ONNO Donor Research Articles

Synthesis, DFT calculation, DNA-binding, antimicrobial, cytotoxic and molecular docking studies on new complexes VO(II), Fe(III), Co(II), Ni(II) and Cu(II) of pyridine Schiff base ligand

A new H2L ligand (6, 6′-(pyridine-2, 6-diylbis(azan-1-yl-1-ylidene))bis(methan-1-yl-1-ylidene)bis(2-ethoxyphenol) was obtained from the reaction of 2, 6- diamino pyridine and 3- ethoxy salicyaldehyde in 1:2 molar ratio and fully characterized using elemental analyses and spectroscopic tools. The reaction of a ligand with the different metal salts yields five new complexes CuL, CoL, NiL, FeL, and VOL. The new complexes were identified according to the results of elemental analyses, IR and UV–vis spectra, magnetic moment, molar conductance and thermal analyses (TGA). From the conductivity data, it is deduced that all complexes are non-electrolytes. FT-IR spectra displayed that the Schiff base ligand coordinated to the metal ions in a manner with ONNO donor sites, the nitrogen atom of the pyridine ring, the nitrogen of one azomethine group and two oxygen atoms of the two phenolic OH groups. The results of electronic spectra and magnetic susceptibility confirmed octahedral geometry of FeL complex and square pyramidal geometry for CoL, CuL and VOL and square planar for NiL. The electronic structure of H2L ligand and its complexes were investigated theoretically at the DFT-B3LYP-311 G** level of the theory. FT-IR spectra established the involvement of pyridine nitrogen in the coordination process. The presence of coordinated water molecules inside the coordination sphere of the complexes CoL, CuL and FeL are supported by TGA studies. The antimicrobial activities of the ligand and its complexes were determined against two Gram-positive bacteria (B. subtitles and S. aureus) and two Gram-negative (E. coli and P. vulgaris) and two fungus (Candida albicans and Aspergilla’s fumigates). The results showed that the complexes behaved as better antimicrobial agents than the ligand, VOL complex shows exceptional antimicrobial efficacy. The order of increasing the antibacterial and antifungal potency is H2L < NiL < CuL < CoL < FeL < VOL. The binding of the complexes with CT-DNA was followed using electronic absorption, viscosity and gel-electrophoresis measurements. These studies confirmed that the complexes bind to CT-DNA through a groove binding mode with certain affinities (Kb = 6.25 × 105, 5.50 × 105, 3.20 × 105, 2.50 × 105 and 1.52 × 105 for CuL, FeL, VOL, NiL, and CoL respectively). Moreover, cytotoxic effect against hepatocellular carcinoma cell line (HEP-G2) was screened. The IC50 values of the ligand and complexes suggest that the compounds possess very good cytotoxic activity and follow the order: CuL >FeL>VOL>NiL>CoL > H2L. These results strongly agree with results of binding constant of CT-DNA with different metal complexes.

Synthesis Characterization and Biological Activities of an Enamine Derivative and Its Coordination Compounds

The medicinal uses and applications of metal complexes are of increasing clinical and commercial importance; this is as a result of some level of success achieved so far. In this regard, novel enamine free-base ligands were synthesized by the condensation of terephthalaldehyde and 2-(methylamino)ethanol. This afforded a dinegative ONNO donor enamine, free base, characterized using 1H and 13C NMR, Fourier-transformed infrared and UV-vis spectroscopy. Coordination compounds of the enamine were also synthesized using Cu(II), Ni(II), Co(II) and VO(IV) ions. These complexes were characterized by electronic, IR spectrophotometry, mass spectrometry, magnetic susceptibility and EDX. The compounds were thereafter evaluated for their antimicrobial and cytotoxic activities. The data obtained were supportive of an octahedral geometry for the Cu(II) complex, a square-pyramidal geometry for the vanadium complex and a 4-coordinate square-planar geometry for both the cobalt and nickel complexes. The magnetic susceptibility data revealed that the complexes are magnetically dilute and mononuclear with exception of the cobalt complex. The ligands and the complexes did not exhibit significant antimicrobial and cytotoxic assays, indicative of the nontoxicity of the ligand and complexes.

