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New surfactant octahedral Co(III) chelates 4–7 were prepared from sodium hexanitrocobaltate(III) and EDTA derivatives 8–11, respectively. The molecular compositions of 4–7 were established by combustion analyses and electrospray mass spectrometry, and their structures by 1H and 13C NMR, IR, and UV–vis spectroscopy. Surfactants 4–7 were characterized by measurement of their Krafft temperatures and critical aggregation concentrations in water. The Krafft temperatures of 4 and 5 are >23 °C, and the values of the former are greater than the corresponding values of the latter. The Krafft temperatures of 6 and 7 are ≤23 °C. Aggregated surfactants were characterized by 1H NMR spectroscopy in D2O, and 5a in water was studied by cryo-etch high resolution scanning electron microscopy. The NMR results suggested that 4–7 form small aggregates such as micelles or small vesicles, and 5a displayed characteristic segregation patterns in electron micrographs that are likely formed during the freezing and/or cryo-etch processes of sample preparation. |
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