Synthesis and spectroscopic studies on the Schiff base ligand derived from condensation of 2-furaldehyde and 3,3'-diaminobenzidene, L and its complexes with Co(II), Ni(II), Cu(II) and Zn(II): comparative DNA binding studies of L and its Cu(II) and Zn(II) complexes

The Schiff base ligand, N,N'-bis-(2-furancarboxaldimine)-3,3'-diaminobenzidene (L) obtained by condensation of 2-furaldehyde and 3,3'-diaminobenzidene, was used to synthesize the mononuclear complexes of the type, [M(L)](NO3)2 [M=Co(II), Ni(II), Cu(II) and Zn(II)]. The newly synthesized ligand, (L) and its complexes have been characterized on the basis of the results of the elemental analysis, molar conductance, magnetic susceptibility measurements and spectroscopic studies viz, FT-IR, 1H and 13C NMR, mass, UV-vis and EPR. EPR, UV-vis and magnetic moment data revealed a square planar geometry for the complexes with distortion in Cu(II) complex and conductivity data show a 1:2 electrolytic nature of the complexes. Absorption and fluorescence spectroscopic studies support that Schiff base ligand, L and its Cu(II) and Zn(II) complex exhibit significant binding to calf thymus DNA. The highest binding affinity in case of L may be due to the more open structure as compared to the metal coordinated complexes.     

Synthesis, spectroscopic studies and crystal structure of the Schiff base ligand L derived from condensation of 2-thiophenecarboxaldehyde and 3,3'-diaminobenzidine and its complexes with Co(II), Ni(II), Cu(II), Cd(II) and Hg(II): Comparative DNA binding studies of L and its Co(II), Ni(II) and Cu(II) complexes

The Schiff base ligand, N,N'-bis-(2-thiophenecarboxaldimine)-3,3'-diaminobenzidine (L) obtained from condensation of 2-thiophenecarboxaldehyde and 3,3'-diaminobenzidine, was used to synthesize the complexes of type, [M2L2]Cl4 [M=Co(II), Ni(II), Cu(II), Cd(II) and Hg(II)]. The newly synthesized ligand (L) was characterized on the basis of the results of elemental analysis, FT-IR, 1H NMR, 13C NMR, mass spectroscopic studies and single crystal X-ray crystallography. The characteristic resonance signals in 1H NMR and 13C NMR spectra indicated the presence of azomethine group as a result of condensation reaction. The stoichiometry, bonding and stereochemistries of complexes were ascertained on the basis of results of elemental analysis, magnetic susceptibility measurements, molar conductance and spectroscopic studies viz., FT-IR, 1H and 13C NMR, UV-vis and EPR. EPR, UV-vis and magnetic moment data revealed an octahedral geometry for complexes with distortion in Cu(II) complex and conductivity data show 1:2 electrolytic nature of complexes. Absoption and fluorescence spectroscopic studies supported that Schiff base ligand L and its Co(II), Ni(II) and Cu(II) complexes exhibited significant binding to calf thymus DNA. The complexes exhibited higher affinity to calf thymus DNA than the free Schiff base ligand L.     

Synthesis,characterization and in vitro biological activity of cobalt(II), copper(II) and zinc(II) Schiff base complexes derived from salicylaldehyde and D,L‐selenomethionine

New cobalt(II), copper(II) and zinc(II) complexes of Schiff base derived from D,L ‐selenomethionine and salicylaldehyde were synthesized and characterized by elemental analysis, IR, electronic spectra, conductance measurements, magnetic measurements and biological activity. The analytical data showed that the Schiff base ligand acts as tridentate towards divalent metal ions (cobalt, copper, zinc) via the azomethine‐N, carboxylate oxygen and phenolato oxygen by a stoichiometric reaction of M:L (1:1) to form metal complexes [ML(H₂O)], where L is the Schiff base ligand derived from D,L ‐selenomethionine and salicylaldehyde and M = Co(II), Cu(II) and Zn(II). ¹H NMR spectral data of the ligand and Zn(II) complex agree with proposed structures. The conductivity values between 12.87 and 15.63 S cm² mol^?1 in DMF imply the presence of non‐electrolyte species. Antibacterial and antifungal results indicate that the metal complexes are more active than the ligand. Copyright © 2010 John Wiley & Sons, Ltd.     

