Synthesis, characterization and thermal degradation of oligo-2-[(4-fluorophenyl) imino methylene] phenol and some of its oligomer-metal complexes

In this study, the oxidative polycondensation reaction conditions of 2-[(4-fluorophenyl) imino methylene] phenol (FPIMP) with air oxygen and NaOCl were studied in an aqueous alkaline medium between 60 and 90 °C. Synthesized oligo-2-[(4-fluorophenyl) imino methylene] phenol was characterized by ¹H-NMR, FT-IR, UV-Vis, size exclusion chromatography (SEC) and elemental analysis techniques. The yield of oligo-2-[(4-fluorophenyl) imino methylene] phenol (OFPIMP) was found to be 62.00% (for air O₂ oxidant) and 97.70% (for NaOCl oxidant) at the optimum reaction conditions. According to the SEC analysis, the number-average molecular weight (M_n), weight-average molecular weight (M_w) and polydispersity index (PDI) values of OFPIMP were found to be 1370 g mol⁻¹, 1979 g mol⁻¹ and 1.45, using NaOCl, 2105 g mol⁻¹, 2557 g mol⁻¹, and 1.22, using air O₂, respectively. During the oxidative polycondensation reaction, (2.88%) a part of -CHN group oxidized to carboxylic acid (-COOH). TG and TG-DTA analyses were shown to be more stable of oligo-2-[(4-fluorophenyl) imino methylene] phenol and its oligomer metal complexes than monomer against thermo-oxidative decomposition. The weight loss of OFPIMP was found to be 97.00% at 900 °C. The weight losses of OFPIMP-Co, OFPIMP-Ni OFPIMP-Cu oligomer-metal complex compounds were found to be 88.66%, 94.36% and 83.21%, respectively, at 1000 °C.     

Studies on Co(II) and Cu(II) complexes of a ligand derived from 1,3-phenylenediamine and 5-bromosalicylaldehyde synthesis, characterisation, thermal properties and use as new precursors for preparation cobalt and copper oxide nano-particles

A symmetric tetradentate Schiff base ligand, N,N′-bis(5-bromosalicylaldehyde)-1,3-phenylenediamine [(Brsal)₂-1,3-phen) and its Cu(II) and Co(II) complexes with general formula M₂((Brsal)₂-1,3-phen)₂, where M=Co (1) and Cu (2)], have been synthesized and characterized by elemental analyses and FTIR spectroscopy. In addition, Schiff base ligand has been characterized by ¹HNMR spectroscopy. Thermogravimetric analysis of the ligand and its metal complexes reveals their thermal stability and decomposition pattern.     

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.     

Antiozonant activity of the silica modified with 3d metal complexes

Criteria for preliminary selection of the antiozonants based on the silica modified with the complexes of 3d metal were proposed and the activity of the antiozonants as a dependence on the nature of the ligands (Schiff bases, Cl^?, NO ₃ ^? ) and metal ions [Cu(II), Co(II), Mn(II)] was established. We found that advantageous were complexes MnL₂/ $\overline {Si} $ , where L denotes a Schiff base of phenol or quinoline series, whose kinetic and specific stoichiometric energy parameters of the reaction were the largest because of the formation during the reaction of the manganese oxide form which performs the catalytic decomposition of ozone.     

Synthesis,Structures and Magnetic Properties of Cyano‐bridged FeIII/MnIII Heterobimetallic 1D Chain Complexes

Using the tricyanometalate building block, (nBu₄N)[(Tp*)Fe(CN)₃] [Bu₄N⁺ = tetrabutylammonium cation; Tp*^– = hydrotris(3,5‐dimethylpyrazol‐1‐yl)borate], and bidentate Schiff base ligands, HL1 or HL2 {HL1 = 2‐[[(2‐phenylethyl)imino]methyl]phenol; HL2 = 4‐methoxy‐2‐[[(2‐phenylethyl)imino]methyl]phenol}, two heterobimetallic one‐dimensional (1D) chain complexes, [Mn(L1)₂Fe(Tp*)(CN)₃]_n ( 1 ) and [Mn(L2)₂Fe(Tp*)(CN)₃]_n ( 2 ), were synthesized. Single crystal X‐ray diffraction reveal the formation of neutral cyano‐bridged zigzag single chains in 1 and 2 . Magnetic studies demonstrate that both complexes show ferromagnetic interactions between central Fe^III and Mn^III atoms.     

