Copper Coordination Sphere Research Articles

Crystal structures of two copper(II) complexes with N,N-diethylbenzhydrazide

The copper(II) complexes with N,N-diethylbenzhydrazide, [Cu(C6H5CONHN(C2H5)2)]Cl2 (I) and Cu(C6H5CONN(C2H5)2)2 (II), have been studied by X-ray diffraction analysis. In the both compounds, the reactant acts as a bidentate (O, N(2)) ligand, forming five-membered chelate rings with copper. In cationic complex I, the O→Cu and N→Cu bond lengths are 1.954(2) and 2.070(3) A, respectively, and the O(1)CuN(2) chelate angle is 81.89(10°. The Cl− ions are in the coordination sphere of copper (Cu-Cl, 2.1974(11) and 2.2178(10) A). The chelate ring has an envelope conformation with the copper atom in the flap position. The coordination polyhedron of the copper atom is a strongly distorted tetrahedron. Neutral complex II is an inner complex salt. The reactant forms with copper two planar chelate rings. The Cu-O and N→Cu bond lengths are 1.8901(9) and 2.0175(11) A, respectively, and the O(1)CuN(2) chelate cycle is 83.70(4)°. Complex II is planar, and the coordination polygon of the copper atom is a parallelogram. The thermal stability of complexes I and II has been studied.

On In Situ Prepared Cu–Phenanthroline Complexes in Aqueous Alkaline Solutions and Their Use in the Catalytic Oxidation of Veratryl Alcohol

AbstractThe in situ prepared complex based on copper(II) sulfate and 1,10‐phenanthroline (phen) and its performance in the catalytic oxidation of veratryl alcohol (3,4‐dimethoxybenzyl alcohol) to veratraldehyde with O2 in alkaline aqueous solutions have been studied. In aqueous solution, the structure of Cu–phen complexes varies with reaction conditions; by changing either the copper‐to‐ligand molar ratio or the pH, the amount of coordinated 1,10‐phenanthroline and hydroxido ligands in the coordination sphere of copper can be altered in a controlled manner. The highest activities are achieved in the pH range 12.6–13.3, which correlates with the presence of the [Cu(phen)(OH)2] species according to complex distribution curves. According to the UV/Vis and EPR studies, the oxidation reaction is initiated by the reduction of [Cu(phen)(OH)2] to CuI species by veratryl alcohol, which can be seen as a disappearance of the Cu2+ EPR signal and as a shift of the UV/Vis absorbance maximum from about 690 nm to the 410 and 525 nm regions. When molecular oxygen is added, the CuI species is readily oxidised back to CuII species, and the catalytic formation of aldehyde is initiated. On the basis of these observations, a mechanism for the catalytic oxidation is proposed. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

Probing key coordination interactions: configurationally restricted metal activated CXCR4 antagonists

The syntheses of configurationally restricted mono- and bis-macrocyclic copper(II) perchlorate complexes (copper(II) 5-benzyl-1,5,8,12-tetraazabicyclo[10.2.2]hexadecane and dicopper(II) 5,5'-[1,4-phenylenebis(methylene)]-bis(1,5,8,12-tetraazabicyclo[10.2.2]hexadecane)) are reported and the X-ray structure of the copper(II) mono-macrocyclic complex has been determined. EXAFS studies on the bis-macrocyclic species in aqueous solution show that the copper coordination spheres are essentially identical to the solid state structure, and do not vary in the presence of 20 equivalents of sodium acetate per metal centre. DFT calculations were carried out at the BP86/TZP level to determine the nature of potential binding interactions with CXCR4 aspartate residues. The alkylated single macrocyclic compound was modelled with an acetate included to represent the aspartate residue, demonstrating that the predicted macrocycle configuration has the lowest energy and the acetate interaction is effectively monodentate giving a distorted trigonal bipyramidal geometry at the copper centre. In vitro anti-HIV infection assays show that the configurationally restricted dicopper(II) complex is more active (average EC(50) = 0.026 microM against HIV-1) than the non-constrained dicopper(II) 1,1'-[1,4-phenylenebis(methylene)]-bis(1,4,8,11-tetraazacyclotetradecane) (average EC(50) = 0.047 microM against HIV-1) although it is an order of magnitude less active than the configurationally restricted dizinc(II) complex.

