The influence of pH on the coordination of copper(II) by 2-amino-2-deoxy-D-gluconate and 2-amino-2-deoxy-D-glucose oxime as studied by 1H and 13C NMR relaxation rate measurements and EPR spectroscopy
摘要:
Copper(II) binding to the D-glucosamine derivatives 2-amino-2-deoxy-D-gluconate and 2-amino-2-deoxy-D-glucose oxime has been studied by C-13 and H-1 NMR relaxation rate measurements, visible and EPR spectroscopy, at two different pH values. From the Cu(II) induced relaxation rate enhancements distance information of the Cu(II) metal ion to the carbon nuclei of the ligands has been obtained, strongly affirming and further revealing the coordination mode of the ligands to Cu(II) as indicated by the visible and EPR measurements. It is shown that the coordination of the compounds is dependent on the pH. At pH 6.9, Cu(II) forms 1:2 complexes with 2-amino-2-deoxy-D-gluconate in which the copper is bound via two carboxylate and two amino groups at about equal distances, with the C3 hydroxyl groups probably hydrogen bonded to axially located water molecules. At pH 10.7 the ligand is interacting with the amino and C3 hydroxyl group in a nearly square plane and the carboxylate group is possibly in the axial position. Concerning the 2-amino-2-deoxy-D-glucose oxime only the E isomer coordinates to copper. At pH 6.9 Cu(II) complexes are formed wherein the ligand binds in a didentate fashion via the amino and oxime nitrogen. At pH 10.7, there is substantial contribution of a complex wherein the Cu(II) is monodentately bound via the oxime oxygen.
The influence of pH on the coordination of copper(II) by 2-amino-2-deoxy-D-gluconate and 2-amino-2-deoxy-D-glucose oxime as studied by 1H and 13C NMR relaxation rate measurements and EPR spectroscopy
作者:Jacco van Haveren、Herman van Bekkum、Joop A. Peters
DOI:10.1016/s0020-1693(00)87347-8
日期:1993.3
Copper(II) binding to the D-glucosamine derivatives 2-amino-2-deoxy-D-gluconate and 2-amino-2-deoxy-D-glucose oxime has been studied by C-13 and H-1 NMR relaxation rate measurements, visible and EPR spectroscopy, at two different pH values. From the Cu(II) induced relaxation rate enhancements distance information of the Cu(II) metal ion to the carbon nuclei of the ligands has been obtained, strongly affirming and further revealing the coordination mode of the ligands to Cu(II) as indicated by the visible and EPR measurements. It is shown that the coordination of the compounds is dependent on the pH. At pH 6.9, Cu(II) forms 1:2 complexes with 2-amino-2-deoxy-D-gluconate in which the copper is bound via two carboxylate and two amino groups at about equal distances, with the C3 hydroxyl groups probably hydrogen bonded to axially located water molecules. At pH 10.7 the ligand is interacting with the amino and C3 hydroxyl group in a nearly square plane and the carboxylate group is possibly in the axial position. Concerning the 2-amino-2-deoxy-D-glucose oxime only the E isomer coordinates to copper. At pH 6.9 Cu(II) complexes are formed wherein the ligand binds in a didentate fashion via the amino and oxime nitrogen. At pH 10.7, there is substantial contribution of a complex wherein the Cu(II) is monodentately bound via the oxime oxygen.