Bidentate ON Donor Research Articles

Spectroscopic, thermal analysis, and nematicidal evaluation of new mixed ligand complexes of bidentate Schiff base and 1,10 phenanthroline with some transition metals

Mononuclear Co(II), Cu(II), Y(III), Zr(IV), La(III), and U(VI) complexes of 2‐[(2‐hydroxybenzylidene)‐amino]‐benzoic acid (H2L) ligand in presence of 1,10‐phenanthroline (Phen) were synthesized and characterized by elemental analysis, spectroscopic techniques (IR, UV–vis, and 1H‐NMR), X‐ray powder diffraction and magnetic measurements. The results prove that H2L acts with the mentioned metal salts as a bidentate ON donor ligand and Phen as an NN donor ligand. The calculated bond length and force constant F(UO) in the uranyl complex are 1.732 Å and 708.90 nM−1, respectively. The electronic spectra and the magnetic susceptibility data support the octahedral geometry for the mononuclear Co(II), Y(III), Zr(IV), La(III), and U(VI) complexes and square‐pyramidal geometry for the Cu(II) complex. Thermogravimetric analysis was performed to determine the thermal stability of the synthesized compounds. The kinetic parameters, that is, the activation energy (E*), pre‐exponential factor (A), entropy of activation (ΔS*), enthalpy of activation (ΔH*) and free energy of activation (ΔG*), of the thermal degradation process were evaluated using Coats–Redfern (C–R) and Horowitz–Metzger (H–M) methods for all the complexes, and the best fit results could be obtained. In the present work, all the synthesized complexes showed nematicidal activity against the root knot nematode (Meloidgyne javanica) by inhibiting egg hatching and causing larval mortality of second‐stage juveniles.

Synthesis characterization, crystal structures, and antibacterial activity of 8-hydroxyquinoline-coordinated oxidovanadium(V) complexes with tridentate hydrazone ligands

Two new oxidovanadium(V) complexes, [VO(L1)(L)] (I) and [VO(L2)(L)] (II), where L1 and L2 are the dianionic form of N'-(2-hydroxy-5-methoxybenzylidene)pivalohydrazide (H2L1) and N'-(2-hydroxy-3-methoxybenzylidene)pivalohydrazide (H2L2), respectively, and L is the monoanionic form of 8-hydroxyquinoline (HL), were prepared and characterized by elemental analysis, infrared and electronic spectra, and 1H NMR spectra. Structures of the complexes were further confirmed by single crystal X-ray determination (CIF files CCDC nos. 1477854 (I), 1477856 (II)). H2L1 and H2L2 coordinate to the V atoms through the phenolate O, imino N, and enolate O atoms. 8-Hydroxyquinoline coordinates to the V atoms through bidentate ON donor set. The V atoms of the complexes are in octahedral coordination with the oxo group furnished the octahedral geometry. The complexes show effective antibacterial activity against Bacillus subtilis.

Efficient and versatile catalysis for β-alkylation of secondary alcohols through hydrogen auto transfer process with newly designed ruthenium(II) complexes containing ON donor aldazine ligands

A new series of ruthenium(II) carbonyl complexes, [RuCl(CO)(EPh3)2(L1-2)] (1–4) (E = P or As; H2L1 = salicylaldazine, H2L2 = 2-hydroxynaphthaldazine), have been assembled from ruthenium(II) precursors [RuHCl(CO)(EPh3)3] and bidentate ON donor Schiff base ligands (H2L1-2). Both ligands and their new ruthenium(II) complexes have been characterized by elemental analyses, spectroscopic methods (UV, IR, NMR (1H, 13C, 31P) as well as ESI mass spectrometry. The molecular structures of H2L1 and 1 have been confirmed by single crystal X-ray diffraction. Based on the above studies, an octahedral coordination geometry around the metal center has been proposed for 1–4. To investigate the catalytic effectiveness of 1–4, the complexes have been used as catalysts in β-alkylation of secondary alcohols with primary alcohols and synthesis of quinolines. The effect of solvent, time, base, catalyst loading, and substituent of the ligand moiety on the reaction was studied. Notably, 1 was a more efficient catalyst toward alkylation of a wide range of alcohols and quinolines synthesis. The reusability of the catalyst was checked and the results showed up to six catalytic runs without significant loss of activity.

