Tridentate Schiff Base Ligand Research Articles

Preparation and Characterization of Copper Oxide Nanoparticles Through Solid State Thermal Decomposition of an Aqua Nitrato Copper(II) Complex with a Tridentate Schiff-base Ligand as a New Precursor

Introduction: In this study the synthesis and characterization of copper oxide nanoparticles via solid state thermal decomposition of a recently synthesized aqua nitrato copper(II) complex with a tridentate Schiff-base ligand (1) as a new precursor are reported. Materials & Methods: The copper complexes were obtained by sonochemical and solvothermal process and characterized by Scanning Electron Microscopy (SEM), X-ray powder Diffraction (XRD) and FT-IR spectroscopy. The thermal stability of compound (1) was studied by Thermogravimetric Analysis (TGA). The amount of initial reagents and the role of reaction time on size and morphology of nanostructure compound (1) were studied. CuO nanoparticles were simply synthesized at 500 oC under air atmosphere. Results & Conclusion: The diameter of CuO nanoparticles was estimated to be about 200 and 30 nm from copper complex precursor obtained by sonochemical and solvothermal methods respectively.

Dysprosium Single-Molecule Magnets with Bulky Schiff Base Ligands: Modification of the Slow Relaxation of the Magnetization by Substituent Change.

The synthesis, and magnetic and photoluminescence investigations of two bifunctional dysprosium complexes based on tridentate Schiff base ligands is reported. Magnetic investigations reveal a genuine single-molecule magnet (SMM) behavior, with out-of-phase signals up to 60 K, and tunable emission arising from the Schiff base ligands.

Copper Tridentate Schiff Base Complex Supported on SBA-15 as Efficient Nanocatalyst for Three-Component Reactions under Solventless Conditions.

The anchorage of a supported copper Schiff base complex on SBA-15 materials provides highly efficient heterogeneous catalysts towards the solvent-free synthesis of dihydropyrimidinones derivatives via the Biginelli condensation reaction. The novel nanocatalysts exhibited a highly ordered mesostructure with a surface area of 346 m2g−1 and an average pore diameter of 8.6 nm. Additionally, the supported copper nanocatalysts were reused at least ten times, remaining almost unchanged from the initial activity. Both the mesoporous scaffold and the tridentate Schiff base ligand contributed to the stabilization of copper species.

Syntheses, Crystal Structures, and Antimicrobial Activities of Oxovanadium(V) Complexes with Tridentate Schiff base Ligand

Two structurally similar new oxovanadium complexes, [VO(L)(L1)] (I) and [VO(L)(L2)] (II), where L is the dianionic form of 3-((3-bromo-2-hydroxyphenyl)-{[1-(3-bromo-2-hydroxyphenyl)methylidene]amino}methyl)pentane-2,4-dione (H2L), L1 is the deprotonated form of 8-hydroxyquinoline, L2 is 2,2'-bipyridine, were prepared and characterized by spectroscopic and single crystal X-ray diffraction (СIF files CCDC nos. 1566824 (I), 1566825 (II)). Complex I crystallizes as the monoclinic space group P21/c with unit cell dimensions a = 11.265(1), b = 18.179(2), c = 13.461(2) A, β = 103.376(3)°, V = 2681.8(5) A3, Z = 4, R1 = 0.0659, wR2 = 0.1318, GOOF = 1.003. Complex II crystallizes as the orthorhombic space group Pbca with unit cell dimensions a = 19.958(1), b = 13.600(1), c = 22.8713(2) A, V = 6192.3(8) A3, Z = 8, R1 = 0.0550, wR2 = 0.1008, GOOF = 1.074. X-ray analysis indicates that the complexes are mononuclear oxovanadium(V) species with the V atoms in octahedral coordination. The complexes were evaluated for their antibacterial (Bacillus subtilis, Staphylococcus aureus, Escherichia coli, and Pseudomonas fluorescence) and antifungal (Candida albicans and Aspergillus niger) activities by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) method. Interestingly, complex II has strong activity against S. aureus.