Preparation and Spectroscopic Characterization of Polymer-Supported Transition Metal Complexes

Novel polystyrene supported mixed Schiff base (PSCH2–LH2) and its coordination compounds with copper(II) and zirconium(IV) have been synthesized. PSCH2–LH2 has been synthesized by the reaction of chloromethylated polystyrene crosslinked with divinylbenzene (PSCH2–Cl) and the Schiff base (LH2) derived from 3-formylsalicylic acid, propylenediamine and acetylacetone. The polystyrene supported coordination compounds are of the types: [PSCH2–LCu] and [PSCH2–LZr(OH)2·DMF]. They have been synthesized by the reaction of PSCH2–LH2 and the metal salt in DMF. The coordination compounds have been characterized on the basis of elemental analyses, IR, reflectance, ESR spectral and magnetic susceptibility measurements. The shifts of the ν(C=N) (azomethine), ν(C–O) (phenolic) and ν(C–O) (enolic) stretches indicate the ONNO donor behaviour of PSCH2–LH2. The polystyrene supported Cu(II) compound is square planar and Zr(IV) compound is pentagonal bipyramidal. The coordinated solvent molecules are completely lost from metal bound coordination compound by heating them at definite temperature in an air oven for 3 h. The compound, PSCH2–LCu is paramagnetic, while PSCH2–LZr(OH)2·DMF is diamagnetic.

Preparation, Characterization and Biological Activities of some Unsymmetrical Schiff Bases Derived from m-phenyelenediamine and their Metal Complexes

Unsymmetrical Schiff bases H2L1 = [ 1- (( E )-(( 3-((( E) -2- hydroxybenzylidene) amino)phenyl)imino)methyl) naphthalene-2-ol] and H2L2 = [1-((E)-((3-(((E)-1-(2-hydroxphenyl) ethylidene ) amino ) phenyl ) imino ) methyl ) naphthalene - 2 – ol ] which derived from m - phenylenediamine and 2-hydroxynaphthaldehyde and then with salicyaldehyde or 2- hydroxyacetophenone, and their complexes of the type [M 2Ln 2], where n = 1, 2 and M = Mn(II), Co(II), Ni(II) and Cu(II) have been synthesized. Adduct complexes of the type [M2Ln 2 (py)4] were also prepared in (1 : 4)(complex : py) molar ratio. The complexes and adducts were characterized by elemntal analysis (C. H. N), metal content, (IR, UV- v.s, 1H-NMR) spectroscopy, conductivity and magnetic measurements. The resulted data suggested that the Schiff bases containing ONNO donor atoms acts as dibasic tetradendetate ligands through coordinated with metal ions. Conductivity data in DMSO solution showed that all complexes are non- electrolyte. Magnetic moment and electronic spectra data indicat that the complexes have either tetrahedral or octahedral geometry while [Ni2 Ln 2] complexes have square planer geometry. The legends and their complexes were screened for antibacterial activity against Staphylococcus- aureus and Escherichia coli. The ligands and their complexes showed some biological activities .

Synthesis, characterization and catalytic activity of dioxidouranium(VI) complexes of ONNO tetradentate Mannich bases

