Surfactant-Induced Trans-Interface Transportation and Complex Formation of Giant Polyoxomolybdate-Based Clusters

Abstract

The interaction and complex formation between cationic surfactants dimethyldioctadecylammonium Bromide (DODA-Br) and a polyoxomolybdate (POM)-based giant cluster {Mo₇₂Fe₃₀}, in its both single cluster (in aqueous solution, these clusters exist as anions) format and supramolecular format in aqueous solution, are studies by using laser light scattering (LLS) techniques. DODA/{Mo₇₂Fe₃₀} complexes containing basically single {Mo₇₂Fe₃₀} clusters are observed when the {Mo₇₂Fe₃₀} aqueous solution is freshly prepared and contains mainly unimer or oligmer {Mo₇₂Fe₃₀} anions. The {Mo₇₂Fe₃₀} clusters tend to form supramolecular vesicle structures slowly in solution. At high surfactant concentrations, the DODA cationic surfactants can break the vesicle structure and form single {Mo₇₂Fe₃₀}/DODA complexes. At low surfactant concentrations, complexes containing the whole vesicles coated by a layer of DODA is formed and transferred into the organic phase. For the surfactant concentrations in between, the vesicles are partially destroyed, leading to the formation of complexes with large size distribution. Studying the behaviors of the interaction between DODA and {Mo₇₂Fe₃₀} anionic structures will help to further explore the complicated mechanism of the POM vesicle formation, which was recently discovered but still not fully understood. Such unique complex structures may also have potential applications as nanoreactors or nanocontainers.