Mixed-ligand Copper Complexes Research Articles

Studies on the mixed ligand complexes of copper(II) involving a sulfa drug and some potentially bi or tridentate ligands under physiological conditions

The stability constants of mixed ligand complexes formed in the Cu(II)-sulfathiazole(stz)(A)-glycine(gly), dl-2-aminobutanoic acid(2aba), dl-3-aminobutanoic acid(3aba), 1,2-diaminopropane(dp), 1,3-diaminopropane(tp), dl-2,3-diaminopropanoic acid(dapa), dl-2,4-diaminobutanoic acid(daba), dl-2,5-diaminopentanoic acid(ornithine, orn)(B) systems have been determined pH-metrically at 37°C and I=0.15moldm−3 (NaClO4) using SCOGS program. Analysis of experimental data indicates the presence of CuABH, CuAB, CuAB2H2 or CuAB2 species. The ΔlogK values demonstrate higher stabilities for the mixed ligand complexes compared to the binary analogues. The CuAB complexes with B=gly, 2aba, dapa & orn systems were isolated and characterized using micro analytical, magnetic moment, ESR, electrochemical studies, TG/DTA, power XRD and SEM analysis. Magnetic susceptibility and electronic spectral studies suggest square planar geometry for the CuAB complexes. The g values indicate that the unpaired electron lies in the dx2-y2 orbital. The TG/DTA studies reveal that the complexes are non hydrated and possesses high thermal stability. The powder XRD data suggest that the complex is microcrystalline. The antimicrobial activity and CT DNA cleavage studies of the complexes are also reported.

Synthesis, structural characterization, antimicrobial, DNA-binding, and photo-induced DNA cleavage activity of some bio-sensitive Schiff base copper(II) complexes

Schiff base mixed-ligand copper complexes [CuL1(phen)Cl2], [CuL1(bipy)Cl2], [Cu(L1)2Cl2], [Cu(L2)2Cl2], [CuL2(bipy)Cl2], and [CuL2(phen)Cl2] (where L1 = 4-[3,4-dimethoxy-benzylidene]-1,5-dimethyl-2-phenyl-1,2-dihydro-pyrazole-3-one; L2 = 4-[3-hydroxy-4-nitro-benzylidene]-1,5-dimethyl-2-phenyl-1,2-dihydro-pyrazole-3-one; phen = 1,10-phenanthroline; and bipy = 2,2′-bipyridine) have been synthesized and characterized. Their DNA-binding properties have been studied by electronic absorption spectra, viscosity, and electrochemical measurements. The absorption spectral and viscosity results suggest that the copper(II) complexes bind to DNA via partial intercalation. The addition of DNA resulting in the decrease of the peak current of the copper(II) complexes indicates their interaction. Interaction between the complexes and DNA has also been investigated by submarine gel electrophoresis. The copper complexes cleave supercoiled pUC19 DNA to nicked and linear forms through hydroxyl radical and singlet oxygen in the presence of 3-mercaptopropionic acid as the reducing agent. These copper complexes promote the photocleavage of pUC19 DNA under irradiation at 360 nm. Mechanistic study reveals that singlet oxygen is likely to be the reactive species responsible for the cleavage of plasmid DNA by the synthesized complexes. The in vitro antimicrobial study indicates that the metal chelates have higher activity against the bacterial and fungal strains than the free ligands.

Synthesis, spectroscopic properties, structural characterization and electrochemistry of mixed ligand complexes of copper(I) halide with PPh 3 and naphthylazoimidazole

