Synthesized Schiff Base Ligand Research Articles

Synthesis, characterization, theoretical study and biological activity of Schiff base nanomaterial analogues

The ligand named (H2L: 2,2'-((1E, 1′E)-(1,3 phenylene bis (azanylylidene)) bis (methanylylidene))diphenol) was prepared from the reaction of m-phenylenediamine and 2-hydroxybenzaldehyde. A series of Co(II), Ni(II), Cu(II), Cr(III), Mn(II), Fe(III), Zn(II) and Cd(II) complexes of the ligand were prepared and characterized using different physicochemical techniques. The infrared spectral data showed that the chelation occurs through the deprotonated phenolic oxygen and azomethine nitrogen atoms of the ligand. The data showed that the complexes have composition of ML type. An octahedral geometry around the central metal ions in the complexes was suggested. The molecular structures of the ligand and its metal complexes were optimized theoretically. Scanning electron microscope micrographs proved that the ligand and its Co(II) and Cd(II) complexes were formed in nano size. The synthesized Schiff base ligand and its complexes have been screened for antimicrobial activities against bacterial species and fungi. A comparative study of the inhibition zones of the ligand and its metal complexes indicates that most complexes exhibit higher antibacterial and antifungal effect against bacterial species than the free ligand. The molecular docking is used to predict the efficiency of binding between Schiff base ligand and both receptors of crystal structure of Escherichia coli (3T88) and crystal structure of Staphylococcus aureus (3Q8U).

Synthesis and characterization of newly synthesized Schiff base ligand and its metal complexes as potent anticancer

2-((2-mercaptophenyl)imino)-1,2-diphenylethan-1-ol(H2L) Schiff base ligand from benzoin and 2-aminothiophenol was prepared and characterized. The Co(II),Cd(II),La(III), and Gd (III) complexes was prepared in bulk size and La(III) complex also prepared in nano size. The Schiff base and its complexes was characterized by elemental analysis, 1HNMR, IR, Mass spectroscopy, UV-VIS spectra, thermal analysis, conductivity measurements, and magnetic moments. The selected analyses showed that the complexes are octahedral and non-electrolytic in nature and the azomethine nitrogen wasn't participated in complexation. The ability of the free ligand to remove different heavy metals was studied. The cytotoxicity effect of Cd(II) complex sing MTT method exhibited a significant nontoxic behavior and higher cell viability on Vero, Caco-2 and MCF-7 cells than the free ligand itself. The cytotoxicity results revealed that the Cd(II) complex could become safe to be used as anticancer agent for Vero, Caco-2 and MCF-7 cells. By examining its pharmacological activity, we were able to identify new potent and selective anticancer.

Highly Selective Solid Contact Sensor for Low Level Concentration Measurements of Iron(III) in Pharmaceutical and Biological Media

A symmetrical tetradentate Schiff base ligand was derived by the condensation of the corresponding o-vanillin with urea. The synthesized Schiff base ligand was studied to characterize its ability as a cation carrier in poly(vinylchloride) membrane solid contact sensor. The constructed sensor showed excellent response characteristics to iron(III) ion. The electrode exhibited Nernstian slope of 19.5 mV/decade over a wide concentration range of iron(III) from 3.0 × 10–6 to 1.3 × 10–2 M with a detection limit of 1.2 × 10–6 M. The sensor has fast response time, good reproducibility and excellent selectivity toward iron(III) ion with respect to many alkali, alkaline earth, transition and heavy metal ions. The potentiometric response of the sensor is independent of pH of the test solution in the range of 2.5–4.5. The applicability of the sensor was investigated by the determination of iron(III) concentration in pharmaceutical, biological and water samples.