Novel Schiff base metal complexes: synthesis,characterization, DNA binding,DNA cleavage and molecular docking studies

A novel Schiff base, 3-(((1H-1,2,4-triazol-3-yl)imino)methyl)-4H-chromen-4-one (L) was synthesized and used as ligand for the synthesis of Co(II), Ni(II), Cu(II), Zn(II) and Pd(II) complexes. The structural characterization of the ligand and its metal complexes was determined by using various physicochemical and spectroscopic methods. The IR data show that the Schiff base ligand acts as a bidentate donor coordinating through the oxygen atom of the chromone and nitrogen atom of the imine group. Based on all spectral data, tetrahedral geometry has been proposed for all the metal complexes except Cu(II) and Pd(II) complexes. However, square-planar geometry has been proposed for Cu(II) and Pd(II) complexes. DNA binding interaction of the ligand and its metal complexes was investigated by using UV–visible absorption, fluorescence and molecular docking studies. The binding constants were in the order of 10⁴ M^?1 suggesting good binding affinity towards CT-DNA. The DNA cleavage activity of the synthesized compounds was investigated by using agarose gel electrophoresis. In vitro antimicrobial activity of the synthesized compounds were screened against two gram-positive bacteria (Bacillus subtilis, Staphylococcus aureu) and two gram-negative bacteria (Escherichia coli, Proteus vulgaris) and one fungi strain Candida albicans using disc diffusion method. Antioxidant activity was carried out by DPPH radical scavenging method. In vitro anti-proliferative activity of the ligand and its metal complexes was also carried on the HEK-293, HeLa, IMR-32 and MCF-7 cancer cell lines using MTT assay.     

A Kinetic Study of Phenolic Oxidation by H2O2 Using the Schiff Base Complexes As Mimetic Peroxidases

The Schiff base complexes containing a transition metal ion, Co^II and Cu^II, were used as mimetic peroxidase in the catalytic oxidation of phenol by H₂O₂. The characteristic spectra of the Schiff base complexes in H₂O₂-buffered solution were recorded and analyzed, respectively. The mechanism and the kinetic mathematic model of the phenol catalytic oxidation were studied. The results showed that the Schiff base complexes containing the transition metal ion, Co^II and Cu^II, as peroxidase mimics exhibited good catalytic activity and the character of the peroxidase in the catalytic oxidation of phenol by H₂O₂ under different conditions.     

Synthesis,crystal structures,and antibacterial activities of Schiff base nickel(II) and cadmium(II) complexes with tridentate Schiff bases

Reaction of tridentate Schiff bases with nickel and cadmium salts in methanol afforded two new mononuclear complexes, [Ni(L¹)₂] (I) and [Cd(L²)₂] (II), where L¹ and L² are the anions of 2-bromo-4-chloro-6-[(3-dimethylaminopropylimino)methyl]phenol (HL¹) and 2-bromo-4-chloro-6-[(3-morpholin-4-ylpropylimino)methyl]phenol (HL²), respectively. The complexes were characterized by singlecrystal X-ray diffraction (CIF files CCDC nos. 1428653 (I) and 1428654 for (II)), FT-IR, and elemental analysis. Complex I crystallizes in the monoclinic space group P2 ₁/c, with a = 8.8216(8), b = 14.0424(8), c = 11.8687(12) Å, β = 111.238(2)°, V = 1370.4(2) ų, Z = 2. Complex II crystallizes in the monoclinic space group P2 ₁/n, with a = 9.6774(4), b = 15.8970(6), c = 20.3144(7) Å, β = 90.408(2)°, V = 3125.1(2) ų, Z = 4. The metal atoms in the complexes are coordinated by two tridentate Schiff base ligands, forming octahedral coordination. The free Schiff bases and the complexes were assayed for antibacterial activities. Both complexes are more active against the bacteria than the free Schiff bases. Complex II has the MIC value of 0.39 μg mL^–1 against Bacillus subtilis.     

