Synthesis and crystal structure of a first-generation model for the trinuclear copper site in ascorbate oxidase and of a dinuclear silver precursor

Adams, Harry; Bailey, Neil A.; Dwyer, Matthew J. S.; Fenton, David E.; Hellier, Paul C.; Hempstead, Paul D.; Latour, Jean Marc

doi:10.1039/dt9930001207

Cited by 64 publications

(39 citation statements)

References 27 publications

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“…The complex nature of these signals could stem from the presence of related conformers in solution or from the magnetic inequivalence of the geminal hydrogen pairs caused by restricted rotation about the C-C bond. [38,39] In the pendant arm, this restriction could possibly be due to hydrogen-bonding effects. The broad singlet at δ ϭ 1.84-1.95 may be assigned to the NH 2 by changing the experimental conditions were unsuccessful and it was possible to identify complexes derived from the precursor amine as the major components of the products.…”

Section: Macrocycle 3 and Its Metal Complexesmentioning

confidence: 97%

Synthesis and Characterization of Some Metal Complexes with New Nitrogen–Oxygen Donor Macrocyclic Ligands – X-ray Crystal Structures of a 26-Membered Reduced Monoprotonated Macrocycle and a 20-Membered Pendant-Arm Schiff-Base Macrocyclic Cadmium(II) Complex

Vicente

Lodeiro

Adams

et al. 2000

Eur. J. Inorg. Chem.

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New series of macrocyclic Schiff‐base lanthanide(III), yttrium(III), and cadmium(II) complexes, [M(1)]Xn (X = NO 3–, M = Y, Ln = La–Yb except Pm and Dy; X = ClO 4–, M = Cd, La, Ce, Pr, Sm, Gd, or Er) and [M(3)]Xn (X = NO 3–, M = Dy; X = ClO 4–, M = Er and Cd), have been prepared by cyclocondensation of O1,O7‐bis(2‐formylphenyl)‐1,4,7‐trioxaheptane with O1,O7‐bis(2‐aninyl)‐1,4,7‐trioxaheptane (1) or tris(2‐aminoethyl)amine (3) in the presence of the appropriate metal salt as a template agent. The Schiff‐base macrocycles 1 and 3 are also formed in the absence of a metal ion. Treatment of 1 with NaBH4 in methanol gives the diamine macrocycle 2. The reactions of LnIII, CdII, and YIII ions with 2 have also been investigated. The crystal structures of the monoprotonated ligand 2 and of the complex [Cd(3)](ClO4)2 have been determined by X‐ray diffraction analysis.

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Section: Macrocycle 3 and Its Metal Complexesmentioning

confidence: 97%

Synthesis and Characterization of Some Metal Complexes with New Nitrogen–Oxygen Donor Macrocyclic Ligands – X-ray Crystal Structures of a 26-Membered Reduced Monoprotonated Macrocycle and a 20-Membered Pendant-Arm Schiff-Base Macrocyclic Cadmium(II) Complex

Vicente

Lodeiro

Adams

et al. 2000

Eur. J. Inorg. Chem.

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“…In 2 another oxygen from the phosphate group further links these two copper centres to the third type 2 copper centre, establishing longer Cu ؒ ؒ ؒ Cu separations of 4.561(4) and 5.474(4) Å. Across the aromatic mesitylene spacer, the Cu(1) ؒ ؒ ؒ Cu(3) and Cu(2) ؒ ؒ ؒ Cu(3) distances are 9.426(4) and 9.279(4) Å. Fenton and co-workers 15 have reported the trinuclear copper() complex of a trinucleating Schiff-base ligand in which the separation between the type 3 coppers of 3.62 Å is similar to those in compound 2. The distances to the type 2 copper are slightly longer, vis-à-vis 4.95 and 5.89 Å, due to the absence of a bridging group.…”

Section: Synthesis and Crystal Structurementioning

confidence: 96%

“…Non-SI units employed: µ B ≈ 9.27 × 10 Ϫ24 J T Ϫ1 , G = 10 Ϫ4 T. scarce but have attracted recent attention. A number of studies have reported symmetric and asymmetric trinuclear copper complexes [11][12][13][14][15][16] as structural models for these biosites and there is a very recent report of a trinuclear, mixed-valence complex, vis-à-vis Cu II 2 Cu III , isolated following oxidation of the trigonalplanar copper() complex of N-permethylated cyclohexane-1,2diamine. 17 This has raised questions about the involvement of copper() in the function of the enzymes.…”

mentioning

confidence: 99%

Towards synthetic models for trinuclear copper active sites of ascorbate oxidase and laccase: self-assembly, crystal structure and magnetic properties of the copper(II) complexes of 1,3,5-tris(1,4,7-triazacyclonon-1-ylmethyl)benzene †

