Synthesis and Characterization of Co(II), Ni(II), Zn(II) and Cu(II) Complexes with a New Tetraazamacrocyclic Schiff Base Ligand Containing a Piperazine Moiety: X-Ray Crystal Structure Determination of the Co(II) Complex

Abstract

Two macrocyclic Schiff base ligands, L1 [1+1] and L2 [2+2], have been obtained in a one-pot cyclocondensation of 1,4-bis(2-formylphenyl)piperazine and 1,3-diaminopropane. Unfortunately, because of the low solubility of both ligands, their separation was unsuccessful. In the direct reaction of these mixed ligands (L1 and L2) and the appropriate metal ions only [CoL1(NO<inf>3</inf>)]ClO<inf>4</inf>, [NiL1](ClO<inf>4</inf>)<inf>2</inf>, [CuL1](ClO<inf>4</inf>)<inf>2</inf> and [ZnL1(NO<inf>3</inf>)]ClO<inf>4</inf> complexes have been isolated. All the complexes were characterized by elemental analyses, IR, FAB-MS, conductivity measurements and in the case of the [ZnL1(NO<inf>3</inf>)]ClO<inf>4</inf> complex with NMR spectroscopy. The crystal structure of the Co(II) complex has also been determined and the [CoL(NO<inf>3</inf>)]+ cation contains the Co(II) ion sited in the middle of the macrocyclic cavity endo-macrocyclicly coordinated in a distorted octahedral geometry with a N<inf>4</inf>O<inf>2</inf> core, arising from coordination by the four donor nitrogen atoms from the macrocyclic framework and by two oxygen atoms from a bidentate nitrate ion. Neither positive-ion FAB mass spectrometry nor the X-ray crystal structure shows an indication relevant to the [2+2] macrocyclic products. © 2009 Elsevier Ltd. All rights reserved.