Interaction of TiO⁺ with water: Infrared photodissociation spectroscopy and density functional calculations

We investigated the interaction of TiO⁺ with water by conducting infrared photodissociation spectroscopy and density functional theory calculations on TiO(H₂O)Ar⁺ and TiO(H₂O) _5-7⁺ clusters. The studies show that TiO(H ₂O)Ar⁺ has two isomers, Ti(OH)₂Ar⁺ and (H₂O)-TiOAr⁺, coexisting in our experiments. The structure of TiO(H₂O)₅⁺ is characterized by attaching four water molecules to a Ti(OH)₂⁺ core with their O atoms interacting with the Ti atom directly. With the increasing number of water molecules, the additional water molecules start to form hydrogen bonds with the inner shell water molecules and the OH groups of Ti(OH) ₂⁺ instead of coordinating directly with the Ti atom. Therefore, the structures of TiO(H₂O)₆⁺ and TiO(H₂O)₇⁺ clusters are evolved from that of TiO(H₂O)₅⁺ by adding the sixth and seventh water molecules to the second solvent-shell. Our results demonstrate that a Ti(OH)₂⁺ type of product is dominant when TiO⁺ interacts with water, especially when more water molecules are involved.