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CuII Complexes (cuii + complex)

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Chemistry100%
Distribution within Chemistry
Crystallography18%

Selected Abstracts

Synthesis, Protonation and CuII Complexes of Two Novel Isomeric Pentaazacyclophane Ligands: Potentiometric, DFT, Kinetic and AMP Recognition Studies

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 1 2009
Andrés G. Algarra
Abstract The synthesis and coordination chemistry of two novel ligands, 2,6,9,12,16-pentaaza[17]metacyclophane (L1) and 2,6,9,12,16-pentaaza[17]paracyclophane (L2), is described. Potentiometric studies indicate that L1 and L2 form a variety of mononuclear complexes the stability constants of which reveal a change in the denticity of the ligand when moving from L1 to L2, a behaviour that can be qualitatively explained by the inability of the paracyclophanes to simultaneously use both benzylic nitrogen atoms for coordination to a single metal centre. In contrast, the formation of dinuclear hydroxylated complexes is more favoured for the paraL2 ligand. DFT calculations have been carried out to compare the geometries and relative energies of isomeric forms of the [CuL]2+ complexes of L1 and L2 in which the cyclophane acts either as tri- or tetradentate. The results indicate that the energy cost associated with a change in the coordination mode of the cyclophane from tri- to tetradentate is moderate for both ligands so that the actual coordination mode can be determined not only by the characteristics of the first coordination sphere but also by the specific interactions with additional nearby water molecules. The kinetics of the acid promoted decomposition of the mono- and dinuclear CuII complexes of both cyclophanes have also been studied. For both ligands, dinuclear complexes convert rapidly to mononuclear species upon addition of excess acid, the release of the first metal ion occurring within the mixing time of the stopped-flow instrument. Decomposition of the mononuclear [CuL2]2+ and [CuHL2]3+ species occurs with the same kinetics, thus showing that protonation of [CuL2]2+ occurs at an uncoordinated amine group. In contrast, the [CuL1]2+ and [CuHL1]3+ species show different decomposition kinetics indicating the existence of significant structural reorganisation upon protonation of the [CuL1]2+ species. The interaction of AMP with the protonated forms of the cyclophanes and the formation of mixed complexes in the systems Cu,L1 -AMP, Cu,L2 -AMP, and Cu,L3 -AMP, where L3 is the related pyridinophane containing the same polyamine chain and 2,6-dimethylpyridine as a spacer, is also reported. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]

Anion-Directed Template Synthesis and Hydrolysis of Mono-Condensed Schiff Base of 1,3-Pentanediamine and o -Hydroxyacetophenone in NiII and CuII Complexes

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 21 2008
Pampa Mukherjee
Abstract Bis(o -hydroxyacetophenone)nickel(II) dihydrate, on reaction with 1,3-pentanediamine, yields a bis-chelate complex [NiL2]·2H2O (1) of mono-condensed tridentate Schiff baseligand HL {2-[1-(3-aminopentylimino)ethyl]phenol}. The Schiff base has been freed from the complex by precipitating the NiII as a dimethylglyoximato complex. HL reacts smoothly with Ni(SCN)2·4H2O furnishing the complex [NiL(NCS)] (2) and with CuCl2·2H2O in the presence of NaN3 or NH4SCN producing [CuL(N3)]2 (3) or [CuL(NCS)] (4). On the other hand, upon reaction with Cu(ClO4)2·6H2O and Cu(NO3)2·3H2O, the Schiff base undergoes hydrolysis to yield ternary complexes [Cu(hap)(pn)(H2O)]ClO4 (5) and [Cu(hap)(pn)(H2O)]NO3 (6), respectively (Hhap = o -hydroxyacetophenone and pn = 1,3-pentanediamine). The ligand HL undergoes hydrolysis also on reaction with Ni(ClO4)2·6H2O or Ni(NO3)2·6H2O to yield [Ni(hap)2] (7). The structures of the complexes 2, 3, 5, 6, and 7 have been confirmed by single-crystal X-ray analysis. In complex 2, NiII possesses square-planar geometry, being coordinated by the tridentate mono-negative Schiff base, L and the isothiocyanate group. The coordination environment around CuII in complex 3 is very similar to that in complex 2 but here two units are joined together by end-on, axial-equatorial azide bridges to result in a dimer in which the geometry around CuII is square pyramidal. In both 5 and 6, the CuII atoms display the square-pyramidal environment; the equatorial sites being coordinated by the two amine groups of 1,3-pentanediamine and two oxygen atoms of o -hydroxyacetophenone. The axial site is coordinated by a water molecule. Complex 7 is a square-planar complex with the Ni atom bonded to four oxygen atoms from two hap moieties. The mononuclear units of 2 and dinuclear units of 3 are linked by strong hydrogen bonds to form a one-dimensional network. The mononuclear units of 5 and 6 are joined together to form a dimer by very strong hydrogen bonds through the coordinated water molecule. These dimers are further involved in hydrogen bonding with the respective counteranions to form 2-D net-like open frameworks. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]