Influence of heterocycles arrangement in structural isomeric ligands on coordination sphere of copper(II) complexes: Crystal structures and spectroscopic characterization

New copper complexes with two structural isomeric ligands, 2-(indazol-1-yl)-2-thiazoline (TnInA) and 2-(indazol-2-yl)-2-thiazoline (TnInL), have been synthesized and characterized by magnetic measurements, IR, electronic and EPR spectroscopies. Moreover, the molecular structures of [Cu(NO 3)(TnInA) 2(H 2O)](NO 3) · (H 2O) ( 1) and [Cu(NO 3) 2(TnInL)(H 2O)] ( 2) have been resolved by single-crystal X-ray diffraction studies. In compound 1 the copper ion is in a distorted octahedral geometry, with the equatorial plane formed by four nitrogen donor atoms from two organic ligands and the axial positions occupied by two oxygen atoms from a water molecule and a mono-coordinated nitrate anion. The coordination geometry around the copper atom in compound 2 can be described basically as a square pyramid with two nitrogen atoms from TnInL ligand, one oxygen atom from a water molecule and one oxygen atom from a nitrate group in the equatorial plane. The axial position is occupied by one oxygen atom from a nitrate group. Likewise, a second oxygen atom from the last nitrate group in equatorial position might involve in a weak sixth coordination position to give a (4 + 1 + 1 ∗) coordination mode.

The effects of steric aliphatic–aliphatic interactions in the coordination polymer of bis( N, N-diethylglycinato)copper(II): Experimental evidence and theoretical modeling

New coordination polymer catena-poly[( N, N-diethylglycinato-κ O,κ N)copper(II)-μ-[ N, N-diethylglycinato-κ O 1,κ N: O 2]] has been obtained by single-crystal X-ray diffraction. The copper(II) was surrounded with two amino N and two carboxyl O atoms in trans position in the coordination plane. Discrete polymeric chains were produced by axial coordinative bonding between copper(II) and carbonyl oxygen atom from adjacent asymmetric unit. Molecular mechanics (MM) force field developed to study the properties of copper(II) amino acid complexes reproduced well intermolecular aliphatic–aliphatic interactions between ethyl chains and C–H⋯O hydrogen bonding. The relative unit cell volume reproduction was 0.3%. Theoretical conformational analysis showed that experimentally obtained conformer was not the most stable in vacuo. The calculations of the unit cell packings and intermolecular interactions for a series of conformers elucidated the reasons that governed the experimentally obtained conformer to appear in the real crystal structure. MM results suggest that intermolecular aliphatic–aliphatic interactions between ethyl groups affected a conformational change concurrent with the change in the copper(II) coordination sphere upon crystallization.

Studies of the interaction between bis(dithiocarbamato)copper(II) complexes with nitric oxide in aqueous solution and biological applications

