Complexes Of Hydrazones Research Articles

Co(iii) complexes of (1,3-selenazol-2-yl)hydrazones and their sulphur analogues.

The first Co(iii) complexes with (1,3-selenazol-2-yl)hydrazones as an unexplored class of ligands were prepared and characterized by NMR spectroscopy and X-ray diffraction analysis. The novel ligands act as NNN tridentate chelators forming octahedral Co(iii) complexes. The impact of structural changes on ligands' periphery as well as that of isosteric replacement of sulphur with selenium on the electrochemical and electronic absorption features of complexes are explored. To support the experimental data, density functional theory (DFT) calculations were also conducted. Theoretical NMR chemical shifts, the relative energies and natural bond orbital (NBO) analysis are calculated within the DFT approach, while the singlet excited state energies and HOMO-LUMO energy gap were calculated with time-dependent density functional theory (TD-DFT). The electrophilic f- and nucleophilic f+ Fukui functions are well adapted to find the electrophile and nucleophile centres in the molecules. Both (1,3-selenazol-2-yl)- and (1,3-thiazol-2-yl)hydrazone Co(iii) complexes showed potent antimicrobial and antioxidant activity. A significant difference among them was a smaller cytotoxicity of selenium compounds.

Synthesis, characterization and biological applications of new copper(II) complexes of aryl hydrazones

On treatment of copper(II) acetate with aryl hydrazone ligands, four new solid derivatives of copper(II) were produced in appreciable yields. Various characterization techniques including infrared, UV–visible, NMR, electron paramagnetic resonance and mass spectroscopies, elemental analysis, scanning electron microscopy, powder X‐ray diffraction and thermogravimetric analysis revealed a tetra‐coordination in all the mononuclear crystalline complexes with high thermal stability. Further, significant interaction of these novel complexes with calf thymus DNA via intercalative mode of binding was revealed by electronic absorption spectroscopy. The chemical nuclease activity of the complexes on pBR322 DNA was investigated in the presence and absence of oxidizing agent (H2O2). A potent nuclease activity was observed only in the presence of H2O2. Further, antibacterial and antifungal studies of the new ligands and complexes revealed that the latter possessed comparatively better activity.

Ligational, potentiometric and floatation studies on Cu(II) complexes of hydrazones derived from p and o-vanillin condensed with diketo hydrazide

Copper (II) complexes of both 2-(2-(4-hydroxy-3-methoxybenzylidene) hydrazinyl)-2-oxo-N-phenylacetamide (H2L1) and 2-(2-(2-hydroxy-3-methoxybenzylidene) hydrazinyl)-2-oxo-N-phenylacetamide (H2L2) have been prepared and investigated by analytical, magnetic and spectroscopic techniques. IR spectra displayed that (H2L1) behaves as mono-negative tridentate or mono-negative tetradentate in both of [Cu(HL1)Cl]·(2H2O) and [Cu2(HL1)Cl3(H2O)](1.5H2O), respectively. But (H2L2) behaves as neutral bidentate or bi-negative pentadentate in both of [Cu(H2L2)2Cl2]·(2H2O) and [Cu2(L2)Cl2(H2O)]·(2H2O), respectively. 1H NMR spectra showed the replaceable hydrogens of the prepared ligands. The magnetic moment values helped to investigate the geometry of the complexes. Thermogravimetric studies gave a general pattern for the main stages of the thermal decomposition with kinetic data to evaluate thermodynamic parameters ΔH* and ΔG* for each step of degradation to compare between stability of those complexes. Also pH-metric measurements were used to evaluate the proton–ligand formation constants and the stability constants of metal complexes at 298°K. Floatation procedure was carried out to investigate the optimum conditions for Cu(II) separation by ligand molecules.

