Tetradentate ONNO Research Articles

Eu(III) complexes derived from 2-quinolinecarbohydrazide Schiff base ligand, relations between structure and luminescence properties

A series of Eu(III) complexes were obtained following the template condensation of 2-quinolinecarbohydrazide and 2,6-diacetylpyridine, namely: [Eu(H2pbqh)(NO3)3]·MeOH (1), [Eu(Hpqh)(NO3)3]·2MeCN (2), [Eu(H2pbqh)(SCN2)(MeOH)2](SCN) (3) and [Eu2(pbqh)2(NO3)2(H2O)2]·2.5MeOH (4). The structures of complexes and a new H2pbqh ligand (N',N'''-((1E,1′E)-pyridine-2,6-diylbis(ethan-1-yl-1-ylidene))bis(quinoline-2- carbohydrazides)) were elucidated by single-crystal X-ray diffraction. H2pbqh coordinate pentadentate ONNNO and forms mononuclear complexes 1 and 3. The bis-deprotonated ligand pbqh2- act as hexadentate/bridging mode generates the binuclear complex in 4. The partially condensed ligand Hpqh, tetradentate ONNO, was recorded in complex 2. The crystallographic results reveals that the coordinated H2pbqh/Hpqh ligands and Eu3+ cation form a planar structure in these complexes and nitrate anions coordinate chelate, completing the coordination sphere of Eu3+. The solid state photoluminescent emission was investigated highlighting the nitrate complexes 1 and 2 that exhibit red intense luminescence (λmax = 618 nm). Moreover, the computational calculations reveal different pathways of energy transfer from ligand to Eu3+ electronic states explaining the luminescent behavior.

Unraveling the Potential of Mononuclear Zn(II) and Cu(II) Schiff Base Metal Complexes: Microwave‐Aided Synthesis, Theoretical Analysis and Application in Biomimetic Catalysis, CT‐DNA Interaction, and In Vitro Biological Assays

ABSTRACTGiven the widespread and diverse effects of transition metal ions such as copper and zinc in multiple biological processes, this research endeavor addresses herein the microwave‐aided synthesis of two novel tetradentate ONNO (L1) and tridentate NNO (L2) donor Schiff base ligands derived from 4,5‐dimethyl‐1,2‐phenylenediamine and 4‐bromo‐2‐hydroxybenzaldehyde in a 1:2 ratio and from 4,5‐dimethyl‐1,2‐phenylenediamine and 5‐methoxy‐2‐hydroxybenzaldehyde in a 1:1 ratio, with their respective zinc, ZnL1(1) and ZnL2(3), and copper, CuL1(2) and CuL2(4), Schiff base metal complexes, which are comprehensively characterized utilizing physiochemical and analytical techniques, along with geometry optimization using the DFT approach. Spectrophotometric analyses have been used to assess the biomimetic activity in the conversion of 3,5‐DTBC to 3,5‐DTBQ with turnover numbers 53.4 and 78 h−1 in methanol for 2 and 4, whereas the zinc complexes are found to be ineffective. With CT‐DNA, possible modes of interaction with the synthesized complexes have been explored using absorption spectroscopy, where the associated binding constants ranged between 1.541 × 105 and 2.186 × 105 M−1. EtBr‐bound DNA was used in the fluorescence quenching experiments with Stern–Volmer constant (Ksv) values in the range 4.084 × 104 and 3.402 × 104 M−1, showing a stronger association with CT‐DNA. The compounds' ability to inhibit bacterial strains was also examined in vitro, as well as their ability to reduce inflammation, through the protein denaturation method and the DPPH assay for antioxidant activity have been performed. Furthermore, molecular docking simulations have been carried out to obtain a deeper comprehension of the molecular‐level interactions with CT‐DNA and cyclooxygenase‐2 (COX‐2).