Syntheses,characterization and biological studies of zinc(II), copper(II) and cobalt(II) complexes with Schiff base ligand derived from 2‐hydroxy‐1‐naphthaldehyde and selenomethionine

Novel zinc(II), copper(II), and cobalt(II) complexes of the Schiff base derived from 2‐hydroxy‐1‐naphthaldehyde and D, L ‐selenomethionine were synthesized and characterized by elemental analysis, IR, electronic spectra, conductance measurements, magnetic measurements and powder XRD. The analytical data showed the composition of the metal complex to be ML(H₂O), where L is the Schiff base ligand and M = Co(II), Cu(II) and Zn(II). IR results confirmed the tridentate binding of the Schiff base ligand involving azomethine nitrogen, naphthol oxygen and carboxylato oxygen atoms. ¹H NMR spectral data of lithium salt of the Schiff base ligand [Li(HL)] and ZnL(H₂O) agreed with the proposed structures. The conductivity values of complexes between 12.50 and 15.45 S cm² mol^?1 in DMF suggested the presence of non‐electrolyte species. The powder XRD studies indicated that Co(II) complex is amorphous, whereas Cu(II) and Zn(II) complexes are crystalline. The results of antibacterial and antifungal screening studies indicated that Li(HL) and its metal complexes are active, but CuL(H₂O) is most active among them. Copyright © 2010 John Wiley & Sons, Ltd.     

Synthesis and characterization of Co(II), Ni(II), Cu(II) and Zn(II) complexes of tridentate Schiff base derived from vanillin and DL-alpha-aminobutyric acid

Co(II), Ni(II), Cu(II) and Zn(II) complexes of the Schiff base derived from vanillin and dl-alpha-aminobutyric acid were synthesized and characterized by elemental analysis, IR, electronic spectra, conductance measurements, magnetic measurements, powder XRD and biological activity. The analytical data show the composition of the metal complex to be [ML(H(2)O)], where L is the Schiff base ligand. The conductance data indicate that all the complexes are non-electrolytes. IR results demonstrate the tridentate binding of the Schiff base ligand involving azomethine nitrogen, phenolic oxygen and carboxylato oxygen atoms. The IR data also indicate the coordination of a water molecule with the metal ion in the complex. The electronic spectral measurements show that Co(II) and Ni(II) complexes have tetrahedral geometry, while Cu(II) complex has square planar geometry. The powder XRD studies indicate that Co(II) and Cu(II) complexes are amorphous, whereas Ni(II) and Zn(II) complexes are crystalline in nature. Magnetic measurements show that Co(II), Ni(II) and Cu(II) complexes have paramagnetic behaviour. Antibacterial results indicated that the metal complexes are more active than the ligand.     

Synthesis, spectroscopic and electrochemical studies of N,N-bis[(E)-2-thienylmethylidene]-1,8-naphthalenediamine and its Cu(II) complex: DNA cleavage and generation of superoxide anion

A novel tetradentate Cu(II) complex of the type, [CuL](NO(3))(2) was synthesized by the interaction of Schiff base ligand, N,N-bis[(E)-2-thienylmethylidene]-1,8-naphthalenediamine, L obtained by the condensation of thiophene-2-carboxaldehyde and 1,8-diaminonaphthalene. The formation of Schiff base ligand, L and its Cu(II) complex was confirmed on the basis of results of elemental analyses, mass, FT-IR, (1)H and (13)C{(1)H} NMR spectral studies. UV-Vis, EPR and magnetic susceptibility data support a square planar environment around Cu(II) ion. However, molar conductance values confirmed 1:2 electrolytic nature for the Cu(II) complex. The electrochemical studies of Cu(II) complex was carried out by using cyclic voltammetry which revealed the complex to exhibit quasi reversible process. The biological activity of Cu(II) complex such as ability to bind DNA and DNA cleavage were studied where the Cu(II) complex was shown to cause considerable DNA cleavage and also generated reactive oxygen species such as superoxide anion. Since it is known that various anticancer drugs act through induction of oxidative stress that is mediated by reactive oxygen species, our results suggest a putative role of Cu(II) complex similar to various anticancer drugs.     

