Effect of interfacial presence of oriented thiocyanate on water structure

Infrared visible sum frequency spectroscopy has been used to study the organization of the thiocyanate anion at the air-water interface and its influence on the interfacial water at different electrolyte concentrations. The data reveal the enrichment of the anion at the air-water interface and yield an estimate of its orientation. The orientation of the anion does not change much above a concentration of 0.5 M and the number density saturates above 3 M concentration. The presence of the linear thiocyanate anion at the air-water interface alters the structure of water in a manner similar to that for large and highly polarizable halides. The enhancement of the liquid-like feature at similar to 3450 cm(-1) and the diminishing of the ice-like feature at similar to 3200 cm(-1) are characteristics for this anion in addition to the emergence of a vibrational mode at 3320 cm(-1). The analysis contributes toward a better understanding of the interaction between the biologically important chaotropic anion with water.