CO2 Fixation and Activation by CuII Complexes of 5,5,-Terpyridinophane Macrocycles

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 1 2008
Begoña Verdejo
Abstract An aza-terpyridinophane receptor containing the polyamine 4,7,10,13-tetraazahexadecane-1,16-diamine linked through methylene groups to the 5,5, positions of a terpyridine unit has been prepared and characterized (L). The acid-base behaviour, CuII speciation and ability to form ternary complexes (CuII -L-carbonate) have been explored by potentiometric titrations in 0.15 M NaClO4 and by UV/Vis and paramagnetic NMR spectroscopy. Comparisons are made with a previously reported terpyridinophane containing the polyamine 4,7,10-triazatridecane-1,13-diamine (L1). For this latter receptor, reductive coupling between indigo and carbon dioxide at indigo-modified electrodes produces carboxylated derivatives via a solid-state reaction under electrochemical activation.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]

Synthesis and Characterization of CuII Complexes with Amino Acid Substituted Di(2-pyridyl)amine Ligands

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 23 2007
ko I. Kirin
Abstract The two-step syntheses of the substituted di(2-pyridyl)amine ligands (dpa), dpa-CH2CO2H (1) and dpa-PhCO2H (2), are described. Ligands 1 and 2 are successfully coupled to the amino acid phenylalanine, yielding the derivatives 4 and 6, respectively. Four CuII(dpa)2 complexes, [Cu(dpa-CH2CO2tBu)2(NO3)2] (3Cu), [Cu(dpa-CH2CO-PheOMe)2(H2O)2](NO3)2·2MeOH (4Cu), [Cu(dpa-PhCO2Me)2 (MeOH)2](ClO4)2 (5Cu) and [Cu(dpa-PhCO-PheOMe)2(ClO4)2] (6Cu) have been prepared and characterized, including their single crystal X-ray structures. Fluorescence emission at UV (for 3 and 4) or blue (for 5 and 6) wavelengths of the free ligands is preserved in the corresponding Cu complexes, although with lower intensity. X-band EPR spectra of 4Cu and 6Cu both revealed one axial CuII signal with hyperfine and superhyperfine splittings. Complexes 4Cu and 6Cu are chiral inorganic complexes with amino acid bioconjugates that may serve as nucleoside analogs in modified peptide nucleic acids (PNA). (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source]

A ,3 -Alkoxo-Bridged Tetranuclear [Cu4L2] Copper(II) Complex of a Hexadentate N2O4 Donor Ligand with a [6 + 0] Cu4O4 Cubane Core: Synthesis, Crystal Structure, and Magnetic Properties

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 22 2010
Dipankar Maity
Abstract A novel hexacoordinating non-Schiff base ligand (H4L) with N2O4 donor atoms has been synthesized by simple Mannich reactions. The use of this ligand with Cu(ClO4)2·6H2O in different molar ratios as well as pH leads to the formation of a mononuclear species and a tetranuclear CuII complex possessing a cubane [Cu4L2] core with almost equal Cu···Cu separation. In the presence of an excess amount of copper(II) ions and triethylamine at reflux, the mononuclear [CuH2L] species can be converted into the tetranuclear one, whereas the reverse process was not observed even after prolonged reaction time. Both the complexes have been characterized by single-crystal X-ray diffraction and magnetic measurements. Magnetic studies reveal that complex 1 displays a paramagnetic Curie-type behavior whereas 2 displays a singlet-spin ground state induced by strong intramolecular antiferromagnetic interactions. [source]

Copper Complexes with (2,7-Di- tert -butylfluoren-9-ylidene)methanedithiolate: Oxidatively Promoted Dithioate Condensation,

