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

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(NO3)]ClO4, [NiL1](ClO4)2, [CuL1](ClO4)2 and [ZnL1(NO3)]ClO4 complexes have been isolated. All the complexes were characterized by elemental analyses, IR, FAB-MS, conductivity measurements and in the case of the [ZnL1(NO3)]ClO4 complex with NMR spectroscopy.The crystal structure of the Co(II) complex has also been determined and the [CoL(NO3)]+ cation contains the Co(II) ion sited in the middle of the macrocyclic cavity endo-macrocyclicly coordinated in a distorted octahedral geometry with a N4O2 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.

Four new Co(II), Ni(II), Cu(II) and Zn(II) macrocyclic complexes were synthesized with tetradentate Schiff base ligands derived from cyclocondensation of 1,4-bis(2-formylphenyl)piperazine and 1,3-diaminopropane. The crystal structure of the Co(II) complex has also been determined and the [CoL(NO3)]+ cation contains the Co(II) ion sited in the middle of the macrocyclic cavity, coordinated in a distorted octahedral geometry.Figure optionsDownload as PowerPoint slide