Synthesis,characterization and bioactivity of Schiff base copper(II) complexes derived from L-glutamine and L-asparagine

To investigate the structure–activity relationship of L-glutamine and L-asparagine Schiff base copper complexes in applications, L-glutamine and L-asparagine Schiff bases (GV and AV) and their copper complexes [Cu₃(GV)₂(CH₃COO)₂(H₂O)] · 2H₂O (GVC) and [CuAV(H₂O)₃] (AVC) have been synthesized and characterized by molar conductance, elemental analysis, UV-Vis, IR, ¹H-NMR, and TG-DTG. We examined the geometries of GV, AV, GVC, and AVC through Hartree–Fock method and electronic absorption spectra. We also tested their antibacterial activity against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Bacillus subtilis bacteria and antiproliferation activity on human breast cancer MDA-MB-231 cells. The side chain difference between L-glutamine and L-asparagine results in different geometry of GV and AV, which leads to different geometry of GVC and AVC. GVC, a trinuclear Cu(II) complex, shows the highest antibacterial activity and the highest growth inhibition activity on MDA-MB-231 cells. Our results suggest that GVC has potential as an antibacterial and anticancer agent.     

Synthesis,structural characterization,and antibacterial activity of mononuclear cobalt(III) azido complexes of two pentadentate Schiff bases derived from 2-hydroxynaphthaldehyde

The structural, spectroscopic, and electrochemical properties of [Co{(naph)₂dien}(N₃)] and [Co{(naph)₂dpt}(N₃)], where (naph)₂dien?=?bis-(2-hydroxy-1-naphthaldimine)-N-diethylenetriaminedianion and (naph)₂dpt?=?bis-(2-hydroxy-1-naphthaldimine)-N-dipropylenetriaminedianion have been investigated. These complexes are characterized by elemental analyses, IR, and UV–Vis spectroscopy. The crystal structures of these complexes have been determined by X-ray diffraction. The geometry around cobalt is distorted octahedral. The electrochemical behavior of these complexes in acetonitrile solution was also investigated. Both complexes show an irreversible Co^III–Co^II reduction at ca. ?0.8?V, accompanied by dissociation of the axial Co^II–N₃ bond. The in vitro antibacterial activities of these complexes were tested against Staphylococcus aureus and Bacillus licheniformis.     

Synthesis, crystal structure and antibacterial activity of a group of mononuclear manganese(II) Schiff base complexes

Five mononuclear complexes of manganese(II) of a group of the general formula, [MnL(NCS)₂] where the Schiff base L = N,N′-bis[(pyridin-2-yl)ethylidene]ethane-1,2-diamine (L¹), (1); N,N′-bis[(pyridin-2-yl)benzylidene]ethane-1,2-diamine (L²), (2); N,N′-bis[(pyridin-2-yl)methylidene]propane-1,2-diamine (L³), (3); N,N′-bis[(pyridin-2-yl)ethylidene]propane-1,2-diamine (L⁴), (4) and N,N′-bis[(pyridin-2-yl)benzylidene]propane-1,2-diamine (L⁵), (5) have been prepared. The syntheses have been achieved by reacting manganese chloride with the corresponding tetradentate Schiff bases in presence of thiocyanate in the molar ratio of 1:1:2. The complexes have been characterized by IR spectroscopy, elemental analysis and other physicochemical studies, including crystal structure determination of 1, 2 and 4. Structural studies reveal that the complexes 1, 2 and 4 adopt highly distorted octahedral geometry. The antibacterial activity of all the complexes and their respective Schiff bases has been tested against Gram(+) and Gram(−) bacteria.     