Biomolecular docking,antimicrobial and cytotoxic studies on new bidentate schiff base ligand derived metal (II) complexes

Three new metal complexes [Cu(L)₂] (1), [Co(L)₂] (2) and [Zn(L)₂] (3) have been prepared by the reaction of hydrated salts of metal (II) acetate with new Schiff base ligand HL, [2‐((4‐(dimethylamino)phenylimino)methyl)‐4,6‐di‐t‐butylphenol] and characterized by different physico‐chemical analyses such as elemental analysis, single XRD, ¹H NMR, FTIR and UV–Vis spectroscopic techniques. Their biomolecular docking, antimicrobial and cytotoxicity studies have also been demonstrated. The proposed structure of Schiff base ligand HL and complex 2 are confirmed by Single crystal X‐ray crystallography study. This analysis revealed that metal (II) complexes remain in distorted tetrahedral coordination environments. The electronic properties such as HOMO and LUMO energies are carried out by gaseous phase DFT/B3LYP calculations using Gaussian 09 program. Complex 1 showed a good binding propensity to the DNA and HSA, during the assessment of docking studies. Schiff base ligand HL and its metal (II) complexes, 1–3 screened for their in vitro antimicrobial activities using the disc diffusion method against selected microbes. Complex 1 shows higher antimicrobial activity than complexes 2, 3 and Schiff base ligand HL. According to the results obtained from the cytotoxic studies, Schiff base ligand HL and its metal (II) complexes 1–3 have better cytotoxicity against MCF‐7 cell lines with potency higher than the currently used chemotherapeutic agent cyclophosphamide.     

Rare example of mu-nitrito-1kappa2O,O':2kappaO coordinating mode in copper(II) nitrite complexes with monoanionic tridentate Schiff base ligands: structure, magnetic, and electrochemical properties

Three new copper(II) complexes, [CuL(1)(NO(2))](n) (1), [CuL(2)(NO(2))] (2), and [CuL(3)(NO(2))] (3), with three similar tridentate Schiff base ligands [HL(1) = 6-amino-3-methyl-1-phenyl-4-azahept-2-en-1-one, HL(2) = 6-amino-3-methyl-1-phenyl-4-azahex-2-en-1-one, and HL(3) = 6-diethylamino-3-methyl-1-phenyl-4-azahex-2-en-1-one] have been synthesized and characterized structurally and magnetically. In all three complexes, the tridentate Schiff base ligand and one oxygen atom of the nitrite ion constitute the equatorial plane around Cu(II), whereas the second oxygen atom of the nitrite ligand coordinates to one of the axial positions. In 1, this axially coordinated oxygen atom of the nitrite ligand also coordinates weakly to the other axial position of a Cu(II) ion of another unit to form a one-dimensional chain with the mu-nitrito-1kappa(2)O,O':2kappaO bridging mode. Complexes 2 and 3 are discrete monomers that are joined together by intermolecular H bonds and C-H....pi interactions in 2 and by only C-H....pi interactions in 3. A weak antiferromagnetism (J = -1.96(2) cm(-1)) is observed in complex 1 due to its asymmetric nitrite bridging. Complexes 2 and 3 show very weak antiferromagnetic interactions (J = -0.089 and -0.096 cm(-1), respectively) attributed to the presence of intermolecular H-bonding and C-H....pi interactions. The corresponding Cu(I) species produced by the electrochemical reduction of complexes 1 and 2 disproportionate to Cu(0) and Cu(2+,) whereas the reduced Cu(I) species of complex 3 seems to be stable presumably due to a higher tetrahedral distortion of the equatorial plane in 3 compared to that in 1 and 2.     

Synthesis, characterization, antioxidative activity and DNA binding properties of the copper(II), zinc(II), nickel(II) complexes with 1,2-Di(4'-iminonaringenin)ethane

A novel naringenin Schiff base ligand (1,2-di(4'-iminonaringenin)ethane, H6L) and its three transition metal complexes [Cu(II) complex (1), Zn(II) complex (2), and Ni(II) complex (3)] have been prepared and characterized on the basis of elemental analysis, molar conductivity, 1H-NMR, mass spectra, UV-vis spectra, and IR spectra. The DNA-binding properties of the ligand and its complexes have been investigated by absorption spectroscopy, fluorescence spectroscopy, ethidium bromide (EB) displacement experiments, and viscosity measurement. The results indicated that the ligand and its complexes can bind to DNA. The binding affinity of the Cu(II) complex (1) is higher than that of the ligand and the other two complexes. The intrinsic binding constant (Kb) of the complex (1) is 3.3x10(6). In addition, the suppression ratio for O2-. and HO. was determined. The 50% inhibition obtained for the ligand and its three complexes demonstrates that, compared to the ligand, the complexes exhibit higher antioxidative activity in the suppression of O2-. and HO..     