Three new bis(dithiocarbamato)copper(II) complexes have been prepared and characterized by elemental analysis, UV–Vis, and IR spectroscopy: bis(4-piperidonedithiocarbamato)copper(II), [Cu(Pdtc) 2] 2 ( 1), bis(piperidinedithiocarbamato)copper(II), [Cu(Ppdtc) 2] 2 ( 2), and bis[(2-piperidinecarboxy)dithiocarbamato]copper(II), Cu(Ppidtc) 2 ( 3). The crystal structures of the complexes 1 and 2 have been determined using X-ray diffraction methods and they are dimeric. The coordination sphere of copper(II) ions is described as a distorted square-pyramid: the axial Cu–S bond distances 2.7 and 2.8 Å for 1 and 2, respectively, are longer than the equatorial Cu–S ones (2.3 Å). Complexes 1 and 2 are not soluble in water. In contrast, 3 is water soluble. The interaction of 3, the previously prepared bis[ N-(dithiocarboxy)sarcosine]copper(II), Cu(Sdtc) 2 ( 4), and bis[(dicarboxymethyl)dithiocarbamato]copper(II), Cu(Idadtc) 2 ( 5), with nitric oxide in aqueous solution at pH 7.4 and 20 °C was spectrophotometrically studied and the experimental data were analysed by means of the spefo-letagrop and hyperquad programs, respectively. The stability constants of the complexes CuL 2(NO) and CuL 2(NO) 2 [L = dithiocarbamate] were determined. The interaction of 1 and 2 with nitric oxide was theoretically studied by molecular mechanics methods. Complexes 3, 4 and 5 and the previously studied bis[(dihydroxyethyl)dithiocarbamato]copper(II), Cu(Deadtc) 2 ( 6), decrease the NO produced in vitro either by sodium nitroprusside (NPS) or by cultured murine macrophages J774 stimulated with lipopolysaccharide (LPS) and interferon-γ (IFNγ). Inducible nitric oxide synthase (iNOS) activity was determined by measuring the stable NO end product, nitrite, using a colorimetric assay.

The delivery of copper for thylakoid import observed by NMR

The thylakoid compartments of plant chloroplasts are a vital destination for copper. Copper is needed to form holo-plastocyanin, which must shuttle electrons between photosystems to convert light into biologically useful chemical energy. Copper can bind tightly to proteins, so it has been hypothesized that copper partitions onto ligand-exchange pathways to reach intracellular locations without inflicting damage en route. The copper metallochaperone Atx1 of chloroplast-related cyanobacteria (ScAtx1) engages in bacterial two-hybrid interactions with N-terminal domains of copper-transporting ATPases CtaA (cell import) and PacS (thylakoid import). Here we visualize copper delivery. The N-terminal domain PacS(N) has a ferredoxin-like fold that forms copper-dependent heterodimers with ScAtx1. Removal of copper, by the addition of the cuprous-ion chelator bathocuproine disulfonate, disrupts this heterodimer, as shown from a reduction of the overall tumbling rate of the protein mixture. The NMR spectral changes of the heterodimer versus the separate proteins reveal that loops 1, 3, and 5 (the carboxyl tail) of the ScAtx1 Cu(I) site switch to an apo-like configuration in the heterodimer. NMR data ((2)J(NH) couplings in the imidazole ring of (15)N ScAtx1 His-61) also show that His-61, bound to copper(I) in [Cu(I)ScAtx1](2), is not coordinated to copper in the heterodimer. A model for the PacS(N)/Cu(I)/ScAtx1 complex is presented. Contact with PacS(N) induces change to the ScAtx1 copper-coordination sphere that drives copper release for thylakoid import. These data also elaborate on the mechanism to keep copper(I) out of the ZiaA(N) ATPase zinc sites.

Crystalline products isolated from solutions with commercially available 2,3-bis(2-pyridyl)pyrazine (dpp) as reactant: Detection of a dimerized form of dpp

