Synthesis,spectral, thermal,and magnetic studies of cobalt(II), nickel(II), copper(II), zinc(II), and cadmium(II) complexes with N2O2 donor groups

A new Schiff base ligand was prepared by condensation of 2-hydroxy-4-methoxybenzaldehyde with 1,2-propanediamine. The ligand and its metal complexes were characterized by elemental analysis, FT-IR, ¹H and ¹³C NMR, magnetic moment, molar conductance, UV-Vis, SEM and thermal analysis (TGA). The molar conductance measurements indicated that all the metal complexes were non-electrolytes. IR spectra showed that ligand (L) behaves as a neutral tetradentate ligand and binds to the metal ions by the two azomethine nitrogen atoms and two phenolic oxygen atoms. The electronic absorption spectra and magnetic susceptibility measurements indicated square planar geometry for the Ni(II) and Cu(II) complexes while other metal complexes showed tetrahedral geometry. Also the surface morphology of the complexes was studied by SEM.     

Synthesis,structural features and biochemical activity assessment of N,N′‐bis‐(2‐mercaptophenylimine)‐2,5‐thiophenedicarboxaldehyde Schiff base and its Co(II), Ni(II), Cu(II) and Zn(II) complexes

The tetradentate Schiff base ligand (SB), N,N′‐bis‐(2‐mercaptophenylimine)‐2,5‐thiophenedicarboxaldehyde was prepared via condensation of 2,5‐thiophene‐dicarboxaldehyde with 2‐aminothiophenol in a 1:2 molar ratio by conventional method. Additionally, its Co(II), Ni(II), Cu(II) and Zn(II) complexes have been synthesized and fully characterized by elemental analysis, FT‐IR, ¹H NMR, ¹³C NMR, UV–Vis, ESR, ESI‐mass, conductivity and magnetic susceptibility measurements. Spectral studies suggested that, the Schiff base coordinate metal ions through the azomethine N‐ and deprotonated thiol S‐ atoms. Based on UV–Vis absorption and magnetic susceptibility data, tetrahedral geometry was assigned for both Co(II) and Zn(II) complexes, whereas on the other hand, square planar geometry for both Ni(II) and Cu(II) complexes. The Schiff base and its metal complexes were screened for their in vitro antimicrobial activity by minimum inhibitory concentration (MIC) method. Free radical scavenging activity of the novel compounds was determined by elimination of 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) radicals. In addition, the interactions of the free ligand and its complexes with calf thymus DNA (CT‐DNA) were explored using absorption, emission and viscosity measurements techniques.     

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.     

Synthesis and characterization of heterocyclic Schiff base and its complexes with Cu(II), Ni(II), Co(II), Zn(II), and Cd(II)

A new Schiff base, {1-[(2-hydroxy-naphthalen-1-ylmethylene)-amino]-4-phenyl-2-thioxo-1, 2-dihydro-pyrimidin-5-yl}-phenyl-methanone, has been synthesized from N-amino pyrimidine-2-thione and 2-hydroxynaphthaldehyde. Metal complexes of the Schiff base were prepared from acetate/chloride salts of Cu(II), Co(II), Ni(II), Zn(II), and Cd(II) in methanol. The chemical structures of the Schiff-base ligand and its metal complexes were confirmed by elemental analyses, IR, ¹³C-NMR, ¹H-NMR, API-ES, UV-Visible spectroscopy, magnetic susceptibility, and thermogravimetric analyses. The electronic spectral data and magnetic moment measurements suggest mononuclear octahedral and mononuclear or binuclear square planar structures for the metal complexes. In light of these results, it was suggested that this ligand coordinates to each metal atom by hydroxyl oxygen, azomethine nitrogen, and thione sulfur to form octahedral complexes with Cd(II) and Zn(II).     

