Novel application of the radiotracer technique in the study of molecular complexes

Abstract

A novel application of the radiotracer technique for inferring separately the thermodynamic constants of some model molecular complexes of iodine with π-donors (aromatics) and n-donors (alcohols) in solution has been studied. Labelled tetramethylammonium pentaiodide (TMAI^*₅) was synthesized using molecular iodine (¹³¹I) as a tracer. The solubility equilibria of TMAI^*₅ with and without donor were established, and iodine concentrations were analysed using a thin-wall end-window Geiger–Müller counter.

These data yield equilibrium constants and enthalpies of a series of molecular complexes which are comparable with the literature values, lending support to the applicability of the tracer technique to the study of molecular complexes. Various advantages of this technique over others have been outlined.