Homo‐ and heteropolynuclear copper(II) complexes containing a new diimine–dioxime ligand and 1,10‐phenanthroline: synthesis,characterization, solvent‐extraction studies,catalase‐like functions and DNA cleavage abilities

A series of homo‐, heterodinuclear and homotrinuclear copper(II) complexes containing a new Schiff base ligand and 1,10‐phenanthroline were synthesized. Based on results of elemental analyses, FTIR, ¹H‐ and ¹³C‐NMR spectra, conductivity measurements and magnetic susceptibility measurements, the complexes had general compositions {[Cu(L)(H₂O)M(phen)₂](ClO₄)₂ [M = Cu(II), Mn(II), Co(II)]} and {[Cu₃(L)₂(H₂O)₂](ClO₄)₂}. The metal:L:phen ratio is 2:1:2 for the dinuclear copper(II) complexes and the metal:L ratio was 3:2 for the trinuclear copper(II) complex. The liquid–liquid extraction of various transition metal cations [Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Pb(II), Cd(II), Hg(II)] from the aqueous phase to the organic phase was carried out using the diimine–dioxime ligand. It was concluded that the ligand can effectively be used in solvent extraction of copper(II) from the aqueous phase to the organic phase. Furthermore, catalytic activitiy of the complexes for the disproportionation of hydrogen peroxide was also investigated in the presence of imidazole. Dinuclear copper(II)–manganese(II) complex has some similarity to manganese catalase in structure and activity. The interaction between these complexes and DNA has also been investigated by agarose gel electrophoresis; we found that the homo‐ and heterodinuclear copper complexes can cleave supercoiled pBR322 DNA to nicked and linear forms in the presence of H₂O₂. Copyright © 2009 John Wiley & Sons, Ltd.     

A new binucleating ligand incorporating four oxime groups and its copper(II), manganese(II) and cobalt(III) complexes

A new binucleating ligand incorporating four oxime groups, butane-2,3-dione O-[4-aminooxy-2,3-bis-(2-hydroxyimino-1-methyl-propylideneaminooxymethyl)-but-2-enyl]-dioxime, (H₄mto), has been synthesized and its dinuclear cobalt(III), copper(II), and homo- and hetero-tetranuclear copper(II)–manganese(II) complexes have been prepared and characterized by ¹H- and ¹³C-n.m.r., i.r., magnetic moments and mass spectral studies. Elemental analyses, stoichiometric and spectroscopic data indicate that the metal ions in the complexes are coordinated to the oxime nitrogen atoms (C=N) and the data support the proposed structure for H₄mto and its complexes. Moreover, dinuclear cobalt(III) and copper(II) complexes of H₄mto have a 2:1 metal:ligand ratio.     

Synthesis and structural studies of (2 E ,3 E ,6 R ,9 E ,11 E )-6-isopropenyl-3,6,10-trimethyl-5,8-dioxa-4,9-diazadodeca-3,9-diene-2,11-dione dioxime, ligand and its Mono-, homo, and heterodinuclear copper(II)/nickel(II) complexes

This article describes the synthesis of a new (2E,3E,6R,9E,11E)-6-isopropenyl-3,6,10-trimethyl-5,8-dioxa-4,9-diazadodeca-3,9-diene-2,11-dione dioxime (H₂hmdm), and its mono-, homo, and heterodinuclear copper(II)/nickel(II) complexes. Elemental analyses, stoichiometric and spectroscopic data of the metal complexes indicated that the metal ions are coordinated to the oxime and imine nitrogen atoms (C=N). The Cu(H₂hmdm), molecule coordinates to the second copper(II) ion through the oximate oxygens to afford a binuclear structure doubly bridged by the oximate groups in the cis arrangement. In the dinuclear complexes, in which the first Cu^II ion was complexed with nitrogen atoms of the oxime and imine groups, the second Cu^II ion is ligated with the 1,10-phenanthroline nitrogen atoms. Ligand and its mononuclear copper(II), homo and heterodinuclear copper(II)–nickel(II) complexes of (H₂hmdm) were characterized by elemental analyses, magnetic moments, ¹H-n.m.r. and ¹³C-n.m.r., i.r., and mass spectral studies. The data support the proposed structure of H₂hmdm and its complexes.     