Design,synthesis, DNA binding ability,chemical nuclease activity and antimicrobial evaluation of Cu(II), Co(II), Ni(II) and Zn(II) metal complexes containing tridentate Schiff base

A novel Schiff base has been designed and synthesized using the bioactive ligand obtained from 4-aminoantipyrine, 3,4-dimethoxybenzaldehyde and 2-aminobenzoic acid. Its Cu(II), Co(II), Ni(II), Zn(II) complexes have also been synthesized in ethanol medium. The structural features have arrived from their elemental analyses, magnetic susceptibility, molar conductance, mass, IR, UV–Vis, ¹H NMR and ESR spectral studies. The data show that the complexes have composition of ML₂ type. The electronic absorption spectral data of the complexes suggest an octahedral geometry around the central metal ion. The interaction of the complexes with calf thymus (CT) DNA has been studied using absorption spectra, cyclic voltammetric, and viscosity measurement. The metal complexes have been found to promote cleavage of pUC19 DNA from the super coiled form I to the open circular form II. The complexes show enhanced antifungal and antibacterial activities compared with the free ligand.     

A new mesitylenic cyclobutane substituted Schiff base ligand and its Co(II), Cu(II), Ni(II), and Zn(II) complexes

A new ligand, 4‐(1‐methyl‐1‐mesityl‐3‐cyclobutanyl)‐2‐(2‐hydroxy‐1‐naphthylideneimino)thiazole (LH), has been synthesized starting from 1‐methyl‐1‐mesityl‐3‐(2‐chloro‐1‐oxoethyl)cyclobutane and thiourea and subsequently 2‐hydroxy‐1‐napthalaldehyde. Mononuclear complexes with a metal‐ligand ratio of 1:2 have been prepared with Co(II), Cu(II), Ni(II), and Zn(II) metals. The authenticity of the ligand and its complexes are proposed based on elemental analyses, IR, UV‐vis, ¹³C and ¹H NMR spectra, magnetic susceptibility measurements, thermogravimetric analyses, and differential scanning calorimetry. © 2001 John Wiley & Sons, Inc. Heteroatom Chem 12:42–46, 2001     

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.     

Spectral,thermal, electrochemical,biological and DFT studies on nanocrystalline Co(II), Ni(II), Cu(II) and Zn(II) complexes with a tridentate ONO donor Schiff base ligand

Co(II), Ni(II), Cu(II) and Zn(II) Schiff base complexes derived from 3-hydrazinoquionoxaline-2-one and 1,2-diphenylethane-1,2-dione were synthesized. The compounds were characterized by elemental analyses, molar conductance, magnetic susceptibility measurements, FTIR, UV–vis, ¹H NMR, ¹³C NMR, ESR, and mass spectral studies. Thermal studies of the ligand and its metal complexes were also carried out to determine their thermal stability. Octahedral geometry has been assigned for Co(II), Ni(II), and Zn(II) complexes, while Cu(II) complex has distorted octahedral geometry. Powder XRD study was carried out to determine the grain size of ligand and its metal complexes. The electrochemical behavior of the synthesized compounds was investigated by cyclic voltammetry. For all complexes, a 2 : 1 ligand-to-metal ratio is observed. The ligand and its metal complexes were screened for their activity against bacterial species such as E. coli, P. aeruginosa, and S. aureus and fungal species such as A. niger, C. albicans, and A. flavus by disk diffusion method. The DNA-binding of the ligand and its metal complexes were investigated by electronic absorption titration and viscosity measurement studies. Agarose gel electrophoresis was employed to determine the DNA-cleavage activity of the synthesized compounds. Density functional theory was used to optimize the structure of the ligand and its Zn(II) complex.     

Coordination Behavior of N‐Donor Schiff Base Derived from 2‐Benzoylpyridine Toward Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Pd(II), and Cr(III) Metal Ions: Synthesis,Spectroscopic and Thermal Studies,and Biological Activity

