Aromatic behaviour of benzene and naphthalene upon pnictogen substitution

A thorough study of the structural and aromatic properties of derivatives of benzene and naphthalene where one or more -CH- groups have been substituted by a nitrogen, phosphorous or arsenic atom has been carried out at B3LYP/6-311++G(d,p) level. Relative energies between isomers range from 5.0 to 294 kJ mol−1 finding the largest relative energies in compounds with nitrogen substitutions. In general, most of the compounds show to be planar with a few exceptions, which exhibit twisted structures. Wiberg bond indexes as well as bond distances indicate that in almost all the cases the bond nature is benzene-like. Aromatic characteristics have been addressed calculating NICS values, profiles, isosurfaces and HOMA indexes. NICS(1) and (2) present values close to those of benzene showing aromatic behaviour, confirmed by NICS profiles and 3D NICS isosurfaces. HOMA indexes obtained for those compounds with reported parameterized bonds are in agreement with their corresponding aromatic nature.