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 1 2006
José Vicente
Abstract The reaction of [Cu(NCMe)4]PF6 with piperidinium 2,7-di- tert -butyl-9H -fluorene-9-carbodithioate (pipH)[S2C(tBu-Hfy)] (1; tBu-Hfy = 2,7-di- tert -butylfluoren-9-yl), affords [Cun{S2C(tBu-Hfy)}n] (2), which reacts with various P ligands to give [Cu{S2C(tBu-Hfy)}L2] [L = PPh3 (3a), PCy3 (3b), PiPr3 (3d); L2 = 1,1,-bis(diphenylphosphanyl)ferrocene (dppf, 3c), bis(diphenylphosphanyl)methane (dppm, 3e)]. Compounds 3a,c react with atmospheric oxygen and moisture in the presence of NEt3 to give the dinuclear complexes [Cu2{[SC=(tBu-fy)]2S}L2] [tBu-fy = 2,7-di- tert -butylfluoren-9-ylidene; L = PPh3 (4a), PCy3 (4b); L2 = dppf (4c)], which contain a new dithiolato ligand formally resulting from the condensation of two dithioato ligands with loss of a sulfide ion and two protons. Neutral CuI dithiolate complexes of the type [Cu4{S2C=(tBu-fy)}2L4] [S2C=(tBu-fy) = [2,7-di- tert -butylfluoren-9-ylidene)methanedithiolate; L = PPh3 (5a), P(C6H4OMe- p)3 (5b), PiPr3 (5d) or L2 = dppf (5c)] were obtained by treating 1 with [Cu(NCMe)4]PF6, the corresponding phosphane, and piperidine in a 1:2:2:1 molar ratio. The reaction of 1 with Cu(ClO4)2·6H2O and (Pr4N)OH in a 2:1:2 molar ratio gives the CuII complex (Pr4N)2[Cu{S2C=(tBu-fy)}2] [(Pr4N)26], which readily oxidizes to the CuIII complex Pr4N[Cu{S2C=(tBu-fy)}2] (Pr4N7) in the presence of atmospheric oxygen and moisture. The salt PPN7 [PPN+ =(Ph3P)2N+] was obtained from 1, CuCl2·2H2O, PPNCl, and piperidine in a 2:1:1:2 molar ratio under aerobic conditions. The crystal structures of 3a, 3c·CH2Cl2, 4a·4Me2CO, and 4c·CH2Cl2 have been determined by X-ray diffraction studies. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source]

Dinuclear Complexes of MII Thiocyanate (M = Ni and Cu) Containing a Tridentate Schiff-Base Ligand: Synthesis, Structural Diversity and Magnetic Properties

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 12 2005
Suparna Banerjee
Abstract A dinuclear NiII complex, [Ni2(L)2(H2O)(NCS)2]·3H2O (1) in which the metal atoms are bridged by one water molecule and two ,2 -phenolate ions, and a thiocyanato-bridged dimeric CuII complex, [Cu(L)NCS]2 (2) [L = tridentate Schiff-base ligand, N -(3-aminopropyl)salicylaldimine, derived from 1:1 condensation of salicylaldehyde and 1,3-diaminopropane], have been synthesized and characterized by IR and UV/Vis spectroscopy, cyclic voltammetry and single-crystal X-ray diffraction studies. The structure of 1 consists of dinuclear units with crystallographic C2 symmetry in which each NiII atom is in a distorted octahedral environment. The Ni,O distance and the Ni,O,Ni angle, through the bridged water molecule, are 2.240(11) Å and 82.5(5)°, respectively. The structure of 2 consists of dinuclear units bridged asymmetrically by di-,1,3 -NCS ions; each CuII ion is in a square-pyramidal environment with , = 0.25. Variable-temperature magnetic susceptibility studies indicate the presence of dominant ferromagnetic exchange coupling in complex 1 with J = 3.1 cm,1, whereas complex 2 exhibits weak antiferromagnetic coupling between the CuII centers with J = ,1.7 cm,1. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source]

Carboxy Ester Hydrolysis Promoted by a Dicopper(II) Macrocyclic Polyamine Complex with Hydroxypropyl Pendant Groups

