Isomerism of Trimeric Aluminum Complexes in Aqueous Environments: Exploration via DFT-Based Metadynamics Simulation

The chemistry of aluminum or oxo-aluminum in water is still relatively unknown, although it is the basis for many chemical and industrial processes, including flocculation in water treatment plants. Trimeric species have a predominant role in the formation of the Keggin cations, which are the basic building blocks of aluminum-based chemicals. Despite this, details of the structural evolution of these small solvated clusters and how this is related to the processes leading to the formation of larger aggregates are still an open issue. To address these questions, here, we have applied the metadynamics (MTD) simulation technique [ Barducci, A. ; Wiley Interdiscip. Rev.: Comput. Mol. Sci. 2010, 1, 826−843 ] with density functional theory-based molecular dynamics to disclose the dynamics and structural conversions of trimeric aluminum complexes in an aqueous environment. The existence of a variety of competing metastable conformations, for example, book-like, cyclic boat, and linear shape conformations, is revealed in the MTD simulation. Furthermore, equilibrium simulations of the various intermediate states encountered along the MTD trajectory are used to assess their (meta)­stability, determine the rearrangement of the OH ligands, and discuss the role of the solvating water.