Bonding properties of copper(II)-imidazole chromophores: structures and electronic properties of tetrakis imidazole copper(II) complexes. Molecular structures of Cu(N-methylimidazole)4(ClO4)2 and [Cu(N-methylimidazole)4(H2O)2]Cl2(H2O)

Control of Protein Oligomerization Symmetry by Metal Coordination: C2 and C3 Symmetrical Assemblies through CuII and NiII Coordination

“…The average Cu-N His and Ni-N His distances are 2.08(3) Å and 2.18(6) Å, respectively, which compare well with the distances observed in the Cu(II)-( N -methylimidazole) 4 (OH 2 ) 2 (2.02(3) Å) and Ni(II)- (imidazole) 6 (2.13(3) Å) complexes 11, 12. As expected from a Cu(II) center, the axial aquo ligand in Cu 2 :MBPC-1 2 is subject to Jahn-Teller distortion and positioned at a distance of 2.55(4) Å.…”

“…To further probe control of the supramolecular assembly by metal binding, which should be manifested by ideal tetragonal (Cu) or octahedral (Ni) coordination geometries, we examined in detail the coordination environments in the two structures (Figure ). The average Cu−N His and Ni−N His distances are 2.08(3) and 2.18(6) Å, respectively, which compare well with the distances observed in the copper(II) tetrakis( N -methylimidazole)·2H 2 O [2.02(3) Å] and nickel(II) hexaimidazole [2.13(3) Å] complexes. , As expected from a Cu II center, the axial aquo ligand in Cu 2 :MBPC-1 2 is subject to Jahn−Teller distortion and positioned at a distance of 2.55(4) Å. The N−metal−N angles formed between His residues at cis positions are 90(2)° and 91(3)° respectively for copper and nickel species, and those between the His residues at trans positions are 178(4)° and 180(1)°, indicating near-ideal square-planar and octahedral protein−metal coordination environments.…”

Control of Protein Oligomerization Symmetry by Metal Coordination: C2 and C3 Symmetrical Assemblies through CuII and NiII Coordination

“…The average Cu-N His and Ni-N His distances are 2.08(3) Å and 2.18(6) Å, respectively, which compare well with the distances observed in the Cu(II)-( N -methylimidazole) 4 (OH 2 ) 2 (2.02(3) Å) and Ni(II)- (imidazole) 6 (2.13(3) Å) complexes 11, 12. As expected from a Cu(II) center, the axial aquo ligand in Cu 2 :MBPC-1 2 is subject to Jahn-Teller distortion and positioned at a distance of 2.55(4) Å.…”

“…To further probe control of the supramolecular assembly by metal binding, which should be manifested by ideal tetragonal (Cu) or octahedral (Ni) coordination geometries, we examined in detail the coordination environments in the two structures (Figure ). The average Cu−N His and Ni−N His distances are 2.08(3) and 2.18(6) Å, respectively, which compare well with the distances observed in the copper(II) tetrakis( N -methylimidazole)·2H 2 O [2.02(3) Å] and nickel(II) hexaimidazole [2.13(3) Å] complexes. , As expected from a Cu II center, the axial aquo ligand in Cu 2 :MBPC-1 2 is subject to Jahn−Teller distortion and positioned at a distance of 2.55(4) Å. The N−metal−N angles formed between His residues at cis positions are 90(2)° and 91(3)° respectively for copper and nickel species, and those between the His residues at trans positions are 178(4)° and 180(1)°, indicating near-ideal square-planar and octahedral protein−metal coordination environments.…”

Coordination of Imidazoles by Cu(II) and Zn(II) as Studied by NMR Relaxometry, EPR, far-FTIR Vibrational Spectroscopy and Ab Initio Calculations: Effect of Methyl Substitution

“…Calculations of the σ- and π-bond interaction coefficients were conducted from measured EPR parameters. Electronic transitions were obtained from the literature. , All imidazole ligands attain values of α 2 ≈ 0.82−0.87 indicating a substantial covalent character. The π-interaction coefficients (β 2 ≈ 0.65−0.69, γ 2 ≈ 0.55−0.8) are probably even better indicators of the covalent nature of the imidazole-cupric bond.…”

“…The Cu(II)-N bond length should subsequently follow the inverse order that is in conformity with X-ray crystallography data from the literature. 29,48 This is furthermore a plausible explanation for the NMR relaxation behavior due to its large sensitivity (r -6 ) toward small changes in bond distance according to eq 1. Because of the large sensitivity of the signal intensities as a function of the amount of copper ions the imidazole ligand was in large excess.…”

Control of Protein Oligomerization Symmetry by Metal Coordination: C2 and C3 Symmetrical Assemblies through CuII and NiII Coordination

