Organic Phosphonic Acid And Its Metal Complexes Synthesis, Structure And Magnetic Properties

In this thesis, nine organic phosphonic acid compounds have been prepared and characterized by IR and E.A. Two novel metal phosphonates with three-dimensional open framework structures namely Co3[CH3C(NH3)(PO3H)2]2[CH3C(NH3)(PO3)(PO3H )]2(H2O)4 (1) and Cu4[CH3C(NH2)(PO3)2]2(C10H8N2)(H2O)4 (2) were synthesized under hydrothermal conditions in which the phosphonic acid CH3C(NH3)(PO3H)2 [aedp] was used. The magnetic study indicates there is a antiferromagnetic exchange between the magnetic centers for each metal phosphonate.Single crystal structural determinations for polymer 1 reveals a three-dimensional open framework structure formed with {Co3[CH3C(NH3)(PO3H)2]2[CH3C(NH3)(PO3)(P O3H)]2(H2O)4}n layers, in which each layer is constructed by symmetric {Co3(aedp)4(H2O)4} trimer units. The Co(l)O6 octahedra and Co(2)O6 octahedra is fused by corner-sharing with CPO3 tetrahedra independently, forming a finite chain {CO3[CH3C(NH3)(PO3H)2]2[CH3C(NH3)(PO3)(PO3H)]2(H2O)4} along the c-axis direction. In each chain two CH3C(NH3)(PO3)(PO3H) ligands bridge Co(l) and Co(2) atom to form a {Co3(aedp)4(H2O)4} trimer unit, the neighboring trimers are connected together through 0(9) and 0(11) atoms coordinated to equivalent Co(l) atoms, leading to a two-dimensional layer of {Co3[CH3C(NH3)(PO3H)2]2[CH3C(NH3)(PO3)(PO3H)]2(H 20)4}n in approximately [011] direction. The O(9) and O(11) atoms behave as bridge to connect different layers also, the Co(1)O6 octahedra and Co(2)O6 octahedra from different layers are bridged by the means of corner-sharing with two CPO3 tetrahedra independently, as a result a stair-like structure is formed.OSThe structure of polymer 2 is composed of {Cu4(aedp)2(H2O)2}n layers connected by 4,4'-bipyridine bridges. Each aedp ligand group behaves as a bis(chelating) ligand to bridge Cu(1) and Cu(2) atoms, forming {Cu3(aedp)2} trimer units. The neighboring trimers are fused together by the coordination of the phosphonate oxygen O(2) to the equivalent Cu(1) atom, hence forming an infinite chain along the [ 0 0 1 ] direction with a ladder-like motif. These chains are connected through {Cu(3)O4} units by sharing the remaining phosphonate oxygen O(7) of aedp ligand. As a result a two-dimensional network structure of copper phosphonate is constructed in the ac plane. The layers are linked by 4.4'-bipyridine bridging ligands, thus forming a three-dimensional open framework structure.The magnetic studies of polymer 1 show a dominant antiferromagnetic exchange between the Co ions. The overall magnetic behavior is mainly attributed to the antiferromagnetic interaction between magnetic centers through O-P-O bridge considering the structure of polymer 1 in which composed of {{Co3[CH3C(NH3)(PO3H)2]2[CH3C(NH3)(PO3)(PO3H)]2(H2O)4}n layers connected by O atoms.The magnetic studies of polymer 2 also show a dominant antiferromagnetic exchange between the Cu ions. Theoretical fitting of the data in the temperature range 25-300K results in the parameters g=1.85, J=-75.89398, Na=0.00737. The negative J value confirms the presence of antiferromagnetic interactions.