Oxime Ligands Research Articles

Lanthanide Complexes with Multidentate Oxime Ligands as Single-Molecule Magnets and Atmospheric Carbon Dioxide Fixation Systems.

The synthesis, structure, and magnetic properties of five lanthanide complexes with multidentate oxime ligands are described. Complexes 1 and 2 (1: [La2 (pop)2 (acac)4 (CH3 OH)], 2: [Dy2 (pop)(acac)5 ]) are synthesized from the 2-hydroxyimino-N-[1-(2-pyridyl)ethylidene]propanohydrazone (Hpop) ligand, while 3, 4, and 5 (3: [Dy2 (naphthsaoH)2 (acac)4 H(OH)]⋅0.85 CH3 CN⋅1.58 H2 O; 4: [Tb2 (naphthsaoH)2 (acac)4 H(OH)]⋅0.52 CH3 CN⋅1.71 H2 O; 5: [La6 (CO3 )2 (naphthsao)5 (naphthsaoH)0.5 (acac)8 (CO3 )0.5 (CH3 OH)2.76 H5.5 (H2 O)1.24 ]⋅2.39 CH3 CN⋅0.12 H2 O) contain 1-(1-hydroxynaphthalen-2-yl)-ethanone oxime (naphthsaoH2 ). In 1-4, dinuclear [Ln2 ] complexes crystallize, whereas hexanuclear La(III) complex 5 is formed after fixation of atmospheric carbon dioxide. Dy(III) -based complexes 2 and 3 display single-molecule-magnet properties with energy barriers of 27 and 98 K, respectively. The presence of a broad and unsymmetrical relaxation mode observed in the ac susceptibility data for 3 suggest two different dynamics of the magnetization which might be a consequence of independent relaxation processes of the two different Dy(3+) ions.

Doubly Thiocyanato(S,N)-Bridged Dinuclear Complexes of Mercury(II) from the Use of 2-pyridyl Oximes as Capping Ligands

The reactions between Hg(SCN)2 and the 2-pyridyl oximes, 2-pyridine aldoxime (paoH), methyl 2-pyridyl ketone oxime (mepaoH), pyridine-2-amidoxime (NH2paoH) and di-2-pyridyl ketone oxime (dpkoxH), have been investigated. The products in Me2CO or Me2CO/MeOH are the dinuclear complexes [Hg2(SCN)4(paoH)2] (1), [Hg2(SCN)4(mepaoH)2] (2), [Hg2(SCN)4(NH2paoH)2] (3) and [Hg2(SCN)4(dpkoxH)2] (4), whose structures have been determined by single-crystal X-ray crystallography. The molecular structures consist of centrosymmetric dinuclear molecules in which the two HgII ions are bridged by two bidentate bridging 1: 1: (1,3) SCN- groups forming a planar (1, 2) or non-planar (3, 4), 8-membered metallacyclic ring. The HgII centers are each chelated by a N(2-pyridyl), N(oxime)-bidentate ligand and are bound to one terminal S-bonded thiocyanato group. Due to the very long HgII-N (bridging SCN-) distances in 3, this complex can also be described as pseudodimer. The second 2-pyridyl ring of each dpkoxH ligand in 4 remains uncoordinated. The 2D lattice of 1 and 2 is built through H-bonding and - stacking interactions. Hydrogen bonds and S...S interactions generate 3D networks in 3 and 4. The IR spectra of the complexes are discussed in terms of the coordination modes of the ligands involved (SCN-, 2-pyridyl oximes). 1H NMR spectra in d6-DMSO indicate that the complexes decompose in solution. Keywords: Coordination chemistry, crystal structures, dinuclear mercury(II) complexes, 1H NMR spectra, infrared spectroscopy, oxime group, 2-pyridyl oxime ligands, thiocyanato ligands.

