Novel water clusters in two complexes of pyridine-2,3,5,6-tetracarboxylate

Two complexes, [Zn-4(pdtc)(2)(phen)(4)(H2O)(6)]center dot 20H(2)O (1) and [Ni(H-2)pdtc)(H2O)(3)]-3H(2)O (2), containing the new ligand pyridine-2,3,5,6-tetracarboxylate (pdtc) have been synthesized and characterized by X-ray single-crystal diffraction, elemental analysis, IR, UV-vis, and fluorescence spectroscopies, and thermal gravimetric (TG) analysis. Complex I is a tetranuclear zinc(II) complex bridged by two pdtc and terminated with four phen molecules, whereas 2 is a mononuclear nickel(II) complex. A novel eight-centered (pentafurcate) hydrogen bond has been observed in the huge (H2O)(24) cluster in the crystal packing voids of 1, and a novel L6(4)6(6)10(8) water layer is present in 2.