Microsolvation of sodium acetate in water: Anion photoelectron spectroscopy and ab initio calculations

Abstract

To understand the microsolvation of sodium acetate (CH3COONa, NaOAc) in water, we studied NaOAc(H2O)n(-) (n = 0-3) clusters by photoelectron spectroscopy. We also investigated the structures of NaOAc(H2O)n(-) (n = 0-5) anions and NaOAc(H2O)n (n = 0-7) neutrals by quantum chemistry calculations. By comparing the theoretical results with the photoelectron experiment, the most probable structures of NaOAc(H2O)n(-/0) (n = 0-3) were determined. The study also shows that, with increasing n, the solvent-separated ion pair (SSIP) structures of NaOAc(H2O)n(-) anions become nearly energetically degenerate with the contact ion pair (CIP) structures at n = 5, while the SSIP structures of the neutral NaOAc(H2O)n clusters appear at n = 6 and become dominant at n = 7.

Emergence of Solvent-Separated Na+–Cl– Ion Pair in Salt Water: Photoelectron Spectroscopy and Theoretical Calculations

“…They also play diverse roles in the Hofmeister series and biochemical systems. − To understand the effects of salt ions on water as well as their correlation with the Hofmeister series, , it is especially important to investigate the contact ion pair (CIP) to solvent-separated ion pair (SSIP) transition in salt water , and the arrangement of water molecules in the first solvation shell. Many efforts have been devoted to understanding the solvation of salts in water. − …”

Direct Link between Structure and Hydration in Ammonium and Aminium Bisulfate Clusters Implicated in Atmospheric New Particle Formation

“…Insertion of water into the cation−anion hydrogen bond appears to be the least likely motif, particularly given the paucity of observations of solvent-separated ion pairs in salt clusters. 46,47,57,58 If confirmed, these trends can be used to screen and potentially guide computational structural searches, particularly for larger and more chemically complex hydrated clusters in which exhaustive configurational sampling is currently unfeasible, 37 or to aid the development of models that do not require explicit evaluation of cluster structure. 40 ■ EXPERIMENTAL DETAILS Cationic clusters are produced by electrospray ionization (ESI) of solutions containing 1 mM (NH 4 ) 2 SO 4 and ∼1 mM methylamine (MA), dimethylamine (DMA), or piperidine (PIP), or 0.5 mM hexylamine (HEXA) in 50/50 H 2 O/ CH 3 OH with 0.01% v/v formic acid in an isolated capsule held near atmospheric pressure and purged with dry and CO 2 -free air.…”

“…For clusters in which these sites are not available, particularly clusters composed predominantly of sulfuric acid, direct bridging sites between neighboring bisulfate or sulfuric acid molecules are the next most preferred sites. Insertion of water into the cation–anion hydrogen bond appears to be the least likely motif, particularly given the paucity of observations of solvent-separated ion pairs in salt clusters. ,,, If confirmed, these trends can be used to screen and potentially guide computational structural searches, particularly for larger and more chemically complex hydrated clusters in which exhaustive configurational sampling is currently unfeasible, or to aid the development of models that do not require explicit evaluation of cluster structure …”

Comparison of the Microsolvation of CaX2 (X = F, Cl, Br, I) in Water: Size-Selected Anion Photoelectron Spectroscopy and Theoretical Calculations

“…Understanding the solvation of salts in water is very important in the fields of physical chemistry, biochemistry, marine chemistry, and atmospheric chemistry. − The interactions between salt ions and water molecules have nonnegligible effects on water hydrogen-bond networks, the solubility of different substances, and chemical reactions in aqueous solutions. − Many experimental − and theoretical studies − have been performed to investigate the solvation processes of salts in water at the molecular level. To provide detailed information about the transition between salt contact ion pairs (CIPs) and solvent-separated ion pairs (SSIPs) with an increasing number of water molecules, in the last ten years, we investigated the structures and properties of a series of salt-water clusters using the technique of size-selected anion photoelectron spectroscopy combining with theoretical calculations. − …”