Two-Dimensional Polyoxoniobates Constructed from Lindqvist-Type Hexaniobates Functionalized by Mixed Ligands

By introducing mixed ligands into the hexaniobate system, three novel organic-inorganic hybrids, [Cu(en)(2)](2){[Cu(1,10-phen)][Cu(1,10-phen)(H2O)]Nb6O19}center dot 10.5H(2)O (I), [Cu(en)(2)](2){[Cu(2,2'-bipy)][Cu(2,2'-bipy)(H2O))Nb6O19)center dot 9H(2)O (2) and [Cu(1,2-dap)(2)](2){[Cu(2,2'-bipy)][Cu(2,2'-bipy)(H2O)]Nb6O19}center dot IIH2O (3) (en = ethylenediamine, 1, 0-phen = 1,1 0-phenanthroline, 2,2'-bipy = 2,2'-bipydine, 1,2-dap = 1,2-diaminopropane), have been synthesized by the solution diffusion method and characterized by elemental analyses, IR spectra, UV spectroscopy, thermogravi metric analyses, and single-crystal X-ray diffraction. 1, 2, and 3 can be formularized as [Cu(L-1)(2)](2){[Cu(L-2)][Cu(L-2)(H2O)]Nb6O19}center dot nH(2)O (L-1 =en for 1 and 2, 1,2-dap for 3, L-2= 1,10-phen for 1, 2,2'-bipy for 2 and 3, n = 10.5 for 1, 9 for 2, 11 for 3), and all exhibit the two-dimensional (2D) network architecture built by [Cu(L-1)(2)](2){[Cu(L-2)][Cu(L-2)(H2O)]Nb6O19} units-and [Cu(L-1)(2)](2+) bridges. 1-3 represent the first 2D architecture with (4,4)-connected topology in polyoxoniobate chemistry. Furthermore, the photoluminescent properties of 1 and 2 have been studied. The magnetic behavior of I has been quantitatively investigated and suggests the weak antiferromagnetic exchange interactions.