The reaction of CuX (X = Cl, Br, I) with a mixture of PPh 3 and 1-alkyl-2-(naphthyl-α/β-azo)imidazole has synthesized mixed ligand complexes of the composition, [Cu(α/β-NaiR)(PPh 3)X]. The spectroscopic characterization (IR, UV–Vis, 1H NMR) supports this formulation. The single crystal X-ray diffraction study of [Cu((α-NaiMe)(PPh 3)I] ( 7a) (α-NaiMe = 1-methyl-2-(naphthyl-α-azo)imidazole) shows a distorted tetrahedral geometry about Cu(I). Cyclic voltammograms of the complexes show a high potential Cu(II)/Cu(I) couple and azo reductions. The [Cu(α/β-NaiR)(PPh 3)I] complexes show an additional oxidative response at 0.4 V that is assigned to I/I − A sharp anodic peak at ∼−0.2 V is assigned to the oxidation of metallic Cu, deposited on electrode surface upon scanning to the negative side of the SCE. DFT and TD-DFT computations of [Cu((α-NaiMe)(PPh 3)I] ( 7a), [Cu((α-NaiMe)(PPh 3)I] + ( 7a + ) and [Cu((α-NaiMe)(PPh 3)I] − ( 7a − ) were carried out to examine the electronic configuration and to explain the spectral and redox properties of the complexes.

Synthesis, Characterization, and Crystal Structures of [Cu(phen)2Cl]Cl. 6.5H2O and [Cu(phen)2Br]Br

Two mixed-ligand complexes of copper(II) with 1,10-phenanthroline and halides [Cu(phen)2Cl]Cl.6.5H2O (1) and [Cu(phen)2 Br]Br (2), have been synthesized and characterized by microanalysis, spectroscopic, magnetic and single-crystal X-ray diffraction studies. The two complexes are isostructural in which the coordination geometry about the copper(II) ion is that of a trigonal bipyramid, with the central copper atom bound to one chloride (I) and one bromide (2) atom and four nitrogen atoms of the two phenanthroline ligands. The result of IR, electronic spectra, electron spin resonance (ESR) and magnetic measurements are discussed.

INVESTIGATIONS ON NUCLEASE ACTIVITY OF TRANS MIXED LIGAND- COPPER(II) COMPLEXES WITH ORTHO SUBSTITUTED AROMATIC OXIMES AND HETEROCYCLIC BASES

Mixed ligand complexes of copper(II) with salicyladoxime (SAO), 2-hydroxy acetophenone oxime (HAO) as primary ligands and pyridine( Py), imidazole (Im) as secondary ligands have been synthesized and characterized by molar conductivity, magnetic moments, electronic, IR and ESR spectral data. Cyclic voltammetric studies show quasi-reversible reduction attributable to Cu2+/ Cu+. The binding interactions between metal complexes and calf thymus DNA have been investigated by using UV –Visible titrations and cyclic voltammetry studies. The cleavage activity of complexes was carried out on double-stranded pBR322 circular plasmid DNA by using gel electrophoresis. All complexes show increased nuclease activity in the presence of oxidant (H 2 O 2 ). The nuclease activity of mixed ligand complexes are compared with that of the parent copper(II) complexes. Controlled experiments suggest that the complexes cleave DNA predominantly via an oxidative mechanism.

Mixed-ligand complexes of copper(I) with diimines and phosphines: Effective catalysts for the coupling of phenylacetylene with halobenzene

New copper(I) mixed-ligand complexes 1– 4 of the formula Cu(N–N)PR 3X, where N–N = 1,10-phenanthroline (phen), 2,2′-bipyridine (bpy), 5,5′-dimethyl-2,2′-bipyridine (5,5′dimbpy) and PR 3 = tricyclohexylphosphine, tris(2-cyanoethyl)phosphine and isopropyldiphenylphosphine, have been synthesized. The complexes were characterized by EA, IR, NMR and single crystal X-ray diffraction. The solution fluorescence emission spectra were measured. The single crystal X-ray analysis showed that the copper(I) ion is four-coordinate with a distorted tetrahedral geometry. The complexes catalyze the formation of diphenylacetylene from the coupling of halobenzene with phenylacetylene. The complex Cu(5,5′-dimethylbpy)P{(cyhexyl) 3}I showed the highest catalytic activity. At room temperature all four complexes exhibit, in dichloromethane, emission maxima in the 329–344 nm range, corresponding to intra-ligand excited states.

