Mixed-ligand Copper Complexes Research Articles

Synthesis, structure, antioxidant and SOD-mimetic activity of [Cu(xanthurenate)(nicotinamide)(H2O)] complexes

This study reports the synthesis of novel mixed ligand complexes of copper(II) with the xanthurenate anion (Xan2−) and nicotinamide ligand (NA): [Cu(Xan)(NA)(H2O)]·H2O and [Cu(Xan)(NA)(H2O)]·3H2O. The compounds were characterized by single crystal X-ray diffraction, IR spectroscopy, and thermal analysis. The first coordination sphere of copper(II) in [Cu(Xan)(NA)(H2O)] consists of a water molecule, a nicotinamide ligand coordinated via the pyridine nitrogen and a xanthurenate dianion coordinated in a tridentate manner via carboxylate oxygen, nitrogen, and phenolate oxygen. The five donor atoms define a distorted square pyramid whose apex is occupied by the aqua ligand. The antioxidant activities of the compounds were investigated by the 2,2-diphenyl-1-picrylhydrazyl scavenging method, which showed that the IC 50 values for both compounds are higher than for related [Cu(Xan)(H2O)2] complex. The title compounds also exhibit superoxide dismutase mimetic activity.

X-rayKabsorption spectral studies of copper (II) hydroxamic acid mixed ligand complexes

X-ray absorption spectra at the K-edge of copper have been studied in copper mixed ligand complexes having hydroxamic acid as one of the ligands. The X-ray absorption spectra have been recorded at BL-8 Dispersive Extended X-ray Absorption Fine Structure (EXAFS) beamline at the 2.5-GeV INDUS-2 Synchrotron Source, RRCAT, Indore, India. The data obtained has been processed using EXAFS data analysis program Athena. The energies of the K absorption edge, chemical shifts, edge-widths and shifts of the principal absorption maximum in the complexes have been determined and discussed. The chemical shift data have been utilized to estimate effective nuclear charge on the absorbing atom. The normalized EXAFS spectra have been Fourier transformed. The position of the first peak in the Fourier transform gives the value of first shell bond length, which is shorter than the actual bond length as a result of energy dependence of the phase factors in the sine function of the EXAFS equation. This distance is thus the phase-uncorrected bond length and has also been determined by Lytle, Sayers and Stern's (LSS) graphical method. The results obtained from LSS and the Fourier transformation methods are comparable with each other. The first shell bond length has also been estimated by Lytle's and Levy's methods from the EXAFS data. Copyright © 2014 John Wiley & Sons, Ltd.

A novel type of coordination mode of chloranilic acid leading to the formation of polymeric coordination ribbon in the series of mixed-ligand copper(ii) complexes with 1,10-phenanthroline

A series of four novel mixed-ligand complexes of copper(II) with 3,6-dichloro-2,6-dihydroxy-1,4-benzoquinone (chloranilic acid) and 1,10-phenanthroline was prepared and characterised by X-ray structure analysis and IR spectroscopy. Three complexes exhibit square-pyramidal coordination, whereas one exhibits octahedral coordination. The ligand 1,10-phenanthroline acts in a bidentate chelating mode with N,N-metal binding. The chloranilate dianion coordinates to the Cu(II) atom in a terminal bidentate ortho-quinone-like mode, forming a mononuclear complex species. However, in one structure a novel type of coordination mode of chloranilate is observed. In addition to the bidentate mode, a monodentate bridging mode through a carboxy oxygen of a symmetry-related dianion leads to the formation of polymeric coordination ribbon. The crystal packing of penta-coordinated species, in addition to hydrogen bonding, involves less common stacking interactions of chelate rings with the π-systems of the ligands.

Speciation of Mixtures of Copper (I) and Copper (II) Mixed Ligand Complexes by X-Ray Absorption Fine Structure Spectroscopy

