Investigation of Metal Ion Complexation of π-Coordinate Calixarene Derivatives by Electrospray-Ionization Mass Spectrometry

Complexation of π-coordinate calix4]arene derivatives toward soft metal ions, silver and thallium (I) ions, has been studied by electrospray-ionization mass spectrometry. Competitive metal–ion complexation of three calix4]arene derivatives demonstrates a significant effect of olefinic substituents and its location on the silver ion complexation, but there was no effect of them on the thallium ion complexation. The stability constants for the metal ion complexes of the calixarene derivatives in methanol have been successfully determined by a mass-spectrometric method using 18-crown-6 as the reference ligand.