The reaction of dibasic tetradentate ONNO donor Mannich bases, derived from ethylenediamine and 2,4–di–tert–butylphenol (H2L1) (I), 2,4–di–methylphenol (H2L2) (II), 2–tert–butyl–4–methylphenol (H2L3) (III) and 2,4–di–chlorophenol (H2L4) (IV), with UVIO2(MeCOO)2·2H2O in a 1:1 M ratio in refluxing MeOH gave the corresponding mononuclear trans-dioxidouranium(VI) complexes of the type trans-[UVIO2L(MeOH)] (H2L = H2L1 to H2L4) (1–4). The synthesized complexes are stable in air, reddish-brown in color and soluble in most solvents. These complexes are characterized by elemental analysis, various spectroscopic (FT-IR, UV/Vis, 1H and 13C NMR) techniques and single-crystal X-ray analysis of 3 and 4. The complexes adopt distorted pentagonal bipyramidal geometry around the metal centre. The ligand acts as tetradentate, coordinating through two phenolato oxygen and two imino nitrogen atoms; two oxido groups are trans to each other. These complexes are used as catalysts to study the oxidative bromination of thymol and styrene. The catalytic oxidative bromination of thymol resulted in the formation of three products namely, 2-bromothymol, 4-bromothymol and 2,4-dibromothymol while oxidative bromination of styrene gave two products, 2-bromo-1-phenylethane-1-ol and 1-phenylethane-1,2-diol. In order to find out the optimized reaction conditions for the fixed concentration (10 mmol) of substrate, effects of different amounts of catalyst, KBr, HClO4, and oxidant (H2O2) have been investigated. Under the optimized reaction conditions, all the complexes have shown good catalytic potentials for the oxidative bromination of substrates, establishing the functional similarity to vanadium dependent haloperoxidases. Changes in the UV–visible absorption spectra of dioxidouranium(VI) complexes upon addition of H2O2 suggest the formation of the corresponding oxidoperoxidouranium(VI) complexes.

Oxotitanium(IV) complexes of some bis‐unsymmetric Schiff bases: Synthesis, structural elucidation and biomedical applications

A number of oxotitanium(IV) complexes of the type TiOL with bis‐unsymmetric dibasic tetradentate Schiff base (LH2) containing ONNO donor atoms have been synthesized. Mono‐Schiff base (OPD‐HNP) was prepared by the condensation of 1:3 molar ratio of 2‐hydroxy‐1‐naphthaldehyde (HNP) with o‐phenylenediamine (OPD). Dibasic unsymmetric tetradentate diamine Schiff bases were prepared by the reaction of OPD‐HNP with 2‐hydroxyacetophenone, 2‐hydroxypropeophenone, benzoylacetone, acetylacetone and ethylacetoacetate. Further, titanylacetylacetonate was reacted with these ligands to obtain their metal complexes. On the basis of analytical and physiochemical data, the formation of complexes as TiOL was suggested having square pyramidal geometry. Quantum mechanical approach also confirmed this geometry. The assessment of the synthesized ligands and their complexes showed that some behave as good inhibitors of mycelial growth against selected phytopathogic fungi but weak inhibitors against some selected bacteria. A few of them also showed antioxidant properties.

Two dinuclear oxidovanadium(V) complexes of N2O2 donor amine-bis(phenolate) ligands with bromo-peroxidase activities: Kinetic, catalytic and computational studies

Two dinuclear oxidovanadium(V) complexes [LiVVO(µ2-O)VVO(Li)] (i = 1, H2L1, complex 1 and i = 2 for H2L2, complex 2) of two ONNO donor amine-bis(phenolate) ligands have been synthesized and characterized by X-ray diffraction studies which exhibited distorted octahedral geometry around each V center. In MeCN the complexes exist as dimers as indicated by HRMS studies, however, in the presence of 2 or more equivalents of H+ the dimers turned into monomers, ([LiVV = O]+ which exists in equilibrium with ([LiVV = OH]2+ and evidenced from the shift in λmax from 685 nm to 765 nm for complex 1 and 600 to 765 nm for complex 2. The complexes 1 and 2 efficiently catalyze the oxidative bromination of salicylaldehyde in the presence of H2O2 to produce 5-bromo-salicylaldehyde as the major product with TONs 405 and 450, respectively in the mixed solvent system (H2O:MeOH:THF = 4:3:2, v/v). The kinetic analysis of the bromide ion oxidation reaction indicates a mechanism which is first order in peroxidovanadium complex and bromide ion and limiting first-order on [H+]. The evaluated kBr and kH values are (8.82 ± 0.35) and (65.0 ± 2.23) M−1 s−1 for complex 1 and (6.74 ± 0.19) and (61.87 ± 2.27) M−1 s−1 for complex 2, respectively. The Ka of protonated species ([LiVV = OH]2+ are: Ka = (4.3 ± 0.40) × 10−3 (pKa = 2.37) and (4.7 ± 0.50) × 10−3 (pKa = 2.33) for complex 1 and 2 respectively. On the basis of the chemistry displayed by these model compounds, a mechanism of bromide oxidation and a tentative catalytic cycle have been framed which might be relevant to vanadium haloperoxidase enzymes and supported by DFT calculations.

