Synthesis and redox-responsive self-assembly of ferrocene grafted Anderson-type polyoxometalate hybrid complexes

Abstract

In this paper, we report the synthesis of a novel ferrocene symmetrically modified Mn-Anderson-type polyoxometalate and its long alkyl chain surfactant-enwrapped complexes and the controlled self-assembly in organic solutions. 1H NMR, FT-IR, ESI-MS and X-ray single crystal structure analysis supported the predicted structure of the polyoxometalate hybrid. The characteristic redox properties of the ferrocene group was found to be maintained in the polyoxometalate, as demonstrated by cyclic voltammetry. The interactions between complexes and between ferrocene and polyoxometalate were confirmed through EPR and XPS measurements. The long alkyl chain surfactant cations covered the ferrocene grafted polyoxometalate giving the complex moderate amphiphilicity, forming spherical self-assemblies. The obtained spherical assemblies underwent structural and morphologic transformations upon the oxidization of inorganic oxidizer Ce(IV) and organic oxidizer 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ). The state oxidized by DDQ could be reduced reversibly upon addition of hydrazine, leading to a redox cycle. The reversible control for the assembled structure was checked by the alternate layer spacing and morphologic transformation cycles according to XRD and SEM characterizations.