ABSTRACT Studies on speciation have been done in the mixtures of mixed ligand copper complexes. Three heterogeneous mixtures have been studied, each having one Cu(I) complex and one Cu(II) complex. The Cu(I) complex is [Cu(thu)Cl 0.5H2O] (1) and the Cu(II) complexes are [Cu(L-phen)(bpy) H2O] (2), [Cu(L-tyr)(phn) 2.5H2O] (3), and [Cu(dien)(ina) 4H2O.1/2SO4] (4) (where thu = thiourea, phen = 1,10-phenanthroline, bpy = 2,2′-bipyridine, tyr = tyrosine, dien = diethylenetriamine, and ina = isonicotinate anion). The mixtures have been prepared by mixing the Cu(I) complex with each of the Cu(II) complexes in the ratio of 1:1 by mole percentage. The X-ray absorption fine structure (XAFS) spectra have been recorded at the K-edge of copper in the mixtures as well as in the complexes, separately. The aim of the present work is to make a study of the different methods of speciation using XAFS, viz., principal component analysis (PCA) and the target transformation (TT) method, the linear combination fitting (LCF) method, derivative spectra methods, and normalized difference absorption edge spectra (NDAES) analysis. It has been shown that these methods can be used to determine the relative quantity of the mixed ligand complexes in their mixtures.

EXAFS study of mixed ligand copper complexes having nicotinic acid as one of the ligands

Copper K-edge EXAFS spectra of the copper (II) complexes [Cu3(NA)4(dca)2(H2O)8].2H2O (1) and [Cu2(2,2'-bipy)(NA)2](ClO4)2.H2O (2) (where NA = Nicotinic acid; dca = dicyanamide anion; 2,2'-bipy = 2-2' bipyridine) having different coordination environments and geometries have been investigated. The complex 1 is supposed to have six coordinated geometry and complex 2 five coordinated geometry. EXAFS has been recorded at the K-edge of copper in the complex at the dispersive EXAFS beamline at 2 GeV Indus-2 synchrotron source at RRCAT, Indore, India. Theoretical models have been generated for both the complexes separately using their reported crystal structures. These theoretical models have been fitted to the respective experimental EXAFS data and the structural parameters, which include bond lengths, coordination numbers and thermal disorders, have been determined. The results obtained have been found to be comparable with those reported using crystallography. The coordination geometry about the copper (II) ion has been depicted for both the complexes. Further, copper has been found to be in +2 oxidation state in both the complexes. The study shows that the dispersive EXAFS beamline can be used to obtain information about the coordination geometry of a sample, though the beamline provides limited range of EXAFS data.

Synthesis and Characterization of Mixed Ligand Complexes of Cu(Phen)2(ClO4 )2 with Some Aromatic Ligands

Five mixed-ligand complexes of copper(II) with 1, 10-phenanthroline and some selected aromatic ligands such as imidazole, 2-aminopyridine, 4- dimethylaminobenzonitrile, 2,2'dipyridylketone, 4-methylimidazole-5-carboxaldehyde have been synthesized and characterized by microanalyses, spectroscopic and room temperature magnetic susceptibility measurements. The microanalyses data is satisfactory with the formation of the prepared complexes. The infrared spectra of the complexes reveal the involvement of the donor groups of the selected aromatic compounds attached to the copper metal in the formation of the mixed-ligand complexes. The electronic spectra in the visible region show the high energy, high intensity peaks between 13,647 cm -1 and 15,322 cm -1 . The mass spectra of the complexes are supportive of the microanalytical data.

Mixed ligand copper(II) complexes: Synthesis, characterization and DNA cleavage activities

AimThis study was aimed to examine the DNA cleavage ability of the mixed ligand copper complexes. MethodsThe reduced form of Schiff base ligands L1 and L2 (where L1 is 1-(tetrahydrofuran-2-yl)-N-(thiophen-2-ylmethyl)methanamine and L2 is 1-(1H-benzimidazol-2-yl)-N-(tetrahydrofuran-2-ylmethyl)methanamine) were synthesized. Three new mixed ligand mononuclear copper(II) complexes containing tridentate unsymmetrical and bidentate symmetrical ligands were also synthesized. ResultsThe synthesized complexes were characterized using various physicochemical techniques like cyclic voltammetry and elemental analysis, ESI-MS, UV–Visible, Infra red and EPR. All the three complexes however successfully promoted an oxidative cleavage of plasmid DNA, producing single strand break. In addition, mechanistic SC DNA cleavage results show higher DNA cleavage activity in presence of oxidizing agent, due to the presence of hydroxyl radicals. ConclusionsFrom the present study it was concluded that the complexes were able to cleave plasmid DNA oxidatively in the presence of hydrogen peroxide.

