Non-bonded intra-molecular interactions in 1,8-disubstituted naphthalenes with a cyano group as the electrophilic substituent

Ab initio, self-consistent field, molecular-orbital, calculations were carried out for two 1,8-disubstituted naphthalene compounds to probe non-bonded, intra-molecular, interactions between electrophilic and nucleophilic substituents located at the 1 and 8 positions of the naphthalene rings. The cyano (-C≡N) group is the electrophilic substituent; the cyano carbon atom is the electrophilic center. The nucleophilic substituents were each, a nitro (-NO₂) group in compound I, and a methoxy (-OCH₃) group in compound II. The X-ray structure showed that the nitro-nitrile compound existed as two distinct structures, each with different bond distances and bond-angles of the peri substituents. We probed the nature of intra-molecular interactions in these compounds by calculating the electronic charges and molecular electrostatic potentials adjacent to the substituents. Similar studies for carbonyl group as the electrophilic substituent indicated the presence of electronic interactions for naphthalene compounds with the carbonyl group as the electrophilic substituent.