Cobalt(II), manganese(IV) mononuclear and zinc(II) symmetric dinuclear complexes of an aliphatic hydrazone Schiff base ligand with diversity in coordination behaviors and supramolecular architectures: syntheses, structural elucidations, and spectroscopic characterizations

Three new complexes of cobalt, manganese, and zinc have been synthesized using a hydrazone Schiff base ligand {(E)-N'[1-(2-hydroxyphenyl)ethylidene]acetohydrazide} (LH2) produced by the 1:1 condensation of acetic hydrazide and 2-hydroxyacetophenone. The ligand has shown three different coordination modes in the three complexes: a monoanionic tridentate coordination mode with the Co-II complex ([Co(LH)(2)]center dot CH3OH, 1), a dianionic tridentate coordination mode with the Mn-IV complex ([Mn(L)(2)], 2), and monoanionic mu(2)-phenoxo-bridged tridentate coordination mode with the Zn-II complex ([Zn(LH)(OOCCF3)](2), 3). All three complexes show interesting supramolecular architectures, especially for 3 a nanoporous supramolecular (4, 4) grid 2D framework is formed. The ligand and the complexes are well characterized by elemental analysis, IR and UV-vis spectroscopy. The spin states of the Co-II and Mn-IV metal ions and hence the coordination modes of the ligand in these complexes are in good agreement with the EPR spectroscopic data. The fluorescence emission spectra of LH2 and the zinc complex 3 are measured in acetonitrile solution as well as in solid state.