Theoretical Study On The Structure And Stability Of [Be, N, C, X] (X=O, S) Isomer

In recent years,the construction of Be-X(X=C,N,O)multiple bonds has attracted the attention of many scientists.Beryllium is a relatively special s-block metal element.Comparted to other alkali and alkaline earth metals,its bonding nature is more complex because of its relatively high electronegativity.Theoretically,it can form classical electron-sharing covalent bonds,σ-and/or π-donation dative bonds,electrostaticinteraction-based highly polar covalent and ionic bonds,2p-based multicenter σ-and πbonds.However,in most of molecules,the bonding nature involves the cooperation of various bonding pattern,which is very favorable for the formation of highly thermodynamical stable Be-bearing molecules and is helpful for deeply understanding the bonding nature of Be-bearing bonds.The neutral molecular systems,[Be,N,C,X](X=O,S),are typical metal/nonmetallic mixed systems,which includes not only the s-block metal element Be with the most typical and complex bonding pattern,but also the most common N,C,and O atoms in the second period and the S atom in the third period,which were the most often used in constructing molecules.Furthermore,the two small molecular systems can reflect the various bonding modes of Be,and further can represent the thermodynamically favorable metal-nonmetal reactions based on a certain degree of electronegativity difference.These reactions involve the-NC,-CN,-NCX(X=O,S),-XNC(X=O,S),and-XCN(X=O,S)groups,which were often used to prepare new molecules.In addition,the ground states of the diatomic molecules formed by the combination of O and S atoms with Be are in electronic singlet state,which may result in the products,BeO and BeS,to be strong Lewis acids due to a closed-shell effect.Therefore,they may form stable molecules with-NC or-CN connected with Be.In this study,we conducted a detailed theoretical study of the neutral molecular systems of[Be,N,C,X](X=O,S),in which the dependence of the structures of isomers on theoretical methods and computational levels were discussed.Furthermore,the thermodynamical and kinetic stabilities of the optimized isomers are evaluated using the constructed reaction potential energy profiles.For the kinetically stable isomers,we employed the methods of electronic structure analysis,involving electron density difference,topology analysis of chemical bonds,the Laplacian of electron density,electrostatic potential,and electron localization function,to analyze the bonding nature and electrostatic potential distribution.In addition,we also used high-level computational methods to analyze the anharmonically vibrational and rotational spectrum constants of kinetically stable isomers,as well as some important molecular constants.These data and conclusions provide the most basic information and support for future laboratory synthesis and spectral characterization of the kinetically stable[Be,N,C,X](X=O,S)isomers.