Microscopic solvation of NaBO2 in water: anion photoelectron spectroscopy and ab initio calculationsw

We investigated the microscopic solvation of NaBO2 in water by conducting photoelectron spectroscopy and ab initio studies on NaBO2 (H2O)n (n = 0–4) clusters. The vertical detachment energy (VDE) of NaBO2 is estimated to be 1.00 0.08 eV. The photoelectron spectra of NaBO2 (H2O)1 and NaBO2 (H2O)2 are similar to that of bare NaBO2 , except that their VDEs shift to higher electron binding energies (EBE). For the spectra of NaBO2 (H2O)3 and NaBO2 (H2O)4, a low EBE feature appears dramatically in addition to the features observed in the spectra of NaBO2 (H2O)0–2. Our study shows that the water molecules mainly interact with the BO2 unit in NaBO2 (H2O)1 and NaBO2 (H2O)2 clusters to form Na–BO2 (H2O)n type structures, while in NaBO2 (H2O)3 and NaBO2 (H2O)4 clusters, the water molecules can interact strongly with the Na atom, therefore, the Na–BO2 (H2O)n and Na(H2O)n BO2 types of structures coexist. That can be seen as an initial step of the transition from a contact ion pair (CIP) structure to a solvent-separated ion pair (SSIP) structure for the dissolution of NaBO2.