Isomerism in Hexacoordinate Ti(IV) and Zr(IV) Complexes with a Tetradentate ONNO‐Schiff Base Ligand

AbstractThe reactions of [(thf)2TiCl4] with sodiated 2,2’‐bis[2‐hydroxy‐3,5‐di(tert‐butyl)benzylideneamino]‐1,1’‐biphenyl (1 a) and 2,2’‐bis[2‐hydroxy‐3,5‐di(tert‐butyl)benzylideneamino]‐4,4’‐dimethyl‐1,1’‐biphenyl (1 b) yield the corresponding Ti complexes 2 a and 2 b. Similarly, 1 a reacts with [(thf)2ZrCl4] to the corresponding Zr derivative 3. For 2 a, a mixture of cis‐β and trans isomers were observed in solution whereas the Zr congener exclusively forms the cis‐α form. Quantum chemical calculations verify that these isomers are the preferred molecular structures. The crystal structures of cis‐β isomeric 2 a and cis‐α isomeric 3 have been determined. Metalation of 1 a with Ti(NMe2)4 yields 2,2’‐bis[(2‐oxido‐3,5‐di(tert‐butyl)phenyl)‐dimethylaminomethylamino]‐1,1’‐biphenyl titanium(IV) (4) with a hexadentate ligand.

Pd(II) and Ni(II) complexes containing ONNO tetradentate Schiff base ligand: Synthesis, crystal structure, spectral characterization, theoretical studies, and use of PdL as an efficient homogeneous catalyst for Suzuki–Miyaura cross-coupling reaction

Two new palladium(II) and nickel(II) Schiff base complexes are prepared through the reaction of Pd(OAc)2 and Ni(OAc)2·4H2O with a tetradentate ONNO Schiff base, derived by condensing 4,5-dimethyl-1,2-phenylenediamine and 4-methoxysalicylaldehyde. The elemental analysis (CHN) and other spectroscopic techniques such as FT-IR and 1H NMR were used to characterize the synthesized ligand and its corresponding metal complexes. Moreover, the crystal structure of the Pd(II) complex was investigated by the single crystal X-ray diffraction analysis. The diffraction analysis explores a slightly distorted square planar geometry of the PdL complex due to the coordination with deprotonated phenolic O-atoms and N-atoms from azomethine chromophore. The DFT-based theoretical calculations which employed the B3LYP/Def2-TZVP level of theory explore that the theoretical results corresponded to the actual data obtained via spectroscopic characterization.

Effect of Diamine Bridge on Reactivity of Tetradentate ONNO Nickel(II) Complexes.

Two new square planar ONNO nickel(II) complexes C2_core and C3_core have been synthesized and characterized by single crystal X-ray diffraction, NMR spectroscopy, thermogravimetry, and DFT calculations. The experimental results revealed the effect of the length of diamine bridge in the ligand on the behavior of the studied complexes in the reaction with N-heterocyclic aromatic amines, while DFT calculations provided a basis for the rationalization of this observation. The complex with propylenediamine bridge (C3_core) readily reacts with pyridine and its derivatives to form high-spin (paramagnetic) complexes with octahedral geometry as characterized by X-ray diffraction; electron-donating substituents on the pyridine ring facilitate the coordination of axial ligands. In contrast, the complex with ethylenediamine bridge (C2_core) does not undergo such a reaction because of the high deformation energy of the core required for the formation of C2_Py complex.

Structural characterization, theoretical and antibacterial study of a V-shaped, cyclohexane bridged ONNO Schiff base

