Copper-Linked Hexaniobate Lindqvist ClustersVariations on a Theme
dataset
posted on 2007-05-28, 00:00 authored by Ranko P. Bontchev, Eugene L. Venturini, May NymanFour new one-dimensional materials and one dimer complex based on the linkage of [Nb6O19] clusters and [CuLx]
(L = ethylenediamine (en), NH3, H2O) assemble under ambient conditions. These phases include the following:
Rb4[Cu(en)2(H2O)2]3[(Nb6O19H2)2Cu(en)2]·24H2O (1), space group P1̄; [Cu(en)2(H2O)2]2[(Nb6O19H2)Cu(en)2]·14H2O
(2), space group P1̄; Rb2[Cu(NH3)2(H2O)4][Cu(NH3)4(H2O)2]2{[Nb6O19][Cu(NH3)]2}2·6H2O (3), space group P1̄;
{[Nb6O19][Cu(NH3)2(H2O)]2[Cu(H2O)4]2}·3H2O (4), space group P2/n; and {[Nb6O19][Cu(NH3)2(H2O)]2[Cu(H2O)4]2}
(5), space group C2/m. All structures have been solved by single-crystal methods, and compounds 1−5 were
characterized by thermogravimetric analysis, Fourier transform IR, chemical analysis, and magnetic measurements.
It has been demonstrated that the conformation, charge, and geometry of the [Nb6O19]−[CuLx] chains can be
modulated by varying the type and amount of the [CuLx]2+ species. The charge balance is provided by mixed
Rb+/[CuLx]2+ or [CuLx]2+ cations only for structures 1−3, whereas 4 and 5 are neutral chains with no counterions.
There are weak antiferromagnetic Cu2+−Cu2+ interactions in all phases. Compounds 2−5 represent the first examples
in which the [Nb6O19] Lindqvist ion forms extended solids rather than dimers or decorated monomers when reacted
with transition-metal, cationic complexes.