Synthesis,characterization and biological studies of Co(II), Ni(II), Cu(II) and Zn(II) complexes with pyrral-l-histidinate

The Schiff base ligand, pyrral-l-histidinate(L) and its Co(II), Ni(II), Cu(II) and Zn(II) complexes were synthesized and characterized by elemental analysis, mass, molar conductance, IR, electronic, magnetic measurements, EPR, redox properties, thermal studies, XRD and SEM. Conductance measurements indicate that the above complexes are 1:1 electrolytes. IR data show that the ligand is tridentate and the binding sites are azomethine nitrogen, imidazole nitrogen and carboxylato oxygen atoms. Electronic spectral and magnetic measurements indicate tetrahedral geometry for Co(II) and octahedral geometry for Ni(II) and Cu(II) complexes, respectively. The observed anisotropic g values indicate the presence of Cu(II) in a tetragonally distorted octahedral environment. The redox properties of the ligand and its complexes have been investigated by cyclic voltammetry. Thermal decomposition profiles are consistent with the proposed formulations. The powder XRD and SEM studies show that all the complexes are nanocrystalline. The in vitro biological screening effects of the synthesized compounds were tested against the bacterial species, Escherichia coli, Bacillus subtilis, Pseudomonas aeruginosa and Staphylococcus aureus; fungal species, Aspergillus niger, Aspergillus flavus and Candida albicans by the disc diffusion method. The results indicate that complexes exhibit more activity than the ligand. The nuclease activity of the ligand and its complexes were assayed on CT DNA using gel electrophoresis in the presence and absence of H₂O₂.     

Synthesis,characterization and biological studies of some Co(II), Ni(II) and Cu(II) complexes derived from indole-3-carboxaldehyde and glycylglycine as Schiff base ligand

The Schiff base ligand derived from indole-3-carboxaldehyde(indal) and glycylglycine(glygly) were synthesized and characterized by elemental analysis, IR, electronic spectrum, ¹H NMR and mass spectrum. Co(II), Ni(II) and Cu(II)–indal-glygly Schiff base complexes were synthesized and characterized by elemental analysis, molar conductance, IR, electronic spectra, magnetic measurements, ESR, electrochemical studies, TGA, DSC analysis, XRD and SEM. Conductance measurements indicate that the above complexes are 1:1 electrolytes. IR spectral data show that the ligand is tridentate and the binding sites are azomethine nitrogen, peptide nitrogen and carboxylato oxygen atoms. Electronic spectral measurements indicate tetrahedral geometry for Co(II) and Ni(II) complexes and square planar geometry for Cu(II) complex. Magnetic measurements show weak ferromagnetic behaviour for Co(II) and Ni(II) complexes and paramagnetic behaviour for Cu(II) complex. ESR spectral data shows the ionic link between metal and the Schiff base ligand. The metal complexes are found to be stabilized in the unusual oxidation states of the metal ion during electrolysis. Thermal analysis of the complex indicates that the decomposition takes place in three steps. IR and thermal studies indicate that the fourth position would be occupied by a water molecule in complexes. XRD shows that the complexes have the crystallite size of 31, 40 and 67 nm, respectively. The surface morphology of the complexes was studied by SEM. The antimicrobial activity of the ligand and its complexes were screened by Kirby Bayer Disc Diffusion method. DNA cleavage studies were performed for metal–Schiff base complexes in presence of hydrogen peroxide as oxidant.     

Metallation of ethylenediamine based Schiff base with biologically active Cu(II), Ni(II) and Zn(II) ions: synthesis, spectroscopic characterization, electrochemical behaviour, DNA binding, photonuclease activity and in vitro antimicrobial efficacy

A new ligand [C28H20N6O8] (L2) has been synthesized by the condensation reaction of 3-hydroxy-4-nitrobenzaldehydenephenylhydrazine (L1) with diethyloxalate. This ligand L2 is allowed to react with bis(ethylenediamine)Cu(II)/Ni(II)/Zn(II) complexes. It affords [(L2)Cu(en)2]Cl2(1)/[(L2)Ni(en)2]Cl2(2)/[(L2)Zn(en)2]Cl2(3) complexes, respectively. These complexes (1-3) have been characterized by the spectral and analytical techniques. The interaction of these complexes with calf thymus (CT) DNA is characterized by the absorption spectra which exhibit a slight red shift with hypochromic effect. Electrochemical analyses and viscosity measurements have also been carried out to determine the mode of binding. The shift in ΔEp, E1/2 and Ipc values explores the interaction of CT DNA with the above metal complexes. The slight increase in the viscosity of CT DNA indicates that these complexes bind to CT DNA through a partial non-classical intercalative mode. Cleavage experiments using pBR322 DNA in presence of H2O2 indicate that these complexes behave as efficient artificial chemical nucleases in the order of 1>2>3. Moreover, the antibacterial and antifungal studies reveal that complex 1 is highly active against the bacterial and fungal growth.     