From reaction mixtures of commercially available 2,3-bis(2-pyridyl)pyrazine (dpp) and perchloric acid four different solid products have been isolated and structurally characterized by X-ray crystallography; (dppH 2)(ClO 4) 2·3H 2O ( 1), (dppH 2)(ClO 4) 2 ( 2), (ddppH 2)(ClO 4) 2 ( 3) and (dppH)(ClO 4) ( 4) (dppH is monoprotonated dpp, dppH 2 is the diprotonated dication of dpp, ddppH 2 is the dication 5,5′-bis(2,3-bis(2-pyridyl)pyrazinium), i.e. dimerized dppH). In 1 and 2 the nitrogen atom in both of the pyridyl rings in dpp is protonated. Hydrogen bonding and packing arrangements differ in the two compounds. In 3 a protonated and dimerized form of dpp is found; two 2,3-bis(2-pyridyl)pyrazinium units are connected by a C(sp 2) C(sp 2) bond in the 5-positions of the pyrazine rings, one pyridyl ring in each dpp moiety being protonated at the nitrogen. Strong intra-cation N H⋯N bonds between pyridyl rings are present. In 4 the monomeric dppH moieties display the same type of intramolecular hydrogen bonds as found in 3. Upon reacting dpp with copper(II) salts and oxalate, a dinuclear copper (II) complex, [Cu 2(ddpp)(ox) 2(H 2O) 2] (ddpp = 5,5′-bis(2,3-bis(2-pyridyl)pyrazine)), as well as mononuclear [Cu(dpp)(ox)(H 2O)] have been obtained in the same reaction mixtures. In one of the isolated crystalline products a dimer of dpp is found, as described in the case of compound 3, but no protonation has occurred. The crystal structure determination reveals a dinuclear complex with the neutral ddpp (dimerized dpp) as bridging ligand. Oxalate occurs as a bidentate, terminal ligand; water completes the copper coordination sphere. The dinuclear complex cocrystallizes with a mononuclear Cu-dpp-ox complex; in the mixed crystal two mononuclear units replace one dinuclear unit in 25% of the unit cells, thus the average formula is [Cu 2(ddpp)(ox) 2(H 2O) 2] 0.75[{Cu(dpp)(ox)(H 2O)} 2] 0.25·8H 2O ( 5). The monomeric species also crystallizes in the form of compound 6, [Cu(dpp)(ox)(H 2O)]·2H 2O. In 6 the dpp ligand and oxalate are both chelating to copper in equatorial positions, and [Cu(dpp)(ox)(H 2O)] units are pair-wise connected through weak Cu⋯O (oxalate) interactions (semi-coordination). Geometry optimization through ab initio calculations gave results in good agreement with the experimental molecular geometries of dpp, dppH + and dppH 2 2 + , respectively. An energy minimum was found for the syn conformation of pyridyl rings in the monoprotonated species, conforming to the existence of the intramolecular N H⋯N hydrogen bond. The compounds containing dimerized dpp were minor products (of the order of 1% yield). To determine whether ddpp had been formed in the reaction mixtures, or had been present as a contaminant in the commercially available dpp, an NMR solution study was performed. Samples of dpp, 1, 3, 4 and ddpp (obtained by treating 3 with base) were investigated by 1H (all five compounds) and 13C NMR (the three former compounds) spectroscopy. The results are consistent with the presence of ddpp as a contaminant in commercially available dpp. The study also allowed us to identify the spectral changes involved in going from neutral dpp to the partial ( 4) and fully ( 1) protonated forms.

Copper(I) Complexes with Bis(trimethylsilyl)acetylene: Role of Ancillary Ligands in Determining π Back-Bonding Interactions

We present syntheses and structures of Cu(I) complexes with bis(trimethylsilyl)acetylene (BTMSA) that demonstrate the role of the ancillary ligands in the copper coordination sphere. The bonding interaction between the Cu(I) ion and the coordinated alkyne is influenced by the ancillary ligand. The ligands in this study are the bidentate ligands 1 and 2, which form monomeric, trigonal planar Cu(I) complexes with olefins and alkynes. In these complexes, the ancillary ligands vary from a hard β-diketone 1 to a softer β-diketimine 2. Earlier studies of Cu(I)−acetylene complexes have shown the Cu(I) ion to be a poor π back-bonding ion, but the results here demonstrate that the degree of back-bonding is strongly influenced by the ancillary ligands. Although ligands 1 and 2 provide very similar geometries about the Cu(I) ion, the interaction with the coordinated BTMSA is considerably different. The degree of π back-bonding for the complex with the β-diketimine ligand is indicated by the spectroscopic properties ...

