Copper-linked hexaniobate lindqvist clusters-variations on a theme

Four 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: Rb-4[Cu(en)(2)(H2O)(2)](3)[(Nb6O19H2)(2)Cu(en)(2)]center dot 24H(2)O (1), space group P (1) over bar; [Cu(en)(2)(H2O)(2)](2)[(Nb6O19H2)Cu(en)(2)]center dot 14H(2)O (2), space group P (1) over bar; Rb-2[Cu(NH3)(2)(H2O)(4)][Cu(NH3)(4)(H2O)(2)](2){[Nb6O19][Cu(NH3)](2)}(2)center dot 6H(2)O (3), space group P (1) over bar {[Nb6O19][Cu(NH3)(2)(H2O)](2)[Cu(H2O)(4)](2)}center dot 3H(2)O (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.