Synthesis,crystal structure,antioxidation and fluorescence of two lanthanide complexes with a noncyclic polyether Schiff base ligand

Two lanthanide (Sm and La) complexes with the Schiff base ligand bis(3-methoxysalicylidene)-3-oxapentane-1,5-diamine (Bod) have been synthesized and characterized by physico-chemical and spectroscopic methods. [Sm(Bod)(NO₃)₃] {bis(3-methoxysalicylidene)-3-oxapentane-1,5-diamine samarium(III) trinitrate} (1) is a discrete mononuclear species and [La(Bod)(NO₃)₃(DMF)]_n {bis(3-methoxysalicylidene)-3-oxapentane-1,5-diamine dimethylformamide lanthanum(III) trinitrate}_n (2) formed an inorganic coordination polymer. In the two complexes, the metal ions are both ten-coordinate and the geometric structure around the Ln(III) ions can be described as distorted hexadecahedral. An antioxidant assay in vitro shows that complexes 1 and 2 exhibit better scavenging activity than both the ligand and the usual antioxidants on hydroxyl and superoxide radicals. Under excitation at room temperature, a red shift in the fluorescence band of the ligand in the complexes compared with that of the free ligand can be attributed to coordination of the rare earth ions to the ligand. Furthermore, 1 produced characteristic Sm(III) luminescence, which indicates the ligand Bod is a good organic chelator to absorb energy and transfer it to the Sm³⁺ ion.     

Synthesis,characterization, and crystal structure of two zinc(II) complexes with a Schiff base derived from amantadine

By condensation of amantadine and 4-methoxysalicylaldehyde a new Schiff base HL was synthesized. A mixture of HL and zinc(II) chloride in an alcoholic medium leads to [Zn(HL)₂Cl₂] (1). However, the same reactants gave another different complex (ZnL₂) (2) in the presence of NaOH. The two complexes were characterized by IR, ¹H NMR, elemental analysis, molar conductance, and single-crystal X-ray diffraction. X-ray diffraction analysis reveals that complex 1 crystallizes in the triclinic system, Pī space group; each asymmetric unit consists of one zinc(II), two HL, and two chlorides. The tetra coordination of central zinc is attained by two chlorides and two oxygens from the Schiff base, forming a distorted tetrahedral geometry. Complex 2 crystallizes in the monoclinic system, P2₁/c space group; each asymmetric unit consists of one zinc(II) and two L. The tetra coordination of central zinc is attained by two nitrogens and two oxygens from the Schiff base, forming a distorted tetrahedral geometry.     

Synthesis,crystal structure,and antimicrobial activity of a series of cobalt(III) Schiff base complexes

Abstract

A series of six new mononuclear Schiff base complexes, 1–6 of cobalt(III) of the general formula, [CoLX] or its adduct with methanol, is reported. The pentadentate Schiff base ligand (H₂L) was obtained by the condensation of N-(3-aminopropyl)-N-methylpropane-1,3-diamine with 1-(2-hydroxyphenyl)ethanone (H₂L¹) or 1-(2-hydroxyphenyl)propan-1-one (H₂L²). X stands for the pseudohalides, N₃^–, N(CN)₂^? , and NCS^–. The complexes have been synthesized by the reaction of equimolar amounts of cobalt(II) nitrate with H₂L¹ or H₂L² in the presence of the respective pseudohalide in methanol medium. All the complexes have been characterized by microanalytical, spectroscopic, single crystal XRD (except 3), and other physicochemical studies. Structural studies reveal that the central Co(III) ion in 1, 2, 4, 5, and 6 adopts a distorted octahedral geometry with a CoN₄O₂ chromophore. Weak intermolecular H-bonding and/or π-interactions are operative in these complexes to bind the molecular units. The antimicrobial activity of all the complexes and their constituent Schiff bases has been tested against some common bacteria and fungi.     