A new Schiff base was prepared from the reaction of 4,4′‐methylenedianiline with 2‐benzoylpyridine in 1:2 molar ratio, as well as its different metal chelates. The structures of the ligand and its metal complexes were studied by elemental analyses, spectroscopic methods (infrared [IR ], ultraviolet–visible [UV –vis], ¹H nuclear magnetic resonance [NMR ], electron spin resonance [ESR ]), magnetic moment measurements, and thermal studies. The ligand acts as tetradentate moiety in all complexes. Octahedral geometry was suggested for Mn(II ), Cu(II ), Cr(III ), and Zn(II ) chloride complexes and pentacoordinated structure and square planar geometry for Co(II ), Ni(II ), Cu(NO₃ )₂, CuBr₂ , and Pd(II ) complexes. ESR spectra of copper(II ) complexes ( 4 )–( 6 ) at room temperature display rhombic symmetry for complex ( 4 ) and axial type symmetry for complexes ( 5 ) and ( 6 ), indicating ground state for Cu(II ) complexes. The derivative thermogravimetric (DTG ) curves of the ligand and its metal complexes were analyzed by using the rate equation to calculate the thermodynamic and kinetic parameters, which indicated strong binding of the ligand with the metal ion in some complexes. Also, some of these compounds were screened to establish their potential as anticancer agents against the human hepatic cell line Hep‐G₂ . The obtained IC₅₀ value of the copper(II ) bromide complex (4.34 µg/mL ) is the highest among the compounds studied.     

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.     

Nickel(II), copper(II), cobalt(II), and palladium(II) complexes with a Schiff base: crystal structure,DFT study and copper complex catalyzed aerobic oxidation of alcohol to aldehyde

Ni(II), Cu(II), Co(II), and Pd(II) complexes were synthesized with a Schiff base containing thioether with ONS donors chelating to the metal center. The ligand and complexes were characterized by elemental analysis, FT-IR, ¹H-NMR, UV–visible spectroscopy and magnetic studies. The crystal structures of the ligand and its Ni(II) and Pd(II) complexes were determined by single-crystal X-ray diffraction analysis. Structures revealed that the ligand chelated with Ni(II) and Pd(II) center in slightly distorted octahedral and slightly distorted square planar fashion, respectively. DFT studies of the Pd(II) complex revealed that the calculated structural parameters are very close with the experimentally observed data. The Cu(II) complex shows very good catalytic activity toward the conversion of alcohol to aldehyde under aerobic oxidation with ammonium persulfate.     

Co(II), Ni(II), Cu(II), and Zn(II) complexes of 4-aminoantipyrine-derived Schiff base. Synthesis,structural elucidation,thermal, biological studies,and photocatalytic activity

The Schiff base ligand was prepared from 4-aminoantipyrine, acetamide, and m-phenylenediamine. Metal salts used for the synthesis of these complexes are Co(II), Ni(II), Cu(II), and Zn(II) acetates. The elemental analysis results are in accordance with proposed formula assigned to these complexes. In the IR spectra, the imine band is shifted to a lower wave number in the complexes. UV spectra and magnetic susceptibility measurements proposed square planar geometry for Co(II), Ni(II), and Cu(II) complexes and tetrahedral geometry for Zn(II) complex. The grain size of the metal complexes was estimated by the Scherrer formula using powder XRD. In the present study, the ligand and its metal complexes are found to be nanocrystalline. Thermal decomposition pattern is in agreement with the proposed formula of the complexes. Irreversible redox behavior of the complex was identified by cyclic voltammetric analysis. The photocatalytic activity of the synthesized complexes are high under UV-spectra using methylene blue dye. DNA studies reveal that the synthesized complexes exhibit both DNA cleavage and DNA binding properties. Antibacterial and antifungal activities were done by the minimum inhibitory concentration (MIC) method. Anticancer activity shows that Cu(II) complex has the highest cytotoxic effect in SK-MEL-28 cell line.     

Synthesis,characterization, density functional theory,thermal, antimicrobial efficacy,and DNA binding/cleavage studies of Cu(II), Cr(III), Fe(III), Ni(II), Co(II), Zn(II), and Pt(IV) complexes with a derivative of 2-hydroxyphenoxymethylfuran-5-carbaldehyde

