Two different modes for copper(II) ion coordination to quinine-type ligands

Abstract

Three new copper(II) complexes with the ligands quinuclidine [Cu(C7H13N)2(OH2)Cl]Cl.2H 2O (1), quinine [Cu(C20H23O2N2)(OH 2)2]ClO4 (2), and hydroquinidine [Cu(C20H27O2N2)(OH 2) Cl2]Cl.fraction one-halfH2O (3) have been isolated and characterized. The binding sites were assigned on the basis of vibrational spectroscopy, electron paramagnetic resonance, and thermal analysis results. The possibility of the involvement of the quinuclidinic nitrogen in the coordination was evidenced in complex 1, in which copper(II) is coordinated to two quinuclidine molecules. In the case of quinine-type ligands, if the starting material is deprotonated in both nitrogens, copper(II) coordination occurs through the quinuclidinic nitrogen, as in complex 2. In contrast, if the starting material is protonated in the quinuclidinic nitrogen the binding site is the quinolinic nitrogen, as in complex 3. Therefore, both nitrogens of quinine-type ligands constitute binding sites for copper(II) ions.

Keywords

• quinine
• copper(II)
• thermogravimetry
• IR spectroscopy
• EPR spectroscopy