乙酰丙酮缩联苯胺席夫碱的合成及晶体结构

一个多世纪以来,己有大量有关席夫碱方面的文献报道.许多Schiff碱金属配合物因具有良好的抗肿瘤、抗病毒、杀菌抑霉等多种生物活性而得到了广泛应用[1-3];其特殊的催化行为以及在酶模拟方面的功效引起了化学家的普遍重视[4,5].席夫碱中,β一二酮类化合物是一类良好的金属螯合剂,因为它能够为金属提供两个键合点,形成稳定的六元螯合环,其与稀土离子形成的配合物具有稳定的化学性质和优异的发光性能,因而具有广泛的应用前景[6].     

Synthesis,crystal structures,spectroscopic studies and antibacterial properties of a series of mononuclear cobalt(III) Schiff base complexes

New complexes of cobalt(III) with the tridentate and tetradentate Schiff base ligands: 3-methoxy-2-{(Z)[(2-hydroxyphenyl)imino]methyl}phenol (H₂L¹), 4-[(2-hydroxyphenyl)imino]-2-pentanone (H₂L²); and 2-((E)-1-(2-((E)-1-(2-hydroxy-4,5-dimethylphenyl)ethylideneamino)ethylimino)ethyl)-4,5 dimethylphenol (H₂L³), namely [Co^III(L¹)(N-MeIm)₃]PF₆ (1), [Co^III(L¹)(py)₃]ClO₄ (2), [Co(L¹)(py)₃][Co(L¹)₂] (3) and [Co^III(L²)(N-MeIm)₃]PF₆ (4) and [Co(L³)(N-MeIm)₂]PF₆ (5), were synthesized and characterized by physico-chemical and spectroscopic methods. The crystal structures of the complexes were determined by X-ray crystallography. In each of these complexes, the cobalt(III) centre has a slightly distorted octahedral environment, utilizing all available coordination centres of the ligands. The complexes were also screened for in vitro antibacterial activities against four human pathogenic bacteria, and their minimum inhibitory concentrations indicated good antibacterial activities.     

Synthesis,structure and antibacterial activity of manganese(III) complexes of a Schiff base derived from furfurylamine

Two new mononuclear complexes of manganese(III) viz. [MnL₂(LH)₂]ClO₄ (1) and [MnL₂(N₃)]·0.5CH₃OH (2) have been synthesized by reacting manganese perchlorate with furfurylamine and salicylaldehyde (plus sodium azide in 2) where L = (2-hydroxybenzyl-2-furylmethyl)imine, an asymmetric bidentate Schiff base formed in situ to bind the Mn(III) ion. The complexes have been characterized by elemental analysis, IR spectroscopy, TGA and single crystal X-ray diffraction studies. Structural studies reveal that the complexes 1 and 2 adopt an octahedral and a square pyramidal geometry, respectively. The antibacterial activity of the complexes has been tested against Gram(+) and Gram(?) bacteria.     

Synthesis and antioxidant, antimicrobial evaluation, DFT studies of novel metal complexes derivate from Schiff base

In Iraq, like most developing countries, attempts are being made to synthesize new compounds with several pharmacological properties. (E)-2-(3-(2-imino-1-methylimidazolidin-4-ylidene)-1-methylguanidino)acetic acid (L) has been synthesized and used as a ligand for the formation of Cr(III), Co(II), Ni(II), and Cu(II) complexes. The chemical structures of synthesized compounds were characterized using different spectroscopic methods. All chelates except Ni(II) chelate are found to be octahedral structures, Ni(II) chelate was square planar. The stability for the prepared complexes was studied theoretically using density function theory. The total energy for the complexes was calculated and it was shown that the copper complex is the most stable one. Ligand and complexes were tested against selected types of microbial organisms and showed significant activities. The free-radical scavenging activity of ligand and metal complexes have been determined by their interaction with the stable free-radical DPPH and all the compounds have shown encouraging antioxidant activities.     

