Coordination Polyhedron Of Cu Research Articles

A High-Pressure Investigation of the Synthetic Analogue of Chalcomenite, CuSeO3∙2H2O

Synthetic chalcomenite-type cupric selenite CuSeO3∙2H2O has been studied at room temperature under compression up to pressures of 8 GPa by means of single-crystal X-ray diffraction, Raman spectroscopy, and density-functional theory. According to X-ray diffraction, the orthorhombic phase undergoes an isostructural phase transition at 4.0(5) GPa with the thermodynamic character being first-order. This conclusion is supported by Raman spectroscopy studies that have detected the phase transition at 4.5(2) GPa and by the first-principles computing simulations. The structure solution at different pressures has provided information on the change with pressure of unit–cell parameters as well as on the bond and polyhedral compressibility. A Birch–Murnaghan equation of state has been fitted to the unit–cell volume data. We found that chalcomenite is highly compressible with a bulk modulus of 42–49 GPa. The possible mechanism driving changes in the crystal structure is discussed, being the behavior of CuSeO3∙2H2O mainly dominated by the large compressibility of the coordination polyhedron of Cu. On top of that, an assignation of Raman modes is proposed based upon density-functional theory and the pressure dependence of Raman modes discussed. Finally, the pressure dependence of phonon frequencies experimentally determined is also reported.

A new copper(II) chelate complex with polyamines as fire retardant and epoxy hardener: Synthesis, crystal and electronic structure, and thermal behavior of (ethylenediamine-N,N′)-(diethylenetriamine-N,N′,N″)-copper(II) hexafluoridosilicate

A new (ethylenediamine-N,N′)-(diethylenetriamine-N,N′,N″)-copper(II) hexafluoridosilicate complex, [Cu(eda)(deta)]SiF6 (1) (eda – ethylenediamine; deta – diethylenetriamine), was synthesized by direct interaction of anhydrous CuSiF6 with polyethylenepolyamine (pepa – H2N[C2H4NH]nH, where n = 1 (eda) and 2 (deta)). The crystals of 1 were characterized by IR spectroscopy and X-ray diffraction. Compound 1 consists of SiF62− discrete anions and [Cu(eda)(deta)]2+ complex cations whose Cu2+ ions are chelated by eda and deta. The coordination polyhedron of Cu(II) atom is an elongated square pyramid which consists of four nitrogen atoms belonging to NH2 groups of eda and NH2 and NH groups of deta at the base of the pyramid and of one more nitrogen atom from NH2 group of deta at its apical position. Ab initio quantum-chemical calculations of chelation process were carried out for 1 by the restricted Hartree-Fock method using a 6-31G∗ basis set. The influence of the chelate complex 1 upon its fire retardant properties was analyzed. The calculated electron-stereo-chemical parameters for 1 are in a good agreement with its thermal parameters investigated by differential thermal analysis. The thermal decomposition of 1 is finished off at 368 °C and the maximal combustion temperature of gaseous decomposition products is 544 °C.

Coordination environment of new Co(II), Ni(II) and Cu(II) complexes with 4-bromophenoxyacetic acid: Structural, spectroscopic and theoretical studies

We report the synthesis of new Co(II), Ni(II) and Cu(II) complexes with 4-bromophenoxyacetic acid. We characterize these compounds structurally using various laboratory (XRF, IR, UV–vis) and synchrotron (EXAFS, XANES) spectroscopic methods, magnetic measurements and DFT calculations. We found that in the powder form of complexes Co(II) and Ni(II) cations are coordinated by two monodentate carboxylate ligands and the first coordination sphere is completed by water molecules that form an octahedron. The coordination polyhedron of Cu(II) exhibits a distorted tetragonal–pyramidal geometry with two ligands coordinating in bidentate and monodentate fashion via carboxylate O atoms and two water molecules.The X-ray single crystal structure analysis performed for Cu(II) complex after its recrystallization from N,N-dimethylformamide (DMF) solution revealed the formation of dinuclear complex. In crystals, the carboxylate O atoms occupy the bases of two tetragonal pyramids formed around two Cu(II) ions with the DMF molecules in the apical positions.