Synthesis,characterization and antibacterial activity of indium(III) complexes with adamantane-ring containing Schiff bases

Indium(III) chloride tetrahydrate and Schiff-base ligands derived from adamantaneamine and 3-/4-methoxysalicylaldehyde gave two complexes, C₂₂H₃₂Cl₃InN₂O₃ (1) and C₃₆H₄₄C_l3InN₂O₄ (2), respectively. The complexes were characterized by IR, ¹H NMR, elemental analysis, molar conductance, thermal analysis, and single-crystal X-ray diffraction. Complex 1 crystallizes in the monoclinic system, P2₁/n space group with the asymmetric unit consisting of one indium(III), one N-(3-methoxysalicylidene)-aminoadamantane (L¹), three chlorides and one N,N-dimethylformamide molecule. The indium is six-coordinate with reversed triangular-prism geometry via three oxygens and three chlorides. Complex 2 crystallizes in the triclinic system, P 1 space group; the asymmetric unit consists of one indium(III), two N-(4methoxysalicylidene)-aminoadamantane (L²), and three chlorides. The indium is five-coordinate with distorted trigonal-bipyramidal geometry via two oxygens and three chlorides. Antibacterial activities of the complexes have been investigated against Escherichia coli and Staphylococcus aureus.     

Transition metal complexes of a Schiff base: synthesis,characterization, and antibacterial studies

Synthesis of a new Schiff base derived from 2-hydroxy-5-methylacetophenone and glycine and its coordination with compounds Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II), and UO₂(VI) are described. The ligand and complexes have been characterized on the basis of analytical, electrical conductance, infrared, ESR and electronic spectra, magnetic susceptibility measurements, and thermogravimetric analysis. The ligand is a dibasic tridentate (ONO) donor in all the complexes except Zn(II), where it is a monobasic bidentate (OO) donor. The solid state DC electrical conductivity of ligand and its complexes have been measured over 313–398 K, and the complexes were semiconducting. Antibacterial activities of ligand and its metal complexes have been determined by screening the compounds against various Gram (+) and Gram (?) bacterial strains.     

Synthesis,structural characterization,antimicrobial, DNA-binding,and photo-induced DNA cleavage activity of some bio-sensitive Schiff base copper(II) complexes

Schiff base mixed-ligand copper complexes [CuL¹(phen)Cl₂], [CuL¹(bipy)Cl₂], [Cu(L¹)₂Cl₂], [Cu(L²)₂Cl₂], [CuL²(bipy)Cl₂], and [CuL²(phen)Cl₂] (where L^1?=?4-[3,4-dimethoxy-benzylidene]-1,5-dimethyl-2-phenyl-1,2-dihydro-pyrazole-3-one; L^2?=?4-[3-hydroxy-4-nitro-benzylidene]-1,5-dimethyl-2-phenyl-1,2-dihydro-pyrazole-3-one; phen?=?1,10-phenanthroline; and bipy?=?2,2′-bipyridine) have been synthesized and characterized. Their DNA-binding properties have been studied by electronic absorption spectra, viscosity, and electrochemical measurements. The absorption spectral and viscosity results suggest that the copper(II) complexes bind to DNA via partial intercalation. The addition of DNA resulting in the decrease of the peak current of the copper(II) complexes indicates their interaction. Interaction between the complexes and DNA has also been investigated by submarine gel electrophoresis. The copper complexes cleave supercoiled pUC19 DNA to nicked and linear forms through hydroxyl radical and singlet oxygen in the presence of 3-mercaptopropionic acid as the reducing agent. These copper complexes promote the photocleavage of pUC19 DNA under irradiation at 360?nm. Mechanistic study reveals that singlet oxygen is likely to be the reactive species responsible for the cleavage of plasmid DNA by the synthesized complexes. The in vitro antimicrobial study indicates that the metal chelates have higher activity against the bacterial and fungal strains than the free ligands.     