Synthesis, characterization, and X-ray crystal structures of copper(II) and nickel(II) complexes with Schiff base

New copper(II) complexes, [Cu₂L¹L²] · ClO₄ (I) and [Ni(L³)₂] (II), where L¹ is the monoanionic form of 2-[1-(2-emthylaminoethylimino)ethyl]phenol, L² is the dianionic form of N,N′-ethylene-bis(2-hydroxyacetophenonylideneimine), L³ is the mono-anionic form of 2-(1-iminoethyl)phenol, were prepared and characterized using elemental analysis, FT-IR spectroscopy, and X-ray single-crystal diffraction. In complex I, the Cu(1) atom is coordinated by the NNO tridentate ligand L¹ and the two phenolate O atoms of L², forming a square pyramidal geometry. The Cu(2) atom in complex I is coordinated by the NNOO tetradenate ligand L², forming a square planar geometry. The Ni atom in complex II is coordinated by two phenolate O and two imine N atoms from two ligands L³, forming a square planar geometry. In the crystal structure of I, the perchlorate anions are linked to the dinuclear copper(II) complex cations through intermolecular N-H...O hydrogen bonds. In the crystal structure of II, the mononuclear nickel complex molecules are linked through intermolecular N-H...O hydrogen bonds, forming a trimer.     

Novel 3‐Hydroxy‐2‐naphthoic hydrazone and Ni(II), Co(II) and Cu(II) Complexes: Synthesis,Spectroscopic Characterization,Antimicrobial, DNA Cleavage and Computational Studies

A novel hydrazone ligand derived from condensation reaction of 3‐hydroxy‐2‐naphthoic hydrazide with dehydroacetic acid, and its Ni(II), Cu(II) and Co(II) complexes were synthesized, characterized by spectroscopic, elemental analyses, magnetic susceptibility and conductivity methods, and screened for antimicrobial, DNA binding and cleavage properties. Spectroscopic analysis and elemental analyses indicated the formula, [MLCl₂], for the complexes; square planar geometry for the nickel, and tetrahedral geometry for copper and cobalt complexes. The non‐electrolytic natures of the complexes in Dimethyl Sulphoxide (DMSO) were confirmed by their molar conductance values in the range of 6.11–14.01 Ω^?1cm²mol^?1. The copper complex had the best antibacterial activity against Staphylococcus aureus (ATCC 29213). DNA cleavage activities of the compounds, evaluated on pBR322 DNA, by agarose gel electrophoresis, in the presence and absence of oxidant (H₂O₂) and free radical scavenger (DMSO), indicated no activity for the ligand, and moderate activity for the complexes, with the copper complex cleaving pBR322 DNA more efficiently in the presence of H₂O₂. When the complexes were evaluated for antibacterial and A‐DNA activity using Molecular docking technique, the copper complex was found to be most effective against Gram‐positive (S. aureus) bacteria. [CuLCl₂] showed good hydrogen bonding interaction with the major‐groove (C₂^.G₁₃ base pair) of A‐DNA. Density functional theory (DFT) calculations of the structural and electronic properties of the complexes revealed that [CuLCl₂] had a smaller HOMO‐LUMO gap, suggesting a higher tendency to donate electrons to electron‐accepting species of biological targets.     

Polymeric and monomeric dipicolinate complexes with 4-hydroxymethyl pyridine: spectral, structural, thermal and electrochemical characterization

Polymeric copper(II), [Cu(μ-dpc)(μ-4-hymp)] _n (1), and monomeric nickel(II), [Ni(dpc)(4-hymp)(H₂O)₂]·H₂O (2), (dpc: dipicolinate, 4-hymp: 4-hydroxymethyl pyridine), dipicolinate complexes have been prepared and characterized by spectroscopic (IR, UV–Vis, EPR), thermal (TG/DTA), X-ray diffraction technique and electrochemical methods. In both the dipicolinate complexes, the dpc dianion acts as a tridentate ligand. In polymeric copper(II) complex, the 4-hymp and dpc ligands adopt a bridging position between the Cu(II) centers, forming the elongated octahedral geometry. The polymeric chains are linked to one another via O–H···O hydrogen bond interactions, forming the 3-D polymeric structure. The Ni(II) ion is bonded to dpc ligand through pyridine N atom together with one O atom of each carboxylate group, two aqua ligands and N pyridine atom of 4-hymp, forming the distorted octahedral geometry. The Ni(II) complexes are connected to one another via O–H···O hydrogen bonds, forming R ₄²(18) motifs in 2-D pattern. The powder EPR spectra of copper(II) complex have indicated that the paramagnetic center is in rhombic symmetry with the Cu²⁺ ion having distorted octahedral geometry. IR and UV–Vis spectroscopes all agree with the observed crystal structure.     