Synthesis, spectral characterization, and DNA binding studies of Co(II), Ni(II), Cu(II) and Zn(II) complexes of Schiff base 2-((1H-1,2,4-triazol-3-ylimino)methyl)-5-methoxyphenol

A Schiff base ligand HL has been synthesized by the condensation of an equimolar amount of 2-hydroxy-4-methoxybenzaldehyde and 3-amino-1,2,4-triazole and characterized by elemental analysis, IR, 1H NMR, 13C NMR and ESI-mass spectrometry. The metal complexes 1–4 have been synthesized by the reaction of ligand with Co(II), Ni(II), Cu(II) and Zn(II) chlorides in ethanol in the molar ratio 1:1. All the metal complexes 1–4 were characterized by elemental analysis, molar conductance, electronic spectra, IR, and EPR spectra. TGA has been done to check the stability of the synthesized Schiff base ligand HL and its metal complexes 1–4. Spectral data reveals that the ligand HL acts as uninegative tridentate for metal complexes. The geometries of synthesized ligand and its metal complexes were optimized by using Gaussian 09 W program. On the basis of spectral characterization, octahedral geometry has been allocated for Co(II), tetrahedral for Ni(II), tetragonal for Cu(II) and tetrahedral for Zn(II) complexes. The DNA binding studies of metal complex have been investigated by UV absorbance, fluorescence and CD spectrometry. UV absorbance binding studies show that metal complex 1–3 could bind to ctDNA significantly and the results obtained were consistent with the fluorescence and CD spectra.

Spectroscopic exploration and molecular docking analysis on interaction of synthesized schiff base ligand with serum albumins

The present article reports detailed characterization about interaction between a synthesized Schiff base ligand and serum proteins viz., bovine serum albumin (BSA) and human serum albumin (HSA). The entire interactive phenomena have been diligently investigated through multi spectroscopic studies and quantum mechanical calculations involving density functional theory (DFT) and molecular docking analysis. The ligand induced quenching of intrinsic tryptophenyl fluorescence of the proteins exhibits intriguing characteristics on Stern−Volmer analysis (an upward curvature instead of conforming to a linear regression). Thus, an extensive time-resolved fluorimetric analysis of the quenching process has been carried out in conjugation with temperature-dependent fluorescence quenching studies to divulge the actual quenching mechanism. Using both of these steady state and time resolved fluorescence studies, static and dynamic quenching constants for both the proteins have been calculated appropriately. The thermodynamic parameters, ΔH, ΔS and ΔG for the binding phenomenon as evaluated on the basis of van't Hoff relationship expose the predominance of van der Waal or hydrogen bonding interaction underlying the binding process. The ligand induced modification of native protein conformations have been unmasked using synchronous fluorescence spectra and circular dichroism spectroscopy. Quantum mechanical calculations involving density functional theory (DFT) and molecular docking analysis have been carried out to emphasize the probable binding location of the ligand in protein backbone. Thus this work demonstrates a total assessment of Schiff base-protein interaction.

Crystal structure, optical properties, DFT analysis of new morpholine based Schiff base ligands and their copper(II) complexes: DNA, protein docking analyses, antibacterial study and anticancer evaluation

New morpholine derived Schiff base ligands (HL1 and HL2) and their Cu(II) complexes [Cu(L1)2] (1) and [Cu(L2)2] (2) have been synthesized and characterized by 1H NMR, IR, UV–Vis, EPR studies and cyclic voltammetric analyses. Single crystal X-ray crystallography studies confirm the structure of newly synthesized Schiff base ligands HL1and HL2. The ground state electronic structures of Cu(II) complexes 1 and 2 have been investigated by DFT/B3LYP theoretical analysis with 6-31G (d,p) and LANL2DZ basis set. The affinity towards DNA and protein molecules have been evaluated using computational docking analysis and complex 2 expose significant binding ability with DNA as well as protein due to its towering hydrophobicity. Consequently, complex 2 reveals superior antibacterial activity against some bacterial species besides anticancer activity on human breast cancer (MCF-7) cells than complex 1 and Schiff base ligands (HL1 and HL2). These preliminary investigations strongly recommended that complex 2 can be used as a better antibacterial plus anticancer agent.