Design,synthesis, crystal structure and in vitro cytotoxic properties of a novel Schiff base derived from indole and biphenyl

A novel and potentially active dihydroorotate dehydrogenase (DHODH) inhibitor, namely 3‐({(E )‐[(E )‐1‐(biphenyl‐4‐yl)ethylidene]hydrazinylidene}methyl)‐1H‐indole (BEHI) acetonitrile disolvate, C₂₃H₁₉N₃·2CH₃CN, has been designed and synthesized. The structure of BEHI was characterized by elemental analysis, Q‐TOF (quadrupole time‐of‐flight) MS, NMR, UV–Vis and single‐crystal X‐ray diffraction. The antitumour activity of the target molecule was evaluated by the MTT method. Results indicated that BEHI exhibited rather potent cytotoxic activity against human A549 (IC₅₀ = 20.5 µM ) and mouse breast 4T₁ (IC₅₀ = 18.5 µM ) cancer cell lines. Meanwhile, to rationalize its potencies in the target, BEHI was docked into DHODH and the interactions with the active site residues were analyzed. Single‐crystal structure analysis indicated that hydrogen bonds are present only between BEHI and acetonitrile solvent molecules in the asymmetric unit. The interplay of weak π–π stacking and weak C(N)—H…π interactions between neighbouring BEHI molecules play crucial roles in the formation of the final supramolecular frameworks.     

Synthesis of transition metal complexes containing a Schiff base ligand derived from 1,10-phenanthroline-2,9-dicarboxaldehyde and 2-aminobenzenethiol

The synthesis of a new Schiff base containing 1,10-phenanthroline-2,9-dicarboxaldehyde and 2-aminobenzenethiol subunits is described. The reaction of 1,10-phenanthroline-2,9-dicarboxaldehyde with 2-aminobenzenethiol leads to the isolation of 2,9-bis(2-benzothiazolinyl)-1,10-phenanthroline (I) which undergoes rearrangement when reacted with cobalt, nickel, copper or zinc ions to produce complexes of the tautomeric Schiff base 2,9-bis[2-(2-mercaptophenyl)-2-azaethene]-1,10-phenanthroline (L). The [Cu(L)ClO₄][ClO₄] and [M(L)X₂] complexes (where M = Co(II), Ni(II) and Zn(II) and X = Br) were characterized by physical and spectroscopic measurements which indicated that the ligand is acting probably as a tetradentate N₄ chelating agent.     

Synthesis and spectroscopic studies of binuclear metal complexes of a tetradentate N2O2 Schiff base ligand derived from 4,6-diacetylresorcinol and benzylamine

A tetradentate N2O2 donor Schiff base ligand, H2L, was synthesized by the condensation of 4,6-diacetylresorcinol with benzylamine. The structure of the ligand was elucidated by elemental analyses, IR, 1H NMR, electronic and mass spectra. Reaction of the Schiff base ligand with nickel(II), cobalt(II), iron(III), cerium(III), vanadyl(IV) and uranyl(VI) ions in 1:2 molar ratio afforded binuclear metal complexes. Also, reaction of the ligand with several copper(II) salts, including Cl-, NO3-, AcO-, ClO4- and SO42- afforded different metal complexes that reflect the non-coordinating or weakly coordinating power of the ClO(4)(-) anion as compared to the strongly coordinating power of SO42- and Cl- anions. Characterization and structure elucidation of the prepared complexes were achieved by elemental and thermal analyses, IR, 1H NMR, electronic, mass and ESR spectra as well as magnetic susceptibility measurements. The metal complexes exhibited different geometrical arrangements such as square planar, octahedral, square pyramidal and pentagonal bipyramidal arrangements. The variety in the geometrical arrangements depends on the nature of both the anion and the metal ion.     

Synthesis, spectroscopic characterization and comparative DNA binding studies of Schiff base complexes derived from L-leucine and glyoxal

The mononuclear Schiff base complexes of the type, [ML(CH₃OH)₂] [M = Co(II), Ni(II), Cu(II) and Zn(II)] have been synthesized by template condensation of l-leucine and glyoxal. The complexes have been characterized on the basis of the results of the elemental analysis, molar conductance, magnetic susceptibility measurements and spectroscopic studies viz, FT-IR, Mass, ¹H NMR and ¹³C NMR spectra. The UV–vis and magnetic moment data revealed an octahedral geometry around Co(II), Ni(II) ion with distortion around Cu(II) ion complex confirmed by EPR data. The conductivity data show a non-electrolytic nature of the complexes. Absorption and fluorescence spectroscopic studies support that all the complexes exhibit a significant binding to calf thymus DNA.     

