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, L 1 [1+1] and L 2 [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 (L 1 and L 2) and the appropriate metal ions only [CoL 1(NO 3)]ClO 4, [NiL 1](ClO 4) 2, [CuL 1](ClO 4) 2 and [ZnL 1(NO 3)]ClO 4 complexes have been isolated. All the complexes were characterized by elemental analyses, IR, FAB-MS, conductivity measurements and in the case of the [ZnL 1(NO 3)]ClO 4 complex with NMR spectroscopy. The crystal structure of the Co(II) complex has also been determined and the [CoL(NO 3)] + 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 4O 2 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.