Antimicrobial activity of Schiff Base of 2-Amino 5-Nitrothiazole and its Copper complex

In an attempt to find out a new class of antimicrobial agents new schiff base ligand of 2-amino 5-nitro thiazole and its copper complex were prepared. The Microwave assisted synthesis was carried out by condensation of 2-amino 5-nitro thiazole and substituted salicyldehyde. The newly synthesized schiff base ligand and its copper complex were tested against representatives of gram-positive (Staphylococcus aureus, Bacillus subtilis) and gram- negative bacteria (E. coli, Pseudomonas putida) and fungi (Candida albicans, Aspergillus niger) by disc diffusion method.

Synthesis, Characterization, and Biological Activity of Organotin(IV) Complexes with Schiff Bases

The synthesized Schiff base ligands H2L1, N,N'-bis(2-hydroxybenzylidene)1,2-diaminobenzene, and H2L2, N,N'-bis(2-hydroxybenzylidene)hydrazine, reacted with Alk2SnCl2 to give organotin(IV) complexes 1–10. The products were characterized by elemental analysis, FTIR, 1H and 13C NMR, and mass spectrometry. All organotin(IV) derivatives with [O,N,O] donor ligands retained their 5-coordinated geometry in solid state and solutions. Most of synthesized complexes exhibited significant antibacterial activity. Cytotoxicity was also tested by using the brine shrimp (Artemia salina) lethality bioassay.

Syntheses, characterization, superoxide dismutase, antimicrobial, crystal structure and molecular studies of copper (II) and nickel (II) complexes with 2-((E)-(2, 4-dibromophenylimino) methyl)-4-bromophenol as Schiff base ligand

Three new copper (II) and nickel (II) complexes viz. [Cu(L)2](1a), [Cu(L)2](1b) and [Ni(L)2].DMF(2), where HL = 2-((E)-(2, 4-dibromophenylimino) methyl)-4-bromophenol, have been synthesized and characterized by using various physico-chemical and spectroscopic techniques. The crystal structures of Schiff base (HL) and their metal complexes (1a), (1b) and (2) were determined by single crystal X-ray diffraction. IR and UV–Vis spectra and magnetic susceptibility measurements agree with the observed crystal structures. The crystallographic and spectroscopic studies confirmed four coordinate environments around the metal (II) ions. The synthesized Schiff base ligand (HL) crystallizes in the orthorhombic system of the space group Pbca. Complex (1a) of HL was crystallized in the monoclinic system of the space group P21/c, a = 10.1712(9) Å, b = 10.9299(10) Å,c = 12.7684(11) Å,α = 90̊,β = 104.649(2)̊, γ = 90̊ and Z = 2 whereas complex (1b) and (2) crystallized in the triclinic system of the space group P-1, a = 11.499(5)Å, b = 11.598(5)Å, c = 12.211(5)Å, α = 98.860(5), β = 115.653(5),γ = 100.906(5) and Z = 2 for (1b), a = 9.080(6) Å, b = 9.545(8)Å, c = 9.545(8)Å, α = 101.43(4)º,β = 99.63(3)̊, γ = 117.71(2)º and Z = 1 for (2). The synthesized ligand (HL) was behaved as monobasic bidentate Schiff base ligand having N and O donor sites. The electron paramagnetic resonance spectra indicate a dx2–y2ground state (g|| > g⊥> 2.0023) for (1a) and (1b). Copper (II) complexes display X-band EPR spectra in 100% DMSO and 77 K, giving indicating dx2–y2ground state. Superoxide dismutase-like activities of HL and its complexes were investigated by nitrobluetetrazolium chloride-DMSO assay and IC50 values were evaluated. These complexes were also tested for their in vitro antimicrobial activities against two bacteria (E. coli and Salmonella typhi) and two fungi (Pencillium, Aspergillus sp.) comparing with the Schiff base. The antimicrobial results showed that the complexes were more biologically active compounds to the Schiff base (HL).