Ru(III) mediated C[sbnd]H bond activation of N-(naphthyl)salicylaldimine and related Schiff base ligands: Synthesis, structure, DFT study and catalytic activity

New family of cyclometalated ruthenium(III) Schiff base complexes of the general composition [Ru(LON)(LCNO)(EPh3)] (L=Schiff base ligands of CNO- and ON-donors; E=P, As) have been synthesized and characterized by elemental analysis, FT–IR, UV–Vis and EPR spectral methods. The molecular structure of one of the complexes [Ru(LON)(LCNO)(PPh3)] (5) was determined by X-ray crystallography. The Schiff base ligands readily undergo cyclometalation with the ruthenium metal precursor by CH activation at the peri-position. These Schiff base ligands coordinated to metal center as di-anionic tridentate CNO-donor and bi-dentate ON-donor in these cycloruthenium complexes. TD–DFT calculations were also carried out for the complex (5). The catalytic activity of the complex [Ru(LON)(LCNO)(PPh3)] (5) was performed and found to be an efficient catalyst for the transfer hydrogenation of ketones with excellent conversion in the presence of i-PrOH/KOH at 80°C in 2h.

Synthesis, characterization, thermal study and biological evaluation of Cu(II), Co(II), Ni(II) and Zn(II) complexes of Schiff base ligand containing thiazole moiety

The novel Schiff base ligand 2-(4-(dimethylamino)benzylidene)-N-(4-phenylthiazol-2-yl)hydrazinecarboxamide (L) obtained by the condensation of N-(4-phenylthiazol-2-yl)hydrazinecarboxamide with 4-dimethylaminobenzaldehyde and its newly synthesized Cu(II), Co(II), Ni(II) and Zn(II) complexes have been characterized by microanalysis, magnetic susceptibility, molar conductance, thermal analysis, FT-IR, 1H NMR, ESI mass, UV–Visible, ESR spectroscopy and powder X-ray diffraction data. The newly synthesized ligand behaves as a bidentate ON donor. The IR results confirmed the bidentate binding of the ligand involving oxygen atom of amide carbonyl and azomethine nitrogen. 1H NMR spectral data of the ligand (L) and its Zn(II) complex agreed well with the proposed structures. In order to evaluate the effect of antimicrobial activity of metal ions upon chelation, the newly synthesized ligand and its metal complexes were screened for their antibacterial and antifungal activities by minimum inhibitory concentration (MIC) method. The DNA cleavage activities were studied using plasmid DNA pBR322 as a target molecule by agarose gel electrophoresis method. The brine shrimp bioassay was also carried out to study the in vitro cytotoxicity properties of all the compounds against Artemia salina. Furthermore, the antioxidant activity of the ligand (L) and its metal complexes were determined in vitro by reduction of 1,1-diphenyl-2-picryl hydrazyl (DPPH), the ligand exhibited potent in vitro – antioxidant activity than its metal complexes.

A novel iron complex containing an N,O-type bidentate oxazoline ligand: Synthesis, X-ray studies, DFT calculations and catalytic activity

A five-coordinated Fe(III) complex with the distorted trigonal bipyramidal configuration was synthesized by reactions of FeCl3⋅6H2O and 2-(2′-hydroxyphenyl)oxazoline (Hphox) as a bidentate ON donor oxazoline ligand. Complex [Fe(phox)2Cl] was fully characterized, including by single-crystal X-ray structure analysis. DFT calculations were accompanied with experimental results in order to obtain a deeper insight into the electronic structure and vibrational normal modes of complex. Oxidation of sulfides to sulfoxides in one-step was conducted by this complex as catalyst using urea hydrogen peroxide (UHP) in mixture of CH2Cl2/CH3OH (1:1) under air at room temperature. The results show that using this system in oxidation of sulfides, sulfoxides are obtained as the main products, together with variable amounts of sulfones (⩽13%), depending on the nature of the substrate.