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 9 2004
Jin Huang
Abstract A dinuclear CuII complex containing a hexaaza macrocyclic ligand bearing two 2-hydroxypropyl pendants, 3,6,9,16,19,22-hexaaza-6,19-bis(2-hydroxypropyl)tricyclo[22.2.2.211,14]triaconta-1,11,13,24,27,29-hexaene (L), was synthesized. The title complex [Cu2(H,2L)Cl2]·6.5H2O was isolated as a blue crystal, orthorhombic, space group Fddd, with a = 16.4581(12), b = 32.248(2), c = 35.830(2) Å, V = 19017(2) Å3, Z = 16, R1 = 0.0690, and wR2 = 0.1546 [I > 2,(I)]. The protonation constants of Cu2L were determined by potentiometric titration, and it was found that the alcoholic hydroxypropyl group of the complex Cu2L exhibits low pKa values of pKa1 = 7.31, pKa2 = 7.83 at 25 °C. The hydrolysis kinetics of 4-nitrophenyl acetate (NA) promoted by the title complex have also been studied. The pH-rate profile for Cu2L gave a sigmoidal curve and showed a second-order rate constant of 0.39 ± 0.02 M,1 s,1 in 10% CH3CN/H2O(v/v), which is greater than that of the dinuclear CuII complex formed by a hexaaza macrocycle without pendants. The reason for the higher catalytic activity of the title complex is discussed. We found that the volume of nucleophile RO, can effect the hydrolysis of the carboxy ester, the nucleophilicity of RO, and the Lewis acidity of the metal macrocycle also affect the carboxy ester hydrolysis. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]

Structure, Characterization, and Metal-Complexation Properties of a New Tetraazamacrocycle Containing Two Phenolic Pendant Arms

HELVETICA CHIMICA ACTA, Issue 10 2004
Xiuling Cui
The new tetraazamacrocycle 2 (=2,2,-[[7-Methyl-3,7,11,17-tetraazabicyclo[11.3.1]heptadeca-1(17),13,15-triene-3,11-diyl]bis(methylene)]bis(4-bromophenol)) was synthesized and used as a ligand for different metal-ion complexes. The X-ray crystal structures of the complexes of the general formula [M(H- 2)]+NO,MeOH (M=Ni2+, Zn2+), in which only one of the two pendant phenolic OH groups of 2 is deprotonated, were determined. In both complexes, the coordination environment is of the [5+1] type, the four N-atoms of the macrocyclic framework defining a square-planar arrangement around the metal center, with similar NiN and ZnN distances of 1.961(9) to 2.157(9),Å and 2.021(9) to 2.284(8),Å, respectively. In contrast, the MO distances are markedly different, 2.060(6) and 2.449(8),Å in the NiII complex, and 2.027(7) and 2.941(9),Å in the ZnII complex. The UV/VIS spectra of the NiII and CuII complexes with ligand 2, and the EPR spectra of the CuII system, suggest the same type of structure for the complexes in solution as in the solid state. Theoretical studies by means of density functional theory (DFT) confirmed the experimental structures of the NiII and ZnII complexes, and led to a proposal of a similar structure for the corresponding CuII complex. The calculated EPR parameters for the latter and comparison with related data support this interpretation. The singly occupied molecular orbital (SOMO) in these systems is mainly made of a d orbital of Cu, with a strong antibonding (,*) contribution of the axially bound phenolate residue. [source]

Bis­(acetone-,O)­bis(N,N,-di­methyl­ethyl­enedi­amine-,2N,N,)copper(II) diperchlorate

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 4 2004
Takashiro Akitsu
The title compound, [Cu(C4H12N2)2(C3H6O)2](ClO4)2, is the first structurally characterized CuII complex having acetone as axial ligands. The complex adopts an elongated octahedral trans -[CuN4O2] coordination geometry, with the Cu atom having 222 site symmetry. The axial Cu,O(acetone) and in-plane Cu,N bond lengths are 2.507,(5) and 2.041,(3),Å, respectively. [source]

[N,N,-Bis­(salicyl­idene)-2,2-di­methyl-1,3-propane­diaminato]­nickel(II) and [N,N,-bis­(salicyl­idene)-2,2-di­methyl-1,3-propane­diaminato]copper(II)

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 7 2001
Cengiz Arici
In the title compounds, {2,2,-[2,2-di­methyl-1,3-propane­diyl­bis­(nitrilo­methyl­idyne)]­diphenolato-,4N,N,,O,O,}nickel(II), [Ni(C19H20N2O2)], and {2,2,-[2,2-di­methyl-1,3-propane­diyl­bis­(nitrilo­methyl­idyne)]­diphenolato-,4N,N,,O,O,}copper(II), [Cu(C19H20N2O2)], the NiII and CuII atoms are coordinated by two iminic N and two phenolic O atoms of the N,N,-bis­(salicyl­idene)-2,2-di­methyl-1,3-propane­diaminate (SALPD2,, C17H16N2O22,) ligand. The geometry of the coordination sphere is planar in the case of the NiII complex and distorted towards tetrahedral for the CuII complex. Both complexes have a cis configuration imposed by the chelate ligand. The dihedral angles between the N/Ni/O and N/Cu/O coordination planes are 17.20,(6) and 35.13,(7)°, respectively. [source]