A study of the structure and properties of mixed-ligand Cu(II) complexes with hexafluoroacetylacetone and methyl-, phenyl-ketoimines

The synthesis and X-ray single crystal study of two mixed-ligand Cu(II) complexes are performed: (CH3C(NCH3)CHC(O)CH3)(CF3C(O)CHC(O)CF3)Cu (1) (space group P21/c, a = 7.0848(12) A, b = 17.854(3) A, c = 11.837(2) A, β = 100.495(6)°, V = 1472.4(4) A3, Z = 4), (CH3C(NC6H5)CHC(O)CH3)· (CF3C(O)CHC(O)CF3)Cu (2) (space group P-1, a = 9.1119(4) A, b = 9.6954(4) A, c = 11.1447(6) A, α = 113.784(2)°, β = 92.383(2)°, γ = 95.402(2)°, V = 893.52(7) A3, Z = 2). The structures are molecular, formed from neutral mixed-ligand copper complexes. The central copper atom has the (3O+N) coordination environment with average Cu-O distances of 1.948 A and Cu-N of 1.932 A; the chelate O-Cu-N angle (average) is 94.0°. In the structures, the complexes are linked into dimeric associates with Cu…Cu distances of 3.197 A (for 1) and 3.246 A (for 2). The volatility of mixed-ligand complexes 1 and 2 is in between of that of the starting homo-ligand complexes.

Copper(i) complexes of 1,10-phenanthroline and heterocyclic thioamides: an experimental and theoretical (DFT) investigation of the photophysical characteristics

A series of luminescent mixed ligand complexes of copper(I) halides with 1,10-phenanthroline and the heterocyclic thioamides pyridine-2(1H)-thione (py2SH), pyrimidine-2(1H)-thione (pymtH), 4,6-dimethylpyrimidine-2(1H)-thione (dmpymtH), 1,4,5,6-tetrahydropyrimidine-2-thione (tHpymtH), 1,3-imidazolidine-2-thione (imtH(2)) and 4,5-diphenyl-2-oxazolethiol (dpoxtH) have been synthesized and characterized. The molecular structures of two representative compounds have been established by single-crystal X-ray diffraction. The mononuclear complexes feature the metal in a distorted tetrahedral environment surrounded by the two N atoms of the chelating 1,10-phenanthroline, the thione-S atom of the thioamide, and the halogen atom. The molecular structure, the electronic and photophysical properties and the energetics of the metal-ligand interactions for [CuI(phen)(py2SH)] have been studied by means of density functional calculations.

A Crystallographic, Spectroscopic, Thermal, and DFT Investigation of Mixed Ligand Cu(II) Complexes of 2-benzoylbenzoate

Two mixed ligand complexes of copper(II)-2-benzoylbenzoate (bba) with pyridazine and 4-picoline, namely bis(2-benzoylben- zoate)di(pyridazine)copper(II) 1 and bis(2-benzoylbenzoate)bis(4-picoline)copper(II) 2, have been synthesized and characterized by X-ray crystallography. Complexes 1 and 2 crystallize in the monoclinic P21/c space groups. The calculated frequency shifts have shown that the participation of carboxylate groups in coordination to the metal centers in monodentate fashion (Δ(OCO) > 200 cm−1). The structural features of the complexes have been further studied by DFT/X3LYP extended hybrid functional. The thermal behavior of the complexes was studied by means of simultaneous thermogravimetry, differental thermogravimetry, and differential thermal analysis methods in a static air atmosphere.

Bis[(1,10-phenanthroline-κ2N,N′)bis(triphenylphosphane-κP)copper(I)] nonadecaoxidohexamolybdate(VI)

The title compound, [Cu(C12H8N2)(C18H15P)2]2[Mo6O19], was obtained by co-crystallization of the mixed-ligand copper complex cation (1,10-phenanthroline)bis­(triphenyl­phos­phane)copper(I), [Cu(phen)(PPh3)2]+, with the Lindquist polyanion [Mo6O19]2−. The asymmetric unit consists of half a Lindquist anion and one [Cu(phen)(PPh3)2]+ cationic complex. In the cation, there are intra­molecular π–π inter­actions [centroid–centroid distances = 3.617 (2) and 3.7272 (18) Å]. This inorganic–organic adduct is connected by C—H⋯O hydrogen bonds, forming a two dimensional network lying in the ab plane. These networks are connected by C—H⋯π inter­actions into a three-dimensional structure.

