Effects of Tripositive Cobalt(III)-Complex Ions on the Structure of a Cholesteric Mesophase Composed of PotassiumN-Dodecanoyl-l-alaninate

Abstract

The phase behavior of the aqueous cholesteric mesophase composed of potassium N-dodecanoyl-l-alaninate (L-KDDA) was studied in the presence of various cations such as a cobalt(III) complex and cesium ions using multinuclear magnetic resonance and laser and X-ray scatterings. The cobalt(III) complexes used are [Co(NH3)6]Cl3, [Co(en)3]Cl3 (en = ethylenediamine), Δ-[Co(chxn)3]Cl3 (chxn = (R,R)-1,2-cyclohexanediamine), [Co(tn)3]Cl3 (tn = trimethylenediamine), and [Co(phen)3]Cl3 (phen = 1,10-phenanthroline). Transition temperatures from anisotropic to isotropic phases determined by 2H2O NMR spectra were appreciably dependent on the kinds and concentrations of the added cations. The NH3-, en-, tn-, and phen-complex ions were more favorable for stabilizing the aqueous mesophase of L-KDDA compared to the chxn-complex ion. The change in the order parameters for the surfactant aggregates was monitored by anisotropic splittings of the 1H NMR spectra envelope and was compared to structural parameters of the mesophase...