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

The complexation of two-headed (dicephalic) surfactant molecules (1) to cop per(II) sulfate in aqueous dispersions at pH 5.5 and 9.5 leads to the gener ation of metalloaggregates of the general type Cu(imidazole)(4)(2+). At bot h pH values vesicles are observed which, however, consist of different comp lexes due to the dicephalic nature of the surfactant. At pH 5.5 four imidaz ole 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 gro ups from four different surfactant molecules. The aggregates formed exhibit different physical properties, which have been studied by electron microsc opy, monolayer experiments differential scanning calorimetry, and spectrosc opic techniques.