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 ∼3450 cm -1 and the diminishing of the ice-like feature at ∼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.