Copper(II) coordination chemistry of 2-methyl-2-(2-pyridyl)-1,3-propan-diol: Syntheses and structures of mono-, di-, and tricopper complexes

Six copper(II) complexes with N,O-donor ligand 2-methyl-2-(2-pyridyl)-1,3-propan-diol (H₂ppdo) were synthesized and characterized. Treatment of CuCl₂ or Cu(OTf)₂ with H₂ppdo led to the formation of bis(H₂ppdo) monomers [Cu(H₂ppdo)₂][CuCl₄] (1) and [Cu(H₂ppdo)₂](OTf)₂ (2), respectively. Both 1 and 2 are comprised of the copper atom coordinated by two ligands in an axially-compressed tetragonal geometry with the pyridyl N atoms in the axial positions and the alcohol O atoms in the equatorial plane. The treatment of 1 or 2 with Et₃N produced copper(II) complexes of varying nuclearity. Treatment of 1 with excess Et₃N generated two binuclear Cu(II) clusters [Cu₂(Hppdo)₂Cl₂] (3) and [Cu₂(Hppdo)₂Cl₂(CH₃OH)₂] (4), where only one alcohol OH group per ligand has been deprotonated, while similar treatment of 2 with excess Et₃N afforded the trimeric copper(II) species [Cu₃(Hppdo)₄](OTf)₂ (5). The structures of 3 and 4 are similar, with alkoxo-O ligand atoms bridging between two square pyramidal copper atoms, and the alcohol-O ligand atoms either coordinating in the axial position in 3, or uncoordinated in 4. Treatment of CuCl₂ with H₂ppdo and Et₃N afforded the trinuclear Cu(II) complex, [Cu₃(Hppdo)₄]Cl₂ (6). Complexes 5 and 6 are made up of one square-planar copper sandwiched between two tetragonally distorted six-coordinate Cu(Hppdo)₂ moieties, where the bridging alkoxo-O atoms link the copper atoms.     

Synthesis,characterization, fluorescence and redox features of new <Emphasis Type="Italic">vic</Emphasis>-dioxime ligand bearing pyrene and its metal complexes

A new vic-dioxime ligand, N,N′-bis(aminopyreneglyoxime) (LH₂), and its copper(II), nickel(II) and cobalt(II) metal complexes were synthesized and characterized by elemental analyses, IR, UVVIS and ¹H and ¹³C NMR spectra (for the ligand). Mononuclear complexes were synthesized by a reaction of ligand (LH₂) and salts of Co(II), Ni(II), and Cu(II) in ethanol. The complexes have the metal-ligand ratio of 1: 2 and metals are coordinated by N,N′ atoms of vicinal dioximes. The ligand acts in a polydentate fashion bending through nitrogen atoms in the presence of a base, as do most vic-dioximes. Detection of a H-bonding in the Co(II), Ni(II), and Cu(II) complexes by IR revealed the square-planar MN₄ coordination of mononuclear complexes. Fluorescent properties of the ligand and its complexes arise from pyrene units conjugated with a vic-dioxime moiety. Fluorescence emission spectra of the ligand showed a drastic decrease in its fluorescence intensity upon metal binding. The electrochemical properties of the complexes were studied by the cyclic voltammetry technique. The nickel complex displayed an irreversible oxidation process while the copper complex exhibited a quasi-reversible oxidation and reduction processes based on the copper Cu(II)/Cu(III) and Cu(II)/Cu(I) couples, respectively.     