Structural investigation of a new cadmium coordination compound prepared by sonochemical process: Crystal structure, Hirshfeld surface, thermal, TD-DFT and NBO analyses

A new nanostructured cadmium complex containing a tridentate Schiff base ligand was sonochemically synthesized and characterized by XRPD, FT/IR, NMR, and single crystal X-ray crystallography. Structural data showed that cadmium(II) ion is surrounded by three nitrogen atoms of Schiff base ligand and two iodide anions. The crystal packing was contained the intermolecular interactions such as CH⋯O, CH⋯I and π⋯π interactions organizing the self-assembly process. Hirshfeld surfaces and corresponding fingerprint plots have been used for investigation of the nature and proportion of interactions in the crystal packing. FT/IR, NMR and XRD data were in agreement with the X-ray structure and confirm the phase purity of the prepared sample. The molecular structure of the complex was optimized by density functional theory (DFT) calculation at the B3LYP/LANL2DZ level of theory and the results were compared with experimental ones. For more concise study of structure and spectral aspects of the complex, natural bond orbital (NBO) analysis and time-dependent density functional theory (TD-DFT) have been also performed. Thermal stability of the cadmium iodide complex was investigated by thermogravimetric analysis (TGA). Finally, cadmium oxide nanoparticles was prepared by direct calcination of CdLI2 complex as a new precursor.

Mono- and dinuclear organotin(IV) complexes for solvent free cycloaddition of CO2 to epoxides at ambient pressure

Novel mono- and dinuclear dimethyltin(IV) complexes were synthesized using tridentate Schiff base ligands, derived from 2-amino-2-hydroxymethyl-propane-1,3-diol and various aldehydes. These diorganotin(IV) compounds displayed good catalytic activity for solvent-free cycloaddition of CO2 to epoxides at ambient pressure. These catalysts efficiently completed the insertion of CO2 to various epoxides at low catalyst loadings (0.1–1.0 mol%) in 1–6 hours giving high values of TONs around 1000. The catalyst further usability for three continuous reaction runs in the reaction mixture gives the same activity revealing the remarkable stability of these compounds under the given reaction conditions. Therefore, organotin(IV) complexes are efficient catalysts for the synthesis of the industrially important cyclic carbonates from epoxides at ambient pressure under solvent-free conditions.

Bottom-Up Assembly of a Highly Efficient Metal-Organic Framework for Cooperative Catalysis.

In this study, we demonstrate a bottom-up assembly of a monomeric copper complex and a two-dimensional (2-D) heterometallic metal-organic framework (MOF) from a carboxylate-functionalized tridentate Schiff base ligand and metal ions. The obtained 2-D MOF features a unique bimetallic copper center which is different from its monometallic precursor and acts as an efficient heterogeneous catalyst for the Friedel-Crafts reaction and Henry reaction. The MOF catalyst shows a remarkably superior activity compared to its homogeneous counterparts in a wide range of substrates. It is presumably ascribed to the dual activation of the substrates by the active bimetallic copper center confined in the MOF network, which is supported by the significant changes in catalytic activity at low catalyst/substrates ratios when using the 2-D MOF and its precursor as catalysts, respectively. Moreover, the MOF catalyst also shows an excellent stability and recyclability. Our work, therefore, provides a stepwise strategy to design a heterogeneous cooperative catalyst, by taking advantage of the modulated structure of MOF and tunable functionality of the tridentate Schiff base, with high performance in a variety of organic synthesis.

Discovery of vanadium complexes bearing tridentate schiff base ligands as novel LSD1 inhibitors

Lysine specific demethylase (LSD1) plays a pivotal role in epigenetic modulation of gene expression. Abberrant expression of LSD1 was associated with the progress and oncogenesis of multiple human cancers. Herein, we report the preliminary anti-LSD1 evaluation of the synthetic vanadium (V) complexes. Among them, complex 2 showed a moderate inhibitory effect against LSD1 with IC50 value of 19.0 μM, as well as good selectivity over MAO-A/B. Complex 2 is the first vanadium based LSD1 inhibitor, which provides a novel scaffold for the development of LSD1 inhibitor.

