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

Abstract

A binuclear complex of Zn(II) with formula [Zn(dap(A)₂)]₂·2.25DMF (2·2.25DMF) and a Mn(II) coordination polymer with formula [Mn₃(dap(In)₂)₃(H₂O)₂·2DMSO]_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 µ-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.