Versatility of 2,6-diacetylpyridine (dap) hydrazones in generating varied molecular architectures: Synthesis and structural characterization of a binuclear double helical Zn(II) complex and a Mn(II) coordination polymer

A binuclear complex of Zn(II) with formula [Zn(dap(A)(2))](2) center dot 2.25DMF (2 . 2.25DMF) and a Mn(II) coordination polymer with formula [Mn-3(dap(In)(2))(3)(H2O)(2) center dot 2DMSO](n) (3 . 2DMSO)(n) have been prepared and structurally characterized [dap(A)(2) = dideprotonated form of 2,6- diacetylpyridine bis( anthraniloyl hydrazone); dap(In)(2) = doubly deprotonated form of 2,6-diacetylpyridine bis( isonicotinoyl hydrazone)]. In the Zn( II) complex the molecular units are double helical, with the Zn( II) ions in a square pyramidal environment. The Mn( II) complex on the other hand is a coordination polymer containing two different types of hepta-coordinated Mn( II) ions, which differ in their axial ligands. The magnetic properties of the Mn( II) complex, along with those of a double helical pyridine bridged binuclear Ni(II) complex, earlier synthesized by us, are also reported. The ability of the 2,6- diacetylpyridine bis( aroyl hydrazone) ligands to form double helical complexes is analyzed in terms of the conformational flexibility of the ligands. The differences in the magnetic properties of the mu-N bridged binuclear complexes formed by 1,1 azido N-bridging ligands, and pyridine N-bridging ligands, is analyzed with the help of EHMO calculations.