Synthesis and physico-chemical studies on complexes of 1,2-diaminophenyl-N,N′-bis-(2-pyridinecarboxaldimine), (L): A spectroscopic approach on binding studies of DNA with the copper complex

The Schiff base ligand, 1,2-diaminophenyl-N,N′-bis-(2-pyridinecarboxaldimine), (L) has been synthesized by the reaction of o-phenylenediamine and 2-pyridinecarboxaldehyde, and a series of mononuclear complexes of the type [ML(NO₃)₂] [M = Co(II), Ni(II), Cu(II) and Zn(II)] has also been synthesized. The formation of the Schiff base ligand (L) and its complexes have been envisaged from IR, ¹H and ¹³C NMR studies. The absorption band observed in the electronic spectra and magnetic moment values confirm an octahedral environment around the metal ion. The molar conductivity measurements confirm the non-ionic character of these complexes. Fluorescence and UV–Vis absorption studies performed on the Cu(II) complex revealed a significant binding ability to DNA.     

Some divalent metal(II) complexes of novel potentially tetradentate Schiff base N,N′‐bis(2‐carboxyphenylimine)‐2,5‐thiophenedicarboxaldhyde: Synthesis,spectroscopic characterization and bioactivities

A novel tetradentate dianionic Schiff base ligand, N ,N ′‐bis(2‐carboxyphenylimine)‐2,5‐thiophenedicarboxaldhyde (H₂L) and some first row d‐transition metal chelates (Co(II), Cu(II), Ni(II) and Zn(II)) were synthesized and characterized using various physicochemical and spectroscopic methods. The spectroscopic data suggested that the parent Schiff base ligand coordinates through both deprotonated carboxylic oxygen and imine nitrogen atoms. The free Schiff base and its metal chelates were screened for their antimicrobial activities for various pathogenic bacteria and fungi using the agar well diffusion method. The antibacterial and antifungal activities of all the newly synthesized compounds are significant compared to the standard drugs ciprofloxacin and nystatin. The antioxidant activities of the compounds were determined by reduction of 1,1‐diphenyl‐2‐picrylhydrazyl and compared with that of vitamin C as a standard. DNA binding ability of the novel Schiff base and its complexes was investigated using absorption spectroscopy, fluorescence spectroscopy, viscosity measurements and thermal denaturation. The obtained results clearly demonstrate that the binding affinity with calf thymus DNA follows the order: Cu(II) complex > Ni(II) complex > Zn(II) complex > Co(II) complex >H₂L. Furthermore, the DNA cleavage activity of the newly synthesized ligand and its metal complexes was investigated using supercoiled plasmid DNA (pUC18) gel electrophoresis.     

Synthesis and spectroscopic studies on complexes of N,N'-bis-(2-pyridinecarboxaldimine)-1,8-diaminonaphthalene (L); DNA binding studies on Cu(II) complex

The Schiff base ligand, N,N'-bis-(2-pyridinecarboxaldimine)-1,8-diaminonaphthalene (L), obtained by the condensation of 2-pyridinecarboxaldehyde and 1,8-diaminonaphthalene, has been used to synthesize the mononuclear complexes of the type [MLCl(2)] [M=Co(II), Ni(II), Cu(II) and Zn(II)]. The newly synthesized ligand (L) and its complexes have been characterized on the basis of results of elemental analysis, molar conductance, magnetic susceptibility measurements, Job's method and spectroscopic studies viz., FT-IR, Mass, (1)H and (13)C NMR. The UV-vis and magnetic moment data revealed an octahedral geometry around Co(II), Ni(II) and Cu(II) ions and conductivity data show a non-electrolytic nature of the complexes. Absorption and fluorescence spectroscopic studies support that Cu(II) complex exhibits significant binding to calf thymus DNA.     

