Benzoylhydrazone Ligands Research Articles

Transfer hydrogenation of ketones catalysed by half‐sandwich (η6‐p‐cymene) ruthenium(II) complexes incorporating benzoylhydrazone ligands

Neutral half‐sandwich η6‐p‐cymene ruthenium(II) complexes of general formula [Ru(η6‐p‐cymene)Cl(L)] (HL = monobasic O, N bidendate benzoylhydrazone ligand) have been synthesized from the reaction of [Ru(η6‐p‐cymene)(μ‐Cl)Cl]2 with acetophenone benzoylhydrazone ligands. All the complexes have been characterized using analytical and spectroscopic (Fourier transform infrared, UV–visible, 1H NMR, 13C NMR) techniques. The molecular structures of three of the complexes have been determined using single‐crystal X‐ray diffraction, indicating a pseudo‐octahedral geometry around the ruthenium(II) ion. All the ruthenium(II) arene complexes were explored as catalysts for transfer hydrogenation of a wide range of aromatic, cyclic and aliphatic ketones with 2‐propanol using 0.1 mol% catalyst loading, and conversions of up to 100% were obtained. Further, the influence of other variables on the transfer hydrogenation reaction, such as base, temperature, catalyst loading and substrate scope, was also investigated.

Anion and solvent effects on the coordination behavior of N-(2-pyridinylmethylene)benzoylhydrazone with copper(II): synthesis and structural characterization

The Cu(II) complexes [Cu(HL)Cl2], 1; [Cu(HL)(NO3)(H2O)]NO3, 2a; [Cu(L)(NO3)]2·C3H8O, 2b; [Cu(L)(μ1,1–N3)]2, 3; [Cu(L)(Br)]2, 4; [(H2O)CuL(μ-SO4)CuL], 5a; [CuL(μ-SO4)CuL]·H2O, 5b and [Cu(L)(CH3COO)]2, 6, where HL is a benzoylhydrazone tridentate Schiff base, have been synthesized and characterized by elemental analysis, FTIR, and UV–vis. The structures of 2a, 2b, 3, 4, 5a, and 5b have been determined by single-crystal X-ray diffraction analyses. In 2a, the benzoylhydrazone ligand is neutral and coordinates in its keto form and copper(II) has a distorted octahedral geometry. In dinuclear 2b, 3, 4, 5a, and 5b, there are bridging counter anions and the benzoylhydrazone ligand is monoanionic, coordinating in its enol form. In 5a and 5b, the enolic ligand also supplies a bridging alkoxo to the adjacent copper ion. In 5a, one of the two copper ions is five-coordinate in a distorted square pyramidal geometry, while the other copper ion has an additional water bonded to it in a distorted octahedral geometry. In 5b, both copper ions are five-coordinate with distorted square pyramidal geometries.

Synthesis and molecular structure of ruthenium(III) benzoylhydrazone complexes: Substituents effect on transfer hydrogenation of ketones

An easy and convenient synthesis of a new series of octahedral ruthenium(III) complexes bearing benzoylhydrazone of general formula [Ru(L)Cl(PPh3)2] (where L = 2-hydroxy-1-naphthaldehyde benzoylhydrazone) has been reported. The composition of all the complexes has been unequivocally characterized by microanalysis, IR, electronic, magnetic and EPR spectroscopic techniques. The substituted benzoylhydrazone ligands behave as a dianionic tridentate O, N and O donors and coordinate to ruthenium via the phenolic oxygen, the azomethine nitrogen and the deprotonated amide oxygen. The complexes exhibit moderately strong ligand-to-metal charge transfer transitions in the visible region and intraligand transition in the UV region. Magnetic moment of the complexes (298 K) lies in the range 1.72–1.97 μB reveals the presence of one unpaired electron in the metal centre. The low spin mononuclear Ru(III) benzoylhydrazone complexes display rhombic EPR spectral pattern in frozen solution. The molecular structure of two of the complexes has been established by single crystal X-ray crystallography and indicates the presence of a distorted octahedral geometry in these complexes. Further, the complexes 1–5 have been proven to catalyse the transfer hydrogenation of linear, cyclic and aromatic ketones to their corresponding secondary alcohols in the presence of i-PrOH/KOH at 82 °C and the maximum conversion is up to 99%. The effect of other variables on the transfer hydrogenation reaction such as solvent, base, temperature, time and catalyst loading is also reported.

