Evaluation of Aromaticity NICS of The Substituted Cyclobutadiene Molecule : B3LYP Study

Aromaticity can also be considered as strength of magnetic field around the cyclic molecules is occurred when the delocalization and resonance of electrons in rings exists. In this research the optimized structures of Cyclobutadiene molecules substituted with electronegative substitutions were calculated by B3LYP method, 6-311++G(d,p) basis sets, and Gaussian03w package. After optimization the structure of rings, the NMR or the magnetic field above the rings from zero to about 3 angstrom was calculated by locating the ghost atoms in the each place (NICS). The results are very interesting and similar in all cases. The result in all molecules show that the antiaromaticity of substituted four member rings are decreases as the number of substitution atoms increases.

Keywords:

Aromaticity , NICS , Cyclobutadiene , F , CF₃ , OH and NO₂ substitutions