Synthesis and characterisation of transition-metal-substituted gallium phosphates with the laumontite structure

Three novel metal-substituted gallium phosphates, (C₃N₂H₅)₈[Me₈Ga₁₆P₂₄O₉₆] (Me = Co, Fe, Mn), have been synthesised under solvothermal conditions and their structures determined using single-crystal X-ray diffraction. They are isostructural, with monoclinic symmetry, space group C 2/c and unit-cell dimensions ca. 15 × 13 × 15 Å, β ca. 111°. The materials all have frameworks with the laumontite topology (structure type code LAU), constructed from alternating PO₄ and MO₄ tetrahedra (M = Me and Ga) with imidazole cations occupying sites within the channels of the framework. Magnetic susceptibility measurements show that the materials exhibit Curie-Weiss behaviour over wide ranges of temperature and that the transition metals are present as divalent cations.