Zinc (II) complex with a cationic Schiff base ligand: Synthesis, characterization, and biological studies

A cationic Schiff base ligand, TSB (L) and its Zn (II) complex (1) were synthesized and characterized by using CHN, 1H-NMR, FT-IR, UV, LC–MS, and X-ray methods. Their ability to inhibit topoisomerase I, DNA cleavage activities, and cytotoxicity were studied. X-ray diffraction study shows that the mononuclear complex 1 is four coordinated with distorted tetrahedral geometry. The singly deprotonated Schiff base ligand L acts as a bidentate ON-donor ligand. Complexation of L increases the inhibitory strength on topoisomerase I activity. Complex 1 could fully inhibit topoisomerase I activity at 250μM, while L did not show any inhibitory effect on topoisomerase I activity. In addition, L and complex 1 could cleave pBR322 DNA in a concentration and time dependent profile. Surprisingly, L has better DNA cleavage activity than complex 1. The cleavage of DNA by complex 1 is altered in the presence of hydrogen peroxide. Furthermore, L and complex 1 are mildly cytotoxic towards human ovarian cancer A2780 and hepatocellular carcinoma HepG2.

Synthesis, Characterization and Biological Activity of Cis- Dioxomolybdenum(VI) Schiff base Complex [MoO2(L)2

A new dioxo-molybdenum(VI) complex [MoO2(L)2] was synthesized using 2,4-dihydroxy–benzalmethylene-o,o’- diethylphosphorohydrazonothionate (HL) as bidentate ON donor Schiff base ligand and MoO2(acac)2. This new compound was characterized by elemental analysis, IR, 1HNMR, MS, UV/vis, and molar conductivity, and the six- coordinate structure with [cis-MoO2]2+ group in the complex was proposed on the basis of spectroscopic characterization. The insecticidal activity of the Mo(VI) complex to bollworm was investigated, and its effect on the cell survial rate of mung bean sprouts was also discussed. The results showed that the activities of the complex in killing aphid were more effective than that of methamidophos and lower in killing red spider than that of methamidophos. Moreover, the complex could promote the cell survial rate of mung bean sprouts.

Synthesis, Characterization and Antimicrobial Activity of Oxovanadium(IV) Complexes of Schiff Base Hydrazones Containing Quinoxaline Moiety

AbstractThe oxovanadium(IV) complexes of the Schiff base hydrazones, synthesized from 3‐hydrazinoquinoxaline‐2‐one (HQO) with salicylaldehyde (HSHQO), o‐hydroxyacetophenone (HHAHQO), dehydroacetic acid (HDHAHQO) and o‐nitrobenzaldehyde (NBHQO) were synthesized and characterized on the basis of analytical, conductance, magnetic moment, infrared, NMR, ESR and electronic spectral data. The ligands HSHQO, HDHAHQO behaved as monobasic tridentate ONN donors through phenolic oxygen, azomethine nitrogens. The ligand HAHQO acted as a monobasic bidentate ON donor through the phenolic oxygen, azomethine (free) nitrogen and the ligand NBHQO acted as neutral bidentate ON donor through oxygen of the nitro group and azomethine (free) nitrogen.

Oxovanadium(IV) complexes of bioinorganic and medicinal relevance: Synthesis, characterization and 3D molecular modeling of some oxovanadium(IV) complexes involving O, N-donor environment of salicylaldehyde-based sulfa drug Schiff bases

