Schiff Base Zinc Research Articles

Synthesis, structure, vapour pressure and deposition of ZnO thin film by plasma assisted MOCVD technique using a novel precursor bis[(pentylnitrilomethylidine) (pentylnitrilomethylidine-μ-phenalato)]dizinc(II)

A novel binuclear zinc schiff's base complex bis[(pentylnitrilomethylidine)(pentylnitrilomethylidine-μ-phenalato)]dizinc(II) (hereafter referred as ZSP) was prepared and used as a precursor for the deposition of ZnO thin film by MOCVD. The dynamic TG run of ZSP showed sufficient volatility and good thermal stability. The temperature dependence of vapour pressure measured by transpiration technique yielded a value of 55.8 ± 2.3 kJ mol−1 for the enthalpy of sublimation (ΔH°sub) in the temperature range of 423–503 K. The crystal structure of ZSP was solved by single crystal XRD which exhibits triclinic crystal system with the space group of Pī. The molecular mass of ZSP was determined by mass spectrometry which yielded the m/z value of 891 and 445 Da corresponding to its dimeric as well as monomeric form. The complex ZSP was further characterized by FT-IR and NMR. The demonstration of ZnO thin film deposition was carried out by using plasma assisted MOCVD. The thin film XRD confirmed the highly oriented (002) ZnO thin films on Si(100) substrate. The uniformity and composition of the thin film were analyzed by SEM/EDX. The band gap of ZnO thin film measurement indicated the blue shift with the value of 3.79 eV.

Selective Photocatalytic Degradation of Organic Pollutants Using a Water-Insoluble Zn–Schiff Base Complex

In this study, a novel water-insoluble zinc–Schiff base complex, Zn(II)-N-salicylaldehyde-2-hydroxyanil (abbreviated as Zn-salen), was synthesized and used as a heterogeneous photocatalyst for the activation of molecular oxygen to degrade organic pollutants in aqueous solution under visible light irradiation (λ ≥ 420 nm). The catalyst was characterized by FT-IR, UV–vis spectroscopy, NMR, and MS analysis. Zn-salen displays a selective adsorption and degradation of electropositive organics, such as rhodamine B (RhB), methylene blue (MB), and o-phenylenediamine (OPD). After using cetyl trimethyl ammonium bromide (CTAB) to change sulforhodamine B (SRB) into RhB-like electropositive molecule, the degradation of SRB increased up to 96 % after 4 h of irradiation, indicating that the selectivity arises from the charge interaction between the catalyst and substrates. Zeta potential of Zn-salen also reveals that the catalyst surface is negatively charged in neutral solution, suggesting that the catalyst is selective towards positively charged substrates due to an electrostatic force of attraction. The photocatalyst was active within a wide pH range (pH 3–11) and chemically stable and can be reused over 10 times. In addition, 1O2 and O2·− were involved in photocatalytic degradation but O2·− appears to be the primary reactive oxygen species.

Syntheses, Characterization, and Crystal Structures of Schiff Base Zinc(II) Complexes With Tetrahedral Coordination

Two new mononuclear Schiff base zinc(II) complexes, [ZnClL1(N3)]·2MeOH (1) and [ZnBr2(L2)]·MeOH (2) (L1 = 4-methyl-2-[(2-piperazinium-1-ylethylimino)methyl]phenolate; L2 = 2-[(2-diethylammonioethylimino)methyl]-4-methylphenolate), have been prepared and characterized by elemental analyses, infrared and UV-vis spectroscopy, and single-cyrstal X-ray diffraction. Complex 1 crystallizes in the orthorhombic space group Pbca with unit cell dimensions a = 18.703(1), b = 11.8643(6), c = 19.081(1) Å, V = 4234.0(4) Å3, Z = 8, R1 = 0.0475, and wR2 = 0.1046. Complex 2 crystallizes in the orthorhombic space group P212121 with unit cell dimensions a = 8.863(2), b = 13.360(2), c = 17.066(3) Å, V = 2020.7(7) Å3, Z = 4, R1 = 0.0803, and wR2 = 0.1859. The Zn atoms in the complexes are four-coordinated in tetrahedral geometry by the phenolate O and imine N atoms of the Schiff base ligands, and two halide or pseudohalide ligands. Crystals of the complexes are stabilized by hydrogen bonds.

Syntheses, characterization, crystal structures and fluorescence property of Zinc(II) complexes with Schiff bases

Two new mononuclear Schiff base zinc(II) complexes, [ZnCl2(L1)] ∙ MeOH (I) and [Zn(L2)2] (II) (L1 = 2-bromo-4-chloro-6-[(2-ethylammonioethylimino)methyl]phenolate; L2 = 2-bromo-4-chloro-6-(isopropyliminomethyl)phenolate), have been prepared and characterized by elemental analyses, infrared and UV-Vis spectroscopy, and single-cyrstal X-ray diffraction (CIF files CCDC nos. 1408962 (I), 1408961 (II)). Complex I crystallizes in the triclinic space group \(P\overline 1\) with unit cell dimensions a = 9.859(1), b = 13.015(2), c = 19.817(3) A, α = 73.591(2)°, β = 76.032(2)°, γ = 82.966(2)°, V = 2363.0(5) A3, Z = 4, R1 = 0.0925, and wR2 = 0.2257. Complex II crystallizes in the monoclinic space group P21/c with unit cell dimensions a = 7.6387(7), b = 22.307(2), c = 21.443(2) A, β = 96.216(3)°, V = 3632.4