Synthesis,Characterization, and Reactivity of a Series of Homo- and Hetero-dinuclear Complexes based on an Asymmetric FloH Ligand System

In a previous communication we reported the site-directed generation of a heterodinuclear Fe^IIICu^II complex ( 1 ) by using an asymmetric dinucleating ligand FloH. The iron(III) ion was introduced first on the preferential metal-binding site of the ligand that led to the formation of the thermodynamically favored five-membered chelate ring upon metal-binding. Copper(II) was introduced in the next step. The stepwise metalation strategy reported previously has now been extended to synthesize a series of heterodinuclear Fe^IIIM^II [M = Mn ( 2 ), Fe ( 3 ), Co ( 4 ), and Ni ( 5 )] and Fe^IICu^I ( 1a ) as well as the homodinuclear Cu^ICu^I ( 6 ) complexes. The complexes were characterized by X-ray crystallography (except for 1a and 6 ), and by a limited number of spectroscopic methods. Complex 1 with a labile solvent binding site at Fe^III reacted with H₂O₂ to form a transient intermediate that showed reactivity typical of metal peroxide complexes. The metal centers in the complexes 2 – 5 are coordinatively saturated, and hence they showed no reactivity with H₂O₂. Complex 1a reacted with O₂ via an intermolecular pathway to form a μ-oxo bridged tetrameric complex 1b , which was structurally characterized. This is in contrast to the homodinuclear Cu^ICu^I and heme Fe^IICu^I cores, which prefer an intramolecular pathway for O₂ activation.     

Synthesis,characterization and crystal structure of a novel thiazoline/thiazolidine azine ligand and its nickel,copper and zinc complexes

The new ligand N-(2-acetyl-2-thiazoline)-N′-(2-thiazolidin-2-one) azine (ATHTd) has been synthesized and characterized by X-ray diffraction, elemental analysis, ¹H and ¹³C NMR spectra, elemental analysis, IR and UV–Vis spectra. Also the complexes [NiCl(ATHTd)(H₂O)₂]Cl (1), [Ni(ATHTd)₂](NO₃)₂·H₂O (2), [CuCl₂(ATHTd)] (3) and [ZnCl₂(ATHTd)₂] (4) have been isolated and characterized in the solid state by X-ray diffraction, elemental analysis, IR spectroscopy, UV–Vis–NIR diffuse reflectance, magnetic susceptibility measurements and, in the case of copper(II) complex, EPR spectroscopy. X-ray data indicate that the environment around nickel atoms in 1 and 2 may be described as a distorted octahedral geometry. In 1 the metal ion is coordinated to one chloride ligand, one water molecule and one ATHTd molecule which acts as a tridentate ligand, while in 2 Ni(II) is coordinated to two tridentate ATHTd molecules. With regard to 3, the coordination geometry around copper(II) ion can be considered a distorted square pyramid with the cation coordinated to one tridentate ATHTd ligand and two chloride ligands. Finally, in the case of 4, the Zn(II) is bonded to two ATHTd molecules that acts as a monodentate ligand and two chloride atoms in a distorted tetrahedral geometry. The structure of ATHTd in the complexes presents an amino-2-thiazoline form instead of the iminothiazolidine one observed in free ATHTd. Another significant structural change in complexes, except in 4, is due to the different degree of rotation of the thiazoline rings around the C(1)–C(4) and C(6)–N(3) bonds, which permit the coordination through thiazolinic nitrogen atoms.     

Copper(II) and manganese(II) picrate complexes with the V-shaped ligand 1,3-bis(1-methylbenzimidazol-2-yl)-2-thiapropane: preparation,structure, DNA-binding properties and antioxidant activities

A V-shaped ligand, 1,3-bis(1-methylbenzimidazol-2-yl)-2-thiapropane (L), and its copper(II) and manganese(II) picrate complexes have been synthesized and characterized. The compositions of the complexes are [Cu(L)₂](pic)₂·2DMF (1) and [Mn(L)(pic)₂] (2), respectively. The crystal structure of complex 1 reveals a distorted tetrahedral geometry provided by four N donors from two ligands. Complex 2 is six coordinated, with a distorted octahedral geometry. Experimental studies of the DNA-binding properties indicated that the free ligand and both complexes bind to DNA via the intercalation mode, and the order of the binding affinity is L > 1 > 2. Antioxidant tests in vitro show that the Cu(II) complex possesses significant antioxidant activity against superoxide and hydroxyl radicals, with better scavenging effects than mannitol and vitamin C.     

