Copper(II) complexes of a dicephalic imidazole surfactant. Tunable organization of metalloaggregates

The complexation of two-headed (dicephalic) surfactant molecules (1) to copper(II) sulfate in aqueous dispersions at pH 5.5 and 9.5 leads to the generation of metalloaggregates of the general type Cu(imidazole)42+. At both pH values vesicles are observed which, however, consist of different complexes due to the dicephalic nature of the surfactant. At pH 5.5 four imidazole groups from two surfactant molecules coordinate to one copper center in a bidentate fashion, whereas at pH 9.5 a two-dimensional polymeric network is formed in which each copper(II) ion is surrounded by four imidazole groups from four different surfactant molecules. The aggregates formed exhibit different physical properties, which have been studied by electron microscopy, monolayer experiments differential scanning calorimetry, and spectroscopic techniques.