A Nonanuclear Copper(II) Polyoxometalate Assembled Around a ,-1,1,1,3,3,3-Azido Ligand and Its Parent Tetranuclear Complex

CHEMISTRY - A EUROPEAN JOURNAL, Issue 6 2005
Pierre Mialane Dr.
Abstract Reaction of CuII, [,-SiW10O36]8,, and N3, affords three azido polyoxotungstate complexes. Two of them have been characterized by single-crystal X-ray diffraction. Complex KNaCs10[{,-SiW10O36Cu2(H2O)(N3)2}2],26,H2O (1) is obtained as crystals in few hours after addition of CsCl. This linear tetranuclear CuII complex consists in two [,-SiW10O36Cu2(H2O)(N3)2]6, units connected through two WO bridges. When the filtrate is left to stand for one night, a new complex is obtained. From both elemental analysis and IR spectroscopy, it has been postulated that this compound could be formulated K1.5Cs5.5[SiW10O37Cu2(H2O)2(N3)],14,H2O (1,a), showing the loss of one azido ligand per polyoxometalate unit. Finally, when no cesium salt is added to the reaction medium, the nonanuclear complex K12Na7[{SiW8O31Cu3(OH)(H2O)2(N3)}3(N3)],24,H2O (2) is obtained after three days. Compound 2 crystallizes in the R3c space group and consists in three {Cu3} units related by a C3 axis passing through the exceptional ,-1,1,1,3,3,3-azido bridging ligand. Each trinuclear CuII unit is embedded in the [,-SiW8O31]10, ligand, an unprecedented tetravacant polyoxometalate, showing that partial decomposition of the [,-SiW10O36]8, precursor occurs with time in such experimental conditions. Magnetically, complex 1 behaves as two isolated {Cu2(,1,1 -N3)2} pairs in which the metal centers are strongly ferromagnetically coupled (J=+224 cm,1, g=2.20), the coupling through the WO bridges being negligible. The magnetic behavior of complex 2 has also been studied. Relatively weak ferromagnetic couplings (J1=+1.0 cm,1, J2= +20.0 cm,1, g=2.17) have been found inside the {Cu3} units, while the intertrimeric magnetic interactions occurring through the hexadentate azido ligand have been found to be antiferromagnetic (J3=,5.4 cm,1) and ferromagnetic (J4=+1.3 cm,1) with respect to the end-to-end and end-on azido-bridged CuII pairs, respectively. [source]

Synthesis, Protonation and CuII Complexes of Two Novel Isomeric Pentaazacyclophane Ligands: Potentiometric, DFT, Kinetic and AMP Recognition Studies

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 1 2009
Andrés G. Algarra
Abstract The synthesis and coordination chemistry of two novel ligands, 2,6,9,12,16-pentaaza[17]metacyclophane (L1) and 2,6,9,12,16-pentaaza[17]paracyclophane (L2), is described. Potentiometric studies indicate that L1 and L2 form a variety of mononuclear complexes the stability constants of which reveal a change in the denticity of the ligand when moving from L1 to L2, a behaviour that can be qualitatively explained by the inability of the paracyclophanes to simultaneously use both benzylic nitrogen atoms for coordination to a single metal centre. In contrast, the formation of dinuclear hydroxylated complexes is more favoured for the paraL2 ligand. DFT calculations have been carried out to compare the geometries and relative energies of isomeric forms of the [CuL]2+ complexes of L1 and L2 in which the cyclophane acts either as tri- or tetradentate. The results indicate that the energy cost associated with a change in the coordination mode of the cyclophane from tri- to tetradentate is moderate for both ligands so that the actual coordination mode can be determined not only by the characteristics of the first coordination sphere but also by the specific interactions with additional nearby water molecules. The kinetics of the acid promoted decomposition of the mono- and dinuclear CuII complexes of both cyclophanes have also been studied. For both ligands, dinuclear complexes convert rapidly to mononuclear species upon addition of excess acid, the release of the first metal ion occurring within the mixing time of the stopped-flow instrument. Decomposition of the mononuclear [CuL2]2+ and [CuHL2]3+ species occurs with the same kinetics, thus showing that protonation of [CuL2]2+ occurs at an uncoordinated amine group. In contrast, the [CuL1]2+ and [CuHL1]3+ species show different decomposition kinetics indicating the existence of significant structural reorganisation upon protonation of the [CuL1]2+ species. The interaction of AMP with the protonated forms of the cyclophanes and the formation of mixed complexes in the systems Cu,L1 -AMP, Cu,L2 -AMP, and Cu,L3 -AMP, where L3 is the related pyridinophane containing the same polyamine chain and 2,6-dimethylpyridine as a spacer, is also reported. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]