Inhibition of DNase I Enzyme with Nickel(II) Triphenylphosphine Complexes Incorporating Tridentate Schiff Base Ligands in Vitro

The nickel(II) complexes containing 3-methoxy-salicylaldehyde-N4-R thiosemicarbazones (R:-H2,-propyl)with triphenylphosphine coligands have been synthesized. The structure of Ni(II)-centered metal complex was approved by elemental analysis and melting point. The solid-state structure of complex 2 bearing PPh3 as co-ligand was clarified by single crystal X-ray crystallography, which revealed square planar geometry around Ni(II) ion. Thiosemicarbazone ligands are coordinated by ONS mode to nickel(II). The potential of these complexes to inhibit the DNase I enzyme, which uses DNA as a substrate, was investigated in vitro. The results revealed that the compounds inhibited the DNase enzyme in directly and/or indirectly (by masking of DNA molecules) at ≥0.1 µg/ml concentrations in vitro.

Cu(II) Complexes of 4-[(1E)-N-{2-[(Z)-Benzylidene-amino]ethyl}ethanimidoyl]benzene-1,3-diol Schiff Base: Synthesis, Spectroscopic, In-Vitro Antioxidant, Antifungal and Antibacterial Studies

The current study reports the synthesis of copper complexes of a tridentate Schiff base ligand. The compounds of the type [Cu(L)X]∙n(H2O) (where L = tridentate ONN Schiff base ligand, X = Cl−, Br−, SCN−, NO3−, CH3COO−), were characterized on the basis of elemental analyses, FT-IR, UV-vis, molar conductance, 1H-NMR, XRD and thermal analyses. The spectra revealed that the Schiff base ligand acts as a tridentate ligand through two azomethine nitrogen atoms and a phenolic oxygen atom. The molar conductance measurements of the complexes in DMF correspond to non-electrolytic nature. TGA and DTA studies results gave insight into the dehydration, thermal stability, and thermal decomposition. Square-planar geometry has been assigned to the prepared complexes as indicated by the electronic spectral measurements. Cu(II) compounds showed antiradical potential against DPPH and ABTS radicals. The antimicrobial potential of the Schiff base ligand and its Cu(II) complexes were evaluated by the rapid p-iodonitrotetrazolium chloride (INT) colorimetric assay against some selected bacteria strains: Staphylococcus aureus and Enterococcus faecalis (Gram +ve); Klebsiella pneumoniae and Pseudomonas aeruginosa (Gram −ve), and fungi (Candida albicans and Cryptococcus neoformans). The compounds showed a broad spectrum of antibacterial and antifungal activities, with MIC values ranging from 48.83 to 3125 μg/mL.

5-Methyl-2-hydroxy-acetophenone-S-methyl-thiosemicarbazone and its nickel-PPh3 complex. Synthesis, characterization, and DFT calculations

A tridentate Schiff base ligand (5-methyl-2-hydroxy-acetophenone-S-methyl-thiosemicarbazone, H2L) and its mononuclear nickel complex, [NiL(PPh3)], were obtained and characterized by spectroscopic techniques. Structural analysis of the compounds was supported by complementing crystallographic studies. The X-ray data related to molecular geometries was used in the DFT/B3LYP calculations with 6-311G (d, p) and LANL2DZ (for nickel atom) basis sets. Atomic charge distribution data indicated that the negative charges of free thiosemicarbazidato ligand were transferred to nickel (II) by the formation of the metal complex. To understand the nucleophilic or electrophilic reaction capabilities the ligand and nickel complex, the molecular electrostatic potential (MEP) and electrostatic potential (ESP) analyses have performed.

