A study on the aromaticity and magnetotropicity of 10π-electron azapentalene derivatives

Using toplogical resonance energy and the magnetic resonance energy methods, we examined the aromaticity of those 3a-azapentalene derivatives which have only nitrogen as ring heteroatoms. The local aromaticity of two five-membered rings was studied using bond resonance energy, circuit resonance energy, and ring current (RC) methods. We found that the five-membered rings which contain the –NH– group exhibit less local aromaticity than the adjoining five-membered rings which do not contain the –NH– group. In respect to individual rings, the distributions we obtained of large diatropic RC values are consistent with the nucleus-independent chemical shift values.