Comparative ligational, optical band gap and biological studies on Cr(III) and Fe(III) complexes of hydrazones derived from 2-hydrazinyl-2-oxo-N-phenylacetamide with both vanillin and O-vanillin

The Cr(III) and Fe(III) complexes of hydrazones derived from the condensation of 2-hydrazinyl-2-oxo-N-phenylacetamide with both vanillin and o-vanillin synthesized and characterized by different conventional physicochemical techniques. The kinetic and thermodynamic parameters for the different decomposition steps were calculated using Coats–Redfern and Horowitz–Metzger equations. The bond lengths, bond angles, HOMO, LUMO, dipole moment and binding energy calculated by DFT calculations. The optical band gap (Eg) values equal 3.28, 3.03, 3.58 and 3.57eV for [Cr(HL1)Cl2(H2O)2](0.75H2O), [Cr(HL2)Cl2(H2O)](H2O), [Fe(HL1)Cl2(H2O)2](0.5H2O) and [Fe(HL2)2Cl(H2O)](3H2O) complexes, respectively. The antibacterial activities tested against Bacillus subtilis and Escherichia coli bacteria.

Eco Friendly Microwave Assisted Rapid and Efficient Synthesis, Spectroscopic Studies and Antimicrobial Activity of Bivalent Transition Metal Complexes of Hydrazones

Two new series of Co(II), Ni(II) and Cu(II) metal complexes of the type [M(C14H10N2O3)·2H2O] and [M(C14H11N2O2)·3H2O]Ac, where M = Co(II)/Ni(II)/Cu(II) and Ac = CH3COO−, have been synthesized in good yields at less reaction time by adopting an efficient and eco friendly microwave assisted method. All the synthesized compounds were characterized by running their TLC for single spot, HPLC, elemental analyses, IR, 1H-NMR, 13C-NMR, magnetic susceptibility measurements, electronic spectral studies and screened for antimicrobial activities against two bacteria Staphylococcus aureus (gram +ve) and Escherichia coli (gram −ve) and fungi Aspergillus niger and Aspergillus flavus by adopting disc diffusion method. The antimicrobial activity results indicated that hydrazide exhibited good activity which increases in its hydrazones. However, the metal complexes exhibited maximum activity against both bacteria and fungi.

Oxidative bromination of monoterpene (thymol) using dioxidomolybdenum(VI) complexes of hydrazones of 8-formyl-7-hydroxy-4-methylcoumarin

Condensation of equimolar amount of 8-formyl-7-hydroxy-4-methylcoumarin (fhmc) and hydrazides [benzoylhydrazide (bhz), isonicotinoylhydrazide (inh), nicotinoylhydrazide (nah) and furoylhydrazide (fah)] in methanol results in the formation of potential ONO tridentate ligands H2fhmc-bhz (I), H2fhmc-inh (II), H2fhmc-nah (III), and H2fhmc-fah (IV), respectively. Reaction of these ligands with [MoVIO2(acac)2] in refluxing methanol gives dioxidomolybdenum(VI) complexes, [MoVIO2(fhmc-bhz)(MeOH)] (1), [MoVIO2(fhmc-inh)(MeOH)] (2), [MoVIO2(fhmc-nah)(MeOH)] (3) and [MoVIO2(fhmc-fah)(MeOH)] (4), respectively. The structures of the obtained ligand and their respective metal complexes were elucidated by elemental analyses, spectroscopic techniques (IR, electronic, 1H and 13C NMR) and thermogravimetric analyses. Single crystal X-ray analysis of complex 1a confirms the chelation of the ligand to the metal ion through two oxygen and a nitrogen atoms. These metal complexes have been tested against oxidative bromination of monoterpene (thymol) to yield 2-bromothymol, 4-bromothymol and 2,4-dibromothymol using H2O2 as an oxidant therefore they act as functional models of vanadium dependent haloperoxidases. The effects of various factors, such as amounts of catalyst, oxidant, KBr, HClO4 and different solvents have been considered to optimize the reaction conditions for the maximum brominated products.

ChemInform Abstract: Metal Complexes of Hydrazones and Their Biological, Analytical and Catalytic Applications: A Review

AbstractReview: 142 refs.

Synthesis, Characterization and Catalytic Activity of Oxovanadium(IV) Complexes of Heterocyclic Acid Hydrazones

Synthesis, Characterization and Catalytic Activity of Oxovanadium(IV) Complexes of Heterocyclic Acid Hydrazones

Oxidovanadium(IV) and dioxidovanadium(V) complexes of hydrazones of 2-benzoylpyridine and their catalytic applications.