Synthesis, structural characterization and catalytic transfer hydrogenation of ruthenium(II) carbonyl complexes bearing N,N,O pincer type benzoylhydrazone ligands

The convenient synthesis of four new octahedral ruthenium(II) carbonyl benzoylhydrazone complexes of the general molecular formula [Ru(L)Cl(CO)(PPh3)] (where HL=substituted 2-acetylpyridine benzoylhydrazones; the H represents the dissociable proton) has been described. The characterization of the complexes was accomplished by spectroscopic (FT-IR, 1H NMR, UV–Vis) techniques as well as by elemental (C,H,N) analysis. A single crystal X-ray diffraction study of a representative complex, [Ru(L1)Cl(CO)(PPh3)] (1), confirms a pincer-like N,N,O coordination mode of the benzoylhydrazone ligand via the pyridine N, the azomethine N and the deprotonated amide O atoms, with the formation of two five-membered fused chelate rings, and indicates a distorted octahedral geometry around the ruthenium(II) centre. Further, the catalytic efficiency of complex 1 has been investigated for the transfer hydrogenation of substituted acetophenones to the corresponding secondary alcohols. The influence of base and catalyst loading in the transfer hydrogenation reaction was also evaluated. The complexes were found to be efficient catalysts in the presence of iso-propanol/KOH with conversions up to 99.2%.

Novel pseudohalide-bridged Cu(II) complexes with a hydrazone ligand: Evaluation of antimicrobial activity

Two novel Cu(II) complexes with the ligand pyridine-2-carboxaldehyde 4-hydroxy benzoyl hydrazone ligand (HL) have been successfully prepared and their crystalline structures are reported. These pseudohalide-bridged copper(II) complexes [{Cu(L)(μ1,1-N3)}2] (1) and {Cu(L)(NCS)(MeOH)} (2) were characterised by elemental analysis, IR and UV–Vis spectroscopy. Their solid-state structures were determined by single-crystal X-ray diffraction analysis which revealed that 1 is a μ1,1-N3-bridged dimer, whereas 2 is a mononuclear based structure. Supramolecular interactions involving the adjacent complexes were investigated in detail. The efficiency of the ligand and the two complexes was evaluated against the bacteria Entrobacter facealis, Staphytococcus aureus, Entrobacter aerogenes, Escherichia coli, Klebsiella pneumonia and Proteus mirabilis, with the complexes demonstrating enhanced activity relatively to the free ligand.

DNA-binding studies of two dioxomolybdenum(VI) complexes of salicylaldehyde benzoylhydrazone ligands

The reaction of [MoO2(acac)2] with salicylaldehyde benzoylhydrazone (H2L1) and with one of its derivatives (H2L2) resulted in the production of two neutral mononuclear dioxomolybdenum complexes; MoO2L1(MeOH) 1 and MoO2L2(MeOH) 2, respectively. (H2L1) was derived from the reaction of benzhydrazide and 2-hydroxybenzaldehyde (salicylaldehyde) and (H2L2) was derived from the reaction of benzhydrazide and 2-hyroxy-3-methoxybenzaldehyde. Interactions of the complexes were investigated with calf thymus DNA by UV–Vis, fluorescence and circular dichroism spectroscopies to determine their biological effects. Results evaluated the binding affinity of complexes 1 and 2 to CT-DNA by UV and presented binding constants (Kb) of (3.52±0.1)×103M−1 and (4.49±0.1)×103M−1, respectively. Evaluations of fluorescence approved the binding of the fluorescent complex 2, to DNA. Competitive studies with ethidium bromide (EB) showed that none of the complexes displaced the DNA–EB binding efficiency effectively while they changed the polarity of the environment by occupying the previous place of water molecules around the helix. CD spectral studies revealed that as a result of interaction with both complexes, calf thymus B-DNA turned into A-like structure.According to our results both complexes bind to DNA via a non-intercalative mode, presumably through groove binding.

