Regiochemical influences on dipole-driven hydrogen bonding in cyanoacenaphthylene complexes: A theoretical insight

A detailed investigation of hydrogen bonding interactions in acenaphthylene based polycyclic aromatic hydrocarbons, including the parent C 12 H 8 and cyano substituted derivatives of acenaphthylene (1-, 3-, 4-, and 5-C 12 H 7 CN), with proton donors, H 2 O, HCl, HCN, NH 3 , and C 2 H 2 , has been carried out. These systems have shown various types of hydrogen bonding interactions, such as N ⋯ H-O, N ⋯ H-Cl, N ⋯ H-C and N ⋯ H-N, where nitrile acts as proton acceptor. Among the proton donors, HCl has shown comparatively stronger hydrogen bonding interaction. Among nitriles, the 1-cyano substituted acenaphthylene has shown comparatively better interaction with H 2 O, HCl, HCN and C 2 H 2 , possibly due to the enhanced electron delocalisation within non-Huckel π -system. To investigate these interactions, we examined geometrical features, complexation energies and changes in the vibrational frequencies. QTAIM was used to calculate the electron density [ ρ ( r c ) ] and Laplacian values [ ∇ 2 ρ ( r c ) ] at bond critical points, which provide information on bond character and bond strength. The results can help to explain the impact of substituents on hydrogen bonding and molecular stability.