Transition Metal Ions in Solution: Complexed Ion Speciation at the Air-Liquid Interface.

We have studied the interfacial properties of Zn vs selected transition metal cations such as Fe, Cu, and Cr in a water-ethanol mixture using field-induced droplet ionization. This was in particular inspired by the specific surface activity of Zn that has been observed on several occasions and a desire to clarify the root cause for this behavior. We have found that Zn, due to its unique electronic configuration and atomic size, is the only ion of those under study that gives rise to specific speciation at the air-liquid interface with three ethanol molecules attached to the central atom for optimal polarity.