Crystal structure of aqua-ammine-(μ-succinato)copper(II) dihydrate, Cu(H2O)(NH3)(C4H4O4) ·2H2O

C4H13C11NO7, monoclinic, P\21c (no. 13), a = 8.434(3) Â, b = 7.230(3) Â, c = 8.309(3) Â,/3= 112.209(5)°, V = 469.1 Â3, Z-2, Rgi(F) = 0.020, wRnftF2) = 0.051, T = 293 K. Source of material Crystals of aqua-ammine-(/i-succinato)copper(II) dihydrate were unexpectedly formed during an attempt to synthesize the mixed ligand copper complex. A mixture of copper chloride dihydrate (34.2 mg, 0.2 mmol), NaOH (16 mg, 0.4 mmol), succinic acid (23.6 mg, 0.2 mmol), and 5,7-dimethyl-l,8- naphthyridine-2-amine (35 mg, 0.2 mmol), in ethanol (10 ml) was refluxed for 1 h. The resulted light blue precipitate was collected and dissolved in 3 ml of concentrated ammonia. Blue block-like crystals were obtained by slow evaporation of the ammonia solu- tion at ambient temperature.

Copper complexes of nicotinic-aromatic carboxylic acids as superoxide dismutase mimetics.

Nicotinic acid (also known as vitamin B3) is a dietary element essential for physiological and antihyperlipidemic functions. This study reports the synthesis of novel mixed ligand complexes of copper with nicotinic and other select carboxylic acids (phthalic, salicylic and anthranilic acids). The tested copper complexes exhibited superoxide dismutase (SOD) mimetic activity and antimicrobial activity against Bacillus subtilis ATCC 6633, with a minimum inhibition concentration of 256 µg/mL. Copper complex of nicotinic-phthalic acids (CuNA/Ph) was the most potent with a SOD mimetic activity of IC50 34.42 µM. The SOD activities were observed to correlate well with the theoretical parameters as calculated using density functional theory (DFT) at the B3LYP/LANL2DZ level of theory. Interestingly, the SOD activity of the copper complex CuNA/Ph was positively correlated with the electron affinity (EA) value. The two quantum chemical parameters, highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO), were shown to be appropriate for understanding the mechanism of the metal complexes as their calculated energies show good correlation with the SOD activity. Moreover, copper complex with the highest SOD activity were shown to possess the lowest HOMO energy. These findings demonstrate a great potential for the development of value-added metallovitamin-based therapeutics.

Stability constant of ternary complexes of copper(II) involving Schiff bases as primary ligands and amino acids as secondary ligands

The formation constant of mixed ligand complexes of copper(n) with Schiff bases 1-(2'-hydroxyl benzamido)-2-phenyl azomethine (L 1 ) and 1-(2'-hydroxyl benzamido)-2-(2-methyl phenyl) azomethine (L 2 ) as primary ligands and glycine (R 1 ), DL-valine (R 2 ) as secondary ligands have been determined potentiometrically in 40% (v/v) THF-water mixture at 30 °C and ionic strength of 0.1 M NaClO 4 . The protonation constants of free ligands and stability constant for ternary systems involving Schiff bases and amino acids were also determined under identical conditions. The pH titration data were analysed using the computer SCOGS programme. The relative stability of ternary complexes as compared to that of corresponding binary complexes has been quantitatively explained in terms of A log K, K R , K L and K r values.

Synthesis, structure and spectral studies on mixed ligand copper(II) complexes of diimines and acetylacetonate

Two new mixed ligand complexes of copper(II) with acetylacetonate (acac), 2,2′-bipyridine (bpy) and 1,10-phenanthroline (phen) belonging to the class of cytotoxic and antineoplastic compounds known as CASIOPEINAS ® were synthesized and structurally characterized. Crystals of both complexes [Cu(acac)(bpy)(H 2O)]NO 3 · H 2O ( 1), [Cu(acac)(phen)Br] ( 2) contain square pyramidal Cu(II) complex species. In frozen solution both compounds give well resolved EPR spectra with very similar parameters.

