Metal carboxylate-phosphonates containing flexible N-donor co-ligands

This paper reports mixed ligated metal phosphonates with formula [Zn₂(4-cppH)₂(L¹)] (1), [Zn₃(4-cpp)₂(L²)₂]·2.5H₂O (2), [Zn₃(4-cpp)₂(L³)]·H₂O (3) and [Ni₂(4-cppH)₂(L¹)₃]·2H₂O (4), where L¹ = 1,4-bis(imidazol-1-ylmethyl)benzene, L² = 1,3-bis(imidazol-1-ylmethyl)-benzene, L³ = 1,2-bis(imidazol-1-ylmethyl)benzene and 4-cppH₃ = 4-carboxyphenylphosphonic acid. Compound 1 shows a layer structure in which the inorganic double chains made up of {ZnO₃N} and {PO₃C} tetrahedra are connected by L¹ bridges in a trans-mode. In compound 2, an inorganic hexanuclear cluster is observed where the six zinc atoms are bridged purely through O-P-O units from four 4-cpp³⁻. The L² ligand adopts both cis- and trans-coordination modes to link the hexanuclear clusters into a three-dimensional framework structure with primitive cubic pcu topology. Compound 3 displays another type of layer structure in which the inorganic chains made up of {ZnO₃N} (or {ZnO₄}) and {PO₃C} tetrahedra are linked by both the 4-cpp³⁻ and L³ ligands. The L³ ligand adopts cis-coordination mode. Unlike Zn(II) ions in 1-3, the Ni(II) ions in compound 4 are octahedrally coordinated, and are bridged by both 4-cppH²⁻ and L¹ ligands, resulting in an interesting double layer structure with the lattice water filling in the intralayer space. The thermal stabilities, luminescent and magnetic properties are investigated.