ELECTROSPRAY MASS-SPECTROMETRY STUDY OF SELECTIVE COMPLEXES OF POLYAMMONIUM MACROTRICYCLIC LIGANDS WITH DICARBOXYLIC-ACIDS

The complexation of anionic species plays a very important role in che mical and biological processes, Macrocyclic and macropolycyclic polyam monium host molecules have been shown to complex a variety of inorgani c and organic anions strongly and selectively, The selectivity of the complexation depends on the substrate length and on the size of the ho st cavity of the macrocycle. Several methods can be used to characteri ze the complex formation, We describe here the analysis of the complex ation of dicarboxylic acid substrates (HCO2-(CH2)(n)-CO2H) by a macrot ricyclic host using electrospray mass spectrometry, The soft ionizatio n conditions of the electrospray source allow one to maintain, in the gas phase, the interactions between the diacids and the ligand. The in fluence of dicarboxylic acid size (n = 0-6) on the complexation extent , the effect of the pH of the solution on the charge state of the ions and their relative stability towards dissociation induced by collisio ns, are analysed, In the case of unsaturated diacids, total selectivit y was found in favour of the cis vs. the trans isomer. (C) 1997 by Joh n Whey & Sons, Ltd.