Cobalt(II), copper(II), zinc(II) and palladium(II) Schiff base complexes: Synthesis, characterization and catalytic performance in selective oxidation of sulfides using hydrogen peroxide under solvent-free conditions

Coordination Chemistry, Antibacterial Screening, and In Silico ADME Study of Mononuclear NiII and CuII Complexes of Asymmetric Schiff Base of Streptomycin and Aniline

Two novel metal complexes, that is, Ni (StmAn)2(4) and Cu (StmAn)2(5), were synthesized from unsymmetrical Schiff base ligand StmAn (3). The ligand was prepared by refluxing streptomycin (2) and aniline (1). They were characterized by elemental microanalysis, conductivity measurements, and spectroscopic techniques such as 1H NMR, FT-IR, ESI-mass, and electronic absorption spectral study. Interestingly, the study revealed metal coordination through azomethine nitrogen and N-atom of NH-CH3 of N-methyl-L-glucosamine unit of streptomycin. The electronic absorption spectral study supported an octahedral geometry for complex 4 and a tetrahedral geometry for complex 5. Particle size calculation by Scherrer’s formula indicated their nanocrystalline nature. The geometry optimization of the complexes was achieved by running an MM2 job in Gaussian supported Cs-ChemOffice ultra-12.0.1 and ArgusLab 4.0.1 version software. Based on SwissADME predictions, a theoretical drug profile was generated by analyzing absorption, distribution, metabolism, excretion, and toxicity (ADMET) scores of the compounds. They were screened for in vitro antibacterial activity study against four clinical pathogens such as E. coli, S. pneumoniae, P. vulgaris, and S. aureus. Minimum inhibitory concentration (MIC) study demonstrated greater inhibitory potency of complex (4) (0.024 g/L) for S. aureus relative to ligand (3) and complex (5). Studies show that metal complexes are more toxic to bacteria.

Design, Structural Inspection and Bio-Medicinal Applications of Some Novel Imine Metal Complexes Based on Acetylferrocene

Some novel imine metal chelates with Cr³⁺, Mn²⁺, Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, and Cd²⁺ cations were produced from 2-acetylferrocene and 3-aminophenol. The new acetylferrocene azomethine ligand ((Z)-cyclopenta-1,3-dien-1-yl(2-(1-((3-hydroxyphenyl)imino)ethyl)cyclopenta-2,4-dien-1-yl)iron) and its metal ion chelates were constructed and elucidated using FT-IR, UV/Vis, ¹HNMR, DTA/TGA, CHNClM studies, mass spectrometry and SEM analysis. According to the TGA/DTG investigation, the ferrocene moiety spontaneously disintegrates to liberate FeO. The morphology of the free acetylferrocene azomethine via SEM analysis was net-shaped with a size of 64.73 nm, which differed in Cd(II) complex to be a spongy shape with a size of 42.43 nm. The quantum chemical features of the azomethine ligand (HL) were computed, and its electronic and molecular structure was refined theoretically. The investigated acetylferrocene imine ligand behaves as bidinetate ligand towards the cations under study to form octahedral geometries in case of all complexes except in case of Zn²⁺ is tetrahedral. Various microorganisms were used to investigate the anti-pathogenic effects of the free acetylferrocene azomethine ligand and its metal chelates. Moreover, the prepared ligand and its metal complexes were tested for anticancer activity utilizing four different concentrations against the human breast cancer cell line (MCF7) and the normal melanocyte cell line (HBF4). Furthermore, the binding of 3-aminophenol, 2-acetylferrocene, HL, Mn²⁺, Cu²⁺, and Cd²⁺ metal chelates to the receptor of breast cancer mutant oxidoreductase was discovered using molecular docking (PDB ID: 3HB5).

Synthesis, Spectroscopic, Structural and Molecular Docking Studies of Some New Nano-Sized Ferrocene-Based Imine Chelates as Antimicrobial and Anticancer Agents

The newly synthesized organometallic acetyl ferrocene imine ligand (HL) was obtained by the direct combination of 2-acetyl ferrocene with 2-aminothiophenol. The electronic and molecular structure of acetyl ferrocene imine ligand (HL) was refined theoretically and the chemical quantum factors were computed. Complexes of the acetyl ferrocene imine ligand with metal(II)/(III) ions (Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II)) were fabricated. They were inspected by thermal (DTG/TG), spectroscopic techniques (FT-IR, 1H NMR, mass, UV-Vis), molar conductivity, and CHNClM to explicate their structures. Studies using scanning electron microscope (SEM) were conducted on the free acetyl ferrocene imine ligand and its Cd(II) chelate to confirm their nano-structure. To collect an idea about the effect of metal ions on anti-pathogenic properties upon chelation, the newly synthesized acetyl ferrocene imine ligand and some of its metal chelates were tested against a variety of microorganisms, including Bacillus subtilis, Staphylococcus aureus, Salmonella typhimurium, Escherichia coli, Aspergillus fumigatus, and Candida albicans. The ligand and its metal chelate were tested for cytotoxic activity in human cancer (MCF-7 cell viability) and human melanocyte cell line HBF4. It was discovered that the Cd(II) chelate had the lowest IC50 of the three and thus had the prior activity. Molecular docking was utilized to investigate the interaction of acetyl ferrocene imine ligand (HL) with the receptors of the vascular endothelial growth factor receptor VEGFR (PDB ID: 1Y6a), human Topo IIA-bound G-segment DNA crystal structure (PDB ID: 2RGR), and Escherichia coli crystal structure (PDB ID: 3T88).