Synthesis, structural characterization, electrochemistry and catalytic transfer hydrogenation of ruthenium(II) carbonyl complexes containing tridentate benzoylhydrazone ligands

Convenient synthesis of eight new octahedral ruthenium(II) carbonyl benzoylhydrazone complexes having the general molecular formula [Ru(L)(CO)(EPh3)2] (where E = P or As; H2L = benzoylhydrazone ligand, the two H's representing the two dissociable protons) has been described. The substituted benzoylhydrazone ligands behave as a dianionic tridentate O, N and O donors (L) and coordinates to ruthenium via the phenolate oxygen, the azomethine nitrogen and the deprotonated amide oxygen. The compositions of the complexes have been established by elemental analysis and spectral methods (FT-IR, 1H NMR, 13C NMR, UV–vis). The crystal structure of one of the complexes, [Ru(L2)(CO)(PPh3)2] (2), has been solved by single crystal X-ray crystallography and it indicates the presence of a distorted octahedral geometry in these complexes. All the complexes exhibit metal-to-ligand charge transfer (MLCT) transitions in the visible region and display one quasi-reversible reduction and two irreversible oxidations. Further, the catalytic efficiency of the complexes has been investigated in the case of transfer hydrogenation of ketones to the corresponding secondary alcohols. The influence of base, reaction temperature and catalyst loading in transfer hydrogenation reaction was also evaluated. The complexes were found to be efficient catalysts with conversion up to 99.5% in presence of iso-propanol/KOH.

Bis(μ-2-{[oxido(phenyl)methylidene]hydrazinylidene}propanoato)bis[dibenzyl(ethanol)tin(IV)

In the title complex, [Sn2(C7H7)4(C10H8N2O3)2(C2H5OH)2], the Sn(IV) atom is seven-coordinated in a distorted penta­gonal–bipyramidal geometry by three O atoms and one N atom from the pyruvate benzoyl hydrazone ligand, one ethanol O atom and two axial C atoms from trans-benzyl groups, thus forming a dimeric mol­ecule ( symmetry) via weak Sn—O inter­actions. The C atoms of one phenyl ring and the ethanol mol­ecule are disordered over two sets of sites with site-occupancy factors of 0.57 (5):0.43 (5) and 0.79 (2):0.21 (2), respectively. Intermolecular O—H⋯O hydrogen bonds stabilize the crystal structure.

(E)-N′-(5-Chloro-2-oxidobenzylidene-κO)-3,4,5-trimethoxybenzohydrazidato-κ2N′,O](pyridine-κN)copper(II)

In the title compound, [Cu(C17H15ClN2O5)(C5H5N)], the CuII atom is coordinated by one N atom and two O atoms from an anionic salicyl­aldehyde benzoyl­hydrazone ligand and one pyridine N atom in a distorted square-planar geometry. The bonds displays the usual elongation with mean Cu—O and Cu—N bond lengths of 1.926 and 1.976 Å, respectively. The pyridine ring makes dihedral angles of 26.12 (13) and 11.08 (12)°, respectively, with the trimeth­oxy­phenyl and phenolate rings, which make a dihedral angle of 16.05 (12)° with one another.

