FT-ICR/MS and Quantum Chemical Study of the Aqueous Microsolvation of Cadmium Chloride Complexes

Abstract

Quantum chemical and mass spectrometric studies of hydrogen bonded complexes are of fundamental importance in shaping our understanding of molecular interactions in the bulk liquid phase. The gas phase solvation of Cadmium chloride species according to X·(H2O)n + H2O= X·(H2O)n+1, X=[CdClm] 2-m, provides a suitable model for such studies and, can as such provide insight into the stability and abundance of ionic water clusters in high temperature low density aqueous fluids [1] as well as serve as a model system for ionic dissolution and precipitation reaction in water clusters [2]. The work here presents new results for the stability, structure and abundance of hydrated [CdClm] 2-m complexes via MP2/CBS and CCSD (T)/CBS calculations with cc-pVXZ-PP basis sets (X=D, T, Q) in combination with Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR/MS). Gas phase ion-molecule experiments were conducted on a modified 7 Tesla FT-ICR/MS equipped with electro spray ionization (ESI) source and IRMPD laser for ion fragmentation. A preliminary analysis of results from this study indicates that i) Cd2+ prefers to coordinate six first shell water molecules rather than seven [3, Fig.], ii) the stepwise attachment of Cl- onto hydrated [CdClm] 2-m yields a suite of energetically similar isomers and iii) FT-ICR/MS experiments currently underway, will provide additional insight concerning the stability of these clusters. Implications for metal-halide transport in high temperature vapor will be discussed. [1] Likholyot et al. (2007) GCA 71, 2436. [2] NiednerSchatteburg et al. (2000) Chem. Rev. 100, 4059. [3] Chillemi et al. (2005) J. Phys. Chem. B 109, 9186.