Coordination Number Of Copper Research Articles

Synthesis, X-ray and antibacterial activity of new copper(II) thiosemicarbazone complexes derived from 4-formyl-3-hydroxy-2-naphthoic acid

New thiosemicarbazone ligand derived from 4-formyl-3-hydroxy-2-naphthoic acid (H3L·CH3OH (1)) and their two copper(II) complexes with composition [Cu(H2L)Cl]2.2(dmf) (2), [Cu(H2L)NO3(dmf)] (3) were synthesized and characterized by thermal analysis, IR-, EPR- spectroscopy and single X-ray diffraction method. In both complexes the mono-deprotonated ligand coordinate tridentate to Cu(II) ion by ONS donor atoms provided by phenolic oxygen, azomethine nitrogen and thiol sulfur. In 2 binuclear complex has the square–planar environment of one copper(II) completed by Cl- anion, while a tetragonal pyramid of other metal is formed by Cl- anion and S atom from the neighboring organic ligand. The copper ion in the mononuclear complex 3 adopt a square-pyramidal structure, where the coordination number of copper(II) ion is adjusted to 5 by O atoms of NO3− anion and dimethylformamide molecule. Magnetic investigations of complex 2 revealed the presence of noticeable magnetic couplings between Cu(II) ions, while compound 3 shows the behavior typical of magnetically isolated Cu(II) centers. The compounds tested against St. aureus, C. albicans, E. coli and Kl. Pneumonia were found to be more active against gram-positive bacteria strains.

Cytotoxic Copper(II) Complexes Based on 2,2'-Bipyridine/1,10- Phenanthroline and 5-(4-Chlorophenyl)-1H-tetrazole: Synthesis and Structures

Five coordination compounds [Cu2(Bipy)2L4]·C2H5OH (Iа, Ib), [Cu2(Dmbipy)2L4] (II),[Cu2(Phen)2L4]·H2O (IIIa), [Cu2(Dmphen)2L4] (IVa), and [Cu2(Phendione’)2L4]·2C2H5OH·2H2O (V) aresynthesized from 5-(4-chlorophenyl)-1H-tetrazole (HL), where Bipy is 2,2'-bipyridine, Dmbipy is 4,4'-dimethyl-2,2'-bipyridine, Phen is 1,10-phenanthroline, Dmphen is 4,7-dimethyl-1,10-phenanthroline, andPhendione’ is 6-ethoxy-6-hydroxy-1,10-phenanthrolin-5-one. The crystal structures of the complexes aredetermined by X-ray diffraction (XRD) of single crystals (CIF files CCDC nos. 2225368 (Ia), 2225369 (Ib),2225370 (II), 2225372 (IIIa), 2225373 (IVa), and 2225371 (V)). The compounds are binuclear due to thebridging function of the tetrazolate anion, and the coordination number of copper is five in all synthesizedcomplexes. The cytotoxic activity of the complexes against the Hep2 and HepG2 cancer cell lines and noncanceroushuman fibroblasts MRC-5 is studied. The complexes exhibit pronounced cytotoxic properties, andcompound V has the maximum selectivity index with respect to the cancer cells.

Tetra-μ-acetato-bis[(1,3-benzothiazole)copper(II)](Cu—Cu)

The title compound, [Cu2(CH3CO2)4(C7H5NS)2] or [(C7H5NS)Cu]2(μ-O2CCH3)4, crystallizes with one mol­ecule per unit cell. The coordination number of copper is six with four basal O atoms, one axial N atom and one axial Cu atom. Four acetate ligands act as bidentate linker and connect two Cu atoms, with a crystallographic inversion center located at the mid-point of the Cu—Cu bond. The acetate ligands form slightly distorted square planes around each metal ion, while the copper ions are displaced by 0.2089 (4) Å from these planes towards the N atoms. Thus, the Cu—Cu distance is elongated to 2.6378 (7) Å, compared with the 2.2180 (7) Å distance between the two basal planes. The angle between the basal plane and the Cu—N bond is 4.84 (6)°.

What is the coordination number of copper(ii) in metallosupramolecular chemistry?

Analysis of structural and solution data shows a specific stabilisation of copper(II) in ternary complexes containing one 2,2′:6′,2″-terpyridine and one 2,2′-bipyridine ligand. This is not a general phenomenon relating to five-coordinate copper(II), but rather a specific consequence of the two ligand donor sets. The consequences of this observation for metallosupramolecular chemistry are discussed.