A tetradentate ONNO Schiff base bearing two chloro substituents, namely 6,6′-((1E,1′E)-(cyclohexane-1,2-diylbis(azanylylidene))bis(methanylylidene))bis(2-chlorophenol) (AD2C), was obtained through condensation of 3-chlorosalicyladehyde with 1,2-cyclohexanediamine. Structure elucidation was performed through physicochemical and spectroscopic analyses viz. melting point, elemental analysis, FTIR, 1H and 13C NMR, UV-Visible and single crystal X-ray diffraction. The ν(C=N) was observed at 1626 cm−1 while the azomethine proton and carbon chemical shifts appeared at 8.27 ppm and 157.56 ppm, respectively. The n‒π*(C=N) absorption band was observed at 324 nm. The crystal structure was stabilized by intramolecular hydrogen bond O˗H···N and intermolecular hydrogen bonds C˗H···O, C˗H···Cl, C˗H···π as well as π···π interactions. The existence of intermolecular interactions was confirmed through Hirshfeld analysis, showing high contribution of H⋯H contact. The B3LYP method was used to calculate the optimized structure of the molecule through density functional theory (DFT) using the 6–311++G(d, p) basis set and was found to be consistent with the X-ray diffraction value. The frontier molecular orbitals and molecular electrostatic potential of the compound investigated through DFT calculations revealed a significantly large energy gap of 4.615 eV and nucleophilic regions located at the hydroxyl groups. The compound showed no antibacterial activity against five bacterial strains namely Bacillus subtilis (ATCC 6633), Proteus vulgaris (ATCC 6380), Pseudomonas aeruginosa, Staphylococcus aureus subsp. aureus Rosenbach (ATCC 6538) and Streptococcus mutans Clarke (ATCC 700,610).

Biomimetic Oxidative Bromination by cis‐Dioxidotungsten(VI) Complexes of Salan Type N,N’‐Capped Linear Tetradentate Amino Bisphenol

AbstractReaction of [WVIO2(acac)2] (Hacac=acetylacetone) with salan‐type dibasic tetradentate ONNO donor Mannich bases derived from ethylenediamine, formaldehyde and 2,4‐di‐tert‐butylphenol (H2L1), 2‐tert‐butyl‐4‐methylphenol (H2L2), 2,4‐dimethylphenol (H2L3) and 2,4‐dichlorophenol (H2L4) in a 1 : 1 ([WVIO2(acac)2] : H2L) molar ratio in refluxing MeOH gave the corresponding cis‐dioxidotungsten(VI) complexes [WVIO2L1] (1), [WVIO2L2] (2), [WVIO2L3] (3) and [WVIO2L4] (4), respectively. Characterization by elemental analysis, various spectroscopic (FT‐IR, UV‐vis, 1H and 13C NMR) studies, DFT calculations and single‐crystal X‐ray analysis of 2 and 3 suggest six‐coordinated octahedral α‐cis (symmetric) isomeric form of the complexes where ligands coordinate through the two phenolate oxygen and two amine nitrogen atoms (in a cis‐α type symmetric binding mode) with one of the N atoms of the ligand and one of the terminal O atoms of the cis‐WO2 group in the axial position. These complexes are potential catalyst precursors for the oxidative bromination of thymol and styrene. Thymol upon bromination gave three products, namely, 2‐bromothymol, 4‐bromothymol, and 2,4‐dibromothymol; later one being the major product. Oxidative bromination of styrene resulted in 2‐bromo‐1‐phenylethanol and 1‐phenylethane‐1,2‐diol; the later one is the result of nucleophilic attack of water on the α as well as β carbons both of the initially formed 1,2‐dibromo‐1‐phenylethane.

A novel single-pot synthesis of dinuclear and mononuclear copper(II) complexes with sterically demanding Schiff bases: Structural, spectral, magnetic, electrochemical, DNA binding and theoretical investigation