Synthesis,structural and spectroscopic properties of asymmetric Schiff bases derived from 2,3-diaminopyridine

Two Schiff base derivatives, 4-(2-amino-3-pyridyliminomethyl)phenol (I) and 3-(2-amino-3-pyridyliminomethyl)nitrobenzene (II), were synthesised and characterised by spectroscopy. The structure of I was determined by single crystal X-ray diffraction studies. The asymmetric Schiff base derived from 2,3-diaminopyridine selectively recognise transition and heavy metal cations, and some anion. Ligands I and II form stable complexes with Cu²⁺, Zn²⁺, Pb²⁺, Al³⁺ whereas ligand I also binds F~ ions. The stoichiometry for the host: cation is 1: 1 and 2: 1. The addition of F~ ion in CH₃CN to ligand I causes a colour change of the solution from colourless to yellow. The binding behaviour of ligand I towards several ions was investigated using density functional theory calculations.     

Synthesis, structure studies and electrochemistry of molybdenum(VI) Schiff base complexes in the presence of different donor solvent molecules

The reactions between bis(acetylacetonato)dioxomolybdenum(VI) and Schiff base ligands derived from 5-chlorosalicylaldehyde or 3-ethoxy-salicylaldehye, and 3-methoxy-benzoic hydrazide (m-anisic hydrazide), 2-furoic hydrazide or 2,4-dihydroxy-benzoic hydrazide in the presence of donor solvents yielded cis-dioxomolybdenum(VI) complexes with the general formula MoO₂L(D), where L = tridentate Schiff base ligand and D = dimethylsulfoxide, hexamethylphosphoramide, dimethylformamide, imidazole or methanol. The complexes were characterized by elemental analysis, electronic spectra, IR, ¹H and ¹³C NMR spectroscopies, thermogravimetric analysis, cyclic voltammetry, and the molecular structures of five of the dioxomolybdenum complexes were elucidated by single crystal X-ray diffractometion studies. In general, the complexes adopt an octahedral environment around the Mo center with a cis-oxo configuration. The other coordination sites are occupied by the imino nitrogen, phenoxyl oxygen, hydroxyl oxygen of the tridentate Schiff base and the donor atom of the solvent molecule. The structural data revealed that the labile coordination site, which is occupied by N or O atoms from the donor solvents, has a longer Mo-O or Mo-N bond distance.     

Synthesis,crystal structures,and catalytic oxidation properties of oxidovanadium(V) complexes with Schiff base ligands

Two new Schiff base ligands 2-chloro-N′-(5-fluoro-2-hydroxybenzylidene)benzohydrazide (H₂L^a) and 4-fluoro-2-{[2-(2-hydroxyethylamino)ethylimino]methyl}phenol (HL^b) were synthesized and characterized. Their respective oxidovanadium complexes, [VOL^a(OMe)(MeOH)]·MeOH (1) and [VO(μ-O)L^b]₂ (2), were synthesized and characterized by spectroscopy and single-crystal X-ray diffraction. The coordination sphere of each V atom is octahedral. Both complexes showed selective heterogeneous catalytic properties with 74–98 % conversion, for the oxidation of cyclohexene, cyclopentene, and benzyl alcohol using H₂O₂ as primary oxidant.     

Synthesis,structures and Hirshfeld surface analysis of Ni(II) and Co(III) complexes with N2O donor Schiff base ligand

Two octahedral complexes [NiL(HL)]ClO₄.0.5CH₃OH and [CoL₂]ClO₄ have been synthesized with N₂O donor Schiff base ligand {((2-(phenylamino)ethyl)imino)methyl}phenol (HL) and characterized by spectroscopic techniques and single crystal X-ray diffraction studies. The molar conductivities data of the two complexes show that the complexes are 1:1 electrolyte. Single crystal X-ray diffraction data shows both Ni(II) and Co(III) complexes have distorted octahedral geometry and two ligands are coordinated to the metal centers and one ClO₄⁻ ion outside the coordination sphere. The intermolecular interactions in the complexes are evaluated by Hirshfeld surface analysis and revealed a significant contribution of non- or weakly polar interactions to the packing forces for both molecules, with crystal structure of Co(III) complex featuring short H/H contacts.     

