Theoretical Investigation On Resonance Bonding And High-energy Properties Of Noble-gas Hydrides

Noble gases had been considered to exist only as monatomic molecules and not as compounds.However,in 1962,Bartlett first synthesized the noble-gas compound Xe⁺?PtF6?^-containing xenon atoms.Soon after,researchers extended to krypton's noble gas chemistry.In 2000,Khriachtchev successfully prepared and characterized the noble gas hydride HArF in a low temperature matrix.The studies on noble gas chemistry again become a hot topic.So far,more than 30 noble-gas hydrides have been characterized experimentally.These findings provide an opportunity for people to study the bonding of noble gas atoms.Additionally,noble-gas hydrides are potential high-energy materials because they are highly exothermic.In recent years,researchers have successfully prepared and characterized many kinds of inorganic and organic noble-gas hydrides.But the bonding of this kind of molecules,and the relationship between their exothermic and their bonding,are not fully understood.This thesis mainly studied the resonance bonding,Charge-Shift bonding,long bonds and the relationship between long bond orders and high-energy properties of noble-gas hydrides.Serveal innovative results are obtained.The main achievements of this study are divided into three categories.1.We chose HNgCCX?X=H,F,Cl,Br,I,C₆H₅?as research sytems.By using Natural Bonding Orbital?NBO?and Natural Resonance Theory?NRT?methods,we find that HNgCCX molecule is considered as the hybid of three structures:H-Ng^+-:CCX,H:^- Ng⁺-CCX and H^CCX.Moreover,long bond order is well correlated with the two-body dissociation energy of studied molecules.This finding is consistent with the result obtained previously.By comparing the organic noble-gas hydrides with the inorganic noble-gas hydrides,we find that both kinds of hydrides are resonance bonding,and that it is composed of three kinds of resonance structures.2.Some xenon hydrides HXeY?Y=Cl,Br,I?and their hydrogen-bonded complexes HXeY…HX?Y=Cl,Br,I;X=OH,Cl,Br,I,CN,CCH?have been identified in matrixes by observing H-Xe frequencies or its monomer-to-complex blue shifts.However,the H-Xe bonding in HXeY is not yet completely understood.Previous theoretical studies provide two answers.The first one holds that it is a classical covalent bond,based on single ionic structure H-Xe⁺Y^-.The second one holds that it is resonance bonding between H-Xe⁺Y^- and H^-Xe⁺-Y.This study investigates the H-Xe bonding,via unusual blue-shifted phenomena,combining with some NBO/NRT calculations for chosen hydrogen-bonded complexes HXeY…HX?Y=Cl,Br,I;X=OH,Cl,Br,I,CN,CCH?.New insights into the H-Xe bonding in HXeY are provided.The H-Xe bond in HXeY is not a classical covalent bond.It is a new class of electron-pair bonds,to be specific,a Charge-Shift?CS?bond,which is proposed by Shaik and Hiberty et al in 1992.The unusual blue shift in studied hydrogen-bonded complexes is the H-Xe CS bonding character in IR spectroscopy.Additionally,these studies on the H-Xe bonding and its IR spectroscopic property might assist the chemical community understanding this new-class electron-pair bond concept.3.Recently,positive ions formed by beryllium with noble gases and halogen atoms have been observed in experiment.By the study of NgBeX⁺?Ng=He,Ne,Ar,Kr,Xe,Rn;X=F,Cl,Br,I?,it is found that NgBeX⁺is composed of two resonance structure(Ng:^-Be⁺-X⁺?Ng-Be²⁺X:^-)and a classic covalent structure?Ng-Be⁺-X?.This finding indicates that beryllium atoms as the main group of electron-deficient atoms can provide vacant orbitals to bonding with other atoms,just like some transition metal atoms.Such findings open a new direction for the study of catalyst materials.