Synthesis,crystal structure,and antibacterial activity of two new mononuclear nickel(II) complexes of a NNS Schiff base

Two new mononuclear nickel(II) complexes, [Ni(L)(N₃)] (1) and [Ni(L)₂(NCS)₂] (2), where HL = 2-{[phenyl(pyridin-2-yl)methylidene]amino}benzenethiol, a tridentate Schiff base derived from 2-aminothiophenol and 2-benzoylpyridine, have been prepared and characterized. The syntheses of 1 and 2 have been achieved by the reaction of equimolar amounts of nickel perchlorate and HL in the presence of azide and thiocyanate, respectively. The complexes have been characterized by microanalytical, spectroscopic, single-crystal X-ray diffraction, and other physicochemical studies. Structural studies reveal that 1 and 2 adopt two different geometries, distorted square planar in 1 and octahedral in 2. The two mononuclear complex units are held together by π…π or C–H…π weak intermolecular interactions to develop supramolecular networks in their solid states. The antibacterial activity of 1, 2 and their constituent Schiff base has been tested against some gram(+) and gram(?) bacteria.     

Syntheses,crystal structures,and antibacterial activities of two cobalt(III) complexes

Syntheses, structures, and antimicrobial activities of cobalt(III) complexes with two tetradentate Schiff-base ligands, (BA)₂en?=?bis(benzoylacetone)ethylenediimine dianion and (acac)₂en?=?bis(acetylacetone)ethylenediimine dianion, and two axial pyridines (py) have been investigated. These complexes were characterized by FT-IR, ¹H-NMR, UV-Vis spectroscopy, and elemental analysis. The crystal structures of the complexes were determined by X-ray crystallography. Single-crystal X-ray diffraction analyses revealed that both complexes have distorted octahedral environments, Schiff-base ligand coordinates cobalt in four equatorial positions, and the two axial positions are occupied by pyridines. The pyridines and Schiff-base ligands are involved in N–H···O hydrogen bonds with perchlorate. Biological activities of the ligands and metal complexes have been studied on Staphylococcus aureus, Escherichia coli, and Bacillus subtilis by the well diffusion method. The activity data show the metal complexes to be more potent than the parent ligand against two bacterial species.     

Synthesis,characterization, luminescence,antibacterial, and catalytic activities of a palladium(II) complex involving a Schiff base

A new Pd(II) complex of fluorine-containing Schiff base ligand, [Pd₂(L)₂Cl₂] (1) [L?=?N-(4-fluorobenzylidene)-2,6-diethylbenzenamine], has been synthesized using solvothermal method and characterized by elemental analysis, IR-spectroscopy, thermogravimetric analysis, powder X-ray diffraction, UV–vis absorption spectra, and single-crystal X-ray diffraction. Complex 1 is a μ-chloro-bridged dinuclear cyclometallated Pd(II) complex. Thermal analysis indicates that 1 is quite stable to heat. 1 exhibits quadruple emissions in the solid state (λ _max?=?766?nm) and possesses fluorescence lifetimes (τ ₁?=?87.20?ns, τ ₂?=?190.45?ns, and τ ₃?=?1805.10?ns at 616?nm); broad structureless bands at 690–800?nm are tentatively assigned to an excimeric ³IL transition. The Schiff base (L) and its palladium(II) compound (1) have been screened for their antibacterial activity against several bacteria, and the results are compared with the activity of penicillin. Moreover, 1 has been shown to be highly effective in the Heck reaction of 4-bromotoluene with acrylic acid.     

Synthesis and antibacterial activities of metal(II) complexes with Schiff bases derived from 3,5-diiodosalicylaldehyde

