An Inorganic Double Helix: Hydrothermal Synthesis, Structure, and Magnetism of Chiral [(CH3)2NH2]K4[V10O10(H2O)2(OH)4(PO4)7]·4H2O

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Science  12 Mar 1993:
Vol. 259, Issue 5101, pp. 1596-1599
DOI: 10.1126/science.259.5101.1596


Very complicated inorganic solids can be self-assembled from structurally simple precursors as illustrated by the hydrothermal synthesis of the vanadium phosphate, [(CH3)2NH2]K4[V10O10(H2O)2(OH)4(PO4)7]·4H2O, 1, which contains chiral double helices formed from interpenetrating spirals of vanadium oxo pentamers bonded together by P5+. These double helices are in turn intertwined with each other in a manner that generates unusual tunnels and cavities that are filled with (CH3)2NH2+ and K+ cations, respectively. The unit cell contents of dark blue phosphate 1, which crystallizes in the enantiomorphic space group P43 with lattice constants a = 12.130 and c = 30.555 angstroms, are chiral; only one enantiomorph is present in a given crystal. Magnetization measurements show that 1 is paramagnetic with ten unpaired electrons per formula unit at higher temperatures and that antiferromagnetic interactions develop at lower temperatures.