Structure, Bonding, and Tyrosinase‐Like Reactivity of Copper Complexes Coordinated by Mononucleating Tridentate N−O−N Type Ligands

AbstractCopper complexes with mononucleating tridentate ligands of the N−O−N type, including 1,3‐bis(benzimidazol‐2‐yl)‐2‐oxapropane (bbmo), 1,3‐bis(N‐methylbenzimidazol‐2‐yl)‐2‐oxapropane (bbMemo), 1,3‐bis(N‐n‐propylbenzimidazol‐2‐yl)‐2‐oxapropane (bbPrmo), and 1,3‐bis(pyrid‐2‐yl)‐2‐oxapropane (bpmo), were tested for the oxygenation of phenols. Mixed ligand copper complexes of [Cu(N−O−N)(N−N)](ClO4)2, where N−N denotes 2,2′‐bipyridine (bipy), 1,10‐phenanthroline (phen), ethylenediamine (en), and/or N,N,N′,N′‐tetramethylethylenediammine (tmen), were prepared and characterized by elemental analyses, and electronic, vibrational, and epr spectroscopic measurements. The molecular structures of fac‐[Cu(bbMemo)(bipy)(H2O)](ClO4)2(H2O) (1a), fac‐[Cu(bbMemo)(phen)](ClO4)2(CH3CN) (4a), fac‐[Cu(bbPrmo)(phen)](ClO4)2 (5a), and fac‐[Cu(bpmo)(bipy)(ClO4)](ClO4) (7a) were determined by X‐ray diffraction methods. The structures of these complexes are square pyramids or elongated octahedra with the heterocycle nuclei forming the basal or equatorial planes. The terminal heterocycles of the facially coordinated tridentate ligands are nearly perpendicular to the basal or equatorial planes. Similar structures are proposed for the remaining complexes, based on spectroscopic data. Both stoichiometric and catalytic oxidation reactions of 2,4‐di‐tert‐butylphenol and 2,4‐di‐tert‐butylphenolate with dioxygen adducts of [Cu(bbPrmo)]+ at room temperature afforded 3,3′,5,5′‐tetra‐tert‐butyl‐2,2′‐biphenol and 3,5‐di‐tert‐butyl‐o‐quinone. Similar reactions with the dioxygen adduct of [Cu(bpmo)]+ yielded only 3,3′,5,5′‐tetra‐tert‐butyl‐2,2′‐biphenol. In light of the tyrosinase‐like reactivity, the possible intermediates, [(bbPrmo)2Cu2(μ‐η2:η2‐peroxo)]2+, [(bbPrmo)2Cu2(μ‐oxo)2]2+, and [(bpmo)2Cu2(μ‐oxo)2]2+ are proposed. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

Magnetic, spectroscopic, structural and biological properties of mixed-ligand complexes of copper(II) with N, N, N′, N″, N″-pentamethyldiethylenetriamine and polypyridine ligands

Two new mixed ligand complexes of copper(II) with N, N, N ′, N″, N″-pentamethyldiethylenetriamine and polypyridine ligands have been prepared and characterized by means of spectroscopic, magnetic and single-crystal X-ray diffraction methods. These two complexes are isomorph and isostructure in which the coordination polyhedron about the copper(II) ion is distorted square pyramidal. [Cu(PMDT)(bipy)] 2+ and [Cu(PMDT)(phen)] 2+ show an absorption wavelength maximum at 625 and 678 nm, respectively, assigned to the d–d transition. Antibacterial, antifungal and superoxide dismutase activities of these complexes have also been measured. It was observed that [Cu(PMDT)(bipy)](ClO 4) 2 was more effective against P. Pyocyanea and Klebsiella sp. than S. aureus. Similarly, Fusarium sp. was highly susceptible against [Cu(PMDT)(bipy)](ClO 4) 2 but less susceptible against [Cu(PMDT)(phen)](ClO 4) 2.

Synthesis and bioactivity of ternary mixed ligand complexes of copper(II) and zinc(II) with substituted pyrimidine

Six new mixed ligand complexes of Cu and Zn with 5-substituted-2-dimethylamino-4-hydroxy-6-melhylpyrimidine have been prepared. Their herbicidal, fungicidal and insecticidal activities have been evaluated. Complex, Cu(C 8 H 1 3 N 3 O) 2 Cl 2 (3) has 81.9% of herbicidal activity against barnyardgrass.