Two new Schiff bases (2,4-diiodo-6-[(2-morpholin-4-yl-ethylimino)-methyl]-phenol and 2,4-diiodo-6-[(3-morpholin-4-yl-propylimino)-methyl]-phenol), condensed from 3,5-diiodosalicylaldehyde with 2-morpholinoethylamine and 3-morpholinopropylamine, have been designed and synthesized. Reaction of the Schiff bases with Zn(OAc)₂ · 2H₂O, Cu(OAc)₂ · H₂O, Ni(OAc)₂ · 4H₂O, Co(OAc)₂ · 4H₂O, Cd(OAc)₂ · 2H₂O, Mn(OAc)₂ · 4H₂O, Fe(SO4)₂ · 7H₂O, and Hg(OAc)₂ led to the formation of 16 new mononuclear complexes. The complexes were characterized by UV, Infrared, ESI-MS, and elemental analyses, and 3,5-diiodosalicylalidene-2-morpholinoethylaminozinc(II) (1) and 3,5-diiodosalicylalidene-2-morpholinoethylaminocopper(II) (2) were characterized by single crystal X-ray diffraction. Based on crystal structural analysis of 1 and 2, coupled with their spectral similarity with 3–16, it can be concluded that 3–16 have structures similar to 1 and 2. All the complexes were assayed for antibacterial activities against three Gram positive bacterial strains (Bacillus subtilis, Staphylococcus aureus, and Streptococcus faecalis) and three Gram negative bacterial strains (Escherichia coli, Pseudomonas aeruginosa, and Enterobacter cloacae) by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide method. Among the complexes tested, 8 and 16 showed the most favorable antibacterial activity with minimum inhibitory concentration of 0.781, 12.5, 6.25, 3.125, 3.125, 6.25 and 1.562, 6.25, 1.562, 3.125, 3.125, 1.562 µg mL^?1 against B. subtilis, S. aureus, S. faecalis, P. aeruginosa, E. coli, and E. cloacae, respectively.     

Bioactivity of some divalent M(II) complexes of penicillin based Schiff base ligand: Synthesis,spectroscopic characterization,and thermal study

A series of four novel metal complexes of Co(II), Ni(II), Cu(II) and Zn(II) were synthesized from Schiff base derived from amoxicillin (AMX) and picolinaldehyde (PC2). The ligand and metal complexes were fully characterized by physical and spectral techniques such as elemental microanalysis, conductivity, FT-IR, ¹H & ¹³C NMR, UV–vis, mass spectra, EPR, magnetic moment measurement, TGA/DTA, PXRD and antibacterial activity study. The spectroscopic study revealed 1:2 metal ligand ratio and coordination sites in the ligand for metal ions were evaluated by analysis of the spectral results. The surface morphology of the complexes was evaluated by SEM analysis. Molar conductivity implies non-electrolytic nature of the complexes. UV–vis. spectral study nicely supports octahedral geometry for Co(II) and Zn(II) complexes and tetrahedral geometry for Cu(II) complex. The kinetic parameters were extracted from Coats-Redfern equation. The PXRD study revealed nano-crystalline nature of Co(II), Ni(II) & Cu(II) complexes and amorphous nature of Zn(II) complex. The proposed geometry of the complexes was optimized by MM2 calculation supported in Cs-ChemOffice Ultra-11 program. The ligand and metal complexes were screened for antibacterial potency against four human pathogenic clinical strains of bacteria and the data revealed their promising antibacterial activity.     

Synthesis,characterization, biological applications,and molecular docking studies of amino-phenol-derived mixed-ligand complexes with Fe(III), Cr(III), and La(III) ions

A new series of Fe(III), Cr(III), and La(III) mixed-ligand complexes, resulting from the interaction of 2-aminophenol with 2-hydroxy acetophenone (HL₁) as primary ligand and L- histidine (L₂) as a secondary ligand, has been investigated using various physicochemical studies such as elemental analyses, molar conductivity, magnetic moment, infrared, UV/Vis, ¹H NMR, and mass spectroscopic techniques. The microanalytical results indicate that the mixed ligand complexes were designed in a 1:1:1 M ratio. The electronic spectral data indicated that all the synthesized complexes have an octahedral structure. The disc diffusion assay was used to determine the disc inhibition zone (IZ, mm) and minimum inhibitory concentration (MIC, g/mL) of the investigated compounds against the growth of the pathogenic bacterial strains S. aureus, E. faecalis, P. aeruginosa, Klebsiella sp., and E. coli. The MTT test was used to determine the cytotoxicity of these reported compounds against the human hepatocellular liver cancer (HEPG-2) cell lines. The molecular docking study for the compounds against the EGFR tyrosine kinase receptor (PDB code: 1 M17) was conducted to examine the interactions in protein–ligand complexes. Furthermore, the biological activity of the ligand was investigated using quantitative structure–activity relationship studies (QSAR).     