The effect of metal and substituent on DNA binding, cleavage activity, and cytotoxicity of new synthesized Schiff base ligands and Zn(II) complex

New water soluble Schiff base ligands [N,Nʹ-bis{5-[(triphenylphosphonium percholorate)-methyl]salicylidine}-1,3-diamino-2-propanol] (L1) and [N,Nʹ-bis(salicylidine)-1,3-diamino-2-propanol] (L2) and zinc (II) complex of L1: [N,Nʹ-bis{5-[(triphenylphosphonium percholorate)-methyl]salicylidine}-1,3-diamino-2-propanol]Zn(II) were synthesized and characterized by elemental analysis, FT-IR, 1HNMR and UV–Vis spectroscopy. In vitro DNA binding of the compounds were investigated by UV–Vis absorption spectroscopy, viscosity measurement, cyclic voltammetry, fluorescence spectroscopy, and gel electrophoresis. The present study aimed to investigate the effect of metal and substituent on DNA binding, cleavage activity and cytotoxicity of new synthesized Schiff base ligands and Zn(II) complex. The order of DNA binding affinity (Kb) calculated from the absorption spectroscopy was: ZnL1 > L2 > L1. Molecular docking studies explore more details on the mode of binding and binding energies. Although the compounds revealed strong DNA binding affinity but electrophoresis studies don't show any effects on the DNA structure and single or double strand breaks. The cytotoxicity experiments against human Hepatoma (HepG2) showed the order: L1 > ZnL1 > L2.

Palladium(II) complexes with diaminomaleonitrile-based Schiff-base ligands: Synthesis, characterization and application as Suzuki–Miyaura coupling catalysts

The characterization of synthesized Schiff base ligands (L1–L5); (where L1=N-salicyliden- 2,3-diamino-cis-2-butenedinitrile, L2=3- methoxy-N-salicyliden-2,3-diamino-cis-2-butenedinitrile, L3=5-bromo-N-salicyliden-2,3-diamino-cis-2-butenedinitrile, L4=5-nitro-N-salicyliden-2,3-diamino-cis-2-butenedinitrile, and L5=5-methoxy-N-salicyliden-2,3-diamino-cis-2-butenedinitrile) and their palladium complexes [PdL(PPh3)] (L1–L5) were carried out by FT-IR, UV–vis, 1H NMR, 13C NMR and elemental analysis. The coordination geometry of [PdL3(PPh3)] was determined by single crystal X-ray crystallography. In this structure the palladium center was in a partially distorted NNOP square planar coordination environment. The catalytic potential of the synthesized complexes was evaluated in Suzuki–Miyaura cross-coupling reaction by choosing different arylhalides and phenylboronic acid. The results showed that arylhalides with electron withdrawing substituents were more appropriate in this reaction. In all cases, the desired product of cross coupling Suzuki reaction was the major product. It is also worth to mention that the product of homo-coupling reaction was also observed as a minor product. In this regards, a blank reaction with just phenylboronic acid was performed and the results showed the occurrence of the homo-coupling product in a good yield.

English

A series of several diazenyl schiff base molecules were designed and synthesized through azo coupling of diazotised primary amines with the novel synthesized schiff base ligand (E)-N-((2-chloroquinolin-3-yl)methylene)-4-phenylthiazol-2-amine. All the synthesized molecules have been characterized by different spectral techniques for their structural confirmation. The results of in vitro antioxidant activity of the molecules by 2,2-diphenyl-1- picryl hydrazyl (DPPH) assay method revealed that the molecules (NZ)-N-(((4-chlorophenyl) diazenyl) (2-chloroquinolin-3-yl) methylene) -4- phenylthiazol -2-amine (5A) and 4-(((Z)-(2-chloroquinolin-3-yl)(4-phenylthiazol-2-ylimino)methyl)diazenyl)phenol (5E) have shown potential free radical scavenging activity. Key words: Schiff base, diazenyl, spectral, antioxidant.