Mono- and dinuclear oxidovanadium(v) complexes of an amine-bis(phenolate) ligand with bromo-peroxidase activities: synthesis, characterization, catalytic, kinetic and computational studies

The mono- and dinuclear oxidovanadium(v) complexes [VVO(L1)(Cl)] (1) and [L1VVO(μ2-O)VO(L1)] (2) of ONNO donor amine-bis(phenolate) ligand (H2L1) were readily synthesized by the reaction between H2L1 and VCl3.(THF)3 or VO(acac)2 in MeOH or MeCN, respectively, and then characterized through mass spectroscopy, 1H-NMR and FTIR techniques. Both the complexes possess distorted octahedral geometry around each V centre. Upon the addition of 1 equivalent or more acid to a MeCN solution of complex 1, it immediately turned into the protonated form, which might be in equilibrium as: [L1ClVV[double bond, length as m-dash]OH]+ ↔ [L1ClVV-OH]+ (in the case of [L1ClVV[double bond, length as m-dash]OH]+ oxo-O is just protonated, whereas in [L1ClVV-OH]+ it is a hydroxo species), with the shift in λmax from 610 nm to 765 nm. Similar was the case for complex 2. The complexes 1 and 2 could efficiently catalyze the oxidative bromination of salicylaldehyde in the presence of H2O2 to produce 5-bromo salicylaldehyde as the major product with TONs of 405 and 450, respectively, in the mixed solvent system (H2O : MeOH : THF = 4 : 3 : 2, v/v). The kinetic analysis of the bromide oxidation reaction indicated a first-order mechanism in the protonated peroxidovanadium complex and a bromide ion and limiting first-order mechanism on [H+]. The evaluated kBr and kH values were 5.78 ± 0.20 and 11.01 ± 0.50 M-1 s-1 for complex 1 and 6.21 ± 0.13 and 20.14 ± 0.72 M-1 s-1 for complex 2, respectively. The kinetic and thermodynamic acidities of the protonated oxido species of complexes 1 and 2 were pKa = 2.55 (2.35) and 2.16 (2.19), respectively, which were far more acidic than those reported by Pecoraro et al. for peroxido-protonation instead of oxido protonation. On the basis of the chemistry observed for these model compounds, a mechanism of halide oxidation and a detailed catalytic cycle are proposed for the vanadium haloperoxidase enzyme and these were substantiated by detailed DFT calculations.

Oxygen atom transfer between DMSO and benzoin catalyzed by cis-dioxidomolybdenum(vi) complexes of tetradentate Mannich bases

Dioxidomolybdenum(vi) complexes of tetradentate ONNO donor Mannich base ligands for the catalytic oxygen atom transfer between benzoin and DMSO are reported.

Synthesis, crystal structure and magnetic properties of a dinuclear and a trinuclear Ni(II) complexes derived from tetradentate ONNO donor Mannich base ligands

