Three new zinc(II) complexes: design, synthesis, characterization and catalytic performance

Three new Zn(II) complexes, [Zn2L2(OAc)2]2CH3OH (1), [ZnL(3-NA)2]·H2O (2) and [ZnL(2-NA)2] (3) were synthesized by the reaction of Zn(CH3COO)2·2H2O or Zn(ClO4)2·6H2O with 2-amino-N'-(pyridin-2-ylmethylene)benzohydrazide (HL), 3-nitrobenzoic acid (3-NA) or 2-nitrobenzoic acid (2-NA). The complexes were characterized by elemental analyses, single crystal X-ray diffraction, IR, UV-Vis and 1H NMR spectroscopy. The single crystal X-ray diffraction analyses revealed that the Zn ions in the complexes are five-coordinate in tetragonal pyramid configuration. The complexes and their starting materials Zn(CH3COO)2·2H2O and Zn(ClO4)2·6H2O were studied for their catalytic performance in the selective oxidation of cyclohexane (Cy) with aqueous H2O2 as oxidant. The conditions such as time, the amount of H2O2, solvent and HNO3 additive were optimized. The results showed that 3 has the best activity under mild conditions compared to the starting zinc materials and the referenced zinc complexes.