Synthesis, structural characterization and DNA interaction of zinc complex from 2,6-diacetylpyridine dihydrazone and {4-[(2E)-2-(hydroxyimino)acetyl]phenoxy} acetic acid

A new water soluble zinc complex has been prepared and structurally characterized. The Zn(II) complex was synthesized by the reaction of 2,6-diacetylpyridine dihydrazone (dph) with {4-[(2E)-2-(hydroxyimino)acetyl]phenoxy} acetic acid (H2L) in the presence of zinc(II) acetate. Single crystal X-ray diffraction study revealed that the zinc ion is situated in distorted trigonal-bipyramidal environment where the equatorial position is occupied by the nitrogen atom of pyridine ring and the oxygen atoms of acetate groups of two oxime ligands (H2L) whereas the axial positions of the zinc complex are occupied by the imine nitrogen atoms of dph ligand. Characterization of the complex with FTIR, 1H and 13C NMR, UV–vis and elemental analysis also confirmed the proposed structure. Interaction of the Zn(II) complex with calf-thymus DNA (CT-DNA) was investigated through UV–vis spectroscopy and viscosity measurements. The results suggest that the complex preferably bind to DNA through the groove binding mode. The zinc complex cleaves plasmid pBR 322 DNA in the presence and absence of an oxidative agent (H2O2), possibly through a hydrolytic pathway which is also supported by DNA cleave experiments in the presence of different radical scavengers. The nuclease activity of the zinc complex significantly depends on concentration of the complex and incubation time both in the presence and absence of H2O2. DNA cleave activity is inhibited in the presence of methyl green indicating that the zinc complex seems to bind the major groove of DNA.

Spectroscopic and biological studies of new mononuclear metal complexes of a bidentate NN and NO hydrazone–oxime ligand derived from egonol

A novel ligand, vicinal dioxime ligand (egonol-hydrazone glyoxime) (LH2) was synthesized and characterized using 1H NMR, 13C NMR, MS, AAS, infrared spectroscopy, and magnetic susceptibility measurements. Mononuclear nickel (II), copper (II) and cobalt (II) complexes with a metal:ligand ratio of 1:2 for LH2 were also synthesized. Zn(II) forms complex [Zn(LH)Cl2] with a metal to ligand ratio of 1:1. IR spectrum shows that the ligand act in a bidentate manner and coordinates N4 donor groups of the ligands to NiII, CuII, CoII and ZnII ions. The detection of H-bonding (OH⋯O) in the [M(LH)2] metal complexes by IR spectra supported the square–planar MN4 coordination of Ni(II), Cu(II) and Co(II) complexes.The antimicrobial activities of compounds LH2 and their Ni(II), Cu(II), Co(II) and Zn(II) complexes were evaluated using the disc diffusion method against 16 bacteria and 5 yeasts. The minimal inhibitory concentrations (MICs) against all the bacteria and yeasts were also determined. Among the attempted test compounds, it is showed that all the compounds (L, LH2, [Ni(LH)2], [Cu(LH)2], [Co(LH)2(H2O)2], [Zn(LH)Cl2]) were effective against used test microorganisms.

Design and synthesis of a novel trinuclear palladium(ii) complex containing an oxime chelate ligand: determining the interaction mechanism with the DNA groove and BSA site I by spectroscopic and molecular dynamics simulation approaches

The trinuclear Pd(II) complex containing an oxime ligand showed significant interaction with both CT-DNA and BSA.

Crystal structure of bis-(acetato-κO)bis-(pyridine-2-carboxamide oxime-κ(2) N,N')cadmium ethanol disolvate.

In the title compound, [Cd(CH3COO)2(C6H7N3O)2]·2C2H5OH, the Cd(II) atom, which lies on a twofold rotation axis, is coordinated by two monodentate acetate groups and two N,N'-chelating pyridine-2-carboxamide oxime ligands, leading to a distorted octahedral coordination sphere. The mononuclear complex mol-ecules are assembled into chains along the c-axis direction via N-H⋯O hydrogen-bonding inter-actions. These chains are further assembled by O-H⋯O hydrogen bonds involving the ethanol solvent mol-ecules into a three-dimensional supramolecular structure.