The present paper reports the synthesis and characterization of some new sulfa drug based Schiff base oxovanadium(IV) complexes of composition, [VO(sal-sdz)2(H2O)]·H2O, [VO(sal-sgn)2(H2O)]·H2O, [VO(sal-snm)(H2O)]·H2O, [VO(sal-smr)2(H2O)]·H2O and [VO(dadps)(H2O)]2·2H2O, where sal-sdzH=N-(salicylidene)sulfadizine, sal-sgnH=N-(salicylidene)sulfaguanidine, sal-snmH=N-(salicylidene)sulfanilamide, sal-smrH=N-(salicylidene)sulfamerizine, sal-dadpsH2=N,N′-bis(salicylidene)-4,4′-diaminodiphenylsulfone, respectively. Complexes, (1)–(4) were prepared by the reaction of VOSO4·5H2O with the Schiff bases in 1:2 metal-ligand ratio while complex (5) in 2:2 metal-ligand ratio in DMF-ethanol medium. The compounds so obtained were characterized by different physico-chemical studies, such as, elemental analysis, molar conductance and magnetic measurements, infrared, ESR, thermogravimetric studies, mass and electronic spectral studies. The overall IR studies conclude that the ligand in complex (1)–(4) behave as monobasic bidentate ON donor, while the ligand in the complex (5) behaves as dibasic tetradentate O2N2 donor. The 3D-molecular modeling and analysis for bond lengths and bond angles have also been carried out for two representative compounds, [VO(sal-snm)2(H2O)]·H2O (3) and [VO(dadps)(H2O)]2·2H2O (5) to substantiate the proposed structures. Based on these studies suitable octahedral structures have been proposed for these complexes.

Synthesis, Characterization, Antifeeding and Insect Growth-Regulating Activities of Cr(III), Mn(II), Fe(III), Co(II), Ni(II) and Cu(II) Complexes with N-Acetylacetonyl-3-Aminocoumarin

Metal complexes of Cr(III), Mn(II), Fe(III), Co(II), Ni(II) and Cu(II) have been synthesized using N-acetylacetonyl-3-aminocoumarin as chelating agent. The ligand behaves as a monobasic tridentate ONO donor towards Ni(II) and as monobasic bidentate ON donor towards other cations. All the complexes have been proposed to have octahedral geometry on the basis of analytical, thermal conductivity, spectral and magnetic data. The complexes have been screened against Spodoptera litura; F (Lepidoptera: noctuiidae) for antifeeding and insect growth-regulating activities The results show appreciable antifeeding and insect growth-regulating activities associated with metal complexation at higher and lower doses respectively. Keywords: Metal complexes; N-Acetylacetonyl-3-aminocoumarin; Antifeeding activity; Insect growth-regulating activity. © 2010 JSR Publications. ISSN: 2070-0237 (Print); 2070-0245 (Online). All rights reserved. DOI: http://dx.doi.org/10.3329/jsr.v2i3.4673 J. Sci. Res. 2 (3), 525-537 (2010)

Synthesis, characterization and antimicrobial activity of 3d transition metal complexes of a biambidentate ligand containing quinoxaline moiety

A new series of oxovanadium(IV), chromium(III), manganese(II), iron(III), cobalt(II), nickel(II), and copper(II) complexes of the 3-hydrazino quinoxaline-2-one (HQO) were prepared and characterized. The ligand exhibits biambidenticity. It behaves as a bidentate ON donor in oxovanadium(IV), iron(III) and copper(II) complexes and as a bis bidentate ONNN donor in chromium(III), manganese(II), cobalt(II) and nickel(II) complexes. The nature of bonding and the stereochemistry of the complexes have been deduced from elemental analyses, thermal, infrared, 1H NMR, electronic spectra, magnetic susceptibility and conductivity measurements. An octahedral geometry was suggested for all the complexes. All the complexes show subnormal magnetic moments. The ligand, HQO, and its complexes were tested against one strain Gram +ve bacteria ( Staphylococcus aureus), Gram −ve bacteria ( Escherichia coli). The prepared metal complexes exhibited higher antimicrobial activities than the parent ligand.

