3D hydrogen bonded heteronuclear CoII, NiII, CuII and ZnII aqua complexes derived from dipicolinic acid

The heteronuclear water-soluble and air-stable compounds [M(H2O)5M′(dipic)2] · mH2O (M/M′ = CuII/CoII (1), CuII/NiII (2), CuII/ZnII (3), ZnII/CoII (4), NiII/CoII (5), m = 2–3; H2dipic = dipicolinic acid) have been prepared by self-assembly synthesis in aqueous solution at room temperature, and characterized by IR, UV–Vis and atomic absorption spectroscopies, elemental and X-ray diffraction single crystal (for 1 and 2) analyses. 1–5 represent the first examples of heteronuclear dipicolinate compounds with 3d metals. Extensive H-bonding interactions involving all aqua ligands, dipicolinate oxygens and lattice water molecules further stabilize the dimetallic units by linking them to form three-dimensional polymeric networks.