Equilibrium and solution structural study of the interaction of tri- and tetra-dentate polyimidazole ligands with transition metal ions

Copper(II) and zinc(II) complexes of two polyimidazole derivatives, 4-(imidazol-4-ylmethyl)-2-(imidazol-2-ylmethyl)imidazole (TRIM) and bis[4-(imidazol-4-ylmethyl)-imidazol-2-yl]methane (TIM), containing three and four methylene-linked imidazole rings as donor groups, have been studied by potentiometry, UV–VIS, EPR and NMR spectroscopic methods. The data revealed that both ligands form extremely stable and varied complexes with zinc(II) and copper(II). In equimolar solutions of the metal ions and TRIM, two and three imidazole co-ordinated MAH and MA species were formed. The complex Zn(TRIM) probably has tetrahedral geometry. The formation of bis-complexes has also been detected with the ligand in excess. The data revealed 6N and 5N co-ordinated central ions in ZnA2 and CuA2, respectively. In MA complexes of TIM, the ligand is co-ordinated to the metal ions via all the four imidazole units. Formation of bis-complexes has only been found in the zinc(II) containing system. Ternary systems of zinc(II)–TRIM and –TIM have also been studied with L-cysteine as a second ligand. The potentiometric and NMR results established the formation of ternary complexes with different protonation states in relatively high amount, in spite of the high stability of the parent complexes.

[1]  G. Guillot,et al.  Crystallographic, Electrochemical, and Pulsed EPR Study of Copper(II) Polyimidazole Complexes Relevant to the Metal Sites of Copper Proteins(,). , 1998, Inorganic chemistry.

[2]  T. Gajda,et al.  Stereoisomerism and Equilibrium Properties of Oxygen-Carrying Cobalt(II) Complexes of Histamine and Its Derivatives: A New Approach to an Old System. , 1997, Inorganic chemistry.

[3]  A. Spek,et al.  Copper(II) Coordination Compounds with Bis(imidazol-2-yl)methylamine and Bis(imidazol-2-yl)methylaminomethane in Relation to Bis(imidazol-2-yl)methylamine-Modified Poly(glycidyl methacrylate) Polymers and Other Bis(imidazol-2-yl)-Containing Ligands , 1996 .

[4]  J. Richardson,et al.  Dinuclear Copper(II) Complexes Incorporating a New Septadentate Polyimidazole Ligand. , 1996, Inorganic chemistry.

[5]  A. Spek,et al.  Synthesis, Characterization, and Single-Crystal EPR Studies of Three Dinuclear Copper(II) Complexes and One Mixed-Valence Tetranuclear Copper(I)-Copper(II) Cluster with an Asymmetric Imidazole-Containing Tripodal Ligand with Copper(II)-Copper(II) Distances between 3.35 and 3.63 Å , 1996, Inorganic chemistry.

[6]  A. Aubry,et al.  Proton and Metal Ion Interactions with Glycylglycylhistamine, a Serum Albumin Mimicking Pseudopeptide , 1996 .

[7]  A. Rockenbauer,et al.  Automatic computer simulations of ESR spectra , 1996 .

[8]  T. Gajda,et al.  POTENTIOMETRIC AND SPECTROSCOPIC STUDY OF NICKEL(II) AND COBALT(II) COMPLEXES OF HISTAMINE-CONTAINING DIPEPTIDES , 1995 .

[9]  Shan Chen,et al.  Synthesis and characterization of copper(II) complexes of new tripodal polyimidazole ligands , 1994 .

[10]  H. Sigel,et al.  The colourless ‘chameleon’ or the peculiar properties of Zn2+ in complexes in solution. Quantification of equilibria involving a change of the coordination number of the metal ion , 1994 .

[11]  E. Mulliez.  Synthesis of polyimidazoles as biomimetic ligands for metalloprotein active site modeling , 1989 .

[12]  B. Krebs,et al.  Pentacoordinate zinc complexes of imidazole nitrogen donors as structural models for the active site in enzymes: preparation and crystal structures of (.mu.-2,2'-biimidazole)tetrakis(2,2'-biimidazole)dizinc(II) tetraperchlorate trihydrate and bis(2,2'-biimidazole)(formato)zinc(II) perchlorate , 1987 .

[13]  A. Gergely,et al.  Complexes of sulphur-containing ligands—II: Binary and ternary complexes of D-penicillamine and L-cysteine with nickel(II) and zinc(II) ions , 1979 .