Synthesis, spectral, thermal and biological studies of mixed ligand complexes with newly prepared Schiff base and 1,10-phenanthroline ligands

A series of mixed ligand complexes were prepared from the Schiff base (L1) as a primary ligand, prepared by condensation of oxamide and furan-2-carbaldehyde, and 1,10-phenanthroline (1,10-phen) as a secondary ligand. The Schiff base ligand and its mixed ligand chelates were characterized based on elemental analysis, IR, 1H NMR, thermal analysis, UV–Visible, mass, molar conductance, magnetic moment. X-ray diffraction, solid reflectance and ESR also have been studied. The mixed ligand complexes were found to have the formulae of [M(L1) (1,10-phen)]Clm.nH2O (M = Cr(III) and Fe(III) (m = 3) (n = 0); M = Mn(II), Cu(II) and Cd(II) (m = 2) (n = 0); and M = Co(II) (m = 2) (n = 1), Ni(II) (m = 2) (n = 2) and Zn(II) (m = 2) (n = 3)) and that the geometrical structure of the complexes were octahedral. The parameters of thermodynamic using Coats–Redfern and Horowitz–Metzger equations were calculated. The synthesized Schiff base ligand, 1,10-phenanthroline ligand and Their mixed ligand complexes were also investigated for their antibacterial and antifungal activity against bacterial species (Gram−Ve bacteria: Pseudomonas aeruginosa and Escherichia coli) and (Gram + Ve bacteria: Bacillus subtilis and Streptococcus pneumonia) and fungi (Aspergillus fumigates and Candida albicans). The anticancer activity of the new compounds had been tested against breast (MFC7) and colon (HCT-116) cell lines. The results showed high activity for the synthesized compounds.

SYNTHESIS, SPECTRAL CHARACTERIZATION AND ANTICANCER EVALUATION OF NEW DIAZENYL SCHIFF BASE DERIVATIVES

A series of several diazenyl Schiff base derivatives were designed and synthesized through azo coupling of diazotised primary amines with the novel synthesized Schiff base ligand (E)-N-((2-chloroquinolin-3-yl) methylene)-4-phenylthiazol-2-amine. All the synthesized compounds have been analysed by different spectral techniques such as elemental analysis, 1H NMR, FT-IR, UV-Vis and LC-MS for their structural confirmation. The above conjugates have been studied for their solvent effects by treating them with different solvents. The results of in vitro cytotoxic study of the synthesized compounds against MCF 7 (human breast cancer cell line) and K562 (Chronic Myeloid Leukemia cell line) revealed that some of the compounds show cytotoxic effect. However, the compounds (NZ)-N-(((4-bromo-3-methylphenyl) diazenyl) (2-chloroquinolin-3-yl) methylene)-4-phenylthiazol-2-amine: (5d) and 4-(((Z)-(2-chloroquinolin-3- yl)(4-phenylthiazol-2-ylimino)methyl)diazenyl)phenol (5e) showed potent cytotoxic activity in comparison to other compounds against MCF 7. Corroborating the results of anticancer activity, it is found to be observed that the compound 4- (((Z)- (2-chloroquinolin-3-yl) (4-phenylthiazol-2-ylimino)methyl) diazenyl) phenol (5e) showed excellent anticancer activity against MCF 7, which is further justified by the apoptosis study through Annexin V-FITC/PI analysis.

Preparation, geometric structure, molecular docking thermal and spectroscopic characterization of novel Schiff base ligand and its metal chelates