Two complexes, [Ni2(HL1)2(NCS)2]·CH2Cl2 (1) and [Ni3(L2)2(NCS)2(H2O)2]·CH3CN (2) have been synthesized using two different tetradentate ONNO donor Mannich base ligands N,N′-bis(3,5-dimethyl-2-hydroxybenzyl)-N,N′-dimethylethylenediamine(H2L1) and N,N′-bis(3-methoxy-5-methyl-2-hydroxybenzyl)-N,N′-dimethylethylenediamine(H2L2), respectively. Compound 1 is μ1,1 isothiocyanato bridged dinuclear compound whereas compound 2 is phenoxido bridged trinuclear compound with SCN− as a terminal ligand. In compound 1 one of the two phenoxido oxygen atoms from each ligand remains protonated and hence makes the compound electrically neutral. X-ray-crystallography reveals that the two Ni(II) centres in compound 1 are in a distorted octahedral geometry and N atom of each of the two SCN− groups bridge the two metal centres. On the other hand, compound 2 possesses a centrosymmetric trinuclear structure where two distorted square pyramidal terminal Ni(II) centres are connected to a central octahedral Ni(II) via phenoxido bridge. Here SCN− ligand occupies the axial positions of the terminal Ni(II) centres by coordinating through N atom. Variable temperature magnetic susceptibility measurements of solid samples reveal that the Ni(II) paramagnetic centres in both 1 and 2 are antiferromagnetically coupled with J values of −30.66cm−1 and −5.92cm−1 for 1 and 2, respectively. These values are in accordance with the magneto structural correlations of previously reported isothiocyanato bridged dinuclear and phenoxido bridged trinuclear Ni(II) compounds.

Synthesis and electronic structure of novel Schiff bases Ni/Cu (II) complexes: Evaluation of DNA/serum protein binding by spectroscopic studies

[Cu(L)] (1) and [Ni(L)] (2) [L=N-2-hydroxyacetophenon-N′-2-hydroxynaphthaldehyde-1,2 phenylenediimine)], Schiff base complexes have been successfully synthesized. Single crystal X-ray crystallography, Fourier Transform infrared spectroscopy (FT-IR), NMR spectroscopy and elemental analysis (EA) have been used to characterize the complexes. Complex 1 shows unsymmetrical ligand coordination to copper (II) ion in a tetradentate fashion through ONNO donor atoms according to single crystal X-ray patterns. Spectroscopic methods have been used to study the interactions between the synthesized Schiff base complexes and Calf Thymus DNA (CT-DNA) and Bovine Serum Albumin (BSA) under physiological conditions. UV–vis absorption, fluorescence, and circular dichroism (CD) spectroscopy and thermal denaturation measurements were used in the investigation of DNA binding properties of these two complexes. The two complexes can bind to Calf Thymus DNA (CT-DNA) via an intercalative mode and complex 1 exhibits stronger interaction with CT-DNA compared with complex 2 based on the results. In addition, both compounds interact with BSA to change its microenvironment during interaction. Cu (II) complex has more affinity for BSA based on the quenching (Ksv) and binding constant (Kb) values of both compounds with BSA. Circular Dichroism technique has been applied to investigate the conformational changes of the interactions of metal complexes with DNA. Also thermal behavior of DNA-complex interaction has been determined.

Synthesis, characterization, DFT calculations and biological studies of Mn(II), Fe(II), Co(II) and Cd(II) complexes based on a tetradentate ONNO donor Schiff base ligand

This study highlights synthesis and characterization of a tetradentate ONNO Schiff base ligand namely (1, 1′- (pyridine-2, 3-dimethyliminomethyl) naphthalene-2, 2′-diol) and hereafter denotes as “HNDAP″ and selected metal complexes including Mn(II), Fe(II), Co(II) and Cd(II) as a central metal. HNDAP was synthesized from 1:2 M ratio condensation of 2, 3-diaminopyridine and 2- hydroxy-1-naphthaldhyde, respectively. The stoichiometric ratios of the prepared complexes were estimated using complementary techniques such as; elemental analyses (-C, H, N), FT-IR, magnetic measurements and molar conductivity. Furthermore, their physicochemical studies were carried out using thermal TGA, DTA and kinetic–thermodynamic studies along with DFT calculations. The results of elemental analyses showed that these complexes are present in a 1:1 metal-to- ligand molar ratio. Moreover, the magnetic susceptibilities values at room temperature revealed that Mn(II), Fe(II) and Co(II) complexes are paramagnetic in nature and have an octahedral (Oh) geometry. In contrast, Cd(II) is diamagnetic and stabilizes in square planar sites. The molar conductivity measurements indicated that all complexes are nonelectrolytes in dimethyl formamide. Spectral data suggested that the ligand is as tetradentate and coordinated with Co(II) ion through two phenolic OH and two azomethine nitrogen. However, for Mn(II), Fe(II) and Cd(II) complexes, the coordination occurred through two phenolic oxygen and two azomethine nitrogen with deprotonation of OH groups. The proposed chemical structures have been validated by quantum mechanics calculations. Antimicrobial activities of both the HNDAP Schiff base ligand and its metal complexes were tested against strains of Gram (-ve) E. coli and Gram (+ve) B. subtilis and S. aureus bacteria and C. albicans, A. flavus and T. rubrum fungi. All the prepared compounds showed good results of inhibition against the selected pathogenic microorganisms. The investigated HNDAP Schiff base complexes showed higher activity and stability than their corresponding HNDAP Schiff base ligand and the highest activity observed for Cd(II) complex. Moreover, the prepared Schiff base ligand and its Mn(II) and Co(II) complexes have been evaluated for their anticancer activities against two cancer cell lines namely; colon carcinoma cells (HCT-116 cell line) and hepatocellular carcinoma (Hep-G2) cell lines The interaction of Mn(II) and Co(II) complexes with calf thymus DNA (CT-DNA) was studied by absorption spectroscopic technique and viscosity measurements. Both complexes showed a successful interaction with CT-DNA via intercalation mode.

