Abstract
Although HNgCCX (Ng = Kr and Xe; X = F and Cl) have been identified in cryogenic matrices, similar Br and I analogues have not been prepared so far. In this paper, the nature of HNgCCX (Ng = Kr and Xe; X = F, Cl, Br and I) have been investigated by ab initio methods. The main characteristic absorption peak of HNgCCX is the vH-Ng, which decreases as X varies from F to I. Moreover, the H-Xe bond is stronger than the H-Kr bond. The vC≡C and vC-X exhibit red- and blue-shift characters, respectively, especially the C-X bond is abnormal blue-shift halogen bond. AIM results show that the H-Ng bond is essentially covalent bond and the covalent character of H-Xe bond is underestimated, and the trend of the covalent character is C-Cl > C-Br > C-F > C-I. Although HNgCCX is instable thermodynamically with respect to Ng + HCCX, it is kinetically stable with respect to the two-/three-body channels due to the relatively larger energy barriers. The three-body channels of HNgCCX is the main decomposition channel, and the kinetically stability of HXeCCX is more than its Kr analogues. This study is helpful for the preparation of new HNgCCX in cryogenic matrices.
Highlights
HNgCCX (Ng = Kr and Xe; X = F and Cl) have been identified in cryogenic matrices, similar Br and I analogues have not been prepared so far
The focuses of our attention are whether HNgCCX (Ng = Kr and Xe; X = Br and I) are enough stable to be prepared and identified experimentally, and what are the differences in the nature of bonding and spectra among HNgCCX molecules? we hope that this study will be helpful for the preparation of HNgCCX (Ng = Kr and Xe; X = Br and I) molecules in cryogenic noble-gas matrices
(1) The vH-Ng with the highest intensity is the characteristic absorption peak of HNgCCX, and decreasing of vH-Ng illustrates that the has been generally considered to (H-Ng) bond is weakened as X varies from F to I. the H-Xe bond is stronger than the H-Kr bond due to the higher vH-Xe
Summary
Previous works proved that no HCCNgX were observed in cryogenic noble-gas matrices there are two possible reactive sites in HCCX (H-C and C-X bonds) for the insertion of Ng atoms. HNgCCX is expected to be higher stable than the corresponding HNgCCH due to the higher H-Ng stretching frequency These studies intrigued our interests in the halogenated organic noble-gas molecule HNgCCX (Ng = Kr and Xe; X = F, Cl, Br and I). Since HNgCCX (Ng = Kr and Xe; X = F and Cl) have been identified by cryogenic matrix isolation technique combined with quantum chemical calculations, similar Br and I analogues are expected to be enough stable to www.nature.com/scientificreports/. We hope that this study will be helpful for the preparation of HNgCCX (Ng = Kr and Xe; X = Br and I) molecules in cryogenic noble-gas matrices
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