“…The average Cu-N His and Ni-N His distances are 2.08(3) Å and 2.18(6) Å, respectively, which compare well with the distances observed in the Cu(II)-( N -methylimidazole) 4 (OH 2 ) 2 (2.02(3) Å) and Ni(II)- (imidazole) 6 (2.13(3) Å) complexes 11, 12. As expected from a Cu(II) center, the axial aquo ligand in Cu 2 :MBPC-1 2 is subject to Jahn-Teller distortion and positioned at a distance of 2.55(4) Å.…”

“…To further probe control of the supramolecular assembly by metal binding, which should be manifested by ideal tetragonal (Cu) or octahedral (Ni) coordination geometries, we examined in detail the coordination environments in the two structures (Figure ). The average Cu−N His and Ni−N His distances are 2.08(3) and 2.18(6) Å, respectively, which compare well with the distances observed in the copper(II) tetrakis( N -methylimidazole)·2H 2 O [2.02(3) Å] and nickel(II) hexaimidazole [2.13(3) Å] complexes. , As expected from a Cu II center, the axial aquo ligand in Cu 2 :MBPC-1 2 is subject to Jahn−Teller distortion and positioned at a distance of 2.55(4) Å. The N−metal−N angles formed between His residues at cis positions are 90(2)° and 91(3)° respectively for copper and nickel species, and those between the His residues at trans positions are 178(4)° and 180(1)°, indicating near-ideal square-planar and octahedral protein−metal coordination environments.…”

Coordination of Imidazoles by Cu(II) and Zn(II) as Studied by NMR Relaxometry, EPR, far-FTIR Vibrational Spectroscopy and Ab Initio Calculations: Effect of Methyl Substitution

“…Calculations of the σ- and π-bond interaction coefficients were conducted from measured EPR parameters. Electronic transitions were obtained from the literature. , All imidazole ligands attain values of α 2 ≈ 0.82−0.87 indicating a substantial covalent character. The π-interaction coefficients (β 2 ≈ 0.65−0.69, γ 2 ≈ 0.55−0.8) are probably even better indicators of the covalent nature of the imidazole-cupric bond.…”

“…The Cu(II)-N bond length should subsequently follow the inverse order that is in conformity with X-ray crystallography data from the literature. 29,48 This is furthermore a plausible explanation for the NMR relaxation behavior due to its large sensitivity (r -6 ) toward small changes in bond distance according to eq 1. Because of the large sensitivity of the signal intensities as a function of the amount of copper ions the imidazole ligand was in large excess.…”

Control of Protein Oligomerization Symmetry by Metal Coordination: C2 and C3 Symmetrical Assemblies through CuII and NiII Coordination

“…The average Cu-N His and Ni-N His distances are 2.08(3) Å and 2.18(6) Å, respectively, which compare well with the distances observed in the Cu(II)-( N -methylimidazole) 4 (OH 2 ) 2 (2.02(3) Å) and Ni(II)- (imidazole) 6 (2.13(3) Å) complexes 11, 12. As expected from a Cu(II) center, the axial aquo ligand in Cu 2 :MBPC-1 2 is subject to Jahn-Teller distortion and positioned at a distance of 2.55(4) Å.…”

“…To further probe control of the supramolecular assembly by metal binding, which should be manifested by ideal tetragonal (Cu) or octahedral (Ni) coordination geometries, we examined in detail the coordination environments in the two structures (Figure ). The average Cu−N His and Ni−N His distances are 2.08(3) and 2.18(6) Å, respectively, which compare well with the distances observed in the copper(II) tetrakis( N -methylimidazole)·2H 2 O [2.02(3) Å] and nickel(II) hexaimidazole [2.13(3) Å] complexes. , As expected from a Cu II center, the axial aquo ligand in Cu 2 :MBPC-1 2 is subject to Jahn−Teller distortion and positioned at a distance of 2.55(4) Å. The N−metal−N angles formed between His residues at cis positions are 90(2)° and 91(3)° respectively for copper and nickel species, and those between the His residues at trans positions are 178(4)° and 180(1)°, indicating near-ideal square-planar and octahedral protein−metal coordination environments.…”

Coordination of Imidazoles by Cu(II) and Zn(II) as Studied by NMR Relaxometry, EPR, far-FTIR Vibrational Spectroscopy and Ab Initio Calculations: Effect of Methyl Substitution

“…Calculations of the σ- and π-bond interaction coefficients were conducted from measured EPR parameters. Electronic transitions were obtained from the literature. , All imidazole ligands attain values of α 2 ≈ 0.82−0.87 indicating a substantial covalent character. The π-interaction coefficients (β 2 ≈ 0.65−0.69, γ 2 ≈ 0.55−0.8) are probably even better indicators of the covalent nature of the imidazole-cupric bond.…”

“…The Cu(II)-N bond length should subsequently follow the inverse order that is in conformity with X-ray crystallography data from the literature. 29,48 This is furthermore a plausible explanation for the NMR relaxation behavior due to its large sensitivity (r -6 ) toward small changes in bond distance according to eq 1. Because of the large sensitivity of the signal intensities as a function of the amount of copper ions the imidazole ligand was in large excess.…”