Synthesis, characterization and biological properties of Co(II), Ni(II), Cu(II) and Zn(II) complexes with an SNO functionalized ligand

Some new metal(II) complexes, ML2[M=Co, Ni, Cu and Zn], of 2-acetylthiophene benzoylhydrazone ligand (HL) containing a trifunctional SNO-donor system have been synthesized and characterized on the basis of physicochemical data by elemental analysis, magnetic moment, molar conductance, thermogravimetric and spectroscopic (electronic, IR, 1H NMR and 13C NMR) data. The ligand functions as monobasic SNO tridentates where the deprotonated enolic form is preferred in the coordination producing distorted octahedral complexes.

Bis[N-(isonitrosoacetophenone)-N′-benzoylhydrazonato-k3O,N,N′]nickel(II) dimethylformamide disolvate hemihydrate: Synthesis, crystal structure, and spectroscopic and electronic properties

In the title complex, [Ni(C30H24N6O4)]2 · 4C3H7NO · H2O (I), the Ni(II) atoms are six-coordinated by two N atoms and one O atom of each of the two tridendate benzoylhydrazone ligands, leading to a distorted octahedral geometry. In the environment of Ni(II) atoms, the equatorial planes are approximately perpendicular. The structure is stabilized by O-H...O, O-H...N, and C-H...O intra- and intermolecular hydrogen bonding, resulting in the formation of infinite chains running along the x axis of the triclinic cell. The structure of the compound was characterized by IR and UV spectra, elemental analyses, and X-ray diffraction techniques.

Novel coordination behavior of a pteridine-benzoylhydrazone ligand (BZLMH): Theoretical calculations, XRD structures and luminescence studies

The XRD structure and the influence of the conformation in the molecular orbitals of the pteridine-benzoylhydrazone ligand (BZLMH = benzoylhydrazone of 6-acetyl-1,3,7-trimethyllumazine, lumazine = (1 H,3 H)-pteridin-2,4-dione) have been studied. Complexes of BZLMH with nickel(II), zinc(II) and mercury(II) have been prepared and spectroscopically characterized by IR, NMR and fluorescence spectroscopy; also XRD studies have allowed to establish two different coordinative patterns in the complexes [Ni 3(BZLMH) 3(OH)(H 2O)(CH 3CN) 2](ClO 4) 5 · 2H 2O · CH 3CN ( 2) and [Zn(NO 3)(BZLMH)(H 2O)](NO 3) ( 3). Compound ( 2) is a trinuclear hydroxo-centered complex with a central hydroxo group bridging the three nickel(II) ions. The [Ni 3(μ 3-OH)] 5+ core is planar with the benzoylhydrazone ligands coordinated in the bis-bidentate [O(4),N(5)]-[N(61),O(63)] mode. The zinc(II) compound displays a BPT coordination geometry in which the BZLMH ligand acts in a tridentate fashion using N(5), N(61) and O(63) donor atoms. Fluorescence spectroscopic properties of benzoylhydrazone (BZLMH) are studied and the fluorescence band shift and changes in intensity is modulated by complexation with different metal ions (Ni 2+, Zn 2+ and Hg 2+), so the binding is signaled such a possible cause.

DNA-binding properties studies and spectra of a novel fluorescent Zn(II) complex with a new chromone derivative

A new chromone derivative (6-ethoxy chromone-3-carbaldehyde benzoyl hydrazone) ligand (L) and its two transition metal complexes [Zn(II) complex and Ni(II) complex] have been prepared and characterized on the basis of elemental analysis, molar conductivity, mass spectra, UV–vis spectra and IR spectra. The Zn(II) complex exhibits light blue fluorescence under UV light, and the fluorescent properties of Zn(II) complex and the ligand in solid state and in different solutions (MeOH, DMF, THF and H 2O) were investigated. In addition, the interactions of the Zn(II) complex and the ligand with calf thymus DNA were investigated using UV–vis absorption, fluorescence, circular dichroic spectral methods and viscosity measurement. It was founded that both two compounds, especially the Zn(II) complex, strongly bind with calf thymus DNA, presumably via an intercalation mechanism.