Synthesis and characterization of novel oxime-imine ligands and their heteronuclear ruthenium(III) complexes

Vicinal carbonyl oxime (HL¹) and oxime-imine (H₂L²) ligands and their mononuclear Ru(III) and Cu(II), heterodinuclear Ru(III)-Mn(II), Ru(III)-Ni(II), Ru(III)-Cu(II), and heterotrinuclear Ru(III)-Cu(II)-Ru(III) chelates were synthesized and characterized by elemental analysis, molar conductivity, IR, ESR, ICP-OES, magnetic moment measurements, and thermal analyses studies. The free ligands were also characterized by ¹H NMR spectra. The carbonyl-oxime ligand coordinates through the oxygen of =N-OH to form a six-membered chelate ring. The quadridentate tetraaza ligand (H₂L²) obtained by condensing of the bidentate ligand 1-p-diphenylmethane-2-hydroxyimino-2-(1-naphthylamino)-1-ethanone (HL¹) with 1,2-phenylenediamine coordinates with Ru(III) through its nitrogen donors in the equatorial position with the loss of one of the oxime protons and concomitant formation of an intramolecular hydrogen bond. Stoichiometric and spectral results of the metal complexes indicated that the metal: ligand ratios in the mononuclear complexes of the ligand (HL¹) were found to be 1: 2, while these ratios were 1: 1 in the mononuclear complexes of the ligand (H₂L²). The metal: ligand ratios of the dinuclear complexes were found to be 2: 1, and this ratio was 3: 2 in the trinuclear complex. The article is published in the original.     

Novel 13,14‐dimethyl‐5,8‐dioxa‐2,11,13,14‐tetraaza‐1,12‐diphosphabicyclo [10.1.1] tetradecane 1,12‐dioxide ligand and its Ni(II), Co(II), and Cu(II) complexes: Synthesis,characterization, antimicrobial,DNA cleavage,and computational studies

A novel diazadiphosphetidine ligand derived from the reaction of 2,4‐dichloro‐1,3‐dimethyl‐1,3,2,4‐diazadiphosphetidine‐2,4‐dioxide and 2,2′‐(ethane‐1,2‐diylbis[oxy])bis(ethan‐1‐amine) and its Ni(II), Cu(II), and Co(II) complexes have been synthesized, characterized by spectroscopic, elemental analyses, magnetic susceptibility, and conductivity methods, and screened for antimicrobial, DNA binding, and cleavage properties. Spectroscopic analysis and elemental analyses indicate the formula [M(H₂L)Cl₂] for the Cu(II), Co(II), Ni(II), and Zn(II) complexes and octahedral geometry for all the complexes. The non‐electrolytic nature of the complexes in dimethyl sulfoxide (DMSO) was confirmed by their molar conductance values, which are in the range 12.32–6.73 Ω^?1 cm² mol^?1. Computational studies have been carried out at the density functional theory (DFT)‐B3LYP/6‐31G(d) level of theory on the structural and spectroscopic properties of diazadiphosphetidine H₂L and its binuclear Cu(II), Co(II), Ni(II), and Zn(II) complexes. Six tautomers and geometrical isomers of the diazadiphosphetidine ligand were confirmed using semiempirical AM1 and DFT method from DMOL³ calculations. The copper complex had the best antibacterial activity against Staphylococcus aureus (ATCC 29213). DNA cleavage activities of the compounds, evaluated on pBR322 DNA by agarose gel electrophoresis in the presence and absence of an oxidant (H₂O₂) and a free‐radical scavenger (DMSO), indicated no activity for the ligand and moderate activity for the complexes, with the copper complex cleaving pBR322 DNA more efficiently in the presence of H₂O₂.     

Synthesis,characterization, spectrophotometric and electrochemistry studies,and DNA cleavage of copper(II) complexes of a new azacrown bis-macrocycle and its mono-cyclic analogue

A new azacrown bis-macrocycle (5) and its mono–cyclic analogue (7) were synthesized and characterized by FT-IR, ¹H NMR, ¹³C NMR, DEPT ¹³C NMR, MS, and elemental analysis. The reaction with copper(II) nitrate yielded the corresponding complexes, formulated as Cu(5)(NO₃)₂·3H₂O (8), and Cu(7)(NO₃)₂·2.5H₂O (9). Also the stoichiometries of the complexes were determined in alcoholic solution and the results show that for both complexes the ratio of ligand to metal was 1:1 in methanol. The redox behavior of both complexes has been studied by cyclic voltammetry in DMF. Cyclic voltamogram of 8 shows quasi-reversible Cu^II/Cu^I redox couple whereas 9 shows a reversible Cu^II/Cu^I redox couple. Mono- and bis-macrocycle copper(II) complexes (8 and 9 respectively) cleaved plasmid pGS2 DNA by using an oxidative mechanism with 3- mercaptopropionic acid (MPA) as the reductant under aerobic conditions. The bis-macrocycle copper(II) complex 8 showed higher cleavage efficiency than their mono-macrocycle analogue 9 at the same Cu²⁺ concentration.     

