Redox-controlled helical self-assembly of a polyoxometalate complex.

Polyoxometalate (POM) complex (DODA)₂[Mo₆O₁₉] with a symmetrical linear structure was prepared conveniently by replacing the tetrabutylammonium (TBA) counterions of Lindquist-type cluster (TBA)2 [Mo₆O₁₉] with cationic surfactant dioctadecyldimethylammonium (DODA). A helical self-assembled structure of the complex was formed in dichloromethane/propanol. The dynamically reversible transformation between helical and spherical assemblies on alternate UV irradiation and H₂O₂ oxidation was characterized by SEM, TEM, and UV/Vis studies. The redox-controlled morphology change is modulated by variation of the electrostatic interactions between the inorganic polyanion and the organic cation DODA through controlling the redox properties of the POM component, as shown by the XRD, X-ray photoelectron spectroscopic, and ¹H NMR measurements. The strategy applied herein is a unique example of targeted smart and helical assembly of POM complexes.