Hydrogen-bridge Si(μ-H)3CeH and inserted H3SiCeH molecules: Matrix infrared spectra and DFT calculations for reaction products of silane with Ce atoms

Charge-Inverted Hydrogen-Bridged Bond in HCa(μ-H)3E (E = Si, Ge, and Sn): Matrix Isolation Infrared Spectroscopic and Theoretical Studies

Matrix isolation infrared spectroscopy combined with quantum-chemical calculations were employed to study the reactions of calcium atoms with silane, germane, and stannane in a 4 K argon matrix. The ion pairs [HCa]⁺ and [EH₃]^- (E = Si, Ge, and Sn) in both the classical structure HCaEH₃ and the bridged structure HCa(μ-H)₃E were identified based on the H/D isotopic substitution experiments and quantum-chemical calculations. The results show that the reaction between ground-state Ca and EH₄ proceeds inefficiently, and only after the photolytic activation of Ca atoms to the Ca(¹P:4s4p) state does insertion occur to give HCaEH₃, which rearranges to HCa(μ-H)₃E upon photolysis. Topological analysis of the electronic structure suggests that the nonclassical structure HCa(μ-H)₃E is formed by the electrostatic interaction with charge-inverted hydrogen bridge bond, while HCaEH₃ is dominated by (HCa)⁺(EH₃)^- ion pair interactions.

Reaction mechanism between small-sized Ce clusters and water molecules II: an ab initio investigation on Cen (n = 1-3) + mH2O (m = 2-6)

Possible reactions between the products of the three independent reactions involving a small Ce cluster and a single water molecule, Cen + H2O (n = 1-3), and an additional H2O molecule are systematically investigated. The ground-state isomers of the final products and the reaction pathways involving multiple water molecules are predicted. We find that under either ambient or UV-irradiation conditions, all the reactions can entail low energy barriers. In addition, the final products of the reaction between Cen and more than two H2O molecules are also predicted through an extensive structural search. The calculated reaction energies suggest that although small-sized Ce clusters can react with more than two water molecules, the reactions with one or two water molecules are dominant. The electronic structures of all the ground-state isomers and the corresponding oxidation states of Ce atoms in these isomers are computed and determined via the natural bond orbital (NBO) method. The results indicate that a single Ce atom and a Ce2 cluster can react with a maximum of four and six water molecules, respectively, while a Ce3 cluster can react with more than six water molecules. This comprehensive study offers an improved understanding of the mechanism underlying the reactions between a single Ce atom or a small Ce cluster and two or more H2O molecules. Knowledge obtained from this study can be helpful for the development of high-performance Ce-doped or Ce-based catalysts.

Reaction mechanism between small-sized Ce clusters and water molecules: an ab initio investigation on Cen + H2O

Reactions of small-sized cerium clusters Cen (n = 1-3) with a single water molecule are systematically investigated theoretically. The ground state structures of the Cen/H2O complex and the reaction pathways between Cen + H2O are predicted. Our results show the size-dependent reactivity of small-sized Ce clusters. The calculated reaction energies and reaction barriers indicate that the reactivity between Cen and water becomes higher with increasing cluster size. The predicted reaction pathways show that the single Ce atom and the Ce2 and Ce3 clusters can all easily react with H2O and dissociate the water molecule. Under UV-irradiation, the reaction of a Ce atom with a single H2O molecule may even release an H2 molecule. The reaction of either Ce2 or Ce3 with a single H2O molecule can fully dissociate the H2O into H and O atoms while it is bonded with the Ce cluster. The electronic configuration and oxidation states of the Ce atoms in the products and the higher occupied molecular orbitals are analyzed by using the natural bond orbital (NBO) analysis method, from which the high reactivity between the reaction products of Cen + H2O and an additional H2O molecule is predicted. Our results offer deeper molecular insights into the chemical reactivity of Ce, which could be helpful for developing more efficient Ce-doped or Ce-based catalysts.