Polymeric Luminescent Zn(II) and Cd(II) Dicarboxylates Decorated by Oxime Ligands: Tuning the Dimensionality and Adsorption Capacity

Ten Zn(II) and Cd(II) metal–organic materials were synthesized and studied by the X-ray method. Among these 10 structures, two represent binuclear clusters, and two are one-dimensional (1D) coordination polymers, while five are laminar two-dimensional (2D) solids and one is the three-dimensional (3D) framework. The investigation has been aimed at rational design of coordination polymers decorated by oxime ligands to increase the accessible adsorption area in these newly synthesized solids. The ligands used include three aliphatic dicarboxylic acids, HOOC-(CH2)n-COOH [n = 1, 2, 4 corresponding to malonic (H2mal), succinic (H2suc), and adipic (H2adi) acids], and three neutral oxime ligands [pyridine-2-aldoxime (2-pyao), pyridine-4-aldoxime (4-pyao), and 1,2-cyclohexanedionedioxime (Niox)]. These novel hybrid solids with the compositions [Zn2(suc)2(2-pyao)4]·2H2O 1, [Cd2(suc)(2-pyao)4(H2O)2][BF4]2 2, [Cd(suc)(2-pyao)2]n 3, [Zn(mal)(4-pyao)(H2O)]n 4, [Cd(mal)(4-pyao)(H2O)]n 5, [Zn(suc)(4-pyao)]n 6, [Zn(adi)(4-pyao)2]n 7, {[Cd(adi)(4-pyao)2]·dmf}n 8, [Zn(adi)(Niox)]n 9, and [Cd(adi)(Niox)]n 10 [dmf – N,N′-dimethylformamide] demonstrate a variable class of coordination supramolecular architectures dictated by the distinctions in the metals’ and oxime ligands’ coordination capacities and preferences, and length and flexibility of the dicarboxylic linkers. The discrete aggregates 1 and 2 differ by the components’ ratio and conformation of the bridging succinate anion; compounds 3 and 7 are 1D arrays, and compounds 4, 5, 6, 8, and 9 represent 2D layers of different topologies. Compound 10 is a 3D grid afforded by the concerted contribution of the longest in this series adipate anion, and the bigger atomic radius Cd(II) vs. Zn(II). The adsorptive properties of 7 and 9 are reported. For the laminar solid 9, the quantum chemical simulations of the adsorption capacity are in line with the experimental results. All new materials reveal dual green-blue wavelength emission in the solid state.

Triple associates based on (oxime)Pt(II) species, 18-crown-6, and water: Synthesis, structural characterization, and DFT study

The associates 2(cis-[PtCl2(acetoxime)2])⋅18-crown-6⋅2H2O (1), 2(cis-[PtBr2(acetoxime)2])⋅18-crown-6⋅2H2O (2), and trans-[PtCl2(acetaldoxime)2]⋅(18-crown-6)⋅2H2O (3) were synthesized by co-crystallization of free corresponding platinum species and 18-crown-6 from wet solvents and characterized by 1H NMR and IR spectroscopies, high-resolution mass-spectrometry (ESI), TG/DTA, and X-ray crystallography. The (oxime)Pt(II) species are assembled with 18-crown-6 and water by hydrogen bonding between the hydroxylic hydrogen atoms of the oxime ligands and the oxygen atom of water and between the hydrogen atoms of water and the oxygen atoms of 18-crown-6. In 2(cis-[PtX2(acetoxime)2])⋅18-crown-6⋅2H2O (where X=Cl (1), Br (2)), the molecule of the crown ether is located between the two cis-[PtX2(acetoxime)2] species. The associate trans-[PtCl2(acetaldoxime)2]⋅(18-crown-6)⋅2H2O (3) crystallizes into a 1D array structure. Water molecules play the role of linkers between the (oxime)Pt(II) species and the crown ether molecules. The electronic structures and vibrational frequencies of the triple associates were studied by density functional theory (DFT/B3LYP).