Spiccia¹,

Graham

Hearn³

et al. 1997

J. Chem. Soc., Dalton Trans.

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Reaction of the hydrobromide salt of 1,3,5-tris(1,4,7-triazacyclonon-1-ylmethyl)benzene, Lؒ9HBr, with copper() nitrate followed by cation-exchange chromatographic purification affordedThe ESR and magnetic susceptibility data indicated that the complex consists of three identical non-interacting copper() centres. Reaction of 1 with a phosphate source produces {[Cu 3 L(µ-OH)(µ 3 -HPO 4 )(H 2 O)][PF 6 ] 3 ؒ3H 2 O} n 2 the polymeric lattice of which contains trinuclear copper() sites with structural similarities to laccase (Lc) and ascorbate oxidase (AO). These trinuclear sites consist of two type 3 copper() centres, at a separation of 3.557(4) Å, linked by an hydroxo bridge and two phosphate oxygens while another phosphate oxygen links these two centres to the further removed type 2 copper() centre, establishing separations of 4.561(4) and 5.474(4) Å. The magnetic properties of 2 were investigated in the temperature range 4.2-300 K and they revealed an S = ¹ 2 molecular ground state arising from antiferromagnetic coupling. A number of models have been employed in order quantitatively to fit the µ eff versus temperature data including those applicable to the resting oxidised state of laccase and ascorbate oxidase, vis-à-vis dimer plus uncoupled monomer, but the best fits were obtained using a symmetrical trinuclear approximation with J 12 for the doubly bridged [CuL(µ-OH)(µ-HPO 4 )Cu] moiety of Ϫ53 or ca. Ϫ80 cm Ϫ1 combined respectively with J for the two equal three-atom phosphato bridges of Ϫ90 or Ϫ77 to Ϫ90 cm Ϫ1 . The 77 K solid-state ESR spectrum of 2 is unusual for S = ¹ 2 ground-state systems and shows six components of a probable seven-line copper hyperfine multiplet between 2500 and 3100 G and a strong x, y resonance at ca. 3200 G, most probably due to weak copper() pair interactions or the superimposition of S = ¹ 2 signals from both molecular doublets. The 77 K solution ESR spectrum (dimethylformamide, water-glycol 1 : 1) for 2 is typical of a monomeric copper() centre and closely resembles the ESR spectrum of the type 2 site in Lc and AO. The ESR, electrospray mass spectrometric and NMR data indicate that 2 dissociates in solution to give a trinuclear unit consisting of two type 3 copper() centres (ESR silent), which are linked by the hydroxo and phosphate group (phosphate is released from the complex only on addition of acid), and an isolated type 2 copper() centre which is probably responsible for the ESR features.

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“…A broad singlet at 1.85 ppm is assigned to the NH 2 groups on the basis of the deuterium exchange noted when D 2 O was added to the CD 3 CN solution. The complex nature of the resonances arising from the aliphatic regions of the molecules most likely stems from magnetic inequivalence of the geminal hydrogen pairs caused by restricted rotation about the C-C bonds, which strongly suggests that coordination of the primary amine nitrogen atoms to the Cd(II) ion is retained in solution [26,27].…”

Section: Nmr Studiesmentioning

confidence: 99%

Synthesis, X-ray characterization, NMR and ab initio molecular-orbital studies of some cadmium(II) macrocyclic Schiff-base complexes with two 2-aminoethyl pendant arms

Taylor

Wainwright

Keypour

et al. 2004

JICS

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Three new pendant arm Schiff-base macrocyclic complexes, [CdL n ] 2+ (n = 5, 6, 7), have been prepared via cyclocondensation of 2,6-diacetylpyridine with three different branched hexaamines in the presence of Cd(II). The ligands are 15-, 16-and 17-membered pentaaza macrocycles having two 2-aminoethyl pendant arms [L 5 = 2,13-dimethyl-6,9-bis(aminoethyl)--pentaene]. All complexes were investigated by IR, 1 H and 13 C NMR, COSY(H,H) and HETCOR(H,C) spectroscopy and X-ray diffraction. In the solid state structure of each complex the Cd(II) ion is situated centrally within an approximately planar pentaaza macrocyclic ring, binding to the five nitrogen atoms, and also to the two pendant amines which are located on opposite sides of the macrocyclic plane. ab initio HF-MO calculations using a standard 3-21G* basis set have been used to verify that these similar basic structures correspond to energy minima in the gas phase.

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Synthesis and crystal structure of a first-generation model for the trinuclear copper site in ascorbate oxidase and of a dinuclear silver precursor

Cited by 64 publications

References 27 publications

Synthesis and Characterization of Some Metal Complexes with New Nitrogen–Oxygen Donor Macrocyclic Ligands – X-ray Crystal Structures of a 26-Membered Reduced Monoprotonated Macrocycle and a 20-Membered Pendant-Arm Schiff-Base Macrocyclic Cadmium(II) Complex

Synthesis and Characterization of Some Metal Complexes with New Nitrogen–Oxygen Donor Macrocyclic Ligands – X-ray Crystal Structures of a 26-Membered Reduced Monoprotonated Macrocycle and a 20-Membered Pendant-Arm Schiff-Base Macrocyclic Cadmium(II) Complex

Towards synthetic models for trinuclear copper active sites of ascorbate oxidase and laccase: self-assembly, crystal structure and magnetic properties of the copper(II) complexes of 1,3,5-tris(1,4,7-triazacyclonon-1-ylmethyl)benzene †

Synthesis, X-ray characterization, NMR and ab initio molecular-orbital studies of some cadmium(II) macrocyclic Schiff-base complexes with two 2-aminoethyl pendant arms

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