Coordination abilities of l-glutamic acid γ-monohydroxamic acid towards copper(II) in the absence and presence of some aliphatic amines

Solution equilibrium studies on the Cu2+–(A)–(Glu-γ-ha) ternary systems ((A) = polyamine: ethylenediamine (en), diethylenetriamine (dien), N,N,N′,N″,N″-pentamethyldiethylenetriamine (Me5dien); (Glu-γ-ha) = l-glutamic-γ-hydroxamic acid) have been performed by pH-potentiometry, UV–Vis spectrophotometry and EPR methods. The obtained results suggest the formation of the heteroligand complexes with [Cu(A)(Glu-γ-ha)]+ stoichiometry in all studied systems. Our spectroscopic results indicate the tetragonal geometry for the [Cu(en)(Glu-γ-ha)]+ species in which Glu-γ-ha acts as a tridentate ligand, the geometry slightly deviated from square pyramidal for [Cu(dien)(Glu-γ-ha)]+ and strongly deviated from square pyramidal towards trigonal bipyramidal for the [Cu(Me5dien)(Glu-γ-ha)]+ species. In the two latter species Glu-γ-ha acts as a bidentate ligand. The coordination modes in these mixed-ligand complexes are discussed.

Graphical abstractSolution equilibrium studies on the Cu(II)–polyamine–l-glutamic-hydroxamic acid mixed-ligand systems (polyamine: ethylenediamine, diethylenetriamine, N,N,N′,N″,N″-pentamethyldiethylenetriamine) have been performed by pH-potentiometry, UV–Vis spectrophotometry and EPR methods. Our spectroscopic results indicate the tetragonal geometry for the six-coordinate [Cu(en)(Glu-γ-ha)] species, the geometry slightly deviated from square pyramidal for the [Cu(dien)(Glu-γ-ha)] and strongly deviated from square pyramidal towards trigonal bipyramidal for the [Cu(Me5dien)(Glu-γ-ha)] species. The coordination modes in these mixed-ligand complexes are discussed.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Glu-gamma-ha acts as a bidentate or tridentate ligand. ► The formation of five-coordinate complexes in the Cu(II)–triamines–Glu-gamma-ha. ► In the [Cu(dien)(Glu-gamma-ha)] coordination thorough (N,O) or (N,N) donor atoms. ► In the [Cu(Me5dien)(Glu-gamma-ha)] species – by (O,O) donor atoms.