In-situ EXAFS study of copper in the electrokinetic remediation process.

The speciation of copper in the early stage of the electrokinetic remediation (EKR) process has been studied by extended X-ray absorption fine structure (EXAFS) spectroscopy in the present work. By in-situ EXAFS, we found that copper in a contaminated soil possessed a Cu-O bond distance of 1.98 A with a coordination number (CN) of 5.8. In the second shell, the bond distance of Cu-(O)-Cu was 2.87 A with a CN of 6.4. However, possibly due to the fact that incompact copper atoms in the outer shells were distorted by EKR, the Cu-(O)-Cu (2nd shell) bond distance and the CN of copper in the contaminated soil decreased by 0.08 A and 5.4, respectively in the early stage of the EKR process. Interestingly, after prolonging the contact time to about 80 minutes, the 1st-shell copper atoms were also perturbed by EKR. This work is an example of usefulness of the in-situ EXAFS spectroscopy for detailed studies of the speciation of copper in the contaminated soil during EKR process.

Counterion effects in the spectra and structure of solvatochromic copper(II) chelates containing 1,2-diamines and β-ketoenols

The contemporaneous reaction of copper(II) ‘salts’ with certain β-diones and N-substituted 1,2-diaminoethanes (enR) is reported. The influence of γ-position derivatives of 2,4-pentanedione, X-acacH (XH, CN, NO 2), is described and the contribution of anions to the stability, the stereochemistry and the electronic structure of the resulting mixed-ligand chelates is discussed. Spectroscopic observations disclose that the bidentate ligands form chelate rings with copper(II) as common vertex. Whenever the [Cu(β-dionato)enR] + entity pertains, the IR and the electronic excitation spectra, in conjunction with other physicochemical measurements, suggest that the CuN 2O 2 chromophore attains a virtually square-planar structure. Copper(II) in the [Cu(β-dionato)enR] + entity lacks coordination saturation and, in addition to electrostatic interactions that prevail when bulky polyatomic anions counterbalance the positive charge, it is capable of forming covalent bonds with neutral molecules and charged species such as the halides and pseudohalides. The basal CuN 2O 2 plane is distorted upon coordination of unidentate ligands residing on the apex of the resulting square-pyramidal structure. Further increase in the coordination number of copper(II) by bidentate anions or neutral molecules leads to tetragonally distorted octahedral structures. This change in the symmetry of the field induced on copper(II) is revealed by spectral shifts that also disclose covalent interactions in the encounters of the CuN 2O 2 chromophore with polar or polarisable molecules. These interactions are enhanced with increasing ability of the attacking species to act as an electron pair donor. Linear dependence of the ligand field excitation maxima on the donicity of the attacking species is established. Rearrangement involving rapture of the CuO bond and formation of the CuN 4 chromophore accompanies the addition of N,N-dimethylethylenediamine, Me 2en, to Cu(CN-acac) 2. The charge in the resulting [Cu(Me 2en) 2] 2+ entity is neutralised by the anion of the 3-cyano-2,4-pentanedione, CN-acac −, that binds to copper(II) through the nitrogen atom coordinating as nitrile. The coordination of a β-ketoenol as unidentate ligand through an atom other than oxygen or carbon has no precedence.

ChemInform Abstract: X‐Ray Absorption Edge Determination of the Oxidation State and Coordination Number of Copper: Application to the Type 3 Site in Rhus vernicifera Laccase and Its Reaction with Oxygen

Cu X-ray absorption edge features of 19 Cu(I) and 40 Cu(II) model complexes have been systematically studied and correlated with oxidation state and geometry. Studies of Cu(I) model complexes with different coordination number reveal that an 8983-8984-eV peak (assigned as the Cu 1s ..-->.. 4p transition) can be correlated in energy, shape, and intensity with ligation and site geometry of the cuprous ion. These Cu(I) edge features have been qualitatively interpreted with ligand field concepts. Alternatively, no Cu(II) complex exhibits a peak below 8985.0 eV. The limited intensity observed in the 8983-8985-eV region for some Cu(II) complexes is associated with the tail of an absorption peak at approx. 8986 eV which is affected by the covalency of the equatorial ligands. These models studies allow accurate calibration of a normalized difference edge procedure which is used for the quantitative determination of Cu(I) content in copper complexes of mixed oxidation state composition. This normalized difference edge analysis is then used to quantitatively determine the oxidation states of the copper sites in type 2 copper-depleted (T2D) and native forms of the multicopper oxidase, Rhus vernicifera laccase. The type 3 site of the T2D laccase is found to be fully reduced and stable tomore » oxidation by O/sub 2/ or by 25-fold protein equivalents of ferricyanide, but it can be oxidized by reaction with peroxide. The increase in intensity of the 330-nm absorption feature which results from peroxide titration of T2D laccase is found to correlate linearly with the percent of oxidation of the binuclear copper site.« less