Synthetic, spectral and antimicrobial activity studies of first row transition metal complexes derived from lansoprazole drug

Transition metal complexes of II , VO, Mn, Fe III , Co, Ni, Cu, Zn, Cd and II have been synthesized with lansoprazole drug, that is 2-{3-methyl-4-(2,2,2-trifluoroethane)-2-pyridyl)methyl}sulphonyl benzimidazole. Elemental analysis suggest that these metal ions forms ML 2 Cl 2 stoichiometry for Mn, Fe III , Co, Ni, Cu, Zn, Cd and Hg and ML 2 (metal-ligand) stoichiometry for II and II . These complexes are non-electrolytic in nature. The ligand behaves as bidentate ON donor and forms coordinate bonds through C=N and S=O groups. Magnetic susceptibility, IR, UV-Visible and ESR spectral studies suggest that Mn, Fe III , Co, Ni, Cu, Zn, Cd and Hg complexes posses octahedral geometry, whereas, ZrO and VO exhibit square pyramidal geometry. The ligand and its complexes were tested for their antimicrobial activity against Klebsiella, Pseudomonas arginousa, Aspergillus niger and Aspergillus flavous.

<b>Synthesis and structural studies of first row transition metal complexes of N-(2-nitro)-benzilidine-3-hydrazino quinoxaline-2-one</b>

Cr(III), Mn(II), Fe(III), Co(II), Ni(II) and Cu(II) complexes of N-(2-nitro)-benzilidene-3-hydrazino quinoxaline-2-one (NBHQO) have been synthesized and characterized by elemental analysis, conductance, thermal, spectral and magnetic data. NBHQO acts as a bidentate ON donor in all the complexes except in Ni(II) complex in which it acts as a tridentate ONO donor. Octahedral geometries have been proposed for all the complexes except for Cu(II) complex to which the square planar geometry is assigned. KEY WORDS: Metal c omplexes, N-(2-nitro)-benzilidene-3-hydrazino quinoxaline-2-one, ON donor Bull. Chem. Soc. Ethiop. 2008 , 22(3), 385-390.

Synthesis and characterization of polystyrene-anchored monobasic bidentate Schiff base and its complexes with bi-, tri-, tetra- and hexavalent metal ions

A new monobasic bidentate ON donor Schiff base PS–LH2 (where PS–LH2 = polystyrene-anchored Schiff base obtained by condensation of chloromethylated polystyrene (containing 1.17 mmol of chlorine per gram of resin cross-linked with 2% divinylbenzene), 2-hydroxy-1-naphaldehyde and 4-aminosalicylic acid has been synthesized. PS–LH2 reacts with metal complexes to form polystyrene-anchored complexes: PS–LHM(CH3Coo) · DMF (where M = Cu, Zn, Cd, UO2), PS–LHZr(OH)2(CH3Coo) · 2DMF, PS–LHFeCl2 · 2DMF, PS–LHM′(CH3Coo) · 3DMF (where M′ = Mn and Ni) and PS–LHMoo2(acac), where acacH = acetylacetone. The polystyrene-anchored complexes have been characterized by elemental analysis, IR, ESR and magnetic susceptibility measurements. The per cent reaction conversion of PS–LH2 to polystyrene supported coordination compounds lies between 30–95. Shifts of the azomethine ν(C=N) and phenolic ν(C–O) stretches are indicative of ON donor behaviour of the polystyrene-anchored ligands. The complexes, PS–LHCu(CH3Coo) · DMF, PS–LHFecl2 · 2DMF, PS–LHMn(CH3Coo) · 3DMF and PS–LHNi(CH3Coo) · 3DMF are paramagnetic, while PS–LHZn(CH3Coo) · DMF, PS–LHCd(CH3COO) · DMF, PS–LHUo2(CH3Coo) · DMF, PS–LHZr(OH)2(CH3COO) · 2DMF and PS–LHMoO2(acac) are diamagnetic. The copper(II) complex exhibits a square planar structure, zinc(II) and cadmium(II) complexes have tetrahedral structures, nickel(II), manganese(II), iron(III), dioxomolybdenum(VI) and dioxouranium(VI) complexes have octahedral structure and zirconium(IV) complex is pentagonal bipyramidal.