3D supramolecular networks based on hydroxyl-rich Schiff-base copper(II) complexes

Reactions of the Schiff base ligand OH-C6H4-CHNC(CH2OH)3 (H4L) with copper(II) salts in various reaction media afforded complexes [Cu4(H2L)4]·MeOH (1·MeOH), [Cu2(O2CMe)2(H3L)2] (2), [Cu4(H2L)4(H2O)2]·1.5dmf (3·1.5dmf), [Cu4(H2L)4(H2O)]·MeOH (4·MeOH) and [Cu4(H2L)4]2·2H2O·7MeOH (5·2H2O·7MeOH). Compounds 1, 3 and 4 consist of neutral tetranuclear entities in which the CuII ions are coordinated by the tridentate Schiff base ligands, forming a tetranuclear Cu4O4 cubane-like configuration. Compound 5 contains similar cubane-like tetranuclear entities which are further linked through the hydroxyl groups of the ligands thus forming dimers of cubanes. Compound 2 contains a neutral dinuclear entity in which the CuII ions are bridged through the Schiff base and the acetate ligands, comprising distorted Cu2O2 core. The Schiff base ligand adopts five different coordination modes and two deprotonation states in the structures of 1–5 acting simultaneously as chelating and bridging agent between the metal ions. The lattice structures of 1–5 exhibit interesting 3D networks based on hydrogen bonded metal clusters and they are studied with Hirshfeld Surface analysis methods.

New complexes of Ni(II) and Cu(II) with tridentate ONO Schiff base ligand: synthesis, crystal structures, electrochemical and theoretical investigation

In this research, we prepared a new series of the Cu(II) (1) and Ni(II) (2) metal complexes of a tridentate Schiff base ligand, (E)-2-(5-bromo-2-hydroxybenzylideneamino) phenol (H2L). These complexes were characterized by elemental analysis, FT-IR, UV–Vis, and 1H-NMR spectroscopy. The crystal structures of (1) and (2) were determined by X-ray diffraction studies. The single crystal X-ray diffraction analyses revealed that copper(II) cation is five-coordinated and the coordination polyhedron is a slightly distorted square pyramid. Nickel(II), on the other hand, is four-coordinated, and has a regular, square planar geometry. Further discussed were the electrochemical reduction of these complexes. We also analyzed the nature of the metal–ligand bond in the complexes through NBO and EDA analysis. Besides, vibrational sample magnetometer (VSM) revealed complex (1) was ferromagnetic.

Synthesis, crystal structure and antimicrobial activity of a novel oxidovanadium(V) complex with tridentate Schiff base ligand

A novel oxidovanadium complex, [VOLL’]·CH3OH, where L is the dianionic form of 3-((3-bromo-2-hydroxyphenyl)-{[1-(3-bromo-2-hydroxyphenyl)methylidene]amino}methyl)pentane-2,4-dione (H2L), L’ is 1,10-phenanthroline, was prepared and characterized by spectroscopic and single crystal X-ray diffraction. The complex crystallizes as the monoclinic space group Cc, with unit cell dimensions a = 18.806(2) Å, b = 14.960(2) Å, c = 12.954(2) Å, β = 123.719(2)°, V = 3031.5(6) Å3, Z = 4, R1 = 0.0638, wR2 = 0.0825, Goof =1.069. X-ray analysis indicates that the complex is a mononuclear oxidovanadiumm(V) species, with the V atom in octahedral coordination. The complex was evaluated for their antibacterial (Bacillus subtilis, Staphylococcus aureus, Escherichia coli, and Pseudomonas fluorescence) and antifungal (Candida albicans and Aspergillus niger) activities by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) method. Interestingly, the complex has strong activity against S. aureus.

Synthesis, structure, and biological properties of a Co(II) complex with tridentate Schiff base ligand

A new Co(II) complex of general formula [Co(L)2] has been synthesized from a NNO tridentate Schiff base ligand, 2-[(piperidin-2-ylmethylimino)-methyl]-phenol (L). The title complex is characterized by elemental, spectroscopic, antibacterial, and single crystal X-ray structural studies. X-Ray crystallography reveals that the complex shows a distorted octahedral geometry around the Co(II) ion. The complex was tested against several bacteria and shows good antibacterial activities against almost all of the bacteria. The interactions of the title complex with calf thymus deoxyribonucleic acid (CT-DNA) have been investigated by electronic absorption and fluorescence spectroscopy, showing that the complex interacts with CT-DNA via partial intercalation. Thermogravimetric analysis (TGA) of the complex has also been reported and the result shows that the complex is thermally stable up to 134 °C.