Synthesis, DNA binding and antiproliferative activity of ternary copper complexes of moxifloxacin and gatifloxacin against lung cancer cells

Abstract Mixed ligand Cu(II) complexes of third generation fluoroquinolone antibacterial agents moxifloxacin (MFL) and gatifloxacin (GFL) have been synthesized and characterized spectroscopically. The complexes have been found to bind DNA by intercalative mode and the DNA binding constants K b and K sv have been determined by absorption measurements and florescence quenching experiments respectively. The anti-proliferative and apoptosis inducing activity of the mixed ligand copper complexes against human lung carcinoma cells(A-549) was determined adopting MTT-assay, other specific staining techniques and DNA ladder. All the complexes have been shown to be cytotoxic towards A549 lung cancer cells. The complexes have been shown to bring about apoptosis of the cancerous cells.

X-ray absorption near edge structure (XANES) study of some hydroxamic mixed ligand copper complexes

With the advent of modern bright synchrotron radiation sources, X-ray absorption spectra has emerged as a powerful technique for local structure determination, which can be applied to any type of material. The X-ray absorption measurements of four hydroxamic mixed ligand copper complexes have been performed at the recently developed BL-8 Dispersive EXAFS beamline at 2.5 GeV Indus-2 synchrotron at RRCAT, Indore, India. The X-ray absorption near edge structure (XANES) data obtained has been processed using data analysis program Athena. The energies of the K absorption edge, chemical shifts, edge-widths, shifts of the principal absorption maximum in the complexes have been determined. The values of the chemical shift suggest that copper is in oxidation state +2 in all of the complexes. The chemical shift data has been utilized to estimate effective nuclear charge on copper atom. The order of the chemical shifts has been correlated to the relative ionic character of the bonding in these complexes.

X-ray diffraction and absorption spectroscopic studies of copper mixed ligand complexes with aminophenol as one of the ligands

X-ray diffraction (XRD) and X-ray absorption spectroscopic (XAS) studies have been conducted on two copper complexes, i.e., copper macrocyclic complex of succinic acid and ortho aminophenol (complex-1) and copper macrocyclic complex of pthalic acid and ortho aminophenol (complex-2). The diffraction pattern of the complexes have been recorded using Rigaku RINT-2000 X-ray diffractometer equipped with rotating anode X-ray tube operated at 40 kV and 100 mA. The X-ray absorption spectra of the complexes have been recorded at the K-edge of copper on Cauchois type bent crystal spectrograph having radius 0.4 m employing a mica crystal, oriented to reflect from (100) planes, for dispersion. The X-ray absorption near edge structure (XANES) parameters, viz., chemical shift, energy position of the principal absorption maximum and edge-width have been determined and discussed. From the extended X-ray absorption fine structure (EXAFS) data, the bond lengths have been calculated using three methods, namely, Levy's method, Lytle, Sayers and Stern's (LSS) method and Fourier transformation method. The results obtained have been compared with each other and discussed.

Exceptionally Long-Lived Luminescence from [Cu(I)(isocyanide)2(phen)]+Complexes in Nanoporous Crystals Enables Remarkable Oxygen Gas Sensing

We report crystalline mixed-ligand copper complexes with phenanthroline and isocyanides with almost millesecond emission lifetimes that are efficient dioxygen sensors. The oxygen sensitivity of the prototype ([Cu(CN-xylyl)(2)(dmp)]tfpb, dmp = 2,9-dimethyl-1,10-phenanthroline; CN-xylyl = 2,6-dimethylphenylisocyanide; tfpb = tetrakis(bis-3,5-trifluoromethylphenylborate) is 38 times better than that of [Ru(phen)(3)]tfpb(2) (phen = 1,10-phenanthroline).

Laser induced multi-component luminescence of [CuNCS(1,10-phen)P(CH2N(CH2CH2)2O)3]—the first example of CuNCS complexes with diimines and tris(aminomethyl)phosphanes

[CuNCS(phen)P(CH2N(CH2CH2)2O)3], a novel mixed-ligand complex of copper(I) isothiocyanate with 1,10-phenanthroline and tris(aminomethyl)phosphane derived from morpholine have been synthesized. It was characterized by elemental analysis, thermogravimetric and differential thermal analyses and studied by NMR, mass, UV–Vis, IR and luminescence spectroscopies. The X-ray structure of the complex was determined. The coordination geometry about the Cu(I) center is pseudo-tetrahedral. The complex exhibits a very weak photoluminescence in the solid state. Surprisingly, the luminescence spectra of the crystalline sample at room and LN temperatures show several bands similarly to absorption(reflectance) spectrum. On the basis of TDDFT calculations we interpreted these bands as of MLLCT type resulting mainly from two transitions: π⁎(CuNCS)→π⁎(phen) and σ(CuP)→π⁎(phen). This strongly suggests that all the ligands are involved into absorption and PL spectra, however their complex character (several bands observed) does not allow the more precise interpretation.