Synthesis,characterization, and crystal structure of cobalt(II) and zinc(II) complexes with a bulky Schiff base derived from rimantadine

Two novel complexes, C₃₈H₄₈CoN₂O₂ (I) and C₃₈H₄₈N₂O₂Zn (II), were prepared through an analogous procedure with a corresponding metal chloride and a bulky Schiff base ligand (HL) which derived from rimantadine and salicylaldehyde in appropriate solvents, respectively. They were structurally characterized by the means of IR, UV-Vis, elemental analysis, molar conductance, PXRD and single-crystal X-ray diffraction (CIF files nos. 946735 (I), 893304 (II)). Single-crystal X-ray diffraction analysis reveals that I belongs to the triclinic system, \(P\overline 1 \) space group; each asymmetric unit consists of one cobalt(II) complex and one lattice ethanol molecule. In each complex molecule, cobalt(II) atom is four-coordinated via two oxygen atoms and two nitrogen atoms from the deprotonated Schiff base ligands, forming an approximate planar geometry. The crystal structure also involves strong O–H···O intermolecular hydrogen bonds between the solvent alcoholic and phenol O atoms of complex molecule. Complex II belongs to the monoclinic system, Cc space group. Each asymmetric unit consists of one zinc(II) ion and two deprotonated ligands. Zinc(II) atom lies on a twofold rotation axis and is four-coordinated via two nitrogen atoms and two oxygen atoms from the Schiff base ligands, forming a distorted tetrahedral geometry.     

Synthesis,crystal structures,and biological property of dinuclear oxovanadium(V) complexes derived from tridentate Schiff bases

A pair of structurally similar dinuclear oxovanadium(V) complexes, [VO₂L¹]₂ (I) and [VO₂L²]₂ (II), where L¹ and L² are the mono-anionic form of 2-[(2-isopropylaminoethylimino)methyl]-4-methylphenol (HL¹) and 4-fluoro-2-[(2-isopropylaminoethylimino)methyl]phenol (HL²), respectively, have been synthesized and characterized by elemental analysis, FT-IR spectra, and single crystal X-ray determination. The crystal of I is monoclinic: space group P2₁/c, a = 12.528(1), b = 12.266(1), c = 9.432(1) Å, β = 104.814(3)°, V = 1401.2(3) ų, Z = 2. The crystal of I is monoclinic: space group P2₁/n, a = 12.3128(5), b = 6.5124(3), c = 17.1272(7) Å, β = 105.863(1)°, V = 1321.1(1) ų, Z = 2. The V…V distances are 3.210(1) Å in I and 3.219(1) Å in II. The V atoms in the complexes are in octahedral coordination. Biological assay indicates that complex II, bearing fluoro-substitute groups, has stronger antimicrobial activity against most bacteria than complex I which bearing methyl-substitute groups.     

Synthesis, crystal structure, and DNA interaction studies of a mixed-ligand copper(II) complex of 1,10-phenanthroline and a Schiff base derived from isoleucine

A mixed-ligand Cu(II) complex, [Cu(o-van-ile)(phen)]·1.5H₂O (o-van-ile = Schiff base derived from o-vanillin and l-isoleucine, phen = 1,10-phenanthroline), has been synthesized and structurally characterized. The crystal structure shows 1-D linear chains formed by C?CH??O hydrogen bond interactions. The DNA-binding interactions of the Cu(II) complex with calf thymus DNA (CT-DNA) have been investigated by spectroscopic methods and agarose gel electrophoresis. The results indicate that the complex can bind to CT-DNA via an intercalative mode and show efficient cleavage activity in both the absence and presence of reducing agents.     

Antiferromagnetically coupled iso-structural CrIII,MnIII and FeIII complexes of a tetradentate Schiff base ligand derived from o-phenylenediamine

Transition Metal Chemistry - Three isostructural, Iron(III), Manganese(III) and Chromium complexes, with a tetradentate Schiff base ligand (H2L2) from o-phenylenediamine and o-vanillin having the...     