Synthesis and Crystal Structure of a Heptanuclear and an Octanuclear Copper(II) Complex Derived from ,- D -Glucofuranoses

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 23 2007
Michael Gottschaldt
Abstract CuII complexes of different 6-(,-keto-enamino)-6-deoxy-1,2- O -isopropylidene-,- D -glucofuranoses 3a,f have a high tendency to build up oligonuclear clusters. Two new oligonuclear copper(II) complexes could be synthesised, crystallised and their structures determined. The complex Cu(3a) was found to consist of a heptanuclear cluster in which two ,-cubane like substructures share one copper ion. The structure is highly asymmetric and in the cluster every CuII ion has a different coordination geometry. Variation of the residues of the ,-ketoenaminic unit leads to the formation of the octanuclear copper(II) complex Cu(3e). Similarly, this has two ,-cubane subunits consisting of a heptanuclear structure with an additionally attached copper ion. In the crystal, two Cu8 cluster molecules are found differing in their geometries due to intermolecular interactions responsible for the formation of a supramolecular network. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source]

Funnel Complexes with CoII and NiII: New Probes into the Biomimetic Coordination Ability of the Calix[6]arene-Based Tris(imidazole) System

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 9 2004
Olivier Sénèque
Abstract The coordination properties of the calix[6]arene-based tris(imidazole) ligand X6Me3Imme3 were further explored with CoII and NiII. This imidazole system stabilizes tetrahedral mononuclear CoII complexes with an exchangeable fourth exogenous ligand (water, alcohol, amide) located at the heart of the hydrophobic calixarene cavity. With a weak donor ligand such as a nitrile, both four-coordinate tetrahedral and five-coordinate trigonal bipyramidal complexes were obtained. The latter contains a second nitrile molecule trans to the included guest nitrile. These complexes were characterized in solution as well as in the solid state. The NiII complexes are square-based pyramidal five-coordinate edifices with a guest nitrile inside the cavity and a water molecule outside. A comparison with previously described ZnII and CuII complexes emphasizes the flexibility of this ligand. A comparison with carbonic anhydrase, a mononuclear zinc enzyme with a tris(histidine) coordination core, shows that X6Me3Imme3 displays many structural features of this enzyme except for the cis coordination of the exogenous ligands. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]

Extended X-ray Absorption Fine Structure Study of Copper(I) and Copper(II) Complexes in Atom Transfer Radical Polymerization

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 11 2003
Tomislav Pintauer
Abstract Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy has been used to investigate structural features of CuIBr and CuIIBr2 complexes with dNbpy, PMDETA, Me6TREN, tNtpy, and Me4CYCLAM in various solvents {dNbpy = 4,4,-bis(5-nonyl)-2,2,-bipyridine, PMDETA = N,N,N,,N,,,N,, -pentamethyldiethylenetriamine, Me6TREN = tris[2-(dimethylamino)ethyl]amine, tNtpy = 4,4,,4,,-tris(5-nonyl)-2,2,:6,,2,,-terpyridine, Me4CYCLAM = 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane}. The structures of the CuI and CuII complexes were found to depend on the solvent polarity and the number of nitrogen atoms in the ligand. Generally, in non-polar media and with monomers typically used in ATRP, CuI complexes preferred a tetracoordinate geometry, and were either ionic as observed in [CuI(dNbpy)2]+[CuIBr2], (CuI,NAV = 2.00 Å, CuI,BrAV = 2.25 Å) and [CuI(Me4CYCLAM)]+[CuIBr2], (CuI,NAV = 2.06 Å, CuI,BrAV = 2.23 Å), or neutral as in [CuI(PMDETA)Br] (CuI,NAV = 2.12 Å, CuI,BrAV = 2.33 Å), and [CuI(tNtpy)Br] (CuI,NAV = 2.03 Å, CuI,BrAV = 2.29 Å). The EXAFS analysis of CuIIBr2 complexes indicated a preference for a coordination number of five, such as in [CuII(dNbpy)2Br]+[Br], (CuII,NAV = 2.03 Å, CuII,BrAV = 2.43 Å), [CuII(PMDETA)Br2] (CuII,NAV = 2.03 Å, CuII,Br1,AV = 2.44 Å, CuII,Br2,AV = 2.64 Å) and [CuII(Me6TREN)Br]+[Br], (CuII,NAV = 2.09 Å, CuII -BrAV = 2.39 Å), with the exception of the neutral tetracoordinate [CuII(dNbpy)Br2] (CuII,NAV = 2.02 Å, CuII,BrAV = 2.36 Å), which has been observed in non-polar media. Additionally, polar media were found to favor bromide dissociation in [CuII(Me6TREN)Br]+[Br], and [CuII(PMDETA)Br2], as indicated by a decrease in the Br and Cu coordination numbers at the Cu- and Br- K -edges, respectively. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source]

