Theoretical Study On The Structures And Properties For Organic Compounds With Rare Gas Elements

The extreme chemical inertness of rare gas atoms is attributable to the remakable stability of the closed-shell electronic configuration. The birth of the field of rare-gas chemistry can be attributed to the discovery of Xe(Pt F6)n(1≤n≤2), the first compound of Xe. To rare-gas nonmetallic compounds, rare-gas hydrides(HRg Y) are of great importance. At present, a number of experimental and theoretical studies have attracted much attention at home and abroad. Now about twenty eight members are prepared in rare-gas matries. HRg Y can be divided into two categories, organic rare-gas hydrides and inorganic rare-gas hydrides. In previous studies, the researches on inorganic rare-gas hydrides are more than organic rare-gas hydrides. In addition, the studies of organic hydrides mainly focus on alkynes and their derivatives. Quantum chemistry plays an important role in predicting new rare gas hydrides and their properties. The calculated frequencies and infrared intensities can serve as experimental fingerprints for identifying these compounds. In this work we report a computational study of structure, stability and bonding of the organic rare gas hydrides(Rg=Ar, Kr, and Xe). At the same time, the influence of different functional group is investigated. The contents are as follow:1) The equilibrium structures, harmonic frequencies, decomposition reaction pathways, and energetics of HXe C2H5, HXe C2H3, and HXe CCH were studied by ab initio calculations. NBO analysis was also carried out. Among these three compounds, HXe CCH is the most stable one. The theoretical results strongly suggest that HXe C2H3 is an excellent candidate for experimental observation. The stability of HXe C2H3 is attributed to its ionic character and the electron delocalization of LP(Xe) → π*(C–C).2) As an extension of the HRg Y family from hydrocarbons to carboxylic acid, we have investigated the equilibrium structures, harmonic frequencies, and stabilities of HCOORg H(Rg=Ar, Kr, and Xe) using the MP2/aug-cc-p VTZ(aug-cc-p VTZ-PP) method. There are two structural isomers for each HCOORg H molecule, i.e., trans- and cis-configurations, based on the position of the hydrogen atom. trans-HCOORg H(Rg=Ar, Kr, and Xe) is more stable than cis-HCOORg H. The calculations suggested that the compounds containing Kr and Xe are metastable and could be observed in matrix isolation experiments using the fingerprint of the H–Rg stretching mode. In contrast, the argon derivatives are rarely observed in experiments due to their thermodynamic instability relative to the three-body decomposition products. NBO, NPA, NHO, NRT, MO and AIM analyses further confirmed that H–Rg bonds are definitively covalent interactions, and Rg–O bonding is mostly attributed to the electrostatic force. Besides, the electron delocalization of LP(O)→σ*(H-Rg) plays an important role in the Rg–O bonding.3) Additionaly, CH3 COORg H(Rg = Ar, Kr, and Xe) were examined by the same methods and basis sets with HCOORg H(Rg=Ar, Kr, and Xe). The calculated results indicate that the stability of CH3 COORg H compounds increases with the order of Rg=Ar, Kr, and Xe, respectively. The Kr- and Xe-derived compounds could be possibly prepared in experiments. The electron delocalization of LP(O)→σ*(H-Rg) make these compounds are more stable.4) Based on HCOORg H and CH3 COORg H(Rg=Ar, Kr, and Xe), herein the optimized geometries, harmonic frequencies, and decomposition pathways of C2H3 COORg H(Rg=Ar, Kr, and Xe) were examined by using MP2/AVTZ calculations. Two con?gurations(i.e., isomers A and B) were identi?ed and denoted as s-cis syn and s-cis anti structures. The two structures have similar energies and properties. The barriers for isomerization of s-cis syn into s-cis anti are also small. The presented study suggests that the Kr- and Xe-derived compounds are metastable species and could be possibly prepared in matrixisolation experiments. In contrast, the argon derivative of acrylicacid is thermodynamically unstable and is therefore unlikely to be observed experimentally. NBO, NEDA, and AIM analyses provide evidence that the H-Rg bonds of the C2H3 COORg H compounds are covalent interactions, whereas the bonding within the Rg-O bond is mainly attributed to ionic forces. The donor-acceptor interaction, i.e., LP(O)→σ*(H-Rg) and π(C=C) → π*(C=O) is also important. Indeed, increasing the size of the molecule have negligible effects on the H-Rg-O group specifics.