Mediated effect of substitutes on the strength of both types of hydrogen bonds formed between HNgF (Ng = He, Ar, Kr) and HCCX (X = H, F, Cl, Br, I, At, and CH3)

In this paper, three complexes of HArF and acetylene have been observed and they are combined through ArH⋯π and CH⋯F H-bonds, respectively. The former H-bond is weaker than the latter one. The F substituent in acetylene expands their strength difference, the Cl and Br substitutents attenuate their strength difference, but the I and At substituents make the former H-bond stronger than the latter one. The methyl group in propyne brings out a similar effect with the I and At substitutents but the effect is more prominent. The CH⋯F H-bond has an unmonotonic dependence on the noble atomic number and HArF forms the strongest CH⋯F H-bond. Both types of H-bonds have been analyzed with the natural bond orbital (NBO) and symmetry adapted perturbation theory (SAPT) methods.