital (NBO)... 

The nature of alumazine⋯M (M = Li+, Na+, K+, Be2+, Mg2+, AND Ca2+) interactions was studied by ab initio calculations. The interaction energies were calculated at MP2/6-311++G(d,p)//B3LYP/6-311++G(d,p) level. The calculations suggest that the size and charge of cation are two important factors that affect the interaction energy, charge transfer values and the variation in aromaticity of alumazine ring upon complexation. The theory of atoms in molecules (AIM) and natural bond orbital (NBO) analyses of complexes indicate that the variation of densities and the extent of charge shifts upon complexation correlate well with the obtained interaction energies. Finally, nucleus independent chemical... 

The geometries of the complexes of Be 2+, Mg 2+, and Ca 2+ metal cations with borazine ring were studied. The complexes were optimized at the B3LYP level and the 6-311++G(d,p) basis set. Then, the interaction energies corrected by basis set super position error were calculated in the same level. The results show that interaction energy is strongly dependent on the charge-to-size ratio of the cation. Therefore, Be 2+ cation has the most interaction energy value with respect to Mg 2+ and Ca 2+ metal cations. Natural bond orbital analysis was performed to calculate the charge transfer and natural population analysis of the complexes. Quantum theory of atoms in molecules was also applied to... 

Retention of lead(II) ions on a polyamide nanofiltration membrane was investigated. Effects of different factors including operating pressure, lead ion concentration, anion nature, pH and composition of feed on the lead ion rejection were studied. The solutions used consisted of Pb(NO3)2, PbCl2 and PbSO4 in the single-salt solution system and Pb(NO3)2, Cu(NO3)2, Zn(NO3)2, Cd(NO3)2, NaNO3 and NH4NO3 in the binary-salt solution system. The influence of divalent and monovalent cations including cadmium, copper, zinc, sodium and ammonium on the rejection of lead ion was examined. The transmembrane pressure and lead ion concentration varied between 10 and 40bar and 20 and 400mg Pb2+/L,...