Reactions between the tridentate ONN donor ligands, Hbzpy-tch () and Hbzpy-inh (), with [V(IV)O(acac)2] in dry methanol give two different types of complexes, [V(IV)O(acac)(bzpy-tch)] () and [V(IV)O(OMe)(bzpy-inh)] (), respectively. Irrespective of their nature in methanol upon aerial oxidation and precipitation both yield dinuclear [{V(V)O(bzpy-tch)}2(μ-O)2] () and [{V(V)O(bzpy-inh)}2(μ-O)2] (). Treatment of or in methanol with H2O2 yields the oxidomonoperoxidovanadium(v) complexes [{V(V)O(bzpy-tch)}2(μ-O2)2] () and [V(V)O(O2)(bzpy-inh)] (). Reactions of and with imidazolomethylpolystyrene cross-linked with 5% divinylbenzene (PS-im) in DMF give the polymer-supported PS-im[V(V)O2(bzpy-inh)] () and PS-im[V(V)O2(bzpy-tch)] (). The compounds are characterized by various spectroscopic techniques and compounds and were also analyzed by thermal, atomic force microscopy (AFM), field-emission scanning electron micrographs (FE-SEM) as well as energy dispersive X-ray (EDAX) studies. The molecular structures of and of [V(V)O(O2)(bzpy-inh)(H2O)]·0.5MeOH () were determined by single-crystal X-ray diffraction, confirming the μ-bis(O) and ONN binding mode in the dinuclear complexes and , as well as the side-on coordination of the peroxido ligand in and . The polymer-grafted compounds and were used for the catalytic oxidation of isoeugenol using aqueous H2O2 as an oxidant. The intermediate peroxido species, expected to be involved during catalytic action, were also generated from solutions of and studied by UV-Vis and (51)V NMR. The catalytic activity of the several systems was tested and the polymer-supported versions showed higher conversions than their neat counterparts. The polymer-supported complexes allow for recyclable catalytic systems, thus providing additional advantages over their homogeneous counterparts in terms of increased catalyst lifetime and easier separation from the reaction mixture.

Supramolecular organization of complexes of aryl hydrazones with SnCl3and SnCl4

Chelate complexes of main group metals with N,O-chelating Schiff Base ligands have been reported as perspective models for biologically active species. The derivatives of aryl hydrazones are among the most widely used ligands of such type. In our study, crystal structures of aryl hydrazones with SnCl3and SnCl4are discussed: the presence of aromatic fragments, amine groups and chlorine atoms therein are responsible for the coexistence of strong hydrogen and halogen bonds as well as stacking and Cl...π interactions. Interplay between these types of interactions and their role in stabilization of crystal structures is the subject of particular interest. We studied all these aspects in complexes of aryl hydrazones using different theoretical approaches: those based on Stockholder partitioning, molecular electrostatic potential, non-covalent interaction index, AIM theory – together with Espinosa-Mollins-Lecomte correlation to estimate the energy of all intermolecular interactions in crystals by means of electron density analysis from periodic quantum chemical calculations (VASP code). Our results showed that the presence of intermolecular interactions led to a noticeable redistribution of electron density in crystal as compared to an isolated molecule. Although Cl...π, stacking interactions and halogen bonds are numerous in the crystals of these complexes, their contribution to the energy of their crystal lattice does not exceed 30%. The work was supported by Council of the President of the Russian Federation (grant MD-3589.2014.3).

Metal complexes of hydrazones and their biological, analytical and catalytic applications: A review

This is the first comprehensive review of the biological activity of hydrazone-transition metal complexes. Hydrazone complexes gained much attention because of their antifugial, antibacterial anticonvulsant, and analgesic, antiinflammatory, antimalarial, antimicrobial, antituberculosis, anticancer, and antiviral activities. Additionally, some of the hydrazone complexes were used in treatment of iron overload diseases. One application, which reflects the importance of hydrazone complexes, is their use in detection and determination of metals and some organic constituents in pharmaceutical formulations. This review will provide an overview of the biological, analytical and catalytic applications of this category of complexes.