In this study, Seven new complexes incorporating (E)-2-(((5-([2-hydroxyphenoxy]methyl)furan-2-yl)methylene)amino)phenol derived from 2-hydroxyphenoxymethylfuran-5-carbaldehyde and 2-aminophenol have been synthesized using Cu(II), Cr(III), Fe(III), Ni(II), Co(II), Zn(II), and Pt(IV) metal salts. Thermal measurements, molar conductance, magnetic moment, elemental analyses, spectral (IR, UV–Vis, ¹H nuclear magnetic resonance (NMR), ESR, Mass), were used to characterize insulated solid complexes. The thermogravimetry (TG) and differential thermoanalysis (DTA) of the complexes were carried out in the range of 30–900°C. Magnetic susceptibility and electronic spectral data, as well as quantum chemical calculations, reveal the square planar geometry for Ni (II) complex, square planar/octahedral geometry for Cu (II) complex, while Co(II), Zn(II), Cr(III), Fe(III), and Pt (IV) complexes are octahedral geometry. Density functional theory (DFT) studies revealed that geometries of metal complexes and Schiff base were entirely optimized in relation to use energy by 6–31 + g (d,p) basis set. The complexes show a well-defined crystal system indicated by a powder-X-ray diffraction pattern. The scanning electron microscope showed complexes were nanocrystalline in nature, in addition to the interaction of the complexes with calf thymus CT-DNA, which was investigated via the UV–visible absorption method. Therefore, the DNA cleavage activity by the H₂L ligand and its metal complexes was performed. Finally, the synthesized complexes were tested for their in-vitro antimicrobial efficacy.     

Synthesis, spectral characterization, and thermal behavior of mononuclear Cu(II), Co(II), Ni(II), Mn(II), and Zn(II) complexes with 5-bromosalycilaldehyde isonicotinoylhydrazone

A bidentate/tridentate 5-bromosalycilaldehyde isonicotinoylhydrazone Schiff base was synthesized by condensing 5-bromosalycilaldehyde with isonicotinoylhydrazine. Cu(II), Co(II), Ni(II), Mn(II) and Zn(II) complexes of this chelating ligand were synthesized using nitrates of these metals. The ligand and the complexes were characterized by elemental analysis, UV–Vis, IR and EPR spectroscopy, conductance and magnetic susceptibility measurements, fluorescence, cyclic voltammetry and thermogravimetric analysis. The ligand and Zn(II) complex exhibits solid-state photoluminescence at room temperature.     

Preparation,Characterization, Biological Activity and 3D Molecular Modeling of Mn(II), Co(II), Ni(II), Cu(II), Pd(II) and Ru(III) Complexes of Some Sulfadrug Schiff Bases

Mn(II), Co(II), Ni(II), Cu(II), Pd(II) and Ru(III) complexes of Schiff bases derived from the condensation of sulfaguanidine with 2,4‐dihydroxy benzaldehyde ( HL1 ), 2‐hydroxy‐1‐naphthaldehyde ( HL2 ) and salicylaldehyde ( HL3 ) have been synthesized. The structures of the prepared metal complexes were proposed based on elemental analysis, molar conductance, thermal analysis (TGA, DSC and DTG), magnetic susceptibility measurements and spectroscopic techniques (IR, UV‐Vis, and ESR). In all complexes, the ligand bonds to the metal ion through the azomethine nitrogen and α‐hydroxy oxygen atoms. The structures of Pd(II) complex 8 and Ru(III) complex 9 were found to be polynuclear. Two kinds of stereochemical geometries; distorted tetrahedral and distorted square pyramidal, have been realized for the Cu(II) complexes based on the results of UV‐Vis, magnetic susceptibility and ESR spectra whereas octahedral geometry was predicted for Co(II), Mn(II) and Ru(III) complexes. Ni(II) complexes were predicted to be square planar and tetrahedral and Pd(II) complexes were found to be square planar. The antimicrobial activity of the ligands and their metal complexes was also investigated against the gram‐positive bacteria Staphylococcus aures and Bacillus subtilis and gram‐negative bacteria, Escherichia coli and Pesudomonas aeruginosa, by using the agar dilution method. Chloramphenicol was used as standard compound. The obtained data revealed that the metal complexes are more or less, active than the parent ligand and standard. The X‐ray crystal structure of HL3 has been also reported.     

