The interaction strengths and spectroscopy parameters of the C2H2∙∙∙HX and HCN∙∙∙HX complexes (X = F, Cl, CN, and CCH) and related ternary systems valued by fluxes of charge densities: QTAIM, CCFO, and NBO calculations

Abstract

This theoretical work exhibits a new systematic study of structural parameters, electronic properties, infrared vibration modes, and molecular topography of hydrogen complexes, namely linear-type HCN⋯HX and T-type CH⋯HX (X = F, Cl, CN, and CCH). Ideally, the knowledge of the ternary systems of CH⋯HCN⋯HF and HCN⋯HCN⋯HF whose subparts integrate the linear and T-shaped complexes were used to give support in this current research. By means of computational calculations carried out in both levels B3LYP and MP2, the variations of the HX bond lengths are clearly overestimated in the HCN⋯HX linear complexes. In agreement with the analyses of the electrostatic potentials, the higher intermolecular energies of these complexes agree with the larger red-shifts in the stretch frequencies in HX. Also, the QTAIM descriptors and NBO calculations were used to inspect the interaction strength as well as to confirm the π cloud as a proton accepting center. By taking into account the absorption intensity ratio as a standard parameter to predict the interaction strength and intermolecular characterization, the formalism of the charge-charge flux-overlap modified (CCFO) was applied.

Characterization of Competing Halogen- and Hydrogen-Bonding Motifs in Simple Mixed Dimers of HCN and HX (X = F, Cl, Br, and I)

“…Other hydrogen halides can also participate in analogous HB interactions with HCN. The linear HCN···HX configuration in which the hydrogen halide is the HB donor has been detected in the gas phase for X = Cl, Br, and I − and has also been characterized in a number of computational studies using quantum mechanical electronic structure techniques and other theoretical models. − To the best of our knowledge, the reversed HB arrangement where HCN is the HB donor (i.e., the HX···HCN configuration) has not been observed experimentally for X = Cl, Br, or I, and it has only been studied computationally for X = Cl. , …”