Theoretic Study On Aromaticity Of 3n(n=1, 2) Membered Rings

We mainly used the B3LYP method of DFT theory to study the aromaticity of 3n(n=1, 2) rings compounds from geometric,energetic, and magnetic aspects, and other different criteria to evaluate aromaticity were also compared.In the first section, we used geometric structure, energies magnetic criteria, magnetic susceptibility isotropic and nucleus independent chemical shifts (NICS) to evaluate aromaticity of deltic oxocarbon acid and several analogues. The result showed significant consistency of the above ECRE and NICS(0)πzz when evaluating molecules which we studied, but aromaticity stabilization energies(ASE), magnetic properties such as magnetic susceptibilities(MS), Nucleus independent chemical Shift(NICS) and Magnetic susceptibility exaltation (Λ) did not speak the same voice. The Aromaticity of three membered rings are effected by electronegativity of substitutesIn the second part, the geometries and chemical bonding of benzenes annelated to three-membered rings have been investigated by density functional theory computations with B3LYP method.The analyses of molecular orbital and nucleus·independent chemical shift for these systems revealed that there is no connection between aromatic and bond localization, and the strength of diamagnetic ring current is govered by the substituent.In the last section, we used MS and NICS, calculated with B3LYP levels at the 6-311+G(d, p) basis set, to study aromaticity of the individual six-membered rings of C4BXH5(X=NH, O, S). The results showed statistically significant correlation consistency among the above criteria. And more importantly, some conclusions drawn from this part would supply us a good reference for our further research.