Synthesis and Characterization of New Mono‐, Di‐, and Trinuclear Copper(II) Triethanolamine‐Carboxylate Complexes

AbstractA series of triethanolamine copper(II) carboxylate complexes have been synthesized and characterized both structurally and spectroscopically. The structures of the compounds and the nuclearity of the resulting coordination complexes are influenced both by the stoichiometry of the reagents and the steric and electronic influences of the anionic ligands present in the copper coordination spheres. The complexes can be prepared in high yields and purity as highly crystalline solids. Herein we report the spectroscopic and structural data for [NaCu(CF3COO)3(TEAH3)] (1), [Cu(C6H5COO)(TEAH2)]2·2H2O (2), [Cu3(CH3COO)4(TEAH2)2] (3), [Cu3(HCOO)4(TEAH2)2] (4) and [Cu3(CF3OO)2(TEAH2)2(CH3OH)2][CF3CO2]2 (5) (TEAH3 = triethanolamine (N(CH2CH2OH)3); [TEAH2]‐ = mono‐deprotonated ion; [TEAH]2‐ = doubly deprotonated ion). Two approaches to these compounds were employed: direct reaction of copper(II) carboxylates with TEAH3 and reaction of the tetrameric compound [{Cu(TEAH)}4] (6) with copper(II) carboxylates. Compound 1 is polymeric in the solid state, being a double salt of sodium trifluoroacetate and (triethanolamine)copper(II) trifluoroacetate, while 2 exists as a simple dimer. Compounds 3, 4 and 5 are trinuclear complexes with Cu3 chains connected by bridging carboxylate and triethanolamine ligands. 3 was characterized as three crystal modifications: an unsolvated form and as a methanol solvate 3·2MeOH that was found to exist in both monoclinic and orthorhombic forms. 4 was also found to exist as a methanol solvate, 4·1.70 MeOH. 5 shows coordination isomerism compared to compounds 3 and 4 in that two of the carboxylate ligands in the metal coordination spheres on the end copper atoms have been replaced by solvent methanol. The magnetic behavior of the di‐ and trinuclear species has been probed and reveals that at low temperatures the metal centers exhibit strong ferromagnetic coupling, which, on warming, switches to simple paramagnetic behavior.

Asymmetric Azido−Copper(II) Bridges: Ferro- or Antiferromagnetic? Experimental and Theoretical Magneto−Structural Studies

Reaction of NaN(3) with the [Cu(II)(tn)](2+) ion (tn = 1,3-diaminopropane) in basic aqueous solution yields the azido-bridged complex of formula [Cu(2)(tn)(2)(N(3))(4)] (1), which is characterized by X-ray crystallography. The structure of 1 is made up of dinuclear neutral complexes, of formula [Cu(2)(tn)(2)(N(3))(4)], resulting from the assembling of two mononuclear units through two equivalent end-on azide bridges connecting asymmetrically two Cu(tn)(N(3))(2) entities. These dinuclear units are connected through two asymmetric end-to-end N(3) bridges to form a chain of dimers. Magnetic measurements for compound 1 show weak antiferromagnetic exchange interactions between the Cu(II) ions. The magnetic data were modeled using the susceptibility expression derived for an alternating AF S = 1/2 chain. A very satisfactory fit over the whole temperature range was obtained with g = 2.1438(4), J(1) = -3.71(2) cm(-1), and J(2) = -3.10(2) cm(-1) (J(1) and J(2) are the singlet-triplet separations). This magnetic behavior differs from those observed for similar examples which were reported as having alternating ferro- and antiferromagnetic exchange interactions; thus, DFT calculations were done to understand the nature of the magnetic coupling in such asymmetric end-on and end-to-end N(3) bridges. Theoretical results show that the double asymmetric end-on bridges produce antiferromagnetic coupling while the end-to-end ones can present ferro- or antiferromagnetic coupling depending on the copper coordination sphere.