Two dinuclear CuII complexes, cyclo[Cu2(LtBu)Cl2]·4EtOH] (monoclinic P21/n) (2) and cyclo[Cu2(LMe)1.5Cl·0·5H2O]Cl·(H2O) (hexagonal P6) (3) (where cycloH2LtBu = cyclobis{2-[benz(N-ethan-1,2-diyl)imidoyl][6-benzimidoyl][4‑tert‑butyl]phenol}, and cycloH2LMe = cyclobis{2-[benz(N-propan-1,3-diyl)imidoyl][6-benzimidoyl][4-methylphenol}, and two mononuclear CuII complexes, [Cu(LtBu)(OH2)] (monoclinic P21/c) (4) and [Cu(mdbp)2] (monoclinic P21/c) (5) (where H2LtBu = bis[2-{6-benzoyl-4‑tert-butylphenol}benzimidoyl]-1,3-propane; mdbpH = 4-methyl-2,6-dibenzoylphenol) have been synthesized by a one–pot condensation involving CuII chloride, ethane-1,2-diamine, propane-1,3-diamine, 4-methyl-2,6-dibenzoylphenol (mdbpH) and 4‑tert‑butyl‑2,6-dibenzoylphenol (bdbpH). The macrocyclic Schiff bases, cyclo[H2LtBu] and cyclo[H2LMe], and the tetradentate Schiff base [H2LtBu], and 2 – 5, have been characterised by elemental analysis, conductivity measurements, mass spectrometry, IR, electronic, 1H and 13C NMR, and ESR spectroscopy, cyclic voltammetry, X-ray crystallography and variable temperature magnetic susceptibility. In 2 and 3, the macrocyclic N4O2 ligand wraps around square pyramidally coordinated copper in a binuclear phenoxo bridged complex. In 2 the apical chlorine atoms are trans with respect to the macrocyclic ligand whereas in 3 they are cis. In the crystalline solid Cl and H2O are disordered on one of the axial positions. Variable temperature magnetic properties indicate weak antiferromagnetic interactions in 1, 2 and 3. Mononuclear complex 4 possesses a tetradentate ONNO ligand with a square pyramidal configuration at Cu and H2O directed at the apical position. Complexes 2 and 3, and 5 are, respectively, examples of square pyramidal and square planar coordinated copper. Density functional theory (DFT) calculations for gas-phase complexes 1, 2, 3, 4 and 5 provide descriptions of electronic properties that are compared with spectroscopic, electrochemical and DNA binding measurements. The binding constants to calf thymus DNA decrease in the order, 2 > 4 > 3 >1 > 5.

Synthesis and XRD of neutral NiL complex using unsymmetrical ONNO tetradentate schiff base: Hirschfeld, spectral, DFT and thermal analysis

The unsymmetrical tetradentate ONNO Schiff base 6,6’-((1E,1’E)-((2-methylpropane-1,2-diyl)bis(azanylylidene))bis(methanylylidene))bis(2,4-di-tert-butylphenol) (H2L) was prepared following a slightly modified known condensation reaction. The neutral NiL complex has been synthesized in high yield via [1H2L:1Ni(II)] direct addition. The XRD-measurement reflects a NiII center with slightly distorted square planar geometry. Moreover, the lattice is stabilized by a number of H-bond and H…π stacking interactions. The structure connections have been illustrated by electrostatic potential surface (Molecular Electrostatic Potential, MEP) and Hirschfeld surface (HSA) and Fingerprint (FP) analysis to support such interactions. IR and UV-visible spectra were measured to compare free H2L with NiL behaviors. The DFT-optimized structure was compared to the XRD-structure parameters. NiL reflects high thermal stability and decomposed mainly via one-step to form NiO as the final product.

Tailored synthesis of unsymmetrical tetradentate ONNO schiff base complexes of Fe(IIl), Co(II) and Ni(II): Spectroscopic characterization, DFT optimization, oxygen-binding study, antibacterial and anticorrosion activity

Abstract Two Schiff base ligands namely bis-2-((1E)-((Z)-2-(1,2-diphenylethylideneamino) phenylimino)methyl)phenol (L1) and bis-2-((1E)-((E)-2-(1-phenylethylideneamino)phenylimino) methyl)phenol (L2) were synthesized by tailored reaction of o-phenylenediamine with o-hydroxybenzaldehyde and 2-hydroxy-1,2-diphenylethanone/o-hydroxyacetophenone. The reaction of these ligands with Fe(III), Co(II), and Ni(II) salts yielded six complexes. Ligands and their metal derivatives have been characterized by elemental analysis, molar conductance, magnetic susceptibility, FT-IR, UV–Vis, ESI-mass, 1H NMR, 13C NMR and EPR analysis. Using Gaussian 09 molecular modelling, bond lengths, bond angles and Mulliken charge were also evaluated. In addition to this study of HOMO and LUMO molecular orbital have been performed. The FT-IR spectra have suggested that ligand is coordinated with metal through azomethine-N and phenolic-O. Experimental and theoretical IR and NMR spectrum of ligand L1 and complex 2 exhibits quite good correlation. ESR spectrum of complex 2 at LNT suggests octahedral geometry around Co(II). Complexes were studied for their oxygen-binding activity and displayed significant oxygenation reaction. The thermodynamic parameters such were also calculated. The compounds were screened for antibacterial activity against gram-negative bacteria Escherichia coli and compared with Amoxicillin. Complexes have exhibited significant antibacterial activity. The corrosion inhibition effect of ligands and complexes on mild steel in acidic medium was studied for 24, 48 and 72 h using weight loss measurement.