Synthesis and Structural Characterization of the Mixed Ligand Complex [Cu(Hml)2(Phen)] · 2 H2O (H2ml = 2-Methyllactic Acid)

Abstract A new mixed-ligand complex of copper(II) with 1,10-phenanthroline and 2-methyllactate was prepared. [Cu(HmL)2(phen)] ·2H2O (where HmL = monodeprotonated 2-methyllactic acid) was characterized by elemental analysis, IR, electronic and EPR spectroscopy, magnetic measurements at room temperature, thermogravimetric analysis and X-ray diffractometry. The copper atom is in a tetragonally distorted octahedral environment and the 2-methyllactato ligand is bidentately chelating. The presence of lattice water molecules mediates the formation of a three-dimensional network.

Synthesis, Structure, and Magnetic Properties of the Mixed-Ligand Complex of Copper(II) Hexafluoroacetylacetonate with the Nitroxide 4-2′-Pyridyl)-2,2,5,5-tetramethyl-3-imidazoline-1-oxyl

Synthesis, Structure, and Magnetic Properties of the Mixed-Ligand Complex of Copper(II) Hexafluoroacetylacetonate with the Nitroxide 4-2′-Pyridyl)-2,2,5,5-tetramethyl-3-imidazoline-1-oxyl

Synthesis, crystal structure, and characterization of mixed-ligand complex of copper(I) with drug of norfloxacin and triphenyl phosphine: [Cu(PPh 3) 2(H-Norf)]ClO 4

The solvothermal reaction of norfloxacin (H-Norf) with [Cu(MeCN) 2(PPh 3)]·ClO 4 yields a mixed-ligand complex [Cu(PPh 3) 2(H-Norf)]·ClO 4 1 which is characterized by single crystal X-ray determination, IR, far-IR and solid state 31 PNMR as well as fluorescent spectrum. Crystallographic data for 1, C 52H 48ClCuFN 3O 7P 2, triclinic P-1 (No. 2), a=10.0434 (15) , b=13.5111 (17) , c=16.651 (2) Å, α=97.478 (2)° , β=93.610 (2)° , γ=115.928 (2)° . Fw=1006.86, Z=2, V=2394.1 (5) A ̊ 3 , R 1=0.0473, wR 2=0.1155, S=0.735.

Mixed-Ligand Complexes of Copper(II) with α-Hydroxycarboxylic Acids and 1,10-Phenanthroline

Eight new two-ligand complexes of copper(II) with 1,10-phenanthroline and one of four different α-hydroxy-carboxylic acids (glycolic, lactic, mandelic and benzylic) were prepared. The complexes of general formula [Cu(HL)2(phen)] · nH2O (HL = monodeprotonated acid) (1–4) were characterized by elemental analysis, IR, electronic and EPR spectroscopy, magnetic measurements and thermo-gravimetric analysis. The complexes of general formulae [Cu(HL)(phen)2](HL) · H2L · nSolv [1 a (HL = HGLYO–, n = 1, Solv = MeCN) and 3 a (HL = HMANO–, n = 0)] and [Cu(L)(phen)(OH2)] · nH2O [2 a (L = LACO2–, n = 4) and 4 a (L = BENO2–, n = 2)] were characterized by X-ray diffractometry. In all these latter a pentacoordinated copper atom has a basically square pyramidal coordination polyhedron, the distortion of which towards a trigonal bipyramidal configuration has been evaluated in terms of the parameter τ. In 1 a and 3 a there are three forms of α-hydroxycarboxylic acid: a monodentate monoanion, a monoanionic counterion, and a neutral molecule lying in the outer coordination sphere; in 2 a and 4 a the α-hydroxycarboxylic acid is a bidentate dianion coordinating through carboxyl and hydroxyl oxygens. Gemischtliganden-Komplexe von Kupfer(II) mit α-Hydroxycarbonsäuren und 1,10-Phenanthrolin Acht neue Zweiligand-Komplexe von Kupfer(II) mit 1,10-Phenanthrolin und einer von vier α-Hydroxycarbonsäuren (Glykol-, Milch-, Mandel-, Benzilsäure) wurden dargestellt. Die Komplexe mit der allgemeinen Formel [Cu(HL)2(phen)] · nH2O (HL = monodeprotonierte Säure) (1–4) wurden elementaranalytisch, durch IR-, UV/Vis- und EPR-Spektroskopie, magnetische Messungen sowie thermogravimetrisch charakterisiert. Die Komplexe [Cu(HL)(phen)2](HL) · H2L · nSolvens [1 a (HL = HGLYO–, n = 1, Solvens = MeCN) und 3 a (HL = HMNO–, n = 0] und [Cu(L)(phen)(OH2)] · nH2O [2 a (L = LACO2–, n = 4) und 4 a (L = BENO2–, n = 2)] wurden röntgenographisch charakterisiert. In allen letztgenannten Komplexen bildet das fünffach koordinierte Kupferatom ein im wesentlichen quadratisch-pyramidales Koordinationspolyeder, die Verzerrung zu einer trigonal-bipyramidalen Konfiguration wird über den Parameter τ definiert. In 1 a und 3 a liegen die α-Hydroxycarbonsäure in drei Formen vor: als einzähniges Monoanion, als monoanionisches Gegenion und als neutrales Molekül in der äußeren Koordinationssphäre; in 2 a und 4 a ist die α-Hydroxycarbonlsäure ein zweizähniges Dianion, das über die Carboxyl- und Hydroxyl-Sauerstoffatome koordiniert.