Co‐Adsorption of Copper(II) and 3‐Amino‐1,2,4‐triazole at a Water–Natural Macromolecular Compound Interface: Molecular Structure from Adsorption Isotherms Combined with X‐ray Absorption Measurements

AbstractThe co‐adsorption of CuII and amitrole at a water–natural macromolecular compound interface was studied by means of batch adsorption experiments, Fourier transform infrared, and X‐ray absorption spectroscopy. The binary systems, aqueous amitrole–CuII complex, and amitrole and CuII adsorbed on the surface of the solid were studied. The ternary system was investigated over the pH range 2–10 and at varying metal concentrations. The combination of macroscopic and molecular information shows that CuII and amitrole interact directly at the water–solid interface to form ternary surface complexes. A two‐step mechanism is proposed whereby initial formation of a CuII–amitrole aqueous complex is followed by the sorption of this complex onto the surface. The structure of the ternary complex was elucidated. Copper(II) is bound to the surface in an inner‐sphere mode, while two amitrole ligands simultaneously bonded in a monodentate fashion to CuII to form a six‐membered coordination sphere around the metal cation. The copper coordination sphere is completed by two water molecules. This structure and the mechanism proposed are supported by a combination of potentiometric data, IR and UV/visible spectroscopies and XAS measurements. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Electrochemical studies of a dinuclear copper complex with imidazole derivative ligand H 3bphenim

A new polynucleating ligand 4,5-bis(phenylalanyl- N-methyl)-2-methylimidazole (H 3bphenim) has been synthesized and characterized. H 3bphenim produces the crystalline dinuclear copper compound, [(Cu 2bphenim)(H 2O) 4]NO 3 the structure of which includes an imidazolato bridge between the two Cu(II) ions. Electrochemical and spectrophotometric evidence is produced for the cleavage of this imidazolato bridge when the complex is dissolved. The absence of the 375 nm band in the UV–Vis spectrum, known to be characteristic for such imidazolato-bridged Cu(II) compounds as well as the presence of two irreversible Cu II → Cu I peaks in the cyclic voltammogram (CV), corroborate the formation of the asymmetric Cu AbphenimCu B ( Cu A II LCu B II ) where each copper coordination sphere is identified by spectroelectrochemical procedures. The key role of the solvent was demonstrated when mixtures of variable CH 3CN:H 2O ratio were studied and the corresponding voltammograms compared. CV studies also confirm the formation of a copper(I) solvated species after Cu A(I) decoordination. Potential step procedures were applied to elucidate the mechanisms of two coupled homogeneous reactions: the decoordination and subsequent solvation of Cu A(I) and the reproportionation reaction between Cu A II LCu B II and Cu A I LCu B I formed during electrolysis. The mechanisms proposed from the electrochemical behavior are verified by the low catalytic activity shown by the complex in the 3,5-di- tert-butylcatechol oxidation, when it is compared with similar compounds having the imidazolato-bridged Cu(II) structure.

Correlation between UV-VIS spectra and the structure of Cu(II) complexes with hydrogenated dextran in alkaline solutions

UV-VIS spectrophotometric investigations of Cu(II) complexes with hydroge-nated dextran showed that the complexation of Cu(II)-ions began at pH > 7. The formation of Cu(II) complexes with dextran monomer units was observed at pH 7-12. With further increase in solution pH > 12, the Cu(II)-dextran complex decomposed to Cu(OH)42~-ions and dextran. With increasing solution pH the absorption maximum of complex solutions increased and shifted to shorter wavelength (hypsochromic shift) compared with uncomplexed Cu(II). The UV spectra displayed bathochromic shifts. The changes of UV-VIS spectra with increasing in solution pH confirmed the formation of different kinds of complex species. The correlation between the results of UV-VIS spectrophotometry and the central metal ionligand coordination predicted that the copper binding within the complex depended on the pH and participation H2O molecules. Dextran complexes with Cu(II) were formed by the displacement of water molecules from the coordination sphere of copper by OH groups. The analysis indicated that the Cu(II) center was coordinated to two glucopyranose units of dextran. The spectrophotometric parameters of the investigated complexes were characteristic of a Cu(II)-ion in a square-planar or tetragon ally distorted octahedral coordination.

