Building block approach to nanostructures: step-by-step assembly of large lanthanide-containing polytungstoarsenate aggregates

Three large cerium-containing polytungstoarsenate aggregates have been synthesized via a step-by-step assembly process. Reaction of Na(9)[AsW(9)O(33)] precursors, ceric sulfate and potassium citrate in an acidic aqueous solution at pH = 3 led to the isolation of a new dimeric sandwich-type compound K(9)Na(7)[{Ce(2)O(H(2)O)(5)}{WO(H(2)O)}{AsW(9)O(33)}(2)](2). approximately 48H(2)O. The presence of the citrate anion prevents precipitation of simple lanthanide salts with polyoxometalates. The reaction of compound with alpha-alanine at pH = 2 resulted in the formation of a new alanine-decorated cryptand compound K(2)Na(10)[Ce(4)As(4)W(44)O(151)(ala)(4)(OH)(2)(H(2)O)(10)]. approximately 40H(2)O. The reaction between compound and MnCl(2) at pH = 5 yielded the other inorganic cryptate Mn(0.5)K(5)Na(18)[Ce(4)As(4)W(41)O(149)]. approximately 50H(2)O. All compounds are characterized by elemental analyses, TG analyses, IR, UV-Vis absorption spectra, X-ray photoelectron spectroscopy (XPS), single crystal X-ray diffraction and electrochemical analyses. The crystal data for these compounds: , triclinic, P1[combining macron], a = 12.314(3) A, b = 17.953(4) A, c = 22.355(5) A, alpha = 90.18(3) degrees , beta = 101.97(3) degrees, gamma = 91.08(3) degrees , Z = 1; monoclinic, P2(1)/n, a = 23.4483(15) A, b = 21.8764(13) A, c = 23.6930(14) A, beta = 111.0560 degrees , Z = 2; , triclinic, P1[combining macron], a = 20.636(4) A, b = 23.000(4) A, c = 25.039(4) A, alpha = 81.991(3) degrees , beta = 73.333(3) degrees, gamma = 74.835(3) degrees, Z = 2. Electrochemical analyses of compounds suggest that tetravalent cerium ion can be stabilized by the polyanions with high negative charges.