Studies of Pyridinyl-Containing 14-Membered Macrocyclic Copper(II) Complexes

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 7 2003
Sabrina Autzen
Abstract Six copper(II) complexes of tetracoordinating, pyridinyl-containing 14-membered macrocycles with varying ratios of nitrogen and oxygen donor atoms were prepared and characterized by IR, UV/Vis, and EPR spectroscopy and cyclic voltammetry. A distorted tetragonal coordination of the copper center in the solid-state was established by X-ray crystallography for the tetraazamacrocyclic complex Cu-3 carrying a methoxybenzyl pendent arm and the trioxaaza complex Cu-6. The superoxide dismutase-like activity of the CuII complexes was investigated by inhibition of NADH oxidation. Although the UV/Vis and EPR spectra of the complexes were strongly affected when the coordinating nitrogen atoms were successively replaced by oxygen atoms, no significant change in their reactivity towards superoxide was observed. In all cases a 1:1 or 1:2 stoichiometry for the reaction with superoxide was found, with the exception of the methoxybenzyl-substituted tetraaza complex, which showed a low catalytic activity with a turnover number of about 10. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source]

Structure, Characterization, and Metal-Complexation Properties of a New Tetraazamacrocycle Containing Two Phenolic Pendant Arms

HELVETICA CHIMICA ACTA, Issue 10 2004
Xiuling Cui
The new tetraazamacrocycle 2 (=2,2,-[[7-Methyl-3,7,11,17-tetraazabicyclo[11.3.1]heptadeca-1(17),13,15-triene-3,11-diyl]bis(methylene)]bis(4-bromophenol)) was synthesized and used as a ligand for different metal-ion complexes. The X-ray crystal structures of the complexes of the general formula [M(H- 2)]+NO,MeOH (M=Ni2+, Zn2+), in which only one of the two pendant phenolic OH groups of 2 is deprotonated, were determined. In both complexes, the coordination environment is of the [5+1] type, the four N-atoms of the macrocyclic framework defining a square-planar arrangement around the metal center, with similar NiN and ZnN distances of 1.961(9) to 2.157(9),Å and 2.021(9) to 2.284(8),Å, respectively. In contrast, the MO distances are markedly different, 2.060(6) and 2.449(8),Å in the NiII complex, and 2.027(7) and 2.941(9),Å in the ZnII complex. The UV/VIS spectra of the NiII and CuII complexes with ligand 2, and the EPR spectra of the CuII system, suggest the same type of structure for the complexes in solution as in the solid state. Theoretical studies by means of density functional theory (DFT) confirmed the experimental structures of the NiII and ZnII complexes, and led to a proposal of a similar structure for the corresponding CuII complex. The calculated EPR parameters for the latter and comparison with related data support this interpretation. The singly occupied molecular orbital (SOMO) in these systems is mainly made of a d orbital of Cu, with a strong antibonding (,*) contribution of the axially bound phenolate residue. [source]