Synthesis, spectroscopic and voltammetric studies of mixed-ligand copper(II) complexes of amino acids

Two CuII complexes of the type [Cu(L1)(L2)] (where L1 = tryptophanate or phenylalaninate; L2 = cysteine thiolate) have been prepared and characterised, and their spectrophotometric and voltammetric behaviour has been investigated. The results obtained by means of FT-IR, e.s.r., u.v.–vis. spectroscopy and by voltammetry revealed the existence of two different [Cu(L1)(L2)] complexes. A significance decrease in the g|| value and, concomitantly, an increase in the d–d transition energy was observed when a mixed-ligand complex is present. The observed anisotropic g-values indicate the presence of CuII in a tetragonally distorted octahedral geometry. Formation of a mixed-ligand copper complex can be considered as a type of synergism in the presence of cysteine. The redox state CuII or CuI of copper in the Cu(L2) complex depends on the analysing conditions, i.e., cysteine forms a CuII complex under aerobic conditions and a CuI complex in anaerobic media. Tryptophan or phenylalanine is bound to CuII ions in the Cu(L1) complexes.

PH-metric and electronic spectral measurements on the mixed ligand complexes of copper(II) containing unsubstituted imidazole and some dipeptides

pH-metric and electronic spectral measurements on the mixed ligand complexes of copper(II) containing unsubstituted imidazole and some dipeptides

Nuclease activity of mixed ligand complexes of copper(II) with heteroaromatic derivatives and picoline

New picoline adducts with carbamic acid [(furan-2-yl)methylene]hydrazide–CuII (CFMH) (1); thiocarbamic acid [(furan-2-yl)methylene]hydrazide–CuII (TFMH) (2); carbamic acid [(furan-2-yl)ethylidene]hydrazide–CuII (CFEH) (3), thiocarbamic acid [(furan-2-yl)ethylidene]hydrazide–CuII (TFEH) (4); carbamic acid [(thiophene-2-yl) methylene]hydrazide–CuII (CTMH) (5), thiocarbamic acid [(thiophene-2-yl)methylene]hydrazide–CuII (TTMH) (6), carbamic acid [(thiophene-2-yl)ethylidene]hydrazide–CuII (CTEH) (7), thiocarbamic acid [(thiophene-2-yl)ethylidene]hydrazide–CuII (TTEH) (8) have been prepared and characterized by analytical, i.r., electronic, e.s.r. and c.v. spectral data. The electronic spectra suggest distorted octahedral geometry for all the picoline adducts. E.s.r. g ∥ values lie between 2.251–2.286 at l.n.t. All the adducts undergo a quasi-reversible one-electron reduction in the range +0.47 to +0.51 V versus s.c.e., attributable to the CuIII/CuII redox couple. The electron transfer is much faster in the semicarbazone complexes than in the thiosemicarbazone complexes. All adducts showed increased nuclease activity in the presence of oxidant; the nuclease activity is compared with that of the parent copper(II) complexes.