DNA interaction studies of Cu(II), Co(II), and Ni(II) chelates derived from schiff base ligand

Chelates of the type M(L)₂ {where, M ?= ?Co(II), Ni(II) and Cu(II), and L ?= ?3-{(E)-[(2-hydroxy-3-methoxyphenyl)methylidene]amino}pyridin-4(1H)-one)} were synthesized by using the Schiff base ligand in the stochiometric ratio 2:1 (L:M) and Schiff base ligand (L) was synthesized by simple condensation between 2-hydroxy-3-methoxybenzaldehyde with 3-aminopyridin-4-ol. The structure and formation of synthesized compounds were established by different analytical and spectroscopic methods like, elemental analysis, UV- spectroscopy, FT-IR, Proton and Carbon NMR, mass spectrometry and Powder XRD. Further, the synthesized chelates screened for the DNA binding studies of Calf Thymus (CT)-DNA by exploiting electronic absorption spectra, relative viscosity measurements and thermal denaturation methods. The proposed DNA binding mode supports the enhancement in the binding activity of the complexes in presence of newly synthesized ligand. The cleavage activities of the PUC-18 DNA in the presence and the absence of the complexes were recorded with the help of gel-electrophoresis. The cleavage experiment results reveals that all the synthesized chelates can cleave pUC-18 DNA effectively.     

Synthesis,characterization, antimicrobial and diuretic study of Mg(II), Mn(II), Fe(II) and VO(II) complexes of chemotherapeutic importance

The synthesis, characterization and diuretic activity of four new biologically active complexes of Mg(II) and VO(II) with bidentate Schiff base ligand acetazolamide–salicylaldimine (L) obtained from the inserted condensation of 5-acetamido-1,3,4-thiadiazole-2-sulphonamide (acetazolamide) with salicylaldehyde in a 1:1 molar ratio have been reported. Using this bidentate ligand complexes of Mg(II), Mn(II), Fe(II) and VO(II) with general formula ML₂ have been synthesized. The synthesized complexes were characterized by several techniques using elemental analysis, FT-IR, electronic spectra, TGA, mass, particle size analysis and molar conductance measurements. The elemental analysis data suggest the stoichiometry to be 1:2 [M:L]. The molar conductance measurements suggest non-electrolytic nature of the complexes. Infrared spectral data agreed with the coordination to the central metal ion through deprotonated phenolic oxygen and azomethine nitrogen atoms. On the basis of spectral studies, octahedral geometry is suggested for Mg(II), Mn(II), Fe(II) and square pyramidal geometry is suggested for VO(II) complexes. The pure drug, synthesized ligand and metal(II) complexes were screened for their antimicrobial activities against Eschericia coli, Bacillus subtilis, Aspergillus niger and Aspergillus flavous. The results show that the metal complexes were more active than the ligand and pure drug against these microbial species as expected. The ligand and its Mg(II) complexes was screened for their diuretic activity also.     

New zinc(II), copper(II), nickel(II), and vanadium(IV) complexes containing disulfide ligand: Synthesis,spectroscopic studies and calf thymus DNA interaction investigation

New Schiff base complexes of zinc(II), copper(II), nickel(II), and vanadium(IV) were synthesized using the Schiff base ligand formed by the condensation of 2-aminoethanethiol and 2-hydroxy-1-naphthaldehyde. The tetradentate Schiff base ligand N,N´-(3,4-dithiahexane-1,6-diyl)bis(2-hydroxy-1-naphthaleneimine), containing a disulfide bond, was coordinated to the metal(II) ions through the two azomethine nitrogen atoms and two deprotonated phenolic oxygens of two different ligands which was connected to each other by sulfur-sulfur bond. The molar conductivity values of complexes in DMSO solvent implied the presence of nonelectrolyte species. The fluorescence properties of the Schiff base ligand and its complexes were studied in dimethylsulfoxide. The Schiff base ligand and its complexes were characterized by FT-IR, ¹H NMR, UV/Vis spectroscopies, elemental analysis, and conductometry. The crystal structure of tetradentate Schiff base ligand was characterized by single crystal X-ray diffraction. The Schiff base ligand was contained disulfide bond. Furthermore, the binding interaction of these complexes with calf thymus DNA (CT-DNA) was investigated by different methods.     