Dioxomolybdenum(VI) complexes of hydrazones of two substituted salicylaldehydes: synthesis, structures, and catalytic properties

Dioxomolybdenum(VI) complexes [MoO2L(CH3OH)] (L = L1 = N′-(2-hydroxy-5nitrobenzylidene)isonicotinoylhydrazide for 1, L = L2 = N′-(4-diethylamino-2-hydroxybenzylidene)-4-methylbenzohydrazide for 2) were prepared and structurally characterized by physicochemical and spectroscopic methods and single-crystal X-ray determination. Mo in the complexes is octahedrally coordinated. Both complexes show effective catalysis in oxidation of cyclohexene, vinylbenzene, 1-butylene, and 1-pentene, to their corresponding epoxides. In general, high epoxide yields (over 89%) and selectivity (100%) were observed for all aliphatic and aromatic substrates.

Mononuclear and binuclear Cu(II) complexes of some tridentate aroyl hydrazones. X-ray crystal structures of a mononuclear and a binuclear complex

Cu(II) complexes of eight N,N,O-donor hydrazone ligands, obtained by condensation of pyridine-2-carbaldehyde and 2-acetylpyridine with four aroyl hydrazides, are reported. Reactions of Cu(ClO4)2·6H2O with the pyridine-2-carbaldehyde hydrazones (L1H, L2H, L3H, L4H) in presence of Et3N, in 1:2:2 molar ratio, lead to isolation of mononuclear octahedral Cu(II) complexes of formula [Cu(L)2] (L=L1−, L2−, L3−, L4−). However, for the 2-acetylpyridine hydrazones (L5H, L6H, L7H, L8H) reactions under similar conditions yield dichloro bridged complexes of the type [Cu2(μ-Cl)2(L′)2] (L′=L5−, L6−, L7−, L8−), where each Cu(II) ion is in a square-pyramidal geometry, the chloride ions coming from the in situ reduction of perchlorate by the 2-acetylpyridine hydrazones. The X-ray crystal structures of [Cu(L1)2] and [Cu2(μ-Cl)2(L5)2] are reported. The spectroscopic and electrochemical behaviors of the complexes are also reported.

Design, synthesis and DNA binding activities of late first row transition metal(II) complexes of bi- functional tri – and tetratopic imines

A series of novel Co(II), Ni(II), Cu(II) and Zn(II) complexes of tri and tetratopic hydrazones have been prepared. Ligands L1H2 and L2H2 were synthesized by the condensation of 2-formylphenoxyacetic acid with 2-hydrazinobenzothiazole and 2-hydroxy-3-hydrazinebenzopyrazine, respectively. The prepared complexes were characterized by the analytical and spectral techniques. All the complexes were found to be monomeric in nature with octahedral geometry. Both ligands were found to be electrochemically active in the working potential range showing single electron transfer process attributed to the deprotonation of carboxylic group of the 2-formylphenoxyacetic acid. The potency of the ligand and its complexes as antimicrobial agents has been investigated and made to interact with Escherichia coli DNA to investigate the binding/cleaving ability by absorption, hydrodynamic and electrophoresis studies.

Transition metal complexes of novel ethyl pyruvate hydrazones as potential antitumor agents: synthesis and physicochemical properties, DNA interactions and antiproliferative activity

A new series of ethyl pyruvate hydrazones and their later first row transition metal(II) complexes have been synthesized and characterized by means of elemental analyses, vibrational, electronic, 1H and 13C NMR, electron paramagnetic resonance, and mass spectroscopic techniques along with thermal and magnetic studies. All complexes were found to be monomeric in nature and have octahedral geometry. The prepared compounds were evaluated for antiproliferative activity against the two human cancer cell lines (HeLa and HepG2). The Cu(II) complexes were found to have potential activity against the cell lines used than the ligand and other complexes. In addition, the DNA-binding/cleaving capacity of the compounds were analyzed by absorption spectroscopy, viscosity measurement, thermal denaturation studies and gel electrophoresis methods.

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.

Antiproliferative effects of metal complexes of new isatin hydrazones against HCT116, MCF7 and HELA tumour cell lines

New hydrazone ligands (HL) derived from 5-substituted isatins and 1-(4-(2-methoxybenzyl)-6-arylpyridazin-3-yl)hydrazines and its complexes with Co(II) and Cu(II) were synthesized. The new hydrazones and their complexes were characterized by means of elemental, spectral analyses and magnetic studies. Primary cytotoxicity evaluation of HL 5a and the new complexes showed that these complexes could act as anticancer agents since they reduced the growth of samples of human tumour cell lines (HCT116(Colon), MCF7(Breast) and HELA(Cervix)) to ≤18.5 μg/mL for the new complexes.