Cytotoxic copper (II) mixed ligand complexes: Crystal structure and DNA cleavage activity

Two new mixed ligand complexes of copper (II) containing an imidazolyl terpyridine ligand, [Cu(Itpy)(bpy)](ClO 4) 2·(H 2O), 1, and [Cu(Itpy)(phen) (ClO 4)](ClO 4)·(H 2O), 2 have been synthesized and characterized. Complex 1 has been found to possess a distorted square pyramidal geometry whereas 2 exhibit a distorted octahedral geometry. Electronic spectral titrations suggest that 1 and 2 bind to DNA intercalatively with the binding constant, K b (4.12 ± 0.13) × 10 4 M −1 ( 1) and (6.04 ± 0.15) × 10 4 M −1 ( 2). Under physiological condition, in the absence of any external cofactor 2 has been found to bring about DNA cleavage via hydrolytic mechanism but 1 does not bring about any DNA cleavage. Both compounds show antitumor effects on the A549 lung adenocarcinoma cancer cell line.

Synthesis, structural characterization and microbial activities of mixed ligand copper(II) complexes of 2,2′-bipyridine and acetylacetonate

Abstract Two new mixed ligand complexes of copper(II) with acetylacetonate (acac) and 2,2′-bipyridine (bpy) belonging to the class of cytotoxic and antineoplastic compounds known as CASIOPEINAS® have been synthesized and characterized on the basis of analytical and spectroscopic data. Molecular structures of the complexes, [Cu(acac)(bpy)Cl][Cu(acac)(bpy)(H2O]Cl.H2O and [Cu(acac)(bpy)Br]H2O, were established by single crystal X-ray study. The Cu(II) ion in both the complexes exhibited square pyramidal geometry with acac and bpy in the equatorial plane and halide/water in the axial position. Interestingly, for the complex with chloride anion, two types of complexes with chloride and water at the axial positions were derived from the same reaction and co-crystallized in the asymmetric unit with strong intermolecular interactions. Microbial property of these two complexes as antibacterial and antifungal agents has been investigated and some of the results are comparable to that of the standard drugs such as E. coli, P. aeruginosa, S. aureus, S. pyogenes, A. niger and C. albicans, used in this study.

Mixed-ligand complexes of copper(I) with Schiff base and triphenylphosphine: Effective catalysts for the amination of aryl halide

Abstract Some copper(I) complexes of the type [Cu(L)(PPh3)2]X (1–4) [where L = 2-chloro-(5-trifluoromethyl-phenyl)-pyridine-2-ylethylene-amine; X = Cl−, CN−, ClO4− and BF4−] have been prepared by the condensation of 3-amino-4-chloro-benzotrifluoride with 2-acetylpyridine followed by the reaction with [Cu(MeCN)2(PPh3)2]Cl, [Cu(MeCN)2(PPh3)2]CN, [Cu(MeCN)2(PPh3)2]ClO4 and [Cu(MeCN)2(PPh3)2]BF4. All the complexes 1–4 were characterized on the basis of elemental analysis, IR, UV–visible and 1H NMR spectral studies. The representative complex of the compound 3 has been characterized by single crystal X-ray diffraction which reveals that the central copper(I) ion assumes highly distorted tetrahedral geometry. All the complexes worked as effective catalyst for the amination of aryl halide.

A new mixed-ligand complex of copper(II) containing N-(2-pyridylmethyl)-2-pyrazinecarboxamide (NPyPzCa): Synthesis, molecular and crystal structure and properties of [Cu(NPyPzCa)(NO3)(DMSO)

Abstract The copper(II) complex [Cu(NPyPzCa)(NO3)(DMSO)] (1) (N-(2-pyridylmethyl)-2-pyrazinecarboxamide [NPyPzCa]) has been synthesized and characterized by single crystal X-ray diffraction and ab-initio calculation, electrochemistry and TGA analysis. The Cu(II) atom exhibits a square base pyramidal geometry due to the coordination of three donor atoms from the carboxamide ligand and one oxygen atom from the NO3− ion in the equatorial plane and one DMSO in the axial position. There are some C H…O, C H…N and C H…π (aromatic) interactions that seem to be effective in the stabilization of the crystal packing. The electrochemistry of this complex shows a quasi-reversible one electron Cu(III/II) reduction near +0.35 V.