Polymer‐Supported Electron‐Rich Oxime Palladacycle as an Efficient Heterogeneous Catalyst for the Suzuki Coupling Reaction

AbstractVarious electron‐rich oxime palladacycle resins designed as heterogeneous catalysts were employed for the Suzuki coupling reaction of aryl halides with arylboronic acids. The electron‐richness of the oxime ligand was controlled by the substituted alkoxy groups. Evaluation based on the electronic effect of the catalysts revealed that the alkoxy‐substituted oxime palladacycle resins showed better catalytic activity than palladated Kaiser oxime resin in the Suzuki coupling reactions and that the catalytic activity of oxime palladacycle resins increased as the electron‐richness of oxime ligand increased. The most electron‐rich oxime palladacycle resin exhibited an excellent catalytic performance for the synthesis of both biaryl and heterobiaryl compounds, despite its heterogeneous system. As a practical application of the catalyst, a valsartan precursor was synthesized in high yield under mild conditions. The electron‐rich oxime resin could also be reused for up to 5 cycles while maintaining good catalytic activity in the Suzuki coupling reaction.magnified image

Chiral palladium complexes with monoterpenoids oximes

Oximes of cis-caran-4-one, 3α- and 3β-hydroxycaran-4-ones, cis-verbanone, menthone, and 2β-hydroxybornan-3-one have been synthesized. The obtained oximes react with lithium tetrachloropalladate to give new chiral palladium complexes containing mono-or bidentate oxime ligands.

Use of the oxime–oximato binding mode to stabilise mixed valence copper iodide polymer networks using dipyridyl ketone oxime ligands

Coordination polymers formed from copper iodide and four isomeric dipyridyl ketone oxime ligands showed the importance the oxime–oximato bridge on the formation of mixed valence Cu(i)/Cu(ii) polymers.

A family of polynuclear cobalt complexes upon employment of an indeno-quinoxaline based oxime ligand

The employment of an indeno-quinoxaline based oxime ligand in cobalt chemistry afforded a new family of polynuclear cobalt clusters.

Oxo-Centered Trinuclear Chromium(III) Complexes with Both Carboxylate and Amidoximate Ligands

Compounds [Cr 3 III (μ3-O)(O2CPh)5(H2N-sao)(EtOH)2]·EtOH (1·EtOH) and [Cr 3 III (μ3-O)(O2CPh)3(H2N-pao)3]NO3·H2N-paoH·EtOH (2·NO3·H2N-paoH·EtOH) have been obtained either in a sequential one-pot, two-step procedure in which Cr(NO3)3·9H2O is first reacted with sodium benzoate in ethanol under reflux, followed by the addition of salicylamidoxime (H2N-saoH2) or pyridine-2-amidoxime (H2N-paoH), or in a one-step protocol starting from [Cr 3 III (μ3-O)(O2CPh)6(EtOH)3]NO3. They were characterized by single-crystal X-ray diffraction, magnetometry and EPR spectroscopy. Complexes 1 and 2 are derived from the parent complex [Cr 3 III (μ3-O)(O2CPh)6(EtOH)3]+ by replacement of one and three benzoate ligands, respectively, by oximate ligands. The salicylamidoximate and pyridine-2-amidoximate ligands display a tridentate coordination mode with the N–O oximate group bridging a pair of Cr atoms and the additional ligating atom substituting for an ethanol ligand of the parent complex. In both cases susceptibility, magnetization and EPR data reveal a S T = 1/2 ground state with a nearly isotropic g-tensor.