Studies on some metal complexes of a quinoxaline based unsymmetrical ONNO donor ligand

Co(II), Ni(II), Cu(II) and Zn(II) complexes of an unsymmetrical tetradentate ONNO donor ligand, 3-(-(3-(-1-(2-hydroxyphenyl)ethylideneamino)propylimino)methyl)quinoxalin-2(1H)-one (L) have been synthesized and characterized by elemental analysis, molar conductance, magnetic susceptibility measurements, FTIR, UV–Vis., mass and 1H NMR spectral studies. ESR spectra of the Cu(II) complex under room (300 K) and liquid nitrogen temperature (77 K) were also recorded. Thermal behavior of the newly synthesized ligand and its metal complexes was assessed by TG–DTG analysis. All the complexes are found to be mononuclear. Crystallinity, average grain size and unit cell parameters were determined from powder X-ray diffraction study. Electrochemical behavior of the compounds was examined by cyclic voltammetry technique. The in vitro antimicrobial screening of the unsymmetrical ligand and corresponding metal chelates was tested against some bacterial strains (E. coli, K. pneumoniae, S. pneumoniae and S. aureus) and fungal strains (A. niger, A. flavus, P. chrysogenum and R. stolonifer). The in vitro antioxidant and anticancer activities of the compounds were also evaluated. DFT studies were done to optimize the structure of the compounds and to calculate nonlinear optical properties of the compounds.

Synthesis, Characterization, Thermal and Catalytic Studies of Oxovanadium(IV) Complexes with Tetradentate ONNO Donor Ligands

Oxovanadium(IV) complexes of N2O2 type Schiff bases derived by the condensation of 5-chloro-2-hydroxyacetopheneone or 5-chloro-2-hydroxy-3-nitroacetophenone with trans-1,2-diaminocyclohexane have been synthesized and characterized by elemental analysis, IR and electronic spectra, magnetic moments, ESR, XRD and thermal analysis. The thermal behaviour of the complexes has been assessed using TG-DTG analysis and both the complexes exhibit loss of crystal water in first step whereas ligand segments in the subsequent steps. The various kinetic and thermodynamic parameters such as Ea, ΔH, ΔS, ΔG have been calculated from the TG data. The complexes act as oxidation catalysts for the oxidation of styrene in presence of hydrogen peroxide. The solid state electrical conductivity of complexes show their semiconducting behavior. The geometry around oxovanadium(IV) in both complexes is square pyramidal. The IR spectra suggest bi-negative tetradentate nature of the ligands with ONNO donor sequence sites of the azomethine nitrogen and phenolic oxygen. The crystal system, lattice parameters and unit cell volume of both the complexes have been determined by XRD and belongs to monoclinic crystallized system.