X-ray absorption edge determination of the oxidation state and coordination number of copper. Application to the type 3 site in Rhus vernicifera laccase and its reaction with oxygen

Cu X-ray absorption edge features of 19 Cu(I) and 40 Cu(II) model complexes have been systematically studied and correlated with oxidation state and geometry. Studies of Cu(I) model complexes with different coordination number reveal that an 8983-8984-eV peak (assigned as the Cu 1s ..-->.. 4p transition) can be correlated in energy, shape, and intensity with ligation and site geometry of the cuprous ion. These Cu(I) edge features have been qualitatively interpreted with ligand field concepts. Alternatively, no Cu(II) complex exhibits a peak below 8985.0 eV. The limited intensity observed in the 8983-8985-eV region for some Cu(II) complexes is associated with the tail of an absorption peak at approx. 8986 eV which is affected by the covalency of the equatorial ligands. These models studies allow accurate calibration of a normalized difference edge procedure which is used for the quantitative determination of Cu(I) content in copper complexes of mixed oxidation state composition. This normalized difference edge analysis is then used to quantitatively determine the oxidation states of the copper sites in type 2 copper-depleted (T2D) and native forms of the multicopper oxidase, Rhus vernicifera laccase. The type 3 site of the T2D laccase is found to be fully reduced and stable tomore » oxidation by O/sub 2/ or by 25-fold protein equivalents of ferricyanide, but it can be oxidized by reaction with peroxide. The increase in intensity of the 330-nm absorption feature which results from peroxide titration of T2D laccase is found to correlate linearly with the percent of oxidation of the binuclear copper site.« less

Syntheses and crystal structures of two copper(II) chloride complexes with 2,3-dimethyl-2,3-butanediol

The crystal and molecular structures of the complexes [CuCl 2(H 2pin)] 2 (H 2pin = 2,3-dimethyl-2,3-butanediol = pinacol) (1) and [CuCl 2(H 2pin)]·H 2pin (2) have been determined. The compound (1) crystallizes in the orthorhombic space group Pbcn with a = 20.710(2), b = 11.401(6), c = 17.469(4), and Z = 8. The dimeric [CuCl 2(H 2pin)] 2 molecules consist of two five-coordinated Cu(II) ions with two different CuO 2Cl 2Cl′ chromophores. The symmetry around one copper atom can be described as a distorted square based pyramid, and around the other as a distorted trigonal bipyramid. The dimers are held together by hydrogen bonds. The compound (2) crystallizes in the monoclinic space group C2/c with a = 18.878(18), b = 12.115(3), c = 7.541(2), β = 104.94(5), and Z = 4. The structure of (2) is a polymer. The copper atom is surrounded by two oxygen atoms of one H 2pin molecule and by two chloride ions (Cu-Cl = 2.223 Å). Two extra chloride ions from adjacent CuCl 2(H 2pin) units are at the distance of 3.223 Å. The coordination number of copper(II) ion is 4 + 2 with an elongated rhombic octahedral symmetry. The second H 2pin molecule is not coordinated to copper atom, but has an anti conformation and connects CuCl 2(H 2pin) units together by hydrogen bonds.

Copper(I) complexes—III: Tetrakis, tris and bis amine copper(I) perchlorates

The treatment of Cu(I)ClO 4 with heterocyclic amines leads to the formation of complexes in which copper is tetra-, tri- and dicoordinated. Evidence that precludes coordination by perchlorate and confirms that the trisamine copper(I) complex contains triligated copper, is presented. I.R. results suggest that the formally dicoordinated complexes in fact possess a higher coordination number in the solid, due to the formation of π-complexes, metal clusters or electron deficient bonds. The overall coordination number of copper(I) in each complex is shown to be a function of the basicity and the steric requirements of the ligands and determines the resistance to air oxidation of copper(I). Unexpectedly, for a d 10 ion, several complexes show apparent magnetic moments which are quite large.