Design and synthesis of two macrocyclic dinuclear copper(II) complexes with reversible binding of nitric oxide

Abstract Two new macrocyclic dinuclear copper(II) complexes, [Cu2L1(MeOH)2]·(ClO4)2 (1) and [Cu2L2(EtOH)2]·(ClO4)2 (2) have been synthesized and characterized by ES-MS spectra and X-ray crystallography determination. The coordination polyhedron of Cu(II) ions in each complex can be described as approximately square pyramind, where the apical position is occupied by a labile coordinated alcoholic molecule. The reactions of complexes with nitric oxide (NO) cause an immediate color change, and the formation of NO complexes has been further confirmed by UV/Vis spectrophotometry. The binding constants are calculated to be 1.71 × 103 M− 1 and 2.0 × 103 M− 1 in 0.2 M anaerobic phosphate buffer solution (PBS), respectively. The control experiments reveal that the binding of NO to complexes is reversible. Moreover, the interactions of the complexes with calf thymus DNA (CT-DNA) have been measured by UV/Vis, cyclic voltammetry and viscosity study. The moderate binding ability and unobvious DNA cleavage ability account for their low toxicity towards DNA. Overall, the results reveal that these two complexes can be served as potential NO regulators.

Synthesis and structural studies of novel Cu(II) complexes with hydroxy derivatives of benzo[b]furan and coumarin

A series of new Cu(II) complexes with the hydroxy derivatives of benzo[b]furan and coumarin have been electrochemically synthesized. The geometry of the metal–ligand interaction has been described using the single crystal X-ray diffraction method and X-ray absorption spectroscopy. Two ligands are bonded to the metal cation via the acetyl and deprotonated hydroxyl O atoms. The centrosymmetric coordination polyhedron of Cu(II) exhibits a square-planar geometry (CuO4), with both ligands coordinating in the chelating mode.

Copper(II) complexes with N-(2-carboxyethyl)anthranilic acid H2CEAnt. Synthesis and crystal structure of [Cu(CEAnt)(H2O)] ⋅ H2O

Protolytic equilibria and complexation of N-(2-carboxyethyl)anthranilic acid (H2CEAnt) with copper(II) ions in aqueous solutions were studied by UV spectroscopy and pH potentiometry. The H2CEAnt compound has no zwitterionic structure, and the protons are localized on the carboxy groups. The acid ionization constants of H3CEAnt+ (T = 25 °C, I = 0.1 M KNO3) are pK0 = 1.3±0.2 (=NH2+), pK1 = 3.88±0.02 (Alk-COOH), and pK2 = 5.28±0.02 (Ar-COOH). The model of complexation of H2CEAnt with copper(II) ions involves two deprotonated complexes [Cu(CEAnt)] and [Cu(CEAnt)2]2− (logβ = 6.31±0.04 and 8.0±0.2, respectively). The [Cu(CEAnt)(H2O)]⋅H2O complex was synthesized by the reaction of H2CEAnt with (CuOH)2CO3, and its structure was established by X-ray diffraction. The coordination polyhedron of Cu is intermediate between the tetragonal pyramid and trigonal bipyramid. The CEAnt2− ligand serves as a tetradentate chelating bridging ligand (Cu-O, 1.944(3) and 1.950(3) A; Cu-O', 2.195(4) A; Cu-N, 2.016(5) A), and the fifth position of the polyhedron is occupied by a water molecule (Cu-Ow, 1.976(4) A).

Copper(II) Complexes with Ethyl [(Pyrazolo-1-carbothioyl)-amino]acetate Derivatives: Synthesis and Structure