Copper(II) complexes of acylhydrazones: synthesis,characterization and DNA interaction

Two new acylhydrazone copper(II) complexes of 4‐hydroxy‐N′‐[(1E)‐1‐(4‐methylphenyl)ethylidene]benzohydrazide (HL¹) and 4 ethyl [4‐({(2E)‐2‐[1‐(4‐methylphenyl)ethylidene]hydrazinyl}carbonyl)phenoxy]acetate (HL²) have been synthesized and characterized. The structures of both acylhydrazone and copper(II) complexes were identified by elemental analysis, infrared spectra, UV–visible electronic absorption spectra, magnetic susceptibility measurements, TGA and powder X‐ray diffraction. DNA binding and DNA cleavage activities of the synthesized copper complexes were examined by using UV‐visible titration and agarose gel electrophoresis, respectively. The effect of complex concentration on the DNA cleavage reactions in the absence and presence of H₂O₂ was also investigated. The results indicate that all the complexes bind slightly to calf thymus DNA and cleavage pBR322 DNA. The mechanistic studies demonstrate that a hydrogen peroxide‐derived species and singlet oxygen (¹O₂) are the active oxidative species for DNA cleavage. Copyright © 2013 John Wiley & Sons, Ltd.     

Synthesis, characterization, and biological properties of N-phenolato-N′-(3-dimethylaminopropyl)oxamide and its binuclear copper(II) complexes

A new asymmetric N,N′-bis(substituent)oxamide ligand, N-phenolato-N′-(3-dimethylaminopropyl)oxamide (H₃pdmapo), and two of its binuclear Cu(II) complexes with different terminal ligands, namely [Cu₂(pdmapo)(phen)(H₂O)](ClO₄) (1) and [Cu₂(pdmapo)(bpy)(CH₃OH)](ClO₄) (2), where phen = 1,10-phenanthroline and bpy = 2,2′-bipyridine, have been synthesized and characterized. The crystal structures of both complexes have been determined by single-crystal X-ray diffraction. Both structures contain binuclear Cu(II) cationic complexes with pdmapo^3? ligands. The asymmetric pdmapo^3? ligands bridge two Cu(II) atoms in the cis conformation and the Cu···Cu separations through the oxamide bridge are 5.2046(18) and 5.207(2) Å for complexes 1 and 2, respectively. The coordination environments of the two Cu(II) atoms in each binuclear complex are different. The copper occupying the inner site of the pdmapo^3? ligand is four-coordinated in a CuN₃O distorted square-planar environment, while the other is five-coordinated in a square pyramid geometry. In complex 1, O–H···O and C–H···O hydrogen bonds link the complex into a one-dimensional chain. In complex 2, O–H···O hydrogen bonds link the molecules to form a dimer, together with two types of strong π–π interactions, giving a two-dimensional network structure. The cytotoxicities and DNA-binding properties of H₃pdmapo and the two complexes were studied. The experimental evidence suggests that the ligand binds to DNA via a groove binding mode, while the binuclear complexes bind intercalatively to DNA.     

2,6-Diacetyl- and 2,6-diformylpyridine bis(N4-substituted thiosemicarbazones) and their copper(II) and nickel(II) complexes

2,6-Diformylpyridine bis(N4-methylthiosemicarbazone) and bis(N4-dimethylthiosemicarbazone), H₂2,6Fo4M and H₂2,6Fo4DM, respectively, and 2,6-diacetylpyridine bis(N4-methylthiosemicarbazone) and bis(N4-dimethylthiosemicarbazone), H₂2,6Ac4M and H₂2,6Ac4DM, and their copper(II) and nickel(II) complexes have been synthesized. The ¹H-n.m.r. spectra of the free bis(thiosemicarbazones) show that, most often, one of the thiosemicarbazone moieties is hydrogen bonded to the pyridine nitrogen, and in [²H₆]-DMSO there is interaction with solvent oxygen. Golden yellow H₂2,6Ac4DM has a bifurcated hydrogen bonding interaction by one of the thiosemicarbazone moieties resulting in conjugation. Coordination to copper(II) and nickel(II) centers is via the pyridine nitrogen, amine nitrogen and thiolato sulfur and most of the complexes formed are polynuclear with thiosemicarbazone moieties from the same ligand coordinating to different metal centers.     