Synthesis and spectroscopic properties of cobalt(III) complexes of some aroyl hydrazones: X-ray crystal structures of one cobalt(III) complex and two aroyl hydrazone ligands

Cobalt(III) complexes of diacetyl monooxime benzoyl hydrazone ( dmoBH 2 ) and diacetyl monooxime isonicotinoyl hydrazone ( dmoInH 2 ) have been synthesized and characterized by elemental analyses and spectroscopic methods. The X-ray crystal structures of the two hydrazone ligands, as well as that of the cobalt(III) complex [Co III(dmoInH) 2]Cl · 2H 2O , are also reported. It is found that in the cobalt(III) complexes the Co(III) ion is hexa-coordinated, the hydrazone ligands behaving as mono-anionic tridentate O,N,N donors. In the [Co III(dmoInH) 2]Cl · 2H 2O complex, the amide and the oxime hydrogens are deprotonated for both the ligands, while the isonicotine nitrogens are protonated. In the [Co III(dmoBH) 2]Cl complex, only the amide nitrogens are deprotonated. It is shown that the additional hydrogen bonding capability of the isonicotine nitrogen results in different conformation and supramolecular structure for dmoInH 2 , compared to dmoBH 2 , in the solid state. Comparing the structure of the [Co III(dmoInH) 2]Cl · 2H 2O with that of the Zn(II) complex of the same ligand, reported earlier, it is seen that the metal ion has a profound influence on the supramolecular structure, due to change in geometrical dispositions of the chelate rings.

Copper(II) complexes of N-heteroaromatic hydrazones: Synthesis, X-ray structure, magnetic behavior, and antibacterial activity

Three novel copper(II) complexes as condensation derivatives of 2-pyridinecarboxaldehyde, 2-acetylpyridine or 2-quinolinecarboxaldehyde with ethyl hydrazinoacetate hydrochloride were synthesized. X-ray crystal structures of all three complexes were determined. Crystallographic data indicate a common basis of the structures with some major differences. Both pyridine derivatives form complexes of the type [CuCl 2L] with distorted square-planar geometry around copper(II), but show a decisive difference in the side chain orientation. The quinoline derivative forms a dimeric complex of type [Cu 2Cl 4L 2] with distorted trigonal bipyramidal geometry around copper(II), but a rather short Cu···Cu contact, which is reflected in its magnetic properties. All three complexes showed antibacterial activity.

Syntheses, spectroscopic characterization and thermal behavior on novel binuclear transition metal complexes of hydrazones derived from 4,6-diacetylresorcinol and oxalyldihydrazine

4,6-Diacetylresorcinol (DAR) serves as precursor for the formation of different hydrazone ligands, which are di-, tetra- or hexa-basic with two symmetrical sets of O 2N tridentate, O 2N 2 tetradentate or O 4N 2 hexadentate chelating sites. The condensation of 4,6-diacetylresorcinol (DAR) with oxalyldihydrazine (ODH), in the molar ratio 1:1 and 1:2, yields the corresponding hydrazone, H 6L a and H 4L b, ligands, respectively. The structures of these ligands were elucidated by elemental analyses and IR, mass, 1H NMR and UV–vis spectra. Reactions of the hydrazone ligands with cobalt(II), nickel(II), copper(II), zinc(II), cadmium(II), iron(III) and chromium(III) ions in 1:2 molar ratio afforded the corresponding transition metal complexes. A variety of binuclear transition metal complexes were obtained in its di-, tetra- or hexa-deprotonated forms. The structures of the newly prepared complexes were identified by elemental analyses and IR, UV–vis, mass, 1H NMR and ESR spectra, as well as, magnetic susceptibility measurements and thermal gravimetric analysis (TGA). The bonding sites are the azomethine and C O oxygen atoms in either keto or enol forms and amino nitrogen atoms, and phenolic oxygen atoms. The metal complexes exhibit different geometrical structures such as tetrahedral and octahedral arrangements.