Optically active derivative of the natural monoterpene (+)-3-carene, namely, ethyl (3bS,4aR)-[(3,4,4-trimethyl-3b,4,4a,5-tetrahydrocyclopropa[3,4]cyclopenta[1,2-c]pyrazole-1-carbothioyl)-amino]acetate (HL1) and ethyl [(3,5-dimethyl-pyrazole-1-carbothioyl)-amino]acetate (HL2) were synthesized. Paramagnetic complexes [CuL1Cl] n (I) and [Cu2L22Cl2] (II) were prepared. According to X-ray diffraction data, complex Iwith anion of (+)-3-carene derivative has chain structure, whereas complex IIwith anion of HL2, which has no carbocyclic fragments, is a pseudodimer. Organic anions act as tetradentate bridging, cyclic ligands forming five-membered CuN3C and CuNOC2metal cycles. Coordination polyhedron of Cu(ClN2O + S) in complexes Iand IIis a square pyramid. The values of μefffor complexes Iand II(1.88 and 1.84 μB, respectively) are constant in the temperature interval 78–300 K, which means that the unpaired electrons of Cu(II) ions do not exhibit any noticeable exchange interactions.

Synthesis and x-ray crystal structure of new complex trans-dinitrodiaqua-bis (1-phenyltetrazole) copper(II)

A new complex CuL 2(NO 3) 2(H 2O) 2 (L = 1-phenyltetrazole) was synthesized and characterized by X-ray crystallography. The coordination polyhedron of Cu has the form of an elongated square bipyramid with site symmetry 1 . Two L ligands (by N 4 donor atoms) and two water molecules are trans-coordinated to copper in the equatorial plane (Cu—N = 1.990(3), Cu—O = 1.984(3) Å). The oxygen atom sof two NO − 3 ions occupy axial positions (Cu—O = 2.403(3) Å). The angle between the tetrazole plane and the Ph group is 4.07°.

New examples of mixed-ligand bis(hexafluoroacetylacenonato)copper(II) complexes with 3-imidazoline nitroxide radicals at a Cu(C5HF6O2)2∶L=3∶2 ratio (L2=C14H19N2O, L3=C13H17N2O3)

The crystal structures of two (hexafluoroacetylacetonato)copper(II) complexes with 3-imidazoline nitroxide radicals, [Cu(C5HF6O2)2]3 (C14H19N2O)2 (I) and [Cu(C5HF6O2)2]3 (C13H17N2O3)2 (II), have been determined. The compounds are triclinic (PI, Z=1) with a=8.730(2), b=10.357(2), c=21.996(5) A, α=103.24(2), β=94.03(2), γ=95.04(2)0, V=1920(1) A3 for I and a=8.679(2), b=14.769(4), c=15.368(4) A, α=85.58(2), β=96.25(1), γ=104.60(1)0, V=1893(1) A3 for II. Complexes I and II are molecular. The trinuclear molecules are centrosymmetric relative to the Cu(1) atom. The coordination polyhedron of Cu(1) is a square bipyramid formed by the O atoms of the hfac anions and nitroxide radicals (average Cu−Ohfac 1.92(1) for I and 1.93(1) A for II; Cu−ON−O 2.47(1) for I and 2.56(1) A for II). The coordination polyhedron of Cu(2) is a trigonal bipyramid formed by the O atoms of the hfac anions (Cu−Ohfac 1.91(1)–2.12(1) for I and 1.91(1)–2.09(1) A for II) and an imine N atom of the radical (Cu(2)−N(2) 2.00(1) for I and 2.03(1) A for II). The molecules are linked by van der Waals forces.

Structure of copper(II) salicylates: bis(3-pyridylmethanol)bis(salicylato)copper(II)

Cu(C7HsO3)2(C6H 7NO)2), Mr = 556.03, orthorhombic, Pbca, a = 12.947(1), b=9.401 (3), c = 20.005 (3) A, V = 2435.16 A 3, z = 4, D m = 1.50, Dx = 1.52 g cm -3, A(fu Ka) = 1.54178 A, # = 16.949 cm- 1, F(000) = 1148, T = 293 K, final R = 0.044 for 1122 observed reflections. The crystal struc- ture consists of molecules bonded together into layers parallel to (100). The coordination polyhedron of Cu H is a distorted octahedron built up by four short bonds in the equatorial plane (two Cu--N and two Cu--O bonds with bond lengths 1.944 (4) and 2.029 (4)A) and two longer apical Cu---O bonds (2.622 (4)). The O atoms forming apical bonds belong to the different molecules of 3-pyridyl- methanol.

