We report an approach of exploring the interaction between cationic surfactants and a type of structurally well-defined, spherical "Keplerate" polyoxometalate (POM) macroanionic molecular clusters, {Mo72V30}, in aqueous solution. The effectiveness of the interaction can be determined by monitoring the size change of the "blackberry" supramolecular structures formed by the self-assembly of {Mo72V30} macroions, which is determined by the effective charge density on the macroions. Long-chain surfactants (CTAB and CTAT) can interact with {Mo72V30} macroions stoichiometrically and lower their charge density.
View Article and Find Full Text PDFWe report the self-assembly processes in solution of three Keplerate-type molybdenum-oxide based clusters {Mo72V30}, {Mo72Cr30} and {Mo72Fe30} (all with diameters of approximately 2.5 nm). These clusters behave as unique weak polyprotic acids owing to the external water ligands attached to the non-Mo metal centers.
View Article and Find Full Text PDFWe show that the equilibrium size of single-layer shells composed of polyoxometalate macroions is inversely proportional to the dielectric constant of the medium in which they are dispersed. This behavior is consistent with a stabilization mechanism based on Coulomb repulsion combined with charge regulation. We estimate the cohesive energy per bond between macroions on the shells to be approximately -6kT.
View Article and Find Full Text PDFA complete, continuous transition from discrete macroions to blackberry structures, and then back to discrete macroions, is reported for the first time in the system of {Mo132}/water/acetone, with {Mo132} (full formula (NH4)42[Mo132O372(CH3COO)30(H2O)72].ca.300H2O.
View Article and Find Full Text PDFThe cluster {(Mo)Mo5}12Fe(III)30 1 a present in compound 1 (cluster diameter approximately 2.3 nm), which belongs to the family of nanoscale spherical porous {(Mo)Mo5}12{Linker}30 capsules that allow a new type of nanochemistry inside their cavities as well as unprecedented aggregation processes under gaseous, solution, and solid-state conditions, is the starting material for the present investigation. In solution it reacts with LnCl3 x nH2O (Ln = Ce, Pr) thereby replacing six Fe(III) ions with Ln(III) ions to form compounds 2 (Ce) and 3 (Pr).
View Article and Find Full Text PDF