Estimation of the Ratio of Hidden Multivalent Ions in Nematic Lyomesophases by Using Heteronuclear NMR

An estimation of the peak areas of the 59Co NMR spectra for cobalt(III) complex ions and of the 25Mg spectra for magnesium aqua ions gave population ratios of their hidden ions, which are defined as too strongly interacting with nematic lyomesophases (composed of cationic or anionic surfactants) to contribute to the NMR spectra. The cobalt(III) complex ions used were [Co(NH3)6]3+, [Co(en)3]3+ (en = ethylenediamine), [Co(phen)3]3+ (phen = 1,10-phenanthroline), and [Co(CN)6]3−. It was revealed that appreciable amounts of multivalent ions are present as hidden ions on the lyomesophase, whose sign of charge is opposite to that of the ion in question. For such hydrophilic ions as [Co(NH3)6]3+, [Co(en)3]3+, [Co(CN)6]3−, and magnesium ions, the ions binding to the mesophases are classified into two states based on the NMR spectra: One is an outer-sphere complex (ion pair); the other is a hidden ion. In these systems the hidden ion/total ion population ratios depending on the composition of the surfactant are rou...