Coordination of transition-metals by chelating cation-exchange resins; Co(II), Ni(II), Zn(II) and Cu(II) coordinated by the 8-quinolinol group in spheron oxine 1000

The interaction between the 8-quinolinol group of the chelating ion-exchange resin Spheron oxine 1000 and Cu(II), Co(II), Ni(II) and Zn(II) has been studied with the aid of electronic spectra and EPR. It is concluded that the 8-quinolinol group in Spheron oxine 1000 coordinates as a bidentate chelating ligand to Cu(II). The Cu(II) binds preferentially to two 8-quinolinol groups although coordination to only one 8-quinolinol group, most probably due to sterical reasons, has also been observed. The coordination polyhedron of the Cu(II) bound in a 1:2 ratio is square planar, resulting in a chromophore [MO 2N 2]. The coordination polyhedron of Cu(II) bound in a 1:1 ratio is completed by water molecules resulting in a chromophore [MO 5N]. No definite conclusions could be drawn about Co(II) and Ni(II), that seem to bind preferentially in a 1:2 ratio, for cases when an excess of the resin is present, although (small amounts of) 1:1 species cannot be excluded.

Polymeric chains of tetranuclear hydroxo-o-phthalatocuprate(II) units and silver(I)–aromatic interactions in the crystal structure of Ag[Cu2(C8H4O4)2(OH)].5H2O

The crystal structure of Ag[Cu2(C~H404)~(OH)I.5H20, CI6H9AgCu209.5H20, has been determined from diffractometer data by Patterson and Fourier methods and refined to R = 0.079 for 2359 counter reflections: a = 11.388 (11), b = 11.772 (12), c = 7.875 (9) A, ,~ = 100.3 (1), fl = 80.2 (1), y = 102.2 (1) °, space group P i , Z = 2. The structure consists of centrosymmetric tetranuclear [ C u 2 ( C s H 4 0 4 ) 2 ( O H ) ] 2 2 anions (linked in polymeric chains by bridging ophthalate anions), Ag ~ cations and water molecules. The tetranuclear hydroxo-o-phthalatocuprate(II) anions contain two independent Cu atoms linked by triplybridging hydroxo O atoms and by carboxylate bridges from o-phthalate anions. The coordination polyhedron of Cu(1) is a trigonal bipyramid whose equatorial plane is tbrmed by three O atoms from three bridging carboxylates [ C u O = 2.049 (10), 2.101 (10), 2.233 (12) A], the axial positions being occupied by an O atom from an OHion [ C u O = 1.911 (11) A] and by an O atom from a monodentate carboxylate group [ C u O = 1.923 (11) AI. The coordination of Cu(2) is square pyramidal, the basal plane comprising two O atoms from OHions [ C u O = 1.955 (9), 1-949 (9) /k] and two O atoms from two bridging carboxylates [ C u O = 1-924(10), 1.928(10) AI. Another O atom from a bridging carboxylate is at the apex of the pyramid [ C u O = 2.352 (13) /k]. The Ag I ion is linked to this last O atom [ A g O = 2.264 (12) ,~,1 and to two water molecules [ A g O w = 2.328 (25), 2.536 (26) AI, and interacts with a benzene C C bond [ A g (midpoint of C C ) = 2.431 (16) ,~1, so that Ag-aromatic complexes, in a distorted tetrahedral configuration, are present.

Temperature dependent stereochemical transformations of distortion isomers of CuBr 2(NH 3) 2

In the present work the influence of temparature on the deformation of the Cu(II) coordination polyhedron in the isomers of CuBr 2(NH 3) 2 was studied. At temperatures of −180, 20 and 150 °C the changes of structure were followed with the aid of electronic spectra and at −180 and 20 °C the powder diffraction patterns were taken. Although in both investigated isomers of CuBr 2(NH 3) 2 certain temperature dependent variations in the deformation of the coordination polyhedron were observed, these could not be interpreted at formation of a new isomer since the crystal structure did not change in such a manner as to lead to stabilization of a new coordination polyhedron. The results of investigation are discussed with regard to the present notions on the plasticity of the coordination polyhedron of Cu(II) complexes.