Crystal Structure and Catalytic Property of an Oxidomolybdenum(VI) Complex Derived from N′-(2-Hydroxy-3,5-Di-Tert-Butylbenzylidene)-4-Methylbenzohydrazide

With a tridentate Schiff base ligand N′-(2-hydroxy-3,5-di-tert-butylbenzylidene)-4-methylbenzohydrazide (H2L) and MoO2(acac)2, an oxidomolybdenum(VI) complex is prepared and characterized by elemental analysis, IR spectroscopy and X-ray structure determination. The complex crystallizes in the monoclinic space group C2/c with unit cell dimensions a = 20.187(2) A, b = 7.9094(8) A, c = 33.233(3) A, β = 97.394(2)°, V = 5262.1(9) A3, Z = 8, R1 = 0.0491, and wR2 = 0.1322. The single crystal X-ray diffraction analysis reveals that the Mo atom is coordinated by NOO donor atoms of the Schiff base ligand, the methanol O atom, and two oxo groups in an octahedral coordination. Catalytic oxidation of the complex on some olefins is performed.

Mn(III) and Mn(II) complexes of tridentate Schiff base ligands; synthesis, characterization, structure, electrochemistry and catalytic activity

Abstract Three Mn(III) complexes [Mn(L1)2] (ClO4) 1, [Mn(L2)2] (ClO4) 2, [Mn(L3)2] (ClO4) 3, and one Mn(II) complex [Mn(L4)2] 4 were studied for their efficiency as catalysts for epoxidation of olefins with H2O2 at room temperature and 0 °C in the presence of ammonium acetate-acetic acid or triethylamine-perchloric acid system as co-catalyst/buffer. The complexes were obtained from the reaction of Mn(ClO4)2.6H20 with NNO tridentate Schiff base ligands HL1-HL4 synthesized from the condensation reaction of 2-(2-aminoethyl)pyridine and 2-hydroxybenzaldehyde (HL1), 5-chloro-2-hydroxybenzaldehyde (HL2), 5-methoxy-2-hydroxybenzaldehyde (HL3), or 5-nitro-2-hydroxybenzaldehyde (HL4) respectively. The complexes were characterized by spectroscopic techniques as well as by single crystal X-ray diffraction analysis. Electronic effect of the substituents on epoxide yield was also investigated. The crystal structures of complexes confirm coordination of the manganese ion to the ligands through the NNO atoms of the ligands. The spectral changes observed as a function of time for the reaction of the complexes with aqueous (30%) hydrogen peroxide indicates possible formation of an intermediate product; hydroperoxo-complex implicated in the epoxidation reaction. The complexes catalyzed epoxidation of cyclohexene with low yield at room temperature but higher yield at 0 °C in the order complex 3 lower than 1, 1 lower than 2, with the Mn(II) complex 4 recording highest epoxide yield of 9% with turnover of 2.25 at room temperature and yield of 58% with turnover of 14.5 at 0 °C in the presence of ammonium acetate-acetic acid system/ buffer. With the triethylamine-perchloric acid system/buffer, epoxide yield of 46% and turnover of 11.5 was recorded at room temperature while 44% with turnover of 11.0 was obtained at 0 °C for complex 4.