DNA binding and cleavage behaviors of copper(II) complexes with amidino-O-methylurea and N-methylphenyl-amidino-O-methylurea,and their antibacterial activities

The two designed copper(II) complexes, [Cu(L^1m)₂]Cl₂ (1) (L^1m = amidino-O-methylurea) and [Cu(L^2m)₂]Cl₂ (2) (L^2m = N-methylphenyl-amidino-O-methylurea), have been investigated for their interaction with calf thymus DNA by utilizing the absorption titration method, viscometric studies and thermal denaturation. The cleavage reaction on pBR322 DNA has been monitored by agarose gel electrophoresis. The results suggest that the two complexes can bind to DNA by non-intercalative modes and exhibit nuclease activities in which supercoiled plasmid DNA is converted to the linear form. Complex 2, with an intrinsic binding constant (K_b) of 1.16 × 10⁵ M⁻¹, shows a higher binding efficiency and a better nuclease activity than complex 1, with a K_b value of 5.67 × 10⁴ M⁻¹. Their DNA cleavage potential can be significantly enhanced by hydrogen peroxide, indicating an oxidative cleavage process. Further examination of the antibacterial activities against Campylobacter has revealed inhibition zones of 9.0 (for 1) and 14.5 mm (for 2), which are in agreement with their minimum inhibitory concentration (MIC) values of 1.56 and 0.78 mg mL⁻¹, respectively. The substantially better reactivity of 2 results from the aromatic moieties on the side chain of the L^2m ligand which act as an additional binding site.     

Synthesis,characterization, DNA binding and nuclease activity of binuclear copper(II) complexes of cuminaldehyde thiosemicarbazones

Binuclear copper(II) complexes of thiosemicarbazones derived from cuminaldehyde (p-isopropyl benzaldehyde) and substituted thiosemicarbazides NH₂NHC(S)NHR, where R = H, Me, Et or Ph have been synthesized and characterized. The ESR indicates that the dissociation of dimeric complex into mononuclear [Cu(L)Cl(DMSO)₃] units in polar solvents like DMSO, where L = monoanionic thiosemicarbazone. The molecular ion peak in the LC-MS coincides with the formula weight of the complexes. The absorption titration studies revealed that each of these complexes is an avid binder to calf thymus-DNA. The apparent binding constants are in the order of 10⁷–10⁸ M⁻¹. The nucleolytic cleavage activities of the ligands and their complexes were assayed on pUC18 plasmid DNA using gel electrophoresis in the presence and absence of H₂O₂. The ligands showed increased nuclease activity when administered as copper complexes. All these copper(II) complexes behave as an efficient chemical nucleases with hydrogen peroxide activation. These studies revealed that the complexes exhibit both oxidative and hydrolytic chemistry in DNA cleavage.     

Synthesis, crystal structures, and properties of inorganic-organic hybrid complexes constructed from copper(II) macrocyclic fragment

Reaction of a macrocyclic copper(II) complex [Cu(L)](ClO₄)₂ · 3H₂O (I) (L = 1,3,10,12,16,19-hexaazatetracyclotetracosane) with a hexapod carboxylate ligand H₆TTHA (H₆TTHA = 1,3,5-triazine-2,4,6-triamine hexaacetic acid) and a tripod carboxylate ligand H₃TATB (H₃TATB = 4,4′,4″-S-triazine-2,4,6-triyl-tribenzoic acid) yielded two mononuclear copper(II) complexes [Cu(L)][H₄TTHA] · 4H₂O (II) and [Cu(L)][HTATB] · 4H₂O (III). The complexes I–III have been structurally characterized. The crystal structures of complexes II and III show the copper(II) ion has a distorted pentacoordinate square-pyramidal geometry with two secondary and two tertiary amines from the macrocyclic complex [Cu(L)]²⁺ and one oxygen atom from the carboxylate ligand group at the axial position. The UV-Vis spectra are utilized to discuss the hydrolysis of the complex II.