Synthesis and spectroscopic studies of some transition metal complexes of a novel Schiff base ligands derived from 5-phenylazo-salicyladehyde and o-amino benzoic acid

Cu(II), Mn(II), Ni(II), and Zn(II) metal complexes with novel heterocyclic Schiff base derived from 5-phenyl azo-salicyladehyde and o-amino benzoic acid have been synthesized and characterized on the basis of elemental analyses, electronic, IR, and (1)H NMR spectra, and also by aid of scanning electron microscopy (SEM), X-ray powder diffraction, molar ratio measurements, molar conductivity measurements, and thermogravimetric analyses. It has been found that the Schiff base behaves as neutral tridentate (ONO) ligand forming chelates with 1:1 (metal:ligand) stoichiometry.     

Synthesis,characterization, crystal structure,and electrochemical property of copper(II) complexes with Schiff bases derived from 5-halogenated salicylaldehyde and amantadine

A mixture of copper(II) chloride dihydrate and ligands derived from amantadine and 5-halogenated salicylaldehyde in anhydrous methanol generated two novel complexes C₃₄H₃₈Cl₂CuN₂O₂ (I) and C₃₄H₃₈Br₂CuN₂O₂ (II), respectively. The complexes were characterized by melting point, elemental analysis, molar conductance, IR, UV-Vis, and single-crystal X-ray diffraction (CIF files nos. 1435429 (I), 1435430 (II)). Single-crystal X-ray diffraction analysis reveals that both complexes crystallize in monoclinic system, P2₁/c space group. Each asymmetric unit consists of two mononuclear copper(II) complex molecules and each complex molecule includes one copper(II) atom two corresponding deprotonated ligands. The central copper(II) atom is four-coordinated via two nitrogen atoms and two oxygen atoms from the corresponding Schiff base ligands, forming a distorted tetrahedral geometry. Electrochemical properties of the complexes were studied by cyclic voltammetry.     

Synthesis and crystal structure of a new Schiff base ligand and its cobalt(II) complex

The crystal structures of cobalt(II) Schiff base complex (Co^IIL₂ · H₂O) and Schiff base ligand 3,5-dichlorosalicylidene-2-chlorophenylmethylamine (HL) have been determined by single-crystal X-ray analysis. The geometry around cobalt in Co^IIL₂ · H₂O is distorted tetrahedral. Co^IIL₂ · H₂O crystallizes in the monoclinic system, in space group C2/c, with crystallographic parameters: a = 12.9143(16) Å, b = 8.8326(16) Å, c = 25.115(3) Å, β = 92.791(10)°, V = 2861.4(7) ų, Z = 4, F(000) = 1420, and the final R indices (I > 2σ(I)) are R ₁ = 0.0440, wR ₂ = 0.1272. HL crystallizes in the monoclinic system, in space group P2₁/c, with crystallographic parameters: a = 11.9764(15), b = 8.2331(10), c = 14.2211(17) Å, β = 98.723(6)°, V = 1386.0(3) ų, Z = 4, F(000) = 640, and the final R indices (I > 2σ(I)) are R ₁ = 0.0397, wR ₂ = 0.1018.     

Synthesis,DNA binding,and antimicrobial studies of novel metal complexes containing a pyrazolone derivative Schiff base

A novel series of Co(II), Ni(II), Cu(II), Zn(II), and VO(IV) complexes has been synthesized from the Schiff base derived from 4-[(3,4-dimethoxybenzylidene)amino]-1,5-dimethyl-2-phenyl-1,2-dihydropyrazol-3-one and 1,2-diaminobenzene. Structural features were determined by analytical and spectral techniques. Binding of synthesized complexes with calf thymus DNA (CT DNA) was studied by spectroscopic methods and viscosity measurements. Experimental results indicate that the complexes are able to form adducts with DNA and to distort the double helix by changing the base stacking. Lower DNA affinity of the VO(IV) complex is caused by the change of coordination geometry by the vanadyl ion resulting in a somewhat unfavorable configuration for the DNA binding. Oxidative DNA cleavage activities of the complexes were studied with supercoiled (SC) pUC19 DNA using gel electrophoresis; the mechanism studies revealed that the hydroxyl radical is likely to be the reactive species responsible for the cleavage of pUC19 DNA by the synthesized complexes. The in vitro antimicrobial screening effects of the investigated compounds were monitored by the disc diffusion method. The synthesized Schiff base complexes exhibit higher antimicrobial activity than the respective free Schiff base.