Synthesis, Structural Isomerism, and Magnetism of Extended Framework Compounds of Type [Cu (dca)2(pyz)]n, Where DCA=Dicyanamide (N(CN)-2) and PYZ=Pyrazine

A new three-dimensional gallium phosphate, [NH3(CH2)4 NH3]2[Ga4(HPO4)2(PO4)3(OH)3]·yH2O (y~5.4), has been synthesized under hydrothermal conditions at 433 K in the presence of 1,4-diaminobutane and its structure determined using room-temperature single-crystal X-ray diffraction data (Mr= 1084.03, tetragonal, space group I41/a, a=15.261(1), c= 28.898(2) ?; V=6730.4 ?3, Z=8, R=4.09% and Rw= 4.45% for 3093 observed data (I>3((I))). The structure consists of chains of GaO6 octahedra and PO4 tetrahedra cross-linked by additional PO4 tetrahedra to generate a three-dimensional framework containing large tunnels in which 1,4-diaminobutane dications and water molecules reside. The tunnels are bounded by 20-ring windows of alternating gallium- and phosphorus-based polyhedra. The framework is closely related to that of a 1,3-diaminopropane encapsulating iron (III) phosphate, [NH3(CH2)3 NH3]2[Fe4(HPO4)2(PO4)3(OH)3]·yH2O (y~ 9), Further syntheses in the presence of V2O5 show that up to 12% of the Ga(III) can be replaced by V(III) with retention of the large-pore framework structure.