Catalysis of alkene epoxidation by manganese(II) and (III) complexes of both Schiff base and reduced Schiff base ligands utilizing environmentally benign H2O2

Mono and disubstituted tridentate Schiff base ligands were synthesized from the reaction of 2(2-aminoethyl)pyridine with 5-bromosalicylaldehyde (H-L1) and 3,5-dibromosalicylaldehyde (H-L2) respectively, which were subsequently reacted with NaBH4 to yield the corresponding reduced Schiff base ligands H-rL1 and H-rL2. The complexes; MnIII-(L1)2 (1), MnIII-(rL1)2 (3), and MnII-(L2)2 (2), MnII-(rL2)2 (4) were obtained by the reaction of the ligands with {Mn(ClO4)2·6H2O}. The ligands and complexes were characterized by UV–Vis, ESI-MS and FT-IR spectroscopy. The 1H NMR spectra of the ligands as well as the crystal structures, and electrochemical properties of the complexes were obtained. The crystal structures of MnIII-(L1)2 and MnII-(L2)2 show coordination of the ligands in tridentate mode in octahedral geometry. Cyclic voltammetric studies of Mn-(L1)2 and Mn-(L2)2 in acetonitrile solution show two prominent reversible peaks attributed to the redox processes: Mn(II)/Mn(III), (E1/2 = 0.203–(−0.204 V) and Mn(III)/Mn(IV), (E1/2 = 1.103–0.195 V) versus Ag/AgCl while that of Mn-(rL4)2 showed three quasi reversible peaks suggesting three redox couples: Mn(II)/Mn(III) (E1/2 = −0.109); Mn(III)/Mn(IV), (E1/2 = 0.125 and (Mn(IV)/Mn(V), (E1/2 = 0.649) vs Ag/AgCl. Epoxidation of cyclohexene and 1-hexene by hydrogen peroxide catalyzed by the manganese complexes gave epoxide yield of 42–53% with a turnover of 10.50–13.25 after 20 h of reaction for the reduced Schiff base complexes {MnIII-(rL1)2 and MnII-(rL2)2} at 0 °C.

Preparation, crystal structure, spectroscopic studies, DFT calculations, antibacterial activities and molecular docking of a tridentate Schiff base ligand and its cis‐MoO2 complex

We synthesized a tridentate Schiff base ligand, 6‐(((2‐hydroxyphenyl)amino)methylene)‐2‐methoxycyclohexa‐2,4‐dienone [H2L], as well as its Mo(VI) complex [MoO2(L)(DMSO)], and then characterized them completely using elemental analysis, FT‐IR, UV–Vis and 1HNMR spectroscopy techniques. X‐ray single crystal diffraction method was used for the determination of the structure of the synthesized ligand and complex. All other spectroscopic techniques performed, confirmed that [MoO2(L)(DMSO)]had an octahedral geometry around the Mo(VI) central ion coordinated by the donor atoms of the deprotonated ligand, two oxido groups and one oxygen atom of DMSO molecule. Hybrid functional B3LYP with DGDZVP as basis set was applied for DFT calculations of the compounds in their ground state. The MEP, Mulliken, HOMO‐LUMO energy gap and thermodynamic properties of the compounds were also theoretically predicted. In‐vitro antimicrobial studies on the synthesized compounds indicated the great antibacterial activities of the Mo(VI) complex against Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa and Bacillus cereus bacteria.

Synthesis, Characterization and Antimicrobial Studies of Co(II), Ni(II), Cu(II) and Zn(II) Complexes of (E)-2-(4-Dimethylbenzydimino)-Glycylglycine, (Glygly-DAB) a Schiff Base Derived from 4-Dimethylaminobenzaldehyde and Glycylglycine

A tridentate Schiff base ligand, (E)-2-(4-dimethylbenzydimino) glycylglycine (glygly-DAB), derived from the condensation of 4-Dimethylaminobenzaldehyde (DAB) and glycylglycine (glygly) together with its Co(II), Ni(II), Cu(II) and Zn(II) complexes have been synthesized and characterized using various physico-chemical methods including C,H,N elemental analysis, melting point determination, molar conductivity measurement, IR, 1H NMR and UV-Vis. The ligand and metal complexes were screened in vitro for antimicrobial and antifungal activities on four bacterial strains (Staphylococcus aureus, Escherichia coli, Salmonella thyphi and Pseudomonas aeruginosa) and two fungal strains (Candida albicans and Cryptococcus neoformans). glygly-DAB showed remarkable antifungal activities on all the fungal strains and antibacterial activities on one bacterial strain.