DNA-Binding Properties Studies and Spectra of a Novel Cu(II) Complex with a New Coumarin Derivative

A new coumarin derivative (8-methylcoumaro-4a,10a-pyrone-3-carbaldehyde benzoyl hydrazone) ligand and its novel Cu(II) complex have been synthesized and characterized on the basis of elemental analyses, molar conductivities, (1)H-NMR, IR spectra, UV-visible spectroscopy and thermal analyses. In addition, the interactions of the Cu(II) complex and the ligand with calf-thymus DNA were investigated by spectrometric titrations, ethidium bromide displacement experiments and viscosity measurements. It was found that both the two compounds, specially the Cu(II) complex, strongly bind with calf-thymus DNA, presumably via an intercalation mechanism.

Synthesis, characterization, antioxidant activity and DNA-binding studies of two rare earth(III) complexes with naringenin-2-hydroxy benzoyl hydrazone ligand

Two novel rare earth complexes, Y(III) complex ( 1) and Eu(III) complex ( 2), with naringenin-2-hydroxy benzoyl hydrazone ligand were synthesized and characterized. The interaction of the two metal complexes and the free ligand with calf thymus DNA (CT DNA) was investigated by electronic absorption spectroscopy, fluorescence spectroscopy and viscosity measurement. All the experimental evidences indicate that these three compounds can strongly bind to CT DNA via an intercalation mechanism. The intrinsic binding constants of the Y(III) complex ( 1), Eu(III) complex ( 2) and the free ligand with CT DNA were 2.1 × 10 4, 8.5 × 10 4 and 1.6 × 10 4 M −1, respectively. Furthermore, the antioxidant activity of the metal complexes was determined by hydroxyl radical scavenging method in vitro.

Synthesis, crystal structure and DNA-binding studies of the Ln(III) complex with 6-hydroxychromone-3-carbaldehyde benzoyl hydrazone

A novel 6-hydroxy chromone-3-carbaldehyde benzoyl hydrazone ligand ( L) and its Ln(III) complexes, [Ln = La( 1) and Sm( 2)], have been prepared and characterized. The crystal and molecular structures of complexes 1 and 2 were determined by single-crystal X-ray diffraction. Antioxidative activity tests in vitro showed that L and its complexes have significant antioxidative activity against hydroxyl free radicals from the Fenton reaction and also oxygen free radicals, and that the effect of the La(III) complex 1 is stronger than that of mannitol and the other compounds. The compounds were tested against tumor cell lines including HL-60 and A-549. The data shows that the suppression rate of complexes 1 and 2 against the tested tumor cells are superior to the free ligand ( L). The interactions of complexes 1 and 2, and L, with calf thymus DNA were investigated by UV–visible (UV–vis), fluorescence, denaturation experiments and viscosity measurements. Experimental results indicated that complexes 1 and 2, and L can bind to DNA via the intercalation mode, and that the binding affinity of complex 1 is higher than that of complex 2 and of free ligand ( L). The intrinsic binding constants of complexes 1 and 2, and L were (7.62 ± 0.56) × 10 6, (3.70 ± 0.47) × 10 6 and (2.41 ± 0.46) × 10 6 M −1, respectively.

Synthesis, characterisation and structural aspects of a new diorganotin(IV) complex with N′-(5-bromo-2-hydroxybenzylidene)benzoylhydrazone ligand

A new diorganotin(IV) complex, Me2Sn[5-Br-(2-OC6H4CH=N–N=C(O)Ph)] (1) has been synthesised from dimethyltin(IV) dichloride and a Schiff base derived from 5-bromosalicylaldehyde and benzoyl hydrazide. The complex has been characterised by elemental analysis, and FT-IR and NMR spectroscopies. Molecular structure has been confirmed by single-crystal X-ray diffraction analysis. Complex 1 crystallises in triclinic system, space group P-1 (no. 2) with a=7.562(6), b=9.980(8), c=11.899(8) A; α=81.08(6)°, β=72.71(5)°, γ=79.64(6)°; Z=2. The ligand N′-(5-bromo-2-hydroxybenzylidene)benzoylhydrazone (H2L) coordinates to the metal centre in enolate form via the phenolic O, imino N and enolic O atoms. The central tin atom is in distorted trigonal bipyramidal geometry with two oxygen atoms of the ligand in axial positions, while the imino nitrogen atom of the ligand and two methyl groups on tin occupy the equatorial sites.