The crystal structure of bis((E)-2-((tert-butylimino)methyl)-4-chlorophenolato-κ2 N,O)zinc(II), C22H26Cl2N2O2Zn

C22H26Cl2N2O2Zn, monoclinic, P21/n (no. 14), a = 10.488(7) Å, b = 10.139(7) Å, c = 22.760(15) Å, β = 99.705°, V = 2386(3) Å3, Z = 4, R gt (F) = 0.0395, wR ref (F 2) = 0.1053, T = 296(2) K.

Synthesis, characterization and crystal structure of 4-methoxybenzylidene-based zinc(II) complexes

Two novel zinc(II) complexes containing 4-methoxybenzylidene moieties namely, Zn(L)Cl2 (L = N, N′-bis(4-methoxybenzylidene)ethane-1, 2-diamine (1) or N-(4-methoxybenzylidene)-ethane-1, 2-diamine (2)) have been synthesized and characterized by infrared spectroscopy and single-crystal X-ray diffraction. Complex 1 crystallizes in the monoclinic space group P21/c with a = 9.2315(4); b = 12.0449(4); c = 18.2164(7) Å; β = 98.472(4)°, V = 1278.9(4) Å3 and Z = 4. Complex 2 crystallizes in the monoclinic space group P21/n with a = 6.5733 (2), b = 13.6595(5), c = 15.1615(5) Å; β = 101.846(4)°, V = 1332.33(8) Å3 and Z = 4. The environment of each Zn(II) atom is distorted tetrahedral with coordination of two terminal Cl atoms and two N atoms of the N,N′ – bis(4-methoxybenzylidene)ethane-1,2-diamine (1) or N-(4-methoxybenzylidene)ethane-1,2-diamine (2) ligand. The stability of the crystalline structure is ensured by the existence of intra- and intermolecular hydrogen bonds of the type C–H…Cl (1) and N–H…Cl (2) leading to supramolecular topologies.

Heteroleptic enantiopure Pd(ii)-complexes derived from halogen-substituted Schiff bases and 2-picolylamine: synthesis, experimental and computational characterization and investigation of the influence of chirality and halogen atoms on the anticancer activity

To investigate the effect of chirality and different halogen substituents on the anticancer activity, seven enantiomeric pairs of palladium complexes were synthesized and characterized.

A palladium(II) complex with the Schiff base 4-chloro-2-(N-ethyliminomethyl)-phenol: Synthesis, structural characterization, and in vitro and in silico biological activity studies

The synthesis and characterization of the Pd(II) complex of the formula [Pd(L)₂] 1 with the Schiff base 4-chloro-2-(N-ethyliminomethyl)-phenol (HL) as derived in situ via the condensation reaction of 5-chloro-salicylaldehyde and ethylamine was undertaken. The structure of 1 was verified by single-crystal X-ray crystallography. The ability of 1 to interact with calf-thymus (CT) DNA was studied by UV-vis and viscosity experiments, and its ability to displace ethidium bromide (EB) from the DNA-EB conjugate was revealed by fluorescence spectroscopy. It was found that intercalation is the most possible mode of interaction with CT DNA. Additionally, DNA electrophoretic mobility experiments showed that 1 interacts with the plasmid pBluescript SK(+) (pDNA) as proved by the formation of unusual mobility DNA bands and degradation of relaxed pDNA at concentration of 5 mM. The interaction of 1 with human (HSA) and bovine serum albumin (BSA) was monitored revealing its reversible binding to albumins. The complex showed noteworthy antimicrobial activity against one (Bacillus subtilis) of the five tested bacteria. In order to explain the described in vitro activity of the compound, we adopted molecular docking studies on the crystal structure of HSA, BSA, CT DNA and DNA-gyrase. Furthermore, in silico predictive tools have been employed to study the properties of the complex. The in silico studies are adopted on a multitude of proteins involved in cancer growth, as well as prediction of drug-induced changes of gene expression profile, protein- and mRNA-based prediction results, prediction of sites of metabolism, cytotoxicity for cancer cell lines, etc.

Cu(ii) and Zn(ii) complexes with a poly-functional ligand derived from o-vanillin and thiophene. Crystal structure, physicochemical properties, theoretical studies and cytotoxicity assays against human breast cancer cells

New ML₂ complexes were extensively characterized showing stability in solution and promising anti-tumoral results, particularly for CuL2.

