A second polymorph of [H3N(CH2)(3)NH3][V4O10]

The title compound, propane-1,3-diammonium tetravanadate, (C3H12N2)[V4O10], represents a second polymorph of composition beta-[H3N(CH2)(3)NH3][V4O10]. It differs from the alpha polymorph [Riou & Ferey(1995). J. Solid State Chem. 120, 137 - 145] in the conformation of the propane-1,3-diammonium dication which, in the present example, lies on a twofold axis and adopts a syn-syn rather than a syn-anti conformation. The twofold symmetry of this conformation thus co-operates with the vanadium oxide framework to result in a higher symmetry for the resultant crystal, viz. C2/c versus P2(1)/n. The overall unit-cell parameters for the two polymorphs are similar, and the inorganic layer within each is topologically identical, comprising edge-sharing (VO5)-O-IV square pyramids linked together via corner-sharing with (VO4)-O-V tetrahedra. A key difference between the two polymorphs is a 'head-to-head' versus 'head-to-tail' stacking of the vanadyl groups in adjacent layers.