Syntheses,crystal structures,and antibacterial activities of manganese(III), nickel(II), and copper(II) complexes containing a tetradentate Schiff base

Three new mononuclear Schiff-base complexes, namely [Mn(L)Cl] (1), [Ni(L)] (2), and [Cu(L)] (3), where L?=?anion of [N,N′-bis(2-hydroxybenzophenylidene)]propane-1,2-diamine, have been synthesized by reacting equimolar amounts of the respective metal chloride and the tetradentate Schiff base, H₂L, in methanol. The complexes have been characterized by microanalytical, spectroscopic, single-crystal X-ray diffraction, and other physicochemical studies. Structural studies reveal that 1 adopts a distorted square-pyramidal geometry whereas 2 and 3 are isotypic with distorted square-planar geometries. The antibacterial activities of 1–3 along with their Schiff base have been tested against some Gram(+) and Gram(?) bacteria.     

双水杨醛缩环己二胺类西佛碱及其配合物的合成、性质研究

合成了两种双水杨醛缩环已二胺类西佛碱N，N’-(二羟苯次甲基)环已二胺(1)和N，N’-二(3，5-二叔丁基-2-羟苯次甲基)环已二胺(2)，以及它们的金属锌配合物(3)和(4)，通过核磁共振、元素分析和红外光谱确定了四种物质的结构，研究了它们的紫外吸收光谱、荧光光谱，测定了(3)和(4)的荧光量子效率．(4)中四个叔丁基的存在使其荧光量子效率提高．此类双西佛碱金属配合物可以应用于有机电致发光材料中．     

Synthesis,characterization and biological evaluation of Ru(III) mercaptopyrimidine Schiff base complexes

A new series of mercaptopyrimidine Ru(III) complexes were synthesized and characterized using various spectral techniques like single‐crystal X‐ray diffraction, Fourier transform infrared and NMR spectroscopies, thermogravimetric analysis and energy‐dispersive X‐ray analysis. The complexes were evaluated for their pharmacological activities like in vitro antimicrobial, anticancer, antituberculosis and antioxidant activities. The DNA binding of the complexes was investigated by absorption and emission spectral measurements which indicated that the complexes bind to DNA via intercalation, with molecular docking studies validating the results. DNA cleavage studies of the complexes were carried out.     

Synthesis,characterization, and antimicrobial activity of two Schiff base silver(I) complexes derived from 4-carboxybenzaldehyde

Two new Schiff base silver(I) complexes, {[Ag(L¹)][H₂O]}_∞ (1) and {[Ag(L²)][H₂O]}_∞ (2), where L¹ = 4-((2-diethylaminoethylimino)methyl)phenecarboxylate and L² = 4-([3-(morpholin-4-yl)propyl]iminomethyl)phenecarboxylate, have been synthesized and characterized. X-ray crystallographic analysis reveals that silver ions in 1 are bridged by L¹ to form a one-dimensional zigzag chain, while three silver ions in 2 are linked by L² to produce a two-dimensional coordination polymer. Guest water molecules in 1 generate a one-dimensional hydrogen-bonded chain. Both 1 and 2 offer high antibacterial activity against Gram-positive bacteria Staphylococcus aureus with MIC values of 0.26 and 0.24 mM and to exhibit good inhibitory activity against urease with the respective IC₅₀ values of 3.5 ± 0.1 and 3.8 ± 0.2 μM.     