One-Pot Synthesis of Core–Shell Structured Metal–Organic Coordination Polymer Microspheres with a Hierarchical Microporous–Mesoporous–Macroporous Structure

New core–shell structured metal–organic coordination polymer (CP) microspheres with a hierarchical microporous–mesoporous–macroporous structure are synthesized by a one-pot template-free method. The ligand L with a Schiff-base functional group is obtained by reacting 3-hydroxy-4-aminobenzoic acid with para-benzaldehyde. The coordination polymer microspheres (Zn-L-CP) are obtained by mixing the ligand L and zinc nitrate hexahydrate together under hydrothermal conditions. The resultant coordination polymer microspheres with a core–shell structure are characterized by FT-IR and solid state NMR spectroscopy, transmission and scanning electron microscopy, and nitrogen adsorption–desorption measurements. The obtained Zn-L-CP microspheres are proved to be effective heterogeneous catalysts for the deacetylation reaction with the merits of easy recycling and stability. The yield is 96% when using methanol as solvent, and the yield can remain at 90% after seven cycles.

Bovine serum albumin-cobalt(ii) Schiff base complex hybrid: an efficient artificial metalloenzyme for enantioselective sulfoxidation using hydrogen peroxide

An artificial metalloenzyme (BSA-CoL) based on the incorporation of a cobalt(ii) Schiff base complex {CoL, H2L = 2,2'-[(1,2-ethanediyl)bis(nitrilopropylidyne)]bisphenol} with bovine serum albumin (BSA) has been synthesized and characterized. Attention is focused on the catalytic activity of this artificial metalloenzyme for enantioselective oxidation of a variety of sulfides with H2O2. The influences of parameters such as pH, temperature, and the concentration of catalyst and oxidant on thioanisole as a model are investigated. Under optimum conditions, BSA-CoL as a hybrid biocatalyst is efficient for the enantioselective oxidation of a series of sulfides, producing the corresponding sulfoxides with excellent conversion (up to 100%), chemoselectivity (up to 100%) and good enantiomeric purity (up to 87% ee) in certain cases.

Palladium complexes containing imino phenoxide ligands: synthesis, luminescence, and their use as catalysts for the ring-opening polymerization of rac-lactide

Abstract

The preparation, structural characterization, luminescence, and catalytic activity of three palladium(II) complexes bearing imino phenoxide ligands are reported. The X-ray studies revealed that the complexes are mononuclear with palladium centres coordinated in a square-planar coordination environment. Two of the complexes are emissive in solution at room temperature. The catalytic activities towards the ring-opening polymerization of rac-lactide (rac-LA) were tested. Polymers with moderate molecular weights and relatively broad dispersity (Ð) were obtained. Kinetic studies revealed that the polymerization followed first-order kinetics.

Graphical abstract

Electronic supplementary material

The online version of this article (10.1007/s00706-017-2119-1) contains supplementary material, which is available to authorized users.

Schiff base Mn(iii) and Co(ii) complexes coated on Co nanoparticles: an efficient and recyclable magnetic nanocatalyst for H2O2 oxidation of sulfides to sulfoxides

In this paper, an effective and selective heterogeneous catalyst was produced by immobilization of manganese and cobalt Schiff base-complexes on Co magnetite nanoparticles (MNP). The catalysts Co@SiO₂[(EtO)₃Si–L³]/M (M = Mn(iii) and Co(ii)) were synthesized using Co@SiO₂ core–shell nanoparticles and amino-functionalized Co@SiO₂. The Schiff base ligand Co@SiO₂[(EtO)₃Si–L³] was synthesized by reacting Co@SiO₂ core–shell nanoparticles with 2-hydroxy 1-naphthaldehyde for the synthesis of Co@SiO₂[(EtO)₃Si–L³]/M. The catalysts were characterized by several techniques, such as FT-IR, TEM, XRD, TGA and VSM. The catalytic activities of the prepared catalysts were studied by oxidation of sulfides to the sulfoxides under different conditions. These catalysts can be easily recovered and reused in at least seven sequential cycles without considerable leaching and loss of reactivity.

In this paper, an effective and selective heterogeneous catalyst was produced by immobilization of manganese and cobalt Schiff base-complexes on Co magnetite nanoparticles (MNP).

Tuning of Catalytic Property Controlled by the Molecular Dimension of Palladium-Schiff Base Complexes Encapsulated in Zeolite Y

Planar palladium-Schiff base complexes are synthesized, maintaining the order of their molecular dimensions as PdL1 < PdL2 < PdL3 < PdL4 < PdL5 in free state, as well as encapsulated in zeolite Y, where L1: N,N'-bis(salicylidene)ethylenediamine and L2, L3, L4, and L5 are derivatives of L1. All encapsulated complexes have shown better catalytic activity for the sulfoxidation of methyl phenyl sulfide in comparison to their homogeneous counter parts. These hybrid systems are characterized with the help of different characterization techniques such as X-ray diffraction analysis, scanning electron microscopy-energy-dispersive X-ray spectrometry, X-ray photoelectron spectroscopy, Fourier transform infrared, and UV-visible spectroscopy; all of these studies have suggested that the largest complex deviates by the maximum from its free-state properties, and a radical change in the reactivity of the complex is observed.