NMR studies on Cu(ii)–peptide complexes: exchange kinetics and determination of structures in solution

The interaction of copper(II) with histidine containing peptides has recently acquired renewed interest following the established link between abnormal protein behaviour in neurodegenerative processes and unpaired copper homeostasis. Five peptide sequences taken from the amyloid precursor protein and the prion protein were considered. Addition of paramagnetic Cu(II) ions to solutions of such peptides was not found to severely affect the appearance of NMR spectra, thus limiting the usual approach for structural determination. Exchange kinetics was shown to play a major role in determining the observed paramagnetic spin-lattice relaxation rates. Two independent methods were suggested for evaluating the exchange rates of His-containing peptides from the copper-coordination sphere and to calculate copper-proton distances. In such a way NMR was demonstrated to have the potential of providing detailed structures of the Cu(II)-peptide complexes in solution.

Copper(II) Schiff base coordination compounds of dien with heterocyclic aldehydes and 2-amino-5-methyl-thiazole: synthesis, characterization, antiproliferative and antibacterial studies. Crystal structure of CudienOOCl 2

A new series of coordination compounds of the starting materials [Cu(dienX 2Y 2)] and their adducts [Cu(dienXXY 2)(2a-5mt)] (where dien=diethylenetriamine, dienXX=Schiff bases of diethylenetriamine with 2-furaldehyde or 2-thiophene-carboxaldehyde, X=O, S, Y=Cl, Br, NO 3 and 2a-5mt=2-amino-5-methylthiazole) were synthesized by stepwise reactions and their structures were established by C, H, N, Cu analysis, spectroscopic, magnetic and molar conductivity measurements. The isolated compounds are monomers, paramagnetic and electrolytic compounds of the type 1:1. In all cases, the pentadentate Schiff base (dienXX) is bonded in a tridentate fashion through the 3 N atoms. In the CudienXXY 2 compounds the coordination sphere is completed by two Cl or Br or NO 3 groups in a square pyramidal arrangement. The proposed structure for this type of compound was further supported by X-ray diffraction analysis of the compound [Cu(dienOO)Cl 2]. Its basal plane consists of three Cu–N contacts [2.017(2), 2.025(2) and 2.012(2) Å] from dienOO, and the Cl(1) atom, while the Cl(2) atom possesses the apical position, the relevant distances being 2.2732(7) Å for Cu–Cl(1) and 2.6051(7) Å Cu–Cl(2). In the CudienX 2Y 2 · 2a-5mt adducts the coordination sphere of copper is further completed by the nitrogen ring atom of the 2a-5mt, forming an octahedral configuration. The study of the biological activity of the compounds synthesized against a panel of different normal and cancer cell lines (MRC5, HeLa, MCF7, HT-29, OAW42, T47D) and bacteria ( E. coli, B. cereus, B. subtilis) showed that the adducts of the type [Cu(dienXXY 2)(2a-5mt)] exhibit increased activity both in cancer cells and in bacteria, compared to the starting material of type [Cu(dienXXY 2)].

Influence of water molecule coordination on the magnetic properties of polyamine copper dinitrate complexes

The magnetic properties of two biogenic polyamine copper complexes were investigated by dc magnetization and electron paramagnetic resonance (EPR) measurements. The variation in temperature of the low field magnetization reveals that the absence or presence of water molecules in the copper coordination sphere results, respectively, in the enhancement or suppression of antiferromagnetic interactions between Cu2+ ions. Analysis of the EPR spectra shows considerable temperature dependence of both the g values and EPR linewidths that persist in the paramagnetic regime for both complexes. Such variation of EPR parameters is attributed to the interplay of demagnetizing field effects, pertinent to the purely paramagnetic compound, and to the presence of short-range magnetic order that applies to the antiferromagnetic polyamine complex.

