Highly Structured Water Networks in Microhydrated Dodecaborate Clusters.

We report a combined photoelectron spectroscopy and theoretical investigation of a series of size-selected hydrated closo -dodecaborate clusters B 12 X 12 2- · n H 2 O (X = H, F, or I; n = 1-6). Distinct structural arrangements of water clusters from monomer to hexamer can be achieved by using different B 12 X 12 2- bases, illustrating the evident solute specificity. Because B-H···H-O dihydrogen bonds are stronger than O···H-O hydrogen bonds in water, the added water molecules are arranged in a unified binding mode by forming highly structured water networks manipulated by B 12 H 12 2- . As a comparison, the hydrated B 12 F 12 2- clusters display similar water evolution for n values of 1 and 2 but different binding modes for larger clusters, while water networks in B 12 I 12 2- share similarities with the free water clusters. This finding provides a consistent picture of the structural diversity of hydrogen bonding networks in microhydrated dodecaborates and a molecular-level understanding of microsolvation dynamics in aqueous borate chemistry.