The condensation of o-benzoyl benzoic acid and 4-aminoantipyrine resulted in the formation of novel Schiff base ligand (HL) with the IUPAC name 2-(((1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)imino)(phenyl)methyl)benzoic acid. The synthesized Schiff base ligand and its complexes with M(II)/(III) transition elements (Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II)) were characterized by elemental, magnetic susceptibility, molar conductivity, spectroscopic (1H NMR, mass, UV–visible, FTIR, ESR), thermal and X-ray powder diffraction. The data showed that the complexes had composition of the MHL type. The diffused reflectance spectra, magnetic susceptibility and ESR spectral data of the complexes confirm an octahedral geometry around metal ions. The thermal analysis data revealed the decomposition of the complexes in three to five successive decomposition steps within the temperature range of 30–1000°C, and the activation thermodynamic parameters were reported. The molecular structures of the Schiff base ligand and its Mn(II) and Zn(II) metal complexes are optimized theoretically, and the quantum chemical parameters are calculated. In order to predict the binding between o-benzoyl benzoic acid, 4-aminoantipyrine and HL ligand with the Escherichia coli bacterial RNA (4p20) receptor, molecular docking was carried out. The in vitro antimicrobial screening of the newly synthesized compounds was tested against different bacterial and fungal organisms. The results showed that the metal complexes have biologically activity more than the new Schiff base ligand against the tested organisms. The Schiff base ligand and its complexes were also screened for their anticancer activity against breast cancer cell line (MCF7). The Mn(II), Cr(III) and Cd(II) complexes were found to have low IC50 values which support the possibility of using them as cytotoxic agents and hence might become good anticancer agent in clinical trials.

A copper chelate induces apoptosis and overcomes multidrug resistance in T-cell acute lymphoblastic leukemia through redox imbalance and inhibition of EGFR/PI3K/Akt expression.

T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive form of cancer and the therapeutic outcome for T-ALL patients remains poor. Thus innovative therapeutic strategies with less toxic drugs are of immense need. Moreover combinational effect of redox imbalance with modulated EGFR/PI3K/Akt axis in T-ALL is still elusive. To explore more effective drugs we developed and characterized 5-SMAG, Cu-5-SMAG and Cu-OBPHA complexes by different spectroscopic methods and revealed that introduction of methoxy group and copper to the previously synthesized Schiff base ligand, NG can efficiently target leukemia by sparing the normal cells and overcomes MDR in T-ALL through induction of caspase3 dependent apoptosis as assessed by MTT, Cell-cycle, Annexin-V and caspase3 activation assay. However the ligand 5-SMAG fails to exert significant cytotoxicity. Moreover introduction of copper does not increase the efficacy of the drug molecule as Cu-OBPHA fails to exert significant effect compared to Cu-5-SMAG. Moreover Cu-5-SMAG targets T-ALL cells more than Cu-OBPHA because Cu-5-SMAG generates greater extent of redox imbalance compared to Cu-OBPHA and when this redox imbalance is reduced by application of NAC and PEG-Catalase, highest abrogation of apoptosis is observed following Cu-5-SMAG treatment In addition, Cu-5-SMAG significantly down-regulates the activation and expression of EGFR1, Akt and PI3K in drug-resistant T-ALL cells. Furthermore Cu-5-SMAG significantly increases the life-span of doxorubicin resistant and sensitive Ehrlich ascites carcinoma bearing Swiss albino mice without inducing any significant systemic toxicity compared to 5-SMAG and Cu-OBPHA treatment. Therefore typical architect of Cu-5-SMAG made it a promising new anti-leukemic agent irrespective of the MDR phenotype.

Synthesis, Spectral Characterization and Antimicrobial Studies of Co(II) Complexes with Tetradentate Schiff bases Derived from Ortho-Phthalaldehyde

A series of cobalt (II) complexes have been synthesized with Schiff bases derived from ortho-phthalaldehyde and various amines in aqueous methanol solution. The newly synthesized Schiff bases and their Co (II) complexes have been characterized by elemental analysis, magnetic susceptibility, thermal, conductance measurements, mass, IR, electronic, 1H,13C-NMR spectral techniques. These ligands act as tetradentate species and coordinate to the metal center through the different potential donor atoms such as N, O and S. The probable octahedral structures have been assigned to these complexes. All the synthesized Schiff base ligands and Co(II) metal complexes have also been screened for their antimicrobial activities and metal complexes found to be more active than respective Schiff-base ligands.

