Noble gas induced surprisingly higher stability of π hydrogen bonded complex: comparative study of hydrogen bonded complexes of HKrCCH and HCCH with H2O, NH3, CH3OH and CH3NH2

Abstract

Structure, energetics and spectroscopic properties of hydrogen bonded complexes of HKrCCH with H₂O, NH₃, CH₃OH and CH₃NH₂ have been explored as well as compared with the hydrogen bonded complexes of its precursor HCCH. The most stable structure for HKrCCH is the π (O/N–H⋯π) hydrogen bonded complex, whereas the σ (C–H⋯O/N) hydrogen bonded complex is most stable for HCCH. Surprisingly, the stabilization energy of the π hydrogen bonded complex of HKrCCH is about two to three fold higher compared to the σ hydrogen bonded complex of HCCH, which is in contrast to the general perception that the strength of π hydrogen bond is less compared to σ hydrogen bond. From the atom in molecule and charge analyses, it has been found that π hydrogen bonded complexes of HKrCCH have a cyclic structure in which O/N–H⋯π hydrogen bonding takes place along with Kr⋯O/N interaction. Higher stabilization energy of the π hydrogen bonded complex of HKrCCH is due to a cooperative phenomena in which Kr⋯O/N interaction contributes to the formation of a strong O/N–H⋯π hydrogen bonding.