Synthesis, structure and solution chemistry of mixed-ligand oxovanadium(IV) and oxovanadium(V) complexes incorporating tridentate ONO donor hydrazone ligands

In the title family, the ONO donor ligands are the acetylhydrazones of salicylaldehyde (H 2L 1) and 2-hydroxyacetophenone (H 2L 2) (general abbreviation, H 2L). The reaction of bis(acetylacetonato)oxovanadium(IV) with a mixture of tridentate H 2L and a bidentate NN donor [e.g., 2,2′-bipyridine(bpy) or 1,10-phenanthroline(phen), hereafter B] ligands in equimolar ratio afforded the tetravalent complexes of the type [V IVO(L)(B)]; complexes ( 1)–( 4) whereas, if B is replaced by 8-hydroxyquinoline(Hhq) (which is a bidentate ON donor ligand), the above reaction mixture yielded the pentavalent complexes of the type [V VO(L)(hq)]; complexes ( 5) and ( 6). Aerial oxygen is most likely the oxidant (for the oxidation of V IV → V V) in the synthesis of pentavalent complexes ( 5) and ( 6). [V IVO(L)(B)] complexes are one electron paramagnetic and display axial EPR spectra, while the [V VO(L)(hq)] complexes are diamagnetic. The X-ray structure of [V VO(L 2)(hq)] ( 6) indicates that H 2L 2 ligand is bonded with the vanadium meridionally in a tridentate dinegative fashion through its phenolic-O, enolic-O and imine-N atoms. The general bond length order is: oxo < phenolato < enolato. The V–O (enolato) bond is longer than V–O (phenolato) bond by ∼0.07 Å and is identical with V–O (carboxylate) bond. 1H NMR spectrum of ( 6) in CDCl 3 solution indicates that the binding nature in the solid state is also retained in solution. Complexes ( 1)–( 4) display two ligand-field transitions in the visible region near 820 and 480 nm in DMF solution and exhibit irreversible oxidation peak near +0.60 V versus SCE in DMSO solution, while complexes ( 5) and ( 6) exhibit only LMCT band near 535 nm and display quasi-reversible one electron reduction peak near −0.10 V versus SCE in CH 2Cl 2 solution. The VO 3+–VO 2+ E 1/2 values shift considerably to more negative values when neutral NN donor is replaced by anionic ON donor species and it also provides better VO 3+ binding via phenolato oxygen. For a given bidentate ligand, E 1/2 increases in the order: (L 2) 2− < (L 1) 2−.

Synthesis and characterization of polystyrene-supported chelating resin containing an ON donor bidentate Schiff base and its copper(II), nickel(II), cobalt(II), iron(III), zinc(II), molybdenum(VI) and uranium(VI) complexes

A new bidentate ON donor Schiff base supported on a polystyrene matrix has been synthesized by the reaction of aminomethylated polystyrene and hydroxyacetone. The chelating resin reacts with metal salt/metal complex and forms metal-bound polymers. The formulae of the metal-bound polymers are: PSLCu(CH 3COO)·S, PSLNi (CH 3COO)·3S, PSLCo(CH 3COO)·S, PSLFeCl 2·2S, PSLZn (CH 3COO)·S, PSLZnCl·S, PSLMoO 2(acac), and PSLUO 2(CH 3COO)·S (where PSLH = polymer-anchored ligand; S = ethanol or methanol and acac = deprotonated acetylacetone). The polymer-anchored complexes have been characterized by elemental analysis, IR and electronic spectra and magnetic susceptibility measurements. The negative shifts of the ν(CO) (alcoholic) and ν(CN) (azomethine) are indicative of the ON donor behaviour of the polymer-anchored ligand. The complexes PSLNi(CH 3COO)·3S, PSLCo(CH 3COO)·S, PSLFeCl 2·2S, and PSLCu(CH 3COO) 2·S are paramagnetic while PSLZn(CH 3COO)·S, PSLZnCl·S, PSLMoO 2(acac), and PSLUO 2(CH 3COO)·S are diamagnetic. The force constant and UO bond distance of the polymer-anchored uranium(VI) complexes are 7.03 mdyn/Å and 1.73 Å, respectively. The copper(II)- and cobalt(II)-bound polymers exhibit a square planar structure, nickel(II), iron(III), molybdenum(VI) and uranium(VI) complexes are octahedral, and zinc(II) complexes are tetrahedral.