Studies on Mononuclear Chelates Derived from Substituted Schiff Base Ligands: Synthesis and Characterization of a New 5-Methoxysalicyliden-<Emphasis Type="Italic">p</Emphasis>-Aminoacetophenoneoxime and Its Complexes with Co(II), Ni(II), Cu(II), and Zn(II)

New complexes of Co(II), Ni(II), Cu(II), and Zn(II) with new Schiff bases derived by the condensation of p-aminoacetophenoneoxime with 5-methoxysalicylaldehyde are synthesized. The compounds are characterized by elemental analyses, magnetic susceptibility measurements, IR, ¹H and ¹³C NMR spectra, electronic spectral data, and molar conductivity. The thermal stabilities of the compounds are also reported. The Schiff base acts as bidentate O,N-donor atoms, and their metal complexes are supposed to possess a tetrahedral geometry with respect to the central metal ion. The general formula of the 5-methoxysalicyliden-p-aminoacetophenoneoxime Co(II), Ni(II), Cu(II), and Zn(II) complexes is Co(L)₂, Ni(L)₂, Cu(L)₂, and Zn(L)₂.     

Synthesis and metal ion complexation of acyclic Schiff base podands with lipophilic amide and ester end groups

A series of acyclic Schiff base podands 14?C19 with lipophilic amide and ester end groups were synthesized in good yield and in a simple way. Their transition metal ions complexation was studied using conductometric method in acetonitrile (AN) at 25 °C. Schiff base podands 14?C16 showed a continuous decrease in the molar conductances in their complexation with Hg²⁺, Pb²⁺, Cu²⁺, Zn²⁺ and Cd²⁺ which begins to level off at a mole ratio of 1:1 crown-to-metal indicating the formation of a stable 1:1 complexes. The order of the stability constants of the metal ions studied with the Schiff base podands 14, 15 and 16 is: Hg²⁺ > Pb²⁺ > Cu²⁺ > Zn²⁺ > Cd²⁺ > Ag⁺. Metal ion complexation by acyclic diamide or diester podands involves presumably the oxygen atoms of the carbonyl groups in addition to the nitrogen atoms of the imino groups.     

Spectroscopic and thermal characterization of biologically and anticancer active novel Schiff base metal complexes

The novel Schiff base ligand 2,2′-((1Z,1′Z)-(1,3-phenylenebis(azanylylidene))-bis(phenylmethanylylidene))dibenzoic acid (H₂L) was obtained by the condensation of m-phenylenediamine with o-benzoylbenzoic acid. The molecular and electronic structure of Schiff base ligand (H₂L) was optimized theoretically, and the quantum chemical parameters are calculated. Molecular docking was used to predict the binding between Schiff base ligand (H₂L) and the receptors of breast cancer mutant 3hb5-oxidoreductase, crystal structure E. coli (3t88) and crystal structure of S. aureus (3q8u). The newly synthesized Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), and Cd(II) complexes were characterized by elemental microanalysis, molar conductance, spectroscopic techniques (IR, ¹H NMR, ESI-mass, ESR, UV–Vis), magnetic susceptibility, thermal (TG/DTG) and powder X-ray diffraction data to explicate their structures. The data showed that the complexes had composition of MH₂L type. The IR results confirmed the bidentate binding of the ligand involving two azomethine nitrogens. ¹H NMR spectral data of the ligand (H₂L) and its Zn(II) and Cd(II) complexes agreed well with the proposed structures. On the basis of electronic spectra and the magnetic measurements, octahedral geometry of the complexes was proposed. Thermogravimetric data (TG and DTG) were also studied. The kinetic and thermodynamic parameters for thermal decomposition of the complexes were calculated using the Coats–Redfern and Horowitz–Metzger methods. In order to appraise the effect of antimicrobial activity of metal ions upon chelation, the newly synthesized ligand and its metal complexes were screened against a number of bacteria organisms as Bacillus subtilis, Staphylococcus aureus, Escherichia coli, and Neisseria gonorrhoeae and against one fungus, Candida albicans, to assess their inhibiting potential by using the disc diffusion method. The results showed that in some cases the antimicrobial activity of complexes was more biologically active than the Schiff base ligand. Anticancer activity of the ligand and its metal complexes were evaluated in human cancer (MCF-7 cells viability). It was found that [Cd(H₂L)(H₂O)₂Cl₂]2H₂O complex showed lowest IC₅₀ than the others, and hence was the more active. The activity index was calculated.     

