Theoretical study of classical isomers tropylium,azatropylium,phosphatropylium,and arsatropylium cations: structure,properties and aromaticity

The electronic structure and properties of the classical isomers tropylium, azatropylium, phosphatropylium and arsatropylium have been investigated using hybrid density functional B3LYP theory. Basic measures of aromatic character were derived from structure, molecular orbital and magnetic properties. Energetic criteria suggest that tropylium cation and similar hetero-systems favour conspicuous stabilisation. On the basis of the magnetic criteria, the N1, P0, As0 isomers are among the most aromatic of the family. The results showed that aromaticity decreases in C₆XH₆⁺ with increasing size of the group 15 element (X = N, P, As).