Synthesis and characterization of ferrocenylcarbaldehyde benzoylhydrazone and its rhenium(I) complex

The novel ferrocenylcarbaldehyde benzoylhydrazone ligand H(Fe)L 1 has been prepared and its reaction with fac-[ReBr(CO) 3(CH 3CN) 2] in chloroform gave [ReBr(CO) 3{H(Fe)L 1}] in good yield. Both compounds have been characterized by elemental analysis, MS, IR, UV–Vis and 1H NMR spectroscopic methods and their structures elucidated by X-ray diffraction. Four crystallographically independent molecules of H(Fe)L 1 are associated by N1–H and N2 or O atoms of a neighbouring ligand or methanol molecules to give chains running along the b axis. The hydrazide group is O,N-bidentate and affords a five-membered chelate ring in the rhenium complex. The geometry around the metal is fac-octahedral. The intermolecular associations based on C(Fc)–H⋯O hydrogen bonds are also discussed.

Controlled Ligand Deprotonation in Lanthanide Chelates with Asymmetric Semicarbazone/Benzoylhydrazone or Semicarbazone/Thiosemicarbazone Coordination Spheres

Asymmetric, potentially pentadentate ligands (H(2)L(3)) are formed by subsequent condensation of a semicarbazide and benzoylhydrazine on 2,6-diacetylpyridine. Two equivalents of H(2)L(3) reacts with CeCl(3).7H(2)O, Ce(SO(4))(2).4H(2)O, or EuCl(3).6H(2)O under formation of [Ln(III)(HL(3))(2)](+) cations (Ln = Ce, Eu) with exclusive deprotonation of the benzoylhydrazone ligand arms. The Ce(4+) ion of the sulfate salt is reduced during the reaction and forms 10-coordinate singly charged complex cations, the structure of which is identical to the product of the reaction of cerium(III) chloride. The exact position of deprotonation in the ligands is resolved by infrared spectroscopy, bond lengths considerations, and the hydrogen bonding in the solid-state structures of the products. A similar approach allows the synthesis of mixed semicarbazone/thiosemicarbazone ligands (H(2)L(4)). The reaction of H(2)L(4) with Sm(NO(3))(3).6H(2)O leads to the first structurally characterized lanthanide complex with thiosemicarbazone coordination. The solid-state structure of the 10-coordinate complex [Sm(HL(4))(2)]NO(3).H(2)O shows exclusive deprotonation of the thiosemicarbazone arms of the ligands. All isolated complexes are air stable and do not undergo ligand exchange reactions or hydrolysis in the presence of water.

Synthesis and Crystal Structures of Mn(II), Co(II), Ni(II), Cu(II), and Zn(II) Metal Complexes with NNO Functionalized Ligands

Some new metal(II) complexes, [M = Mn (1), Co (2), Ni (3), Cu (4), and Zn (5)] of 2-acetylpyridine benzoylhydrazone ligand (HL) containing trifunctional NNO-donor system have been synthesized and crystallographically characterized for the complex 1 and 5. The complexes consist of two ligands to give sixcoordinate, which are bonded to the metal atom on a meridional plane through acetylpyridine ring nitrogen, azomethine nitrogen, and benzoyl oxygen atoms, respectively. The coordination geometry for other complexes was identified on the basis of the physicochemical data by elemental analyses, FAB -MS, IR, NMR, and electronic spectral measurements. The resulting data indicated that the complexes are accordance with the above formulation.