Multinuclear NMR Studies on Micellar Formation of Aqueous [Co(N-octyl- or N-dodecylethylenediamine)(3,7-Diazanonane-1,9-diamine)]3+ Solutions

The aggregation of [Co(R-en)(2,3,2-tet)]X3 (R-en = N-octyl- or N-dodecylethylenediamine, 2,3,2-tet = 3,7-diazanonane-1,9-diamine, and X = Cl or ClO4) in water was investigated by 59Co, 35Cl, 35ClO4, 2H2O, and 1H NMR measurements. NMR parameters, such as the relaxation rates and linewidths for the 59Co and 35Cl nuclei, were appreciably changed by micellar formation. We determined the CMC (critical micelle concentration) values (0.12 mol kg−1 for the octyl complex perchlorate, 0.008 mol kg−1 for the dodecyl perchlorate, and 0.010 mol kg−1 for its chloride) by measuring the NMR relaxations. The obtained CMC values are much larger than those previously reported on these surfactants, and are comparable to those of monovalent surfactants having the same alkyl-chain length. The aggregation of [Co(dod-en)(2,3,2-tet)]X3 (X = Cl or ClO4) in aqueous solution was also measured using vapor-pressure osmometry; the result supports the formation of ion aggregates at the CMCs, which was determined by NMR measurements. The...