Theoretical Investigations On Structures And Properties Of Superatom Compounds

It is well known that the superatom chemistry age has already arrived. Superatoms have become basic units in chemistry and attracted more and more attention. The discovery of superatoms will result in the extension of chemistry periodic table and will provide a novel direction in our scientific research. The investigation on superatom chemistry will obtain compounds with novel structure, special bonding characteristics, and other extraordinary properties, and thus will promote the development of chemistry and material science. As a result, quantum chemical investigations on the geometrical structures and other physical chemistry characteristics of superatom compounds are performed in this thesis. Some conclusions that are made in the present thesis may be helpful for further theoretical and experimental studies on this topic. The main results are summarized as follows:(1) The geometries of the MBeX3 (M = Li, Na; X = F, Cl, Br) series with all real frequencies are reported using the B3LYP and MP2 methods with the 6-311+G(d) basis set. The natural bond orbital (NBO) and atom in molecule (AIM) analyses indicate the ionic character of the M–X bonds connecting the alkali atom M and the superhalogen BeX3. The introduction of a counterion M+ only slightly affects the geometry of BeX3?, but produces a more stable species. The bond energies (Eb) and vertical ionization potentials (VIP) of the MBeX3 species are obtained at the CCSD(T)/6-311+G(3df) level. These alkali–superhalogen species exhibit large Eb (130.4–222.3 kcal mol-1) and VIP values (9.46–14.05 eV) to show considerable stabilities. In addition, both Ebs and VIPs of MBeX3 are found to be closely related to the electronegativity of the X ligands and partial atomic charges.(2) The geometries of the dipole-bound LiBeX3- (X= F, Cl, Br) species with all real frequencies were optimized by the MP2 methods with the aug-cc-pVDZ+5s5p basis set. The natural bond orbital (NBO) and the highest occupied molecular orbital (HOMO) analyses indicate the excess electron"enjoys"locating on the Li atom. The vertical electron detachment energies (VDE) of the LiBeX3- (X= F, Cl, Br) species were obtained at the CCSD(T)/aug-cc-pVDZ+5s5p level. The strong dependence of the VDEs on the partial atomic charge localized on the Be atom (qBe) and the high-order contribution of electron correlation is not negligible and is responsible. In addition, the contributions of the ENreorg, VDE and ?E0vib to the EA were discussed in detail.(3) The geometries of the BX4?(X = F, Cl, Br) series with all real frequencies were optimized by the MP2 methods with the 6-311++G(d) basis set. The natural bond orbital (NBO) analyses were performed at the MP2/6-311++G(d) level. The vertical electron detachment energies (VDE) of the BX4- (X= F, Cl, Br) species were obtained at the CCSD(T)/6-311+G(3df) level. The superhalogen BX4- species exhibit large VDE values in the range of 5.372~ 8.318eV. Several factors that influence the VDEs are analyzed in this thesis.This paper enriches the knowledge of the superatom chemistry, and will give meaningful hints to future theoretical investigation and experimental research, which would open a new branch of supramolecular chemistry.