Three-, two-, and one-dimensional metal phosphonates based on [hydroxy(4-pyridyl)methyl]phosphonate:: M{(4-C5H4N)CH(OH)PO3}(H2O) (M = Ni, Cd) and Gd{(4-C5H4N)CH(OH)P d(OH)O2}3•6H2O

Based on the [hydroxy(4-pyridyl)methyl]phosphonate ligand, three compounds with formula Ni{(4-C5H4N)CH(OH)PO3}(H2O) (1), Cd{(4-C5H4N)CH(OH)PO3}(H2O) (2), and Gd{(4-C5H4N)CH(OH)P(OH)O-2}(3)center dot 6H(2)O (3) have been synthesized under hydrothermal conditions. The crystal data for 1 are as follows: orthorhombic, space group Pbca, a = 8.7980(13) angstrom, b = 10.1982(15) angstrom, and c= 17.945(3) angstrom. For 2 the crystal data are as follows: monoclinic, space group C2/c, a = 23.344(6) angstrom, b = 5.2745(14) angstrom, c = 16.571(4) angstrom, and beta = 121.576(4)degrees. The crystal data for 3 are as follows: rhombohedral, space group r (3) over bar, a = 22.2714(16) angstrom, b = 22.2714(16) angstrom, and c = 9.8838(11) angstrom. Compound 1 adopts a three-dimensional pillared layered structure in which the inorganic layers made up of corner-sharing {NiO5N} octahedra and {CPO3} tetrahedra are connected by pyridyl groups. A two-dimensional layer structure is found in compound 2, which contains alternating inorganic double chains and pyridyl rings. Compound 3 has a one-dimensional chain structure where the Gd atoms are triply bridged by O-P-O linkages. The pyridyl nitrogen atom in 3 remains uncoordinated and is involved in the interchain hydrogen bonds. Magnetic susceptibility studies of 1 and 3 reveal that weak ferromagnetic interactions are mediated between Ni(II) centers in compound 1. For compound 3, the behavior is principally paramagnetic.