Synthesis,crystal structures,and catalytic properties of two oxidovanadium(V) complexes with tridentate Schiff bases

Two new oxidovanadium(V) complexes, [VO₂L¹] (I) and [VO₂L²] (II), where L¹ and L² are the deprotonated forms of 4-methyl-2-[(2-morpholin-4-ylethylimino)methyl]phenol (HL¹) and 2-[(2-isopropylaminoethylimino) methyl]-4-trifluoromethoxyphenol (HL²), respectively, have been prepared and characterized by physico chemical methods and single crystal X-ray diffraction (CIF files CCDC nos. 1443671 (I), 1443672 (II)). The V atom in each complex is coordinated by the phenolate oxygen, imino nitrogen and amino nitrogen of the Schiff base ligand, and two oxo groups, forming trigonal-bipyramidal geometry. The oxidation of olefins with the complexes as catalyst was evaluated, which indicated that both complexes showed effective catalytic efficiency in oxidation of several aliphatic and aromatic substrates by using tert-butyl hydrogen peroxide as oxidant.     

Synthesis,characterization, and crystal structures of two Schiff base zinc(II) complexes with urease inhibitory activities

Two Schiff base zinc(II) complexes, [ZnBr₂L¹] · 2CH₃OH (I) (I) and [ZnBr₂L²] (II), where L¹ is 4-chloro-2-[(2-piperazin-1-ylethylimino)methyl]phenol and L² is 4-chloro-2-[(3-diethylaminopropylimino)methyl]phenol were synthesized and structurally characterized. The crystal of I is monoclinic: space group P2₁/c, a = 9.831(3), b = 18.680(6), c = 11.879(4) Å, β = 94.660(6)°, V = 2174.3(11) ų, Z = 4. The crystal of II is monoclinic: space group P2₁/n, a = 7.2310(14), b = 16.037(3), c = 15.856(3), β = 90.01(3)°, V = 1838.7(6) ų, Z = 4. The Zn atom in each complex is four-coordinated by one phenolate O and one imine N atoms of the Schiff base ligand and two bromide atoms, forming a tetrahedral coordination. The urease inhibitory activities of the complexes were evaluated.     

New metal(II) complexes with ceftazidime Schiff base

Complexes of Co(II), Ni(II) and Cu(II) with the Schiff base (LH) derived from ceftazidime and salicylaldehyde were synthesized. The proposed structures of the new metal complexes based on the results of elemental analyses, molar conductivity, IR, DRUV and ¹H NMR spectra, effective magnetic moment and thermal analysis were discussed. The surface morphology of Schiff base and metal complexes was studied by SEM. The composition of the metal complexes was ML₂, where L is the deprotonated Schiff base ligand and M = Co(II), Ni(II) and Cu(II). IR spectral data indicated the Schiff base ligand being bidentately coordinated to the metallic ions with N and O atoms from azomethine and phenolic groups. All the complexes have square-planar geometry and are nonelectrolytes. The thermal analysis recorded that TG, DTG, DTA and DSC experiments confirmed the assigned composition and gave information about the thermal stability of complexes in dynamic air atmosphere. Theoretical investigation of the molecular structure of Schiff base ligand and its complexes was studied using programs dedicated to chemical modeling and quantomolecular calculation of chemical properties. The newly synthesized complexes were tested for in vitro antibacterial activity against selected Gram-negative and Gram-positive bacterial strains, and they exhibited an antibacterial activity superior to that of the Schiff base ligand.     

Synthesis and Antimicrobial Activity of New Schiff Bases Having the –SiOR Group (R = CH 3or CH2CH3), and their Transition Metal Complexes

Two new Schiff base ligands containing −SiOCH₃ or −SiOCH₂CH₃ groups, 4-{[(3-trimethoxysilanepropyl)imino]methyl}benzene-1,3-diol (1) Hmsb and 4-{[(3-triethoxysilanepropyl)imino]methyl}benzene-1,3-diol (5) Hesb, have been synthesized by the reaction of 2,4-dihydroxybenzaldehyde with 3-aminopropyltrimethoxysilane and 3-aminopropyltriethoxysilane. Six new transition metal [Cu^II, Ni^II and Co^II complexes of these Schiff Base ligands were prepared. The complexes are formed by coordination of N, O atoms of the ligands. Their structures were confirmed by elemental analyses, ¹H nmr, i.r. and u.v.–vis. spectral data. The analytical data shows that the metal-to-ligand ratio in the Schiff Base complexes contains silane in 1:2. In addition, the antimicrobial activity of (1) Hmsb and (5) Hesb Schiff ligands, and their [M(msb)₂] and [M(esb)₂] type coordination compounds, were investigated