Copper(II) Halide Complexes of 2-Aminopyrimidines: Crystal Structures of [(2-aminopyrimidine) n CuCl2] (n=1,2) and (2-amino-5-bromopyrimidine)2CuBr2

The reaction of CuX2(X=Cl, Br) with 2-aminopyrimidine in aqueous solution, or 2-amino-5-bromopyrimidine in aqueous acid yields compounds of the forms [LCuCl2] n (1), [L2CuCl2] (2) and [L'2CuBr2] (3) [L=2-aminopyrimidine; L'=2-amino-5-bromo-pyrimidine]. The three compounds all form layered structures in which each copper ion is coordinated to two 2-aminopyrimidine molecules and two halide ions. Common structural threads involve bridging ligation [either by monomeric (1) or hydrogen bonded ligand dimers (2 and 3)], N-H···X and N-H···N hydrogen bonding and π-π stacking interactions as well as semi-coordinate Cu···X bond formation (1 and 2) or Br···Br interactions (3). Compounds 1 and 2 crystallize as two-dimensional coordination polymers with asymmetrically bihalide bridged (CuX2) n chains cross-linked into sheets by the 2-aminopyrimidine molecules (1) or by hydrogen bonded L2 dimers (2). The halide bibridged chains expand their primary copper coordination spheres to give 4 + 2 coordination spheres in 1 and 2. In 3, the layer structure involves coordination of the hydrogen bonded L'2 dimers and C-Br···Br- interactions. Crystal data: (1): monoclinic, P21/m, a=3.929(1), b=12.373(2), c=7.050(1)å, β=91.206(4)°, V=342.7(1)Åsup3;, Z=2, D calc= 2.225Mg/m3, μ=3.878 mm-1, R=0.0269 for [|I|≥3σ(I)]. For (2): triclinic, P-1, a=4.095(4), b=7.309(5), c=10.123(6) å, α=86.28(6), β=78.44(6), γ=74.55(8)°, V=286.1(4) Å3, Z=1, D calc=1.884 Mg/m3, μ=2.360 mm-1, R=0.0506 for [|I|≥2σ(I)]. For (3): triclinic, P-1, a=6.074(4), b=7.673(3), c=8.887(3) å, α=108.43(3) β=100.86(5), γ=106.96(4)°, V=357.0(3) Å3, Z=1, D calc=2.657 Mg/m3, μ=12.714mm-1, R=0.0409 for [|I|≥2σ(I)].

Performance of Waterborne Cu(II) Octanoate/Ethanolamine Wood Preservatives

Summary Various aqueous wood preservative solutions containing Cu(II) in the form of copper(II) sulphate or copper(II) octanoate, ethanolamine and in one case octanoic acid were investigated by spectrophotometry, polarography and Electron Paramagnetic Resonance (EPR) spectroscopy. Results have shown the same coordination environment around Cu(II) in all solutions with ethanolamine. Computer simulation of the EPR spectra also revealed that the coordination in the first coordination sphere of copper is the same at low concentration of ethanolamine. At 20% ethanolamine concentration, a mixture of two complexes (one with two nitrogens and the other with three) could be detected. The active compound in the investigated ethanolamine containing solutions is the same when previously synthesised copper(II) octanoate was used, or when copper(II) sulphate and octanoic acid were utilized instead. Fungicidal and leaching experiments with the treated wood resulted in the same conclusion: it is not necessary to use pre-synthesised copper(II) octanoate for the preparation of waterborne copper/ethanolamine wood preservatives. Preservative preparation time and costs can be reduced by simply dissolving copper(II) sulphate and octanoic acid in aqueous ethanolamine solutions.

Amino Acid Binding to Copper(II) in (1,4,7-Triazacyclononane) (L-histidine)copper(II) Hexafluorophosphate Monohydrate

The synthesis, characterization, and single-crystal X-ray structure determination of [Cu(tacn)(L-His)](PF6)2 . H2O (tacn = 1,4,7-triazacyclononane, L-His = L-histidine) are reported. Spectroscopic studies indicated the formation of the square pyramidal copper(II) complex [Cu(tacn)(L-His)]2+. This was confirmed through structure determination, which also revealed that the distorted square-pyramidal copper(II) coordination sphere is comprised of three nitrogen donors from the tacn macrocycle plus one carboxylate oxygen atom and the primary nitrogen atom from L-histidine. The L-histidine ligand is zwitterionic, with the negative charge on the carboxylate balanced by protonation at one nitrogen atom on the imidazole ring. It binds to the copper centre, forming a five-membered chelate ring, common in amino acid coordination.