Syntheses and characterization of Cu2+, Ni2+ and Zn2+ binding capability of histidinehydroxamic acid derivatives

Two histidinehydroxamic acid derivatives (N-methyl-histidinehydroxamic acid, N-Me-Hisha and Z-histidinehydroxamic acid, Z-Hisha) have been synthesized and their complexation with Cu2+-, Ni2+- and Zn2+-ions has been studied by using pH-potentiometric, UV–Vis, CD, 1H NMR, EPR and ESI-MS methods. Both of the two new derivatives contain one donor atom less compared to the histidinehydroxamic acid (Hisha). In the case of N-Me-Hisha the hydroxamate-N as donor is eliminated, while the coordination of the amino-N of Z-Hisha is not possible at all.With the ambidentate N-Me-Hisha, the histamine-type coordination mode is favoured if the metal ion is Ni2+ and the bis-[NH2,Nimid] complex is the most stable in this system. The mixed type, [NH2,Nimid] + [O,O], coordination mode dominates in the Cu2+- N-Me-Hisha complexes, while different low stability mono-chelated linkage isomers are formed with Zn2+.With Z-Hisha (having poor water solubility) hydroxamate-type coordination mode predominates in low stability complexes in the Ni2+ and Zn2+ containing systems. Interestingly, the interaction with Cu2+ is very strong and results in the formation of a high stability 12-MC-4 type metallacrown with involvement of 5-membered and 7-membered chelates.

Graphical abstractTwo histidinehydroxamic acid derivatives (N-methyl-histidinehydroxamic acid, N-Me-Hisha and Z-histidinehydroxamic acid, Z-Hisha) have been synthesized and their complexation with Cu2+-, Ni2+- and Zn2+-ions has been studied by using different methods.Figure optionsDownload full-size imageDownload as PowerPoint slide