title: Theoretical investigation on the dimerization of the deprotonated aquo ion of Al(III) in water.
abstract: Reaction pathways, solvent effects and energy barriers have been investigated for the dimerization of the deprotonated aquo ion of Al(III) in aqueous solution by performing supramolecule density functional theory calculations. Two competing reaction pathways were investigated, sharing a common first step and third step, i.e. the formation of the aggregate II of two aluminium monomers and the doubly bridged dimer. One pathway involves a nucleophilic attack to undercoordinated metal center in the first step and then the loss of a coordinated water molecule. Another pathway involves a water exchange reaction in the first step and then the formation of the hydroxo bridge. The calculated results indicate that both pathways I and II are possible in aqueous solution. The direct participation of the solvent water molecule facilitates the dimerization, but the extremely large solvent shifts of the energy barriers for each reaction are attributed mainly to the bulk effect. The computed activation energies for the water exchange reactions are in good agreement with the available experimental values, namely, the calculated value 37.5 kJ mol(-1) compared to the experimental value 36.4 (+/-5) kJ mol(-1). In agreement with experimental observations in aqueous solution, the calculated results favor the transformation of singly-bridged to doubly-bridged aluminium ion, which is helpful to understand the complicated hydrolytic polymerizaiton of Al(III).
authors.affiliation: School of Chemistry and Chemical Engineering, State Key Laboratory of Coordination Chemistry of China & Key Laboratory of MOE for Life Science, Nanjing University, Nanjing, 210093, China. bisp@nju.edu.cn.
authors.forename: Zhaosheng
authors.initials: Z
authors.lastname: Qian
authors.forename: Hui
authors.initials: H
authors.lastname: Feng
authors.forename: Zhenjiang
authors.initials: Z
authors.lastname: Zhang
authors.forename: Wenjing
authors.initials: W
authors.lastname: Yang
authors.forename: Jing
authors.initials: J
authors.lastname: Jin
authors.forename: Qiang
authors.initials: Q
authors.lastname: Miao
authors.forename: Lina
authors.initials: L
authors.lastname: He
authors.forename: Shuping
authors.initials: S
authors.lastname: Bi
mesh_terms: D000535:Aluminum / Q000737:chemistry*; D019281:Dimerization; D006860:Hydrogen Bonding; D006868:Hydrolysis; D007477:Ions; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy; D008956:Models, Chemical; D008962:Models, Theoretical; D008968:Molecular Conformation; D016011:Normal Distribution; D055503:Protein Multimerization; D012984:Software; D012997:Solvents / Q000737:chemistry; D014867:Water / Q000737:chemistry*
chemical_list: D007477:Ions; D008024:Ligands; D012997:Solvents; D014867:Water; D000535:Aluminum