Metal Complexes with Mixed Ligands. 4. The Crystal Structure of Tetrakisimidazole Cu(II) Sulphate, Cu(C3H4N2)4SO4.

Fransson, Gunnar; Lundberg, Bruno K. S.; Møller, Jørgen; Olli, Marianne; Pilotti, Åke

doi:10.3891/acta.chem.scand.26-3969

Cited by 44 publications

(17 citation statements)

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“…The complexes are first synthesized and then analyzed through ESR to identify ligand arrangements and changes to the unpaired electron density. The synthesis methods are based on published work with modifications to simplify and expedite the process for students. ,− The 1-imidazole is prepared at room temperature by mixing equivalent mole amounts of copper(II) perchlorate hexahydrate, diethylenetriamine, and imidazole in a methanol/acetonitrile solvent. The 2-imidazole requires heating a 2:1 mol ratio of 2-methylimidazole to anhydrous copper(II) acetate in a chloroform/methanol solution for 45 min at 50 °C.…”

Section: Methodsmentioning

confidence: 99%

An Undergraduate Experiment To Explore Cu(II) Coordination Environment in Multihistidine Compounds through Electron Spin Resonance Spectroscopy

et al. 2019

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Electron spin resonance (ESR) or electron paramagnetic resonance (EPR) spectroscopy is an incisive technique for the characterization of paramagnetic centers in inorganic, bioinorganic, and organic molecules and materials. These measurements are enabled with the help of paramagnetic species, such as organic free radicals and ions, electronically excited states, and metal−ligand compounds, some of which with biological importance. In this experiment, analogues of histidine− copper coordination compounds are investigated to show students how ESR line shapes depend on the complexed copper ion electronic structure as well as how the spectral features elucidate the coordination environment of copper. These coordinated compounds play an important role in metal ion coordination in proteins and peptides. The experiment has two parts. First, three copper−imidazole complexes that mimic copper−histidine compounds in the human body are synthesized. Second, the ESR spectrum of each complex is obtained at 77 K from frozen chloroform/methanol and acetonitrile/methanol matrixes and used to elucidate the ligand arrangement of the Cu 2+ ion and the effect on the unpaired electron density.

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Section: Methodsmentioning

confidence: 99%

An Undergraduate Experiment To Explore Cu(II) Coordination Environment in Multihistidine Compounds through Electron Spin Resonance Spectroscopy

et al. 2019

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“…After a few days, dark blue colored crystals formed. 49 For the preparation of bis(2-methylimidazole)copper(II) diacetate 50 (see Figure 1b), 0.5 g of Cu(II) acetate hydrate (98% Sigma-Aldrich Co., St. Louis, MO) and 1.0 g of 2-methylimidazole (99% Sigma-Aldrich Co., St. Louis, MO) were added and dissolved in a mixture of chloroform (10 mL) and methanol (2.5 mL). This mixture was stirred for 30 min at 50 °C and filtered.…”

Section: Methodsmentioning

confidence: 99%

ESEEM Analysis of Multi-Histidine Cu(II)-Coordination in Model Complexes, Peptides, and Amyloid-β

et al. 2014

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We validate the use of ESEEM to predict the number of 14N nuclei coupled to a Cu(II) ion by the use of model complexes and two small peptides with well-known Cu(II) coordination. We apply this method to gain new insight into less explored aspects of Cu(II) coordination in amyloid-β (Aβ). Aβ has two coordination modes of Cu(II) at physiological pH. A controversy has existed regarding the number of histidine residues coordinated to the Cu(II) ion in component II, which is dominant at high pH (∼8.7) values. Importantly, with an excess amount of Zn(II) ions, as is the case in brain tissues affected by Alzheimer’s disease, component II becomes the dominant coordination mode, as Zn(II) selectively substitutes component I bound to Cu(II). We confirm that component II only contains single histidine coordination, using ESEEM and set of model complexes. The ESEEM experiments carried out on systematically 15N-labeled peptides reveal that, in component II, His 13 and His 14 are more favored as equatorial ligands compared to His 6. Revealing molecular level details of subcomponents in metal ion coordination is critical in understanding the role of metal ions in Alzheimer’s disease etiology.

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“…It is important to synthesize simple Cu II ±imidazole complexes and study their structures in order to help us understand the interactions of histidyl residues with copper ions in metalloproteins (Jian et al, 1999;Wang et al, 1999;Ohtsu et al, 2001). For example, the counter-ion effects on the structures of copper complexes have been revealed by structural studies and comparisons of nitrate (McFadden et al, 1976), sulfate (Fransson & Lundberg, 1972), perchlorate (Ivarsson, 1973) and tri¯uoromethanesulfonate (Liu & Su, 1995) complexes of tetrakis(imidazole)copper (II). Similarly, the effect of substituents of imidazoles on the structures of their complexes can be investigated via structural studies of the corresponding complexes.…”

Section: Commentmentioning

confidence: 99%

The effects of substitution on tetrakis(substituted imidazole)copper(II) trifluoromethanesulfonates

Wang¹,

Liu²,

Wang³

et al. 2003

Acta Crystallogr C

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The organic ligands 4-methyl-1H-imidazole and 2-ethyl-4-methyl-1H-imidazole react with Cu(CF(3)SO(3))(2).6H(2)O to give tetrakis(5-methyl-1H-imidazole-kappaN(3))copper(II) bis(trifluoromethanesulfonate), [Cu(C(4)H(6)N(2))(4)](CF(3)SO(3))(2), and aquatetrakis(2-ethyl-5-methyl-1H-imidazole-kappaN(3))copper(II) bis(tri fluoromethanesulfonate), [Cu(C(6)H(10)N(2))(4)(H(2)O)](CF(3)SO(3))(2). In the former, the Cu atom has an elongated octahedral coordination environment, with four imidazole rings in equatorial positions and two trifluoromethanesulfonate ions in axial positions. This conformation is similar to those in the analogous complexes tetrakis(imidazole)copper(II) trifluoromethanesulfonate and tetrakis(2-methyl-1H-imidazole)copper(II) trifluoromethanesulfonate. In the second of the title compounds, the ethyl groups block the central Cu atom, and a square-pyramidal coordination environment is formed around the Cu atom, with the substituted imidazole rings in the basal positions and a water molecule in the axial position.

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Metal Complexes with Mixed Ligands. 4. The Crystal Structure of Tetrakisimidazole Cu(II) Sulphate, Cu(C3H4N2)4SO4.

Cited by 44 publications

References 0 publications

An Undergraduate Experiment To Explore Cu(II) Coordination Environment in Multihistidine Compounds through Electron Spin Resonance Spectroscopy

An Undergraduate Experiment To Explore Cu(II) Coordination Environment in Multihistidine Compounds through Electron Spin Resonance Spectroscopy

ESEEM Analysis of Multi-Histidine Cu(II)-Coordination in Model Complexes, Peptides, and Amyloid-β

The effects of substitution on tetrakis(substituted imidazole)copper(II) trifluoromethanesulfonates

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