Activation of Acetyl Ligands through Hydrogen Bonds: A New Way to Platinum(II) Complexes Bearing Protonated Iminoacetyl Ligands

The dinuclear platina-β-diketone [Pt2{(COMe)2H}2(μ-Cl)2] (1) reacted with 2-pyridyl-functionalized monoximes and with dioximes in the presence of NaOMe to yield oxime–diacetyl platinum(II) complexes [Pt(COMe)2(2-pyCR═NOH)] (R = H, 4a; Me, 4b; Ph, 4c) and [Pt(COMe)2(HON═CR–CR═NOH)] (R/R = Me/Me, 5a; Ph/Ph, 5b; (CH2)4, 5c; NH2/NH2, 5d), respectively. The strong intramolecular O–H···O hydrogen bonds in these complexes give rise to an activation of the acetyl ligands for Schiff-base type reactions, thus forming with primary amines iminoacetyl platinum complexes [Pt(COMe)(CMe═NHR′)(2-pyCR═NO)] (R/R′ = H/Bn, 6a; Me/Bn, 6b; Ph/Bn, 6c; H/CH2CH2Ph, 6d; H/CH2CH═CH2, 6e; Bn = benzyl) and [{Pt(CMe═NHR′)2(ON═CR–CR═NO)}2] (R/R = Me/Me, 7a–d; Ph/Ph, 8a–d; (CH2)4, 9a; R′ = Bn, a; CH2CH2Ph, b; CH2CH═CH2, c; CH2CH2OH, d). The intramolecular N–H···O hydrogen bonds in type 6–9 complexes make clear that protonated iminoacetyl ligands (i.e., aminocarbene ligands) and deprotoanted oxime ligands are present. These complexes coul...

Polynuclear complexes of a series of hydrazone and hydrazone–oxime ligands – M2 (Fe), M4 (Mn, Ni, Cu), and Mn (Cu) examples

Tetranuclear, dinuclear and chain complexes involving some polyfunctional hydrazone and thio-carbohydrazone-based ligands are discussed. Ni(II) and Mn(II) [2×2] grids form with μ2-S and μ2-O bridges respectively, and are antiferromagnetically coupled (J=−167(5), −3.59(2) cm−1 respectively). With the Fe(II) based system oxidation to Fe(III) occurs, and a μ2-Ohydrazone bridged dimer results, with antiferromagnetic exchange between the S=5/2 spin centers (J=−22.5(2) cm−1). In the case of Cu(II) the diazine group acts as a μ2-N–N bridge between Cu(II) centers in two cases involving a tetranuclear and a chain complex. Non-orthogonal bridging through N–N and carboxylate bridges leads to antiferromagnetic exchange in the tetranuclear case (J=−32.7(7), −16.1(7) cm−1 respectively) and ferromagnetic exchange in the chain complex due to orthogonal N–N bridging (J=3.3(1) cm−1).

Synthesis, characterization and molecular structure of titanium alkoxide complexes with aromatic oxime ligands

Stoichiometric reactions of pyridine-2-aldoxime (HL1) with titanium 2-propoxide and of salicylaldoxime (H2L2) with titanium 2-propoxide or titanium ethoxide in toluene at room temperature resulted in the formation of [Ti2(μ-O)(μ-L)2(OR)4] (for L1, R = iPr; for L2, R = iPr or Et). These complexes were all characterized by spectroscopic methods; in addition, the molecular structure of [Ti2(μ-O)(μ-L1)2(OiPr)4] was determined by single-crystal X-ray diffraction. The titanium atoms have distorted octahedral geometries that share an apex through a bridging oxygen. Each monoanionic L1 is chelated to one titanium atom through its pyridine and oximate nitrogen atoms and to a second titanium atom through its oximate oxygen atom.

