A CO-59 NMR-STUDY OF THE INTERACTIONS OF SOME COBALT(III) COMPLEXES IN NEMATIC LYOMESOPHASES

Co-59 NMR spectroscopy was used to study the interactions of cationic or neutral octahedral cobalt(III) complexes such as [Co(NH3)6]3+, [Co(en)3]3+ (en=ethylenediamine), [Co(NO2)(NH3)5]2+, and [Co(acac)3] (acac=acetylacetonato) with surfactants in their nematic liquid crystalline solutions. The specific interactions of the complexes with the surfactants were studied in a replacement of one surfactant by another that had a different polar group. The extent of the binding of these complexes was monitored through the Co-59 quadrupole splittings. The relationship between the extent of the binding and the magnitude of the quadrupole splitting did not hold when comparing the three cationic complexes. A comparison between the potassium dodecanoate (KDodec)/tetradecyl (or decyl)trimethylammonium bromide (TDTMABr or DTMABr) and the cesium N-dodecanoyl-L-alaninate (CsDDA)/tetradecyltrimethylammonium bromide (TDTMABr) mixed surfactant systems in the interaction with [Co(NH3)6]3+ and [Co(en)3]3+ complexes showed that these complexes bind to the alaninate polar group through a weakly interacting site in the range of the intermediate composition of the mixed surfactants; such a kind of the binding was negligible or smaller in the dodecanoate system. [CO(acac)3] complex was solubilized to liquid crystals and the interactions with the surfactant depended on their polar groups in spite of the electric neutrality of the complex.