Diaryltelluride complexes of copper(I) halides

Copper(I) halide complexes of stoichiometry CuL nX have been prepared where L is a diaryltelluride (n = 3, L = Ph 2Te, X = Cl; n = 2, L = Ph 2Te, X = Br; n = 2, L = (p-tolyl) 2Te, X = Cl, Br, I; n = 2, L = (p-EtOC 6H 4) 2 Te, X = Cl, Br; n = 1, L = Ph 2Te or (p-EtOC 6H 4) 2Te, X = I). The new compounds have been examined by X-ray powder methods, conductivity studies and vibrational spectroscopy. It is concluded that the coordination number of copper(I) within the series may be 4 or 3 and that the geometry about the metal is either tetrahedral (CN4) or trigonal planar (CN3). Assignments of copper-halogen stretching vibrations are offered.

Preparation, physical properties and reactions of copper(I)-triphenyl-m complexes (M= P, As, Sb)

General methods of preparation, chemical reactions and some physical properties of triphenylphosphine, arsine, and stibine-copper(I) complexes have been studied. The most general methods of preparation involve the reduction of copper(II) salts with triphenylphosphine or the direct reaction of this ligand with copper(I) salts. Displacement reactions on P 3CuCl or [PCuCl] 4 (P=triphenylphosphine) by charged or uncharged ligands have been employed to prepare compounds such as: P 2CuSC 6H 5, P 2CuOC 6H 5, PCuC 5H 5, PCuC≡CC 6H 5, PCuCl·pyr., PCuN 3·pyr., P 3CuB - (C 6H 5) 4, etc. P 3CuCl adds polar molecules to yield P 3CuCl · X (X=2 CHCl 3, 1 CS 2, 2 DMF, etc.). These complexes do not add carbon monoxide, olefins or acetylenes to yield stable compounds. P 2CuN 3 in excess P decomposes smoothly to yield [P=N-Cu] n (250°). A study of the solution molecular weights suggests that many of the these complexes have three coordinated copper(I). This coordination number of copper appears to be of appreciable stability.

The Crystal Structure of Copper Yunainate Trihydrate, Cu(C5H8O3NS)2·3H2O

Abstract The crystal structure of copper yunainate trihydrate, Cu(C5H8O3NS)2·3H2O, has been studied by means of three-dimensional X-ray analysis. The crystal is monoclinic, with two formula units in a unit cell of the dimensions: a=15.94, b=6.33, c=8.60 Å, and β=95.6°; the space group is P21. The intensities were measured visually from equi-inclination integrating Weissenberg photographs taken with CuKα radiation around the b and c axes. The structure was elucidated by Sim’s method, and refined by the block-diagonal-matrix least-squares method, assuming anisotropic thermal motions for all the atoms. The final R factor is 9.2%. The copper atom is coordinated by imino nitrogen and carboxyl oxygen atoms of two yunainate groups, and a water oxygen atom. The first four atoms lie almost on a plane and make a square configuration of the trans type. The last one is bonded to the copper atom nearly in the direction of the normal of the plane. Thus, the coordination number of copper is five in the present crystal. Of the three sorts of water of crystallization, one is connected with the copper atom, as has already been mentioned, and the remaining two are lattice water, forming a hydrogen-bonded spiral chain around the screw axis. Further, these water molecules connect complex molecules to one another by their hydrogen bonds, forming a threedimensional hydrogen-bonded structure.

A reduction in the coordination number of copper(II) by steric hindrance

A reduction in the coordination number of copper(II) by steric hindrance

Fragmentation of acid chlorides and azides of?-amino acids having a tertiary nitrogen atom, and some other properties of these amino acids (copper complexes)

1. Likeα-dibenzylamino acid chlorides, N.N-diethyl-, N,N-bis-p-methylbenzyl-, and N,N-bis-p-nitrobenzylalanyl chlorides can undergo fragmentation. The most essential feature in this reaction is the presence of a tertiary nitrogen atom. 2. In the reaction of nitrous acid with N,N-dibenzyl-3-phenylalanine hydrazide, N,N-dibenzylstyrylamine was isolated. 3. A method was developed for the synthesis of N,N-bis-p-nitrobenzylalanine. 4. In solution, copper complexes ofα-di(aralkyl)amino acids give two types of complexes: a) green complexes, and b) violet complexes. Such dichroism is apparently associated with change in the coordination number of copper as a result of the participation of solvent molecules in the complex.