Copper(II) mediated anion dependent formation of Schiff base complexes

A tetranuclear mixed ligand copper(II) complex of a pyrazole containing Schiff base and a hydroxyhexahydropyrimidylpyrazole and copper(II) and nickel(II) complexes of the Schiff base having N-donor atoms have been investigated. A 2 equiv amount of 5-methyl-3-formylpyrazole (MPA) and 2 equiv of 1,3-diamino-2-propanol (1,3-DAP) on reaction with 1 equiv of copper(II) nitrate produce an unusual tetranuclear mixed ligand complex [Cu4(L1)2(L2)2(NO3)2] (1), where H2L1 = 1,3-bis(5-methyl-3-formylpyrazolylmethinimino)propane-2-ol and HL2 = 5-methyl-3-(5-hydroxyhexahydro-2-pyrimidyl)pyrazole. In contrast, a similar reaction with nickel(II) nitrate leads to the formation of a hygroscopic intractable material. On the other hand, the reaction involving 2 equiv of MPA and 1 equiv each of 1,3-DAP and various copper(II) salts gives rise to two types of products, viz. [Cu(T3-porphyrinogen)(H2O)]X2 (X = ClO4, NO3, BF4 (2)) (T3-porphyrinogen = 1,6,11,16-tetraza-5,10,15,20-tetrahydroxy-2,7,12,17-tetramethylporphyrinogen) and [Cu(H2L1)X]X x H2O (X = Cl (3), Br (4)). The same reaction carried out with nickel(II) salts also produces two types of compounds [Ni(H2L1)(H2O)2]X2 [X = ClO4 (5), NO3 (6), BF4 (7)] and [Ni(H2L1)X2] x H2O [X = Cl (8), Br (9)]. Among the above species 1, 3, and 5 are crystallographically characterized. In 1, all four copper atoms are in distorted square pyramidal geometry with N4O chromophore around two terminal copper atoms and N5 chromophore around two inner copper atoms. In 3, the copper atom is also in distorted square pyramidal geometry with N4Cl chromophore. The nickel atom in 5 is in a distorted octahedral geometry with N4O2 chromophore, where the metal atom is slightly pulled toward one of the axial coordinated water molecules. Variable-temperature (300 to 2 K) magnetic susceptibility measurements have been carried out for complex 1. The separations between the metal centers, viz., Cu(1)...Cu(2), Cu(2)...Cu(2)A, and Cu(2)A...Cu(1)A are 3.858, 3.89, and 3.858 A, respectively. The overall magnetic behavior is consistent with strong antiferromagnetic interactions between the spin centers. The exchange coupling constants between Cu(1)...Cu(2) and Cu(2)...Cu(2A) centers have turned out to be -305.3 and -400.7 cm(-1), respectively, resulting in a S = 1/2 ground state. The complexes are further characterized by UV-vis, IR, electron paramagnetic resonance, and electrochemical studies.     

Synthesis, characterization and biological activities of Cu(II), Co(II), Mn(II), Fe(II), and UO2(VI) complexes with a new Schiff Base hydrazone: O-hydroxyacetophenone-7-chloro-4-quinoline hydrazone

The Schiff base hydrazone ligand HL was prepared by the condensation reaction of 7-chloro-4-quinoline with o-hydroxyacetophenone. The ligand behaves either as monobasic bidentate or dibasic tridentate and contain ONN coordination sites. This was accounted for be the presence in the ligand of a phenolic azomethine and imine groups. It reacts with Cu(II), Ni(II), Co(II), Mn(II), UO(2) (VI) and Fe(II) to form either mono- or binuclear complexes. The ligand and its metal complexes were characterized by elemental analyses, IR, NMR, Mass, and UV-Visible spectra. The magnetic moments and electrical conductance of the complexes were also determined. The Co(II), Ni(II) and UO(2) (VI) complexes are mononuclear and coordinated to NO sites of two ligand molecules. The Cu(II) complex has a square-planar geometry distorted towards tetrahedral, the Ni(II) complex is octahedral while the UO(2) (VI) complex has its favoured heptacoordination. The Co(II), Mn(II) complexes and also other Ni(II) and Fe(III) complexes, which were obtained in the presence of Li(OH) as deprotonating agent, are binuclear and coordinated via the NNNO sites of two ligand molecules. All the binuclear complexes have octahedral geometries and their magnetic moments are quite low compared to the calculated value for two metal ions complexes and thus antiferromagnetic interactions between the two adjacent metal ions. The ligand HL and metal complexes were tested against a strain of Gram +ve bacteria (Staphylococcus aureus), Gram -ve bacteria (Escherichia coli), and fungi (Candida albicans). The tested compounds exhibited high antibacterial activities.