Hydration of oxo anions: a combined computational and experimental structure and dynamics study in aqueous solutions

The structure and dynamics of several hydrated oxo anions were studied using multiple methodologies. Aqueous solutions of sulfate, sulfite, thiosulfate, peroxysulfate, selenite, selenate, hypochlorite, chlorite, chlorate, perchlorate, bromate, iodate and periodate salts were studied using large angle X-ray scattering (LAXS) and extended X-ray absorption fine structure (EXAFS) spectroscopy. The thiosulfate, selenite and selenate salts were also studied using double difference infrared spectroscopy (DDIR). Moreover, the sulfite, sulfate thiosulfate, chlorite, chlorate and perchlorate ions were simulated using quantum mechanical charge field (QMCF). The periodate ion was shown to have only meta configuration in aqueous solution, while both meta and ortho configurations are present in solid state. The studies showed that the anions could be placed in two main groups, one with asymmetric and another with symmetric hydration. In the asymmetric group consisting of sulfite, selenite, chlorite and chlorate ions where the lone electron-pair of the central atom showed substantially weaker interaction with a longer distance to the water molecules near the lone electron-pair than to those near the oxygens bound to the ion. The symmetric group, sulfate, peroxysulfate, selenate, perchlorate, and periodate ions showed a symmetric interaction with one M-(O