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.

Synthesis, characterization and anticancer activity of mono- and dinuclear Ni(II) and Co(II) complexes of a Schiff base derived from o-vanillin

A Schiff base ligand, 6,6′-dimethoxy-2,2′-[o-phenylenebis(nitrilomethylidyne)]diphenolato (LA), and its mononuclear and dinuclear Ni(II) and Co(II) complexes were synthesized. Structural elucidation was carried out via elemental analysis, molar conductivity, IR, NMR, UV–Vis spectroscopy, TGA and magnetic susceptibility. Single crystal X-ray diffraction of the Ni(LA) complex revealed a square planar geometry of the Ni(II) centre, with the ligand acting as a tetradentate ONNO chelate. Upon coordination to the metal centers, the ν(CN) and ν(CO) peaks shifted to lower frequencies, with appearance of new peaks assignable to ν(MN) and ν(MO) in the ranges 535–560 and 421–460 cm−1, respectively. Ni(LA) and Ni2(LA) complexes are diamagnetic, whereas the Co(LA) and Co2(LA) complexes are paramagnetic with 3 unpaired electrons each. All the complexes displayed low molar conductivities in acetonitrile indicating non-electrolytic behavior. Anticancer screening against human colorectal cancer HCT116 cell lines revealed that both dinuclear complexes were more active than their mononuclear counterparts. Ni2(LA) showed the highest potency with an IC50 value of 0.81 μM.

Tetrylenes based on 1,10-phenanthroline-containing diol: the synthesis and application as initiators of ε-caprolactone polymerization

Treatment of 4,7-dichloro-2,9-dimethyl-1,10-phenanthroline with two equivalents of p-tert-butylphenol in the presence of К2СО3 afforded 4,7-di(4-tert-butylphenoxy)-2,9-dimethyl-1,10-phenanthroline (1). Monolithiation of 1 with lithium diisopropylamide followed by treatment with benzophenone resulted in 1-(4,7-bis-p-tert-butylphenoxy-9-methyl-1,10- phenanthrolin-2-yl)methyl-1,1-diphenylethanol (2). 1-(4,7-Bis-p-tert-butylphenoxy-9-hydroxy (diphenyl)methyl-1,10-phenanthrolin-2-yl)-1,1-diphenylethanol (3), a tetradentate ONNO ligand, was prepared analogously from 2. The interaction of 3 with 1 eq. of Lappert’s germylene or stannylene M[N(SiMe3)2]2 (M = Ge, Sn) led to the corresponding germylene 4 and stannylene 5 in moderate yields. According to 1Н, 13С, and 119Sn NMR spectroscopy data, stannylene 5 is monomeric in solution and the coordination number of tin atom is 4. Tetrylenes 4 and 5 demonstrated high activity as initiators of bulk polymerization of e-caprolactone which leads to high-molecular-weight polymers with relatively narrow molecular weight distribution.

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.