Studies on some metal complexes of quinoxaline based unsymmetric ligand: Synthesis, spectral characterization, in vitro biological and molecular modeling studies

Mononuclear Co(II), Ni(II), Cu(II) and Zn(II) complexes of an unsymmetric Schiff base ligand, 3-(-(3-(-3,5-dichloro-2-hydroxybenzylideneamino)propylimino)methyl)quinoxalin-2(1H) -one (L) were synthesized and characterized by various analytical and spectral techniques. The molar conductance values of metal complexes indicate non-electrolytic behavior of the metal complexes. The Schiff base act as tetra dentate ONNO donor ligand in Co(II), Ni(II), Zn(II) complexes and tridentate NNO donor in Cu(II) complex. Thermal stabilities of the newly synthesized compounds were determined by thermal analysis. Crystallinity, average grain size and unit cell parameters were determined from powder X-ray diffraction study. Electrochemical behaviors of the compounds were examined by cyclic voltammetry technique. The Schiff base and its complexes have been screened for their in vitro antimicrobial activities against some bacterial and fungal strains by disc diffusion method. The interaction of the compounds with calf thymus DNA (CT DNA) has been investigated by electronic absorption spectral titration and viscosity measurement (hydrodynamic) methods. Furthermore, the pUC18 DNA cleavage activities of the complexes have been explored. The compounds were also subjected to in vitro antioxidant, anticancer activity screening, druglikeness and bioactivity predictions using Molinspiration software. Molecular docking studies of the present compounds were carried out against B-DNA dodecamer d(CGCGAATTCGCG)2 and vascular endothelial growth factor receptor (VEGFR-2) kinase. Quantum chemical calculations were done with DFT method to determine the optimum geometry of the ligand and its metal complexes. From the quantum chemical parameters, the reactivity parameters of the compounds were established.

Structural and theoretical study of six dinuclear Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II) complexes containing ON-NO donor azodye ligand, 4,4’-(1E,1’E)-(5,5’-(propane- 2,2-diyl)bis(2-hydroxy-5,1-phenylene)bis(diazene-2,1-diyl)dibenzenesulfonic a

Six dimeric transitional metal complexes with ON-NO donor bis-bidentate azodye ligand 4,4’-(1E,1’E)-(5,5’-(propane-2,2-diyl)bis(2-hydroxy-5,1-phenylene)bis(diazene-2,1-diyl)dibenzenesulfonic acid (PDHPDDDBSA) have been synthesised and characterized by elemental, analytical, conductivity measurement, magnetic moments, spectral, thermal, X-ray diffraction (powder pattern) and theoretical methods. The Co(II) and Ni(II) complexes are found to be octahedral, Cu(II) complex is distorted-octahedral and a tetrahedral stereochemistry has been suggested to Zn(II), Cd(II) and Hg(II) complexes. The thermal analysis data provided the kinetic parameters as order of decomposition reaction, activation energy and frequency factor. All theoretical calculations of the ligand and the Cu(II) and Zn(II) complexes were made using Gaussian 03 rev. A.01 programme package hybrid DFT/B3LYP hybrid functional level of theory with LANL2DZ basic set for copper and zinc atoms in gas phase and 6-31 G(d,p) basic set for other atoms. The DFT study of the ligand and the complexes is used to calculate the bond length, bond angle, HOMO, LUMO and dipole moment values. The calculated HOMO-LUMO energy gap shows that a charge transfer occurs within the molecule. The Cd(II) complex is found to have an orthorhombic crystal system. KEY WORDS: Azodye complexes, Thermogravimetric study, Theoretical study (DFT/B3LYP) Bull. Chem. Soc. Ethiop. 2016, 30(1), 87-100. DOI: http://dx.doi.org/10.4314/bcse.v30i1.8

Synthesis, spectral, thermal, XRD and theoretical investigation of dimeric complexes with bis-bidentate ON-NO donor azodye ligand, 4,4´-(1E,1´E)- biphenyl-4,4´-diylbis(diazene-2,1-diyl)bis(4-nitrophenol)