Organotin (IV) complexes derived from tridentate Schiff base ligands: Synthesis,spectroscopic analysis,antimicrobial and antioxidant activity

Organotin complexes of Schiff bases (derived from the condensation of hydrazides with salicylaldehyde derivatives) were prepared and their characterization was done using several spectroscopic techniques like FTIR, NMR (¹H, ¹³C, and ¹¹⁹Sn) and mass spectrometry. The spectroscopic data of the ligands and their corresponding complexes revealed that the Schiff bases chelated to the tin metal in a tridentate manner through –ONO atoms (oxygen atom of the hydroxyl group of the salicylaldehydic derivatives, the nitrogen atom of azomethine group, and the oxygen atom of enolic group present in the carboxylic acid hydrazides). Around tin atom pentacoordinated geometry was exhibited. The synthesized ligands and their complexes have been assessed for their biological potency (antibacterial, antifungal and antioxidant using Ciprofloxacin, Fluconazole and Ascorbic acid as reference compounds) and few of the compounds showed optimistic activity. The ligands having electron withdrawing group attached showed greater antimicrobial activity as compared to the other ligands. The complexes showed the better activity than the ligands. The general trend followed by the complexes was diphenyl ?> ?dibutyl ?> ?dimethyl substituted complexes. Compound 11 was the most active against microbes. The antioxidant activity increased with electron donating group. The phenyl substituted complexes showed better activity as compared to the dibutyl and dimethyl substituted complexes. Compound 20 was the best antioxidant.     

Synthesis, spectroscopy, electrochemistry and thermal study of vanadyl tridentate Schiff base complexes

The VO(IV) complexes of tridentate ONO Schiff ligands were synthesised and characterized by IR, UV–vis and elemental analysis. The electrochemical properties of the vanadyl complexes were investigated by cyclic voltammetry. A good correlation was observed between the oxidation potentials and the electron withdrawing character of the substituents on the Schiff base ligands, showing the following trend: MeO < H < Br < NO₂ and H < Cl. The thermogravimetry (TG) and differential thermoanalysis (DTA) of the VO(IV) complexes were carried out in the range of 20–700 °C. The VOL¹(OH₂) decomposed in two steps whereas the remaining six complexes decomposed in three steps. The thermal decomposition of these complexes is closely related to the nature of the Schiff base ligands and proceeds via first order kinetics.     

Synthesis,structural characterization,antimicrobial, antioxidant and DNA binding studies of some novel homo‐binuclear Schiff base metal (II) complexes

A novel bi‐nucleating Schiff base ligand, 6,6′‐(((1E,1′E)‐thiophene‐2,5‐diylbis (methaneylylidene))bis (azaneylylidene))bis (3,4‐dimethylaniline), and five binuclear M (II) complexes were synthesized. The bi‐nucleating Schiff base ligand and its metal complexes were characterized using various physicochemical techniques, e.g. elemental analyses, spectroscopic methods, conductivity and magnetic moment measurements. The low molar conductance of the complexes in dimethylsulfoxide shows their non‐electrolytic nature. The antibacterial activities were screened against pathogenic bacteria (Staphylococcus aureus, Escherichia coli, Pseudomonas putida and Bacillus subtilis). The antifungal activity was screened against Aspergillus niger, Aspergillus flavus and Rhizoctonia bataicola. The antimicrobial activity data showed that the metal complexes are more potent than the parent Schiff base ligand against microorganisms. The antioxidant activities of the synthesized compounds were investigated through scavenging activity against 2,2‐diphenyl‐2‐picrylhydrazyl, superoxide anion, hydroxyl and 2,2′‐ azinobis (3‐ethylbenzothiazoline‐6‐sulfonic acid) radicals. The complexes have superior radical scavenging activity than the free ligand and the scavenging effects of the Cu (II) complex are stronger than those of the other complexes. DNA binding studies were performed using electronic spectroscopy, fluorometric competition studies and viscosity measurements. The data indicated that there is a marked enhancement in biocidal activity of the ligand under similar experimental conditions because of coordination with metal ions.     

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.