title: Reaction Mechanisms of the Initial Oligomerization of Aluminophosphate.
abstract: The mechanisms of aluminophosphate oligomerization were investigated using density functional theory with the SMD solvation model. Two aluminum species, Al(OH)4(-) and Al(H2O)6(3+), and four phosphorus species, H3PO4, H2PO4(-), HPO4(2-), and PO4(3-), were considered as the monomers for polycondensation reactions. It was found that the most favorable pathway to dimerization was a Lewis acid-base reaction: the aprotic oxygen of phosphoric acid (P═O) performs a nucleophilic attack on the central aluminum atom of Al(OH)4(-). Using this mechanism as a pattern, plausible dimerization mechanisms were investigated by varying the proticity and hydration of the phosphorus and aluminum monomers, respectively. The relative reaction rates of each mechanism were estimated under different pH conditions. The chain growth of aluminophosphates to trimers, tetramers, and pentamers and the cyclization of a linear tetramer were also investigated. For oligomerization reactions beyond dimer formation, it is found that cluster growth favors the addition of the phosphoric monomers rather than aluminum monomers.
authors.forename: Yan
authors.initials: Y
authors.lastname: Xiang
authors.affiliation: State Key Laboratory of Inorganic Synthesis & Preparative Chemistry, Jilin University , Changchun 130012, China.
authors.forename: Liang
authors.initials: L
authors.lastname: Xin
authors.forename: Joshua D
authors.initials: JD
authors.lastname: Deetz
authors.affiliation: State Key Laboratory of Inorganic Synthesis & Preparative Chemistry, Jilin University , Changchun 130012, China.
authors.forename: Huai
authors.initials: H
authors.lastname: Sun