Influence of substituents on CH-π interactions in complexes involving X-acetylene and planar cyclooctatetraene

NMR properties of the CH-π interactions in the X-C2H┴C8H8 complexes (where ┴ denotes CH-π interaction and X = NH2, OH, H, F, NO2, and CN) have been investigated at the M05-2X/6-311++G** level of theory. Correlations of geometrical parameters, Hammett constants, results of atoms in molecules (AIM) analysis, charge transfer (CT) and NMR data, particularly two-bond 13C-1H spin-spin coupling constant 2hJC-H, with binding energies were considered. The binding energies of these complexes were also compared with the X-C6H5┴C8H8 complexes to explore the role of acidic hydrogen of acetylene on binding energies. The results of this study aid us to better realize the nature of the CH-π interactions in complexes which encompass planar cyclooctatetraene as an anti-aromatic molecule.