Novel bio-essential metal based complexes linked by heterocyclic ligand: Synthesis, structural elucidation, biological investigation and docking analysis

New series of bio-essential metal based complexes linked by Schiff base ligand (L) and 2,2′-bipyridine (bpy) have been synthesized and characterized by diverse spectral techniques such as elemental analysis, magnetic susceptibility, molar conductivity measurements, FT-IR, UV–Vis., 1H NMR, 13C NMR, EPR and Mass. The spectral data suggest that the metal complexes espouse octahedral geometry around the metal ions. Interactions of the complexes with CT DNA have been explored by electronic absorption, ethidium bromide displacement assay, viscosity measurements, cyclic voltammetry and differential pulse voltammetry in order to evaluate the possible DNA-binding mode and to calculate the corresponding DNA-binding constants. The DNA interaction studies propose that the intercalative mode of interaction and the complexes exhibit oxidative cleavage of pUC19 DNA in the presence of hydrogen peroxide as activator. The synthesized Schiff base ligand and its metal complexes have been screened for anti-microbial activity by micro dilution method against two Gram-positive bacteria (Staphylococcus aureus and Bacillus subtilis), two Gram-negative bacteria (Escherichia coli and Salmonella typhi) and three fungi strains (Fusarium solani, Aspergillus niger and Candida albicans) revealing that the complexes are good anti-pathogenic agents than the ligand. Moreover, molecular docking analysis has been performed to confirm the nature of binding of the complexes with DNA.

Dielectrical properties and conduction mechanism of quinoline Schiff base and its complexes

The synthesized Schiff base ligand 8-hydroxyquinoline-7-formylidene-4-amino-1-phenyl-2,3-dimethylpyrazolin-5-one (SQL) and its Cu(II), VO(IV) and UO2(II) complexes are characterized by various physicochemical techniques. The thermal properties, dielectric properties, alternating current conductivity (σ ac) and conduction mechanism of SQL and its complexes (1–6) are investigated in the frequency range of 0.1–100 kHz and temperature range 298–583 K. The temperature and frequency dependence of the real and the imaginary part of the dielectric constant are studied. The values of the thermal activation energy of conduction mechanism for SQL and its complexes under investigation are calculated at different test frequencies, and found to be in the range 0.0023–0.0798 eV for ΔE 1 and 0.0897–1.296 eV for ΔE 2. The ac conductivity, σ ac, is related to the frequency as σ ac α ω S where the behavior of the exponent S with temperature determines the operating conduction mechanism. The correlated barrier hopping model is found to be the dominant conduction mechanism for SQL and its complexes (1) and (3–5), and the values of the maximum barrier height (W m) are calculated for SQL and its complexes (1) and (3–5). The quantum–mechanical tunneling is the dominant conduction mechanism for complexes (2) and (6).

Synthesis and Characterization of Cr(III), Mn(III), Fe(III), VO(IV), Zr(IV) and UO2(VI) Complexes of Schiff Base Derived from Isonicotinoyl Hydrazone.

2-hydroxy-5-chloro-3-nitroacetophenone isonicotinoyl hydrazone as a Schiff base ligand and its complexes with Cr(III), Mn(III), Fe(III), VO(IV), Zr(IV) and UO2(VI) metal ions have been synthesized. The ligands as well as their metal complexes were well characterized using various physicochemical techniques such as elemental analyses, molar conductance measurements, magnetic measurements, thermal analysis, electronic and IR spectral studies. On the basis of these studies, square pyramidal stereochemistry for Mn(III) and VO(IV) complexes while octahedral stereochemistry for all the other complexes have been suggested. The complexes were found to be stable up to 60-70° and thermal decomposition of the complexes ended with respective metal oxide as a final product. The thermal data have been analyzed for kinetic parameters using Broido and Horowitz-Metzger methods. The synthesized Schiff base ligand and its complexes were also tested for their antimicrobial activity using various microorganisms.