Synthesis, spectral, thermal, XRD and theoretical investigation of dimeric complexes with bis-bidentate ON-NO donor azodye ligand, 4,4´-(1E,1´E)- biphenyl-4,4´-diylbis(diazene-2,1-diyl)bis(4-nitrophenol)

Synthesis, characterization and thermogravimetric analysis of Co(II), Ni(II), Cu(II) and Zn(II) complexes supported by ONNO tetradentate Schiff base ligand derived from hydrazino benzoxazine

A new series of Co(II), Ni(II), Cu(II) and Zn(II) metal complexes of a novel ligand 3-(2-(1-(2,4-DihydroxyPhenyl)ethylidene)hydrazinyl)-2H-benzo[b][1,4]oxazin-2-one, (DPE-HBO) were prepared and characterized. Microwave synthesis of the ligand was also carried out which gave a high increase in its yield within very short time. 3D molecular modeling structure of the ligand is obtained by using ArgusLab software. The nature of bonding and the stereochemistry of the complexes have been deduced from elemental analysis, thermal, infrared, electronic spectra, magnetic moments and conductivity measurements. ESR spectrum of Cu(II) complex is studied. All the complexes show subnormal magnetic moments. ONNO donor atoms participate in coordination with Cu(II) and Zn(II) complexes exhibiting octahedral geometry. Co(II) and Ni(II) complexes behave differently with ONNO donor atoms showing two types of geometries i.e., octahedral and square planar within the same complex.

Synthesis, Physiochemical, Thermal, Catalytic and Electrical Studies of Mn(III) VO(IV), MoO2(VI) and UO2(VI) Complexes with Unsymmetrical Schiff Base Ligand

The solid complexes of Mn(III), VO(IV), MoO2(VI) and UO2(VI) with unsymmetrical dibasic tetradentate ONNO donor Schiff base derived from the condensation of salicylaldenyde, o-hydroxy acetophenone and ethylene diamine have been synthesized and characterized by elemental analysis, magnetic susceptibility measurements, IR and reflectance spectra. The thermal dehydration and decomposition of these complexes were studied kinetically using the Horowitz- Metzger method. The solid state electrical conductivity of complexes has been measured in the temperature range 313 K≤ T ≥403 K and the complexes exhibited semiconducting behavior. Scanning electron micrograph has also been reported and suggested homogeneous phase material. Complexes were used for the catalytic oxidation of styrene.

Effect of structure and composition of nickel(II) complexes with salicylidene Schiff base ligands on their DNA/protein interaction and cytotoxicity

Three new salicylidene Schiff base nickel(II) complexes [Ni(L1)(CH3COOH)2]2 (1), [Ni2(L1)2(CH3OH)] (2), [Ni(L2)2]·3H2O (3) {H2L1=N,N′-bis(salicylidene)-3,6-dioxa-1,8-diaminooctane, HL2=2-ethyl-2-(2-hydroxybenzylideneamino)propane-1,3-diol} were synthesized and characterized fully by structural, analytical, and spectral methods. The single-crystal X-ray structures of complexes 1 and 2 exhibit the symmetrical ligands coordinated to the nickel(II) ion in a tetradentate fashion via ONNO donor atoms, while the unsymmetrical ligand L2 presented a ONO tridentate coordination mode in complex 3. The nickel(II) ions lie in the six-coordinated octahedral environment for the mononuclear complexes 1 and 3, along with dinuclear complex 2. The interaction of the complexes with calf thymus DNA (CT-DNA) has been explored by absorption and emission titration methods, which revealed that complexes 1–3 could interact with CT-DNA through intercalation. The interactions of the complexes with bovine serum albumin (BSA) were also investigated using UV–Vis, fluorescence and synchronous fluorescence spectroscopic methods. The results indicated that all of the complexes could quench the intrinsic fluorescence of BSA in a static quenching process. Further, the in vitro cytotoxic effect of the complexes examined on cancerous cell lines such as human lung carcinoma cell line (A549), human colon carcinoma cell lines (HCT-116), human promyelocytic leukemia cells (HL-60) and colonic cancer cell line Caco-2 showed that all three complexes exhibited substantial cytotoxic activity.