A series of metal-organic hybrid compounds were synthesized using two new phosphonic acids, pyridyl-4-phosphonic acid and p-xylylenediphosphonic acid (H2O3PCH2C6H4CH2PO3H2). The phosphonic acid ligands have been synthesized from their corresponding bromides following two different types of reactions. The reaction of pyridyl-4-phosphonic acid with three different divalent metal salts results in the formation of molecular structures of different dimensionality. The reaction of Cu(II) with the phosphonic acid under hydrothermal conditions yields a three-dimensional (3D) open framework structure having the molecular formula [Cu-4(NC5H4-PO3)(4)(H2O)(10)] (1). The reactions with Mn(II) and Zn(II) salts with the same phosphonic acid resulted in a two-dimensional layered and a dinuclear compound with molecular formulas [Mn-3(NC5H4-PO3)(4)(H2O)(6)(ClO4)(2)] (2) and [Zn-2(NHC5H4-PO3H)(2)Cl-4] (3), respectively. Compound 1 crystallizes in the triclinic crystal system having space group P $$($) over bar with structural parameters a = 7.4564(15) angstrom, b = 9.1845(19) angstrom, c = 11.582(2) angstrom, alpha = 100.842(3)degrees, beta = 104.303(3)degrees, gamma = 94.774(3)degrees, and Z = 1. Compound 2 crystallizes in the triclinic crystal system, space group P $$($) over bar, with structural parameters a = 7.6871(14) angstrom, b = 10.576(2) angstrom, c = 14.470(3) angstrom, alpha = 81.340(3)degrees, beta = 81.561(3)degrees, gamma = 68.757(3)degrees, and Z = 2, whereas compound 3 crystallizes in a monoclinic crystal system with space group P2(1)/n. The structural parameters are as follows: a = 8.4969 (5) angstrom, b = 9.3911 (5) angstrom, c = 12.3779 (6) angstrom, beta = 90.860(17)degrees, and Z = 4. The pyridylphosphonate ligand shows different ligation behavior toward the three divalent metal ions. On the other hand, p-xylylenediphosphonic acid on reaction with Co(II) formed a 3D compound [Co-2(O3PCH2C6H4CH2PO3)(2)(H2O)(2)] (4) with a layered and pillared structure. Compound 4 crystallizes in an orthorhombic crystal system with space group Pnma. The structural parameters are a = 21.744(4) angstrom, b = 5.6744(10) angstrom, c = 4.7927(9) angstrom, and Z = 4.