Unusual coordination of mononuclear cobalt(III) complexes with sterically demanding Schiff bases: synthesis, spectroscopy, electrochemistry, crystallography, DNA binding, and theoretical investigation

Three mononuclear CoIII complexes, [Co(L1 tBu)(bdbp)]·2EtOH (1), [Co(L2 tBu)(bdbp)] (2), and [Co(L3 tBu)2]ClO4 (3) (where H2L1 tBu = bis[{6-benzoyl-4-tert-butyl-2-hydroxyphenyl}benzi-midoyl]-1,2-ethane, H2L2 tBu = bis[{6-benzoyl-4-tert-butyl-2-hydroxyphenyl}benzimidoyl]-1,3-propane, bdbpH = 4-tert-butyl-2,6-dibenzoylphenol and HL3 tBu = 2-{N-(4-amino-butyl)benzimidoyl}-6-benzoyl-4-tert-butylphenol), have been synthesized by one-pot condensation involving CoII perchlorate, ethane-1,2-diamine, propane-1,3-diamine, and butane-1,4-diamine. The Schiff bases, H2L2 and HL3, and 1–3 have been characterized by elemental analyses, conductivity measurements, mass spectrometry, IR, electronic, 1H and 13C NMR spectroscopy, cyclic voltammetry, and X-ray crystallography. In 1 and 2, the tetradentate ONNO ligand wraps around cobalt in a rare β cis-conformation. Complex 3 possesses a tridentate NNO ligand leading to two seven-membered chelate rings in a fac-CoN4O2 octahedral configuration. Density functional theory (DFT) calculations provide a satisfactory description of the electronic properties of the new compounds. All the complexes are redox active and display the Co(III)–Co(II) couple in the potential range −0.6– + 0.3 V (vs. Ag/AgNO3). Interaction of the complexes with calf thymus DNA (CT-DNA) has been investigated by a spectrophotometric method and cyclic voltammetry. Based on these observations, an intercalative binding mode of DNA has been proposed. The order of their intrinsic DNA binding constants Kb is Kb (1) < Kb (2) < Kb (3). The observed trend in the binding constant values is consistent with the energy gap between the HOMO and LUMO molecular orbitals.

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.

Development, structural investigation, DNA binding, antimicrobial screening and anticancer activities of two novel quari-dentate VO(II) and Mn (II) mononuclear complexes

Two novel VO(II) and Mn(II) imine chelates derived from the condensation of o-phenylenediamine (PN) with 3-ethoxysalicylaldehyde(ES) were synthesized. The prepared ESPN imine ligand and its chelates were investigated via different analytical and physicochemical tools. Correlation between all the obtained results, the parent ligand behaves as tetra-dentate ONNO ligand and coordinates to Mn(II) and VO(II), in octahedral and square pyramidal geometry, respectively. Also, the prepared compounds were screened for their antimicrobial activities on different pathogenic bacteria and fungi. The results show that the complexes have a stronger antimicrobial activity in comparison with its ligand. Moreover, the interaction of the prepared metal chelates with CT-DNA was detected utilizing spectral studies, viscosity and gel electrophoreses measurements. The obtained results clearly demonstrate that, the binding affinity with CT-DNA for ESPN>ESPNV complex. Furthermore, the cytotoxic activity of the tested compounds on human colon carcinoma cells, hepatic cellular carcinoma cells and breast carcinoma cells has been examined. From these results it was found that the investigated complexes have effective cytotoxicity against growth of carcinoma cells with respect of its imine ligand.

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.

Crystal Structure of 2,2′-(((2,2-Dimethylpropane-1,3-diyl)bis(azanylylidene))bis(methanylylidene))bis(4-methoxyphenol)palladium(II)

The structure of 2,2′-(((2,2-dimethylpropane-1,3-diyl)bis(azanylylidene))bis(methanylylidene))bis(4-methoxyphenol)palladium(II) was determined by X-ray crystallography analysis. It crystallizes in the space group P21/n, with cell parameter a = 12.5115(7)Å, b = 10.5337(6)Å, c = 15.0080(9)Å, β = 94.0547(19)°, Z = 4, and V = 1973.0(2)Å3. The crystal structure was solved by direct methods and refined by full-matrix least-squares on F2 to final values of R1 = 0.0415 and wR2 = 0.1251. The Schiff-base ligand was found to coordinate to the palladium(II) through tetradentate ONNO atoms forming a slightly distorted square-planar complex. Two intermolecular hydrogen bonds, C–H···O, stabilized two molecules forming dimers.

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.