Synthesis,Spectral, Thermal and Biological Studies of Mn(II), Co(II), Ni(II) and Cu(II) Complexes with 1‐(((5‐Mercapto‐1H‐1,2,4‐triazol‐3‐yl)imino)‐methyl)naphthalene‐2‐ol

Mn(II), Co(II), Ni(II) and Cu(II) complexes of 5‐mercapto‐1,2,4‐triazol‐3‐imine‐2′‐hydroxynaphthaline have been synthesized and characterized by elemental analysis, IR, ¹H NMR, EI‐mass, UV‐Vis, and ESR (electron spin resonance) spectra, molar conductance, magnetic moment measurements, DC conductivity and thermogravimetric analysis. IR spectra confirm that the ligand molecule existed in both thione and thiole forms. The molar conductance values indicate the complexes are nonelectrolyte. The magnetic moment values of the complexes display paramagnetic behavior. All studies confirm the formation of an octahedral geometry for complex 1 and the other complexes have tetrahedral geometrical structures. The structures of the complexes have also been theoretically studied by using the molecular mechanic calculations by the hyperchem. 8.03 molecular modeling program which confirm the proposed structures. The Schiff‐base ligand and its metal complexes have also been screened for their antimicrobial activities.     

Studies on Mononuclear Chelates Derived from Substituted Schiff Base Ligands: Synthesis and Characterization of a New 5-Methoxysalicyliden-<Emphasis Type="Italic">p</Emphasis>-Aminoacetophenoneoxime and Its Complexes with Co(II), Ni(II), Cu(II), and Zn(II)

New complexes of Co(II), Ni(II), Cu(II), and Zn(II) with new Schiff bases derived by the condensation of p-aminoacetophenoneoxime with 5-methoxysalicylaldehyde are synthesized. The compounds are characterized by elemental analyses, magnetic susceptibility measurements, IR, ¹H and ¹³C NMR spectra, electronic spectral data, and molar conductivity. The thermal stabilities of the compounds are also reported. The Schiff base acts as bidentate O,N-donor atoms, and their metal complexes are supposed to possess a tetrahedral geometry with respect to the central metal ion. The general formula of the 5-methoxysalicyliden-p-aminoacetophenoneoxime Co(II), Ni(II), Cu(II), and Zn(II) complexes is Co(L)₂, Ni(L)₂, Cu(L)₂, and Zn(L)₂.     

Ni(II) and Cu(II) complexes with ONNO asymmetric tetradentate Schiff base ligand: synthesis,spectroscopic characterization,theoretical calculations,DNA interaction and antimicrobial studies

A novel Schiff base, namely Z ‐3‐((2‐((E )‐(2‐hydroxynaphthyl)methylene)amino)‐5‐nitrophenylimino)‐1,3‐dihydroindin‐2‐one, was synthesized from the condensation of 2‐hydroxy‐1‐naphthaldehyde and isatin with 4‐nitro‐o ‐phenylenediamine. It was structurally characterized on the basis of ¹H NMR, ¹³C NMR and infrared spectra and elemental analyses. In addition, Ni(II) and Cu(II) complexes of the Schiff base ligand were prepared. The nature of bonding and the stereochemistry of the investigated complexes were elucidated using several techniques, including elemental analysis (C, H, N), Fourier transform infrared and electronic spectroscopies and molar conductivity. The thermal behaviours of the complexes were studied and kinetic–thermodynamic parameters were determined using the Coats–Redfern method. Density functional theory calculations at the B3LYP/6‐311G++ (d, p) level of theory were carried out to explain the equilibrium geometry of the ligand. The optimized geometry parameters of the complexes were evaluated using LANL2DZ basis set. The total energy of highest occupied and lowest unoccupied molecular orbitals, Mullikan atomic charges, dipole moment and orientation are discussed. Moreover, the interaction of the metal complexes with calf thymus DNA (CT‐DNA) was explored using electronic spectra, viscosity measurements and gel electrophoresis. The experimental evidence indicated that the two complexes could strongly bind to CT‐DNA via an intercalation mechanism. The intrinsic binding constants of the investigated Ni(II) and Cu(II) complexes with CT‐DNA were 1.02 × 10⁶ and 2.15 × 10⁶ M⁻¹, respectively, which are higher than that of the standard ethidium bromide. Furthermore, the bio‐efficacy of the ligand and its complexes was examined in vitro against the growth of bacteria and fungi to evaluate the antimicrobial potential. Based on the obtained results, the prepared complexes have promise for use as drugs. Copyright © 2016 John Wiley & Sons, Ltd.     

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.