Coordination chemistry of pyrazolone based Schiff bases relevant to uranyl sequestering agents: Synthesis, characterization and 3D molecular modeling of some octa-coordinate mono- and binuclear-dioxouranium(VI) complexes

Synthesis of two new series of octa-coordinate dioxouranum(VI) chelates: (i) mononuclear chelates of compositions, [UO2(L1)2(H2O)2] (where L1H = N-(4′-butyrylidene-3′-methyl-1′-phenyl-2′-pyrazolin-5′-one)-p-anisidine (bumphp-paH, I), N-(4′-butyrylidene-3′-methyl-1′-phenyl-2′-pyrazolin-5′-one)-m-phenetidine (bumphp-mpH, II) or N-(4′-butyrylidene-3′-methyl-1′-phenyl-2′-pyrazolin-5′-one)-p-toluidine (bumphp-ptH, III), and [UO2(L2)(H2O)2] (where L2H2 = N,N′-bis(4′-butyrylidene-3′-methyl-1′-phenyl-2′-pyrazo-lin-5′-one)-o-phenylenediamine (bumphp-ophdH2, IV), and (ii) the ligand bridged binuclear chelate of composition [UO2(μ-L3)(H2O)2]2 (where L3H2 = N,N′-bis(4′-butyrylidene-3′-methyl-1′-phenyl-2′-pyrazo-lin-5′-one)-benzidine (bumphp-bzH2, V), are described. These complexes have been characterized by elemental analyses, uranium determination, molar conductance, decomposition temperature and magnetic measurements, thermogravimetric studies, 1H NMR, IR, and electronic spectral studies. The 3D molecular modeling and analysis for bond lengths and bond angles have also been carried out for the two representative compounds, [UO2(bumphp-pa)2(H2O)2] (1) and [UO2(bumphp-bz)(H2O)2]2 (5) to substantiate the proposed structures.