Synthesis of New Late Transition Metal P,P-, P,N-, and P,O- Complexes Using Phosphonium Dimers as Convenient Ligand Precursors

The phosphonium dimer [-Cy2PCH(OH)CH2-]2(X)2, X = Cl(-), Br(-) was used to synthesize and characterize a variety of late transition metal complexes containing chelating phosphino-enolate (PCy2CH═CHO(-)), imine (PCy2CH2CH═NR, R = Ph, (S)-CHMePh), and oxime (PCy2CH2CH═NOH) ligands. The phosphonium dimer, when deprotected with base, generates the phosphine aldehyde PCy2CH2CHO in situ, which, in the presence of [M(COD)Cl]2, M = Rh, Ir, and a PF6(-) salt, or [Ni(H2O)6][BF4]2, facilitates a condensation reaction with an amine or hydroxylamine to form phosphino-imine or phosphino-oxime metal complexes [M(COD)(P-N)][PF6] or [Ni(P-N)2][X]2, X = ClO4(-), BF4(-), respectively. In the absence of an amine, phosphino-enolate containing complexes are formed. A neutral Ni(II) complex Ni(PCy2CH═CHO)2 with trans-bis(phosphino-enolate) ligands which resemble ligands used on nickel for olefin oligomerization, as well as neutral Rh(I) and Ir(I) 1,5-cyclooctadiene complexes M(COD)(PCy2CH═CHO) are characterized. Both the rhodium and iridium complexes are active olefin hydrogenation catalysts. Reaction of the phosphino-aldehyde with Pt(COD)Cl2 results in the formation of trans-PtCl2(PCy2CH2CHO)2 with pendant aldehyde groups, and under certain conditions, they undergo an intraligand aldol condensation to form a disphosphine ligand.

A palladium(II) complex containing both carbonyl and imine oxime ligands: Crystal structure, experimental and theoretical UV–vis, IR and NMR studies

A new palladium(II) complex, [Pd(ppeieo)(inap)]·DMSO (ppeieo=(1E,2E)-phenyl-[(1-phenylethyl)imino]-ethanal oxime and inap=isonitrosoacetophenone) has been synthesized and characterized by elemental analysis, UV–vis, IR, NMR. X-ray diffraction analysis of the DMSO solvate of the complex shows that the palladium(II) ion is coordinated in a distorted square-planar geometry by ppeieo and inap, which is formed during the hydrolysis of ppeieo. DFT (B3LYP/LANL2DZ) calculations on the complex have been carried out to correlate geometry and spectroscopic properties such as electronic, vibrational and NMR chemical shifts. The complete vibrational frequency assignments were made and the calculation results were applied to simulate infrared spectra of the title compound which shows good agreement with observed spectra. The calculated HOMO and LUMO energies show that several transitions including the π→π* and charge transfer occur within the molecule. The chemical shifts reasonably correspond to the calculated spectra.

Synthesis and characterization of mixed-ligand complexes using a precursor mononuclear oxidovanadium(V) complex derived from a tridentate salicylhydrazone oxime ligand

The mononuclear oxidovanadium(V) complex [VO(L)(OEt)(EtOH)] (1), where H2L=Salicyloyl hydrazone of diacetyl monooxime, reacts separately with five different reactants viz. pyridine (py), 4-methylpyridine (4mepy), 4,4′bipyridine (4,4′bipy), 8-hydroxyquinoline (Hox) and KOH to yield the mononuclear oxidovanadium complexes [VO(L)(OEt)(py)] (2), and [VO(L)(OEt)(4mepy)] (3), the binuclear complex [VO(L)(OEt)]2(μ-4,4′bipy) (4), the mononuclear bis chelate complex [VO(L)(ox)] (5) and the water soluble dioxidovanadium salt K[VO2L]·H2O (6) respectively. Complex 5 has been characterized by X-ray crystallography, and crystallizes in the orthorhombic space group Pna21 having a distorted octahedral O4N2 coordination environment. All five complexes are characterized by elemental analysis, various spectroscopic techniques (UV–Vis, IR, NMR and ESI Mass) and cyclic voltammetry. The spectral and electrochemical data of these five complexes are compared with those of the precursor complex.

Syntheses, structures and catalase-like activities of mono-, tri- and pentanuclear Cu(II), Cu(II)-Co(II) complexes with cyanide and ONO tridentate oxime ligand

Syntheses, structures and catalase-like activities of mono-, tri- and pentanuclear Cu(II), Cu(II)-Co(II) complexes with cyanide and ONO tridentate oxime ligand