Structure correlation study of four-coordinate copper(I) and (II) complexes

ACTA CRYSTALLOGRAPHICA SECTION B, Issue 3 2000
Paul R. Raithby
The geometries of four-coordinate CuI and CuII complexes in the Cambridge Structural Database (CSD) have been analysed systematically and compared using symmetry-deformation coordinates and principal component analysis. The observed stereochemistries have been rationalized in terms of the d -electron configurations, interligand repulsion and ,-bonding effects. The results confirm that the majority of four-coordinate copper(I) complexes in the CSD adopt tetrahedral geometries and deviations from tetrahedral symmetry are caused by the presence of chelating ligands or by the incorporation of copper centres into dimeric or polymeric structures. Four-coordinate copper(II) complexes generally adopt geometries close to square planar; this is particularly evident for bis(chelate) complexes where ,-bonding is important. Distortions towards tetrahedral geometries are attributable to steric interactions of bulky substituents in the bidentate ligands. [source]

Dimeric copper(II) 3,3-dimethyl­butyrate adducts with ethanol, 2-methylpyridine, 3-methylpyridine, 4-methylpyridine and 3,3-dimethylbutyric acid

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 1 2000
Masato Goto
In the crystals of the five title compounds, tetrakis-(,-3,3-dimethylbutyrato- O:O,)bis(ethanol- O)dicopper(II),ethanol (1/2), [Cu2(C6H11O2)4(C2H6O)2]·2C2H6O, (I), tetrakis(,-3,3-dimethylbutyrato- O:O,)bis(2-methylpyridine- N)di­copper(II), [Cu2(C6H11O2)4(C6H7N)2], (II), tetrakis-(,-3,3-dimethylbutyrato- O:O,)bis(3-methylpyridine- N)di-copper(II), [Cu2(C6H11O2)4(C6H7N)2], (III), tetrakis-(,-3,3-dimethylbutyrato- O:O,)bis(4-methylpyridine- N)di-copper(II), [Cu2(C6H11O2)4(C6H7N)2], (IV), and tetrakis-(,-3,3-dimethylbutyrato- O:O,)bis(3,3-dimethylbutyric acid- O)dicopper(II), [Cu2(C6H11O2)4(C6H12O2)2], (V), the di­nuclear CuII complexes all have centrosymmetric cage structures and (IV) has two independent molecules. The Cu,Cu separations are: (I) 2.602,(3),Å, (II) 2.666,(3),Å, (III) 2.640,(2),Å, (IV) 2.638,(4),Å and (V) 2.599,(1),Å. [source]

The Structure of Metallomicelles

CHEMISTRY - A EUROPEAN JOURNAL, Issue 8 2004
P. C. Griffiths Dr.
Abstract The morphology of micelles formed by two novel metallosurfactants has been studied by small-angle neutron scattering (SANS) and small-angle-X-ray scattering (SAXS). The two surfactants both contain a dodecyl chain as the hydrophobic moiety, but differ in the structure of the head group. The surfactants are CuII complexes of monopendant alcohol derivatives of a) the face-capping macrocycle 1,4,7-triazacyclanonane (tacn), and b) an analogue based upon the tetraazamacrocycle 1,4,7,10-tetraazacyclododecane. Here, neutron scattering has been used to study the overall size and shape of the surfactant micelles, in conjunction with X-ray scattering to locate the metal ions. For the 1,4,7,10-tetraazacyclododecane-based surfactant, oblate micelles are observed, which are smaller to the prolate micelles formed by the 1,4,7-triazacyclononane analogue. The X-ray scattering analysis shows that the metal ions are distributed throughout the polar head-group region, rather than at a well-defined radius; this is in good agreement with the SANS-derived dimensions of the micelle. Indeed, the same model for micelle morphology can be used to fit both the SANS and SAXS data. [source]

Copper(II) Complexes Containing N,N-Donor Ligands and Dipeptides Act as Hydrolytic DNA-Cleavage Agents

CHEMISTRY & BIODIVERSITY, Issue 6 2004
Pulimamidi
Copper(II) complexes are known to play a significant role in both naturally occurring biological systems and pharmaceutical agents. Recently, CuII complexes have gained importance in DNA cleavage essential for the development of anticancer drugs and chemotherapeutic agents. Therefore, we have designed small molecules, consisting of a metal ion, N,N-donor ligands, and dipeptides, to probe their DNA-cleaving potential. Accordingly, the interaction of CuII with ethylenediamine, histamine and the dipeptides histidylglycine, histidylalanine, and histidylleucine has been investigated. The binding modes, stabilities, and geometries of these complexes were determined by various physicochemical techniques. Their DNA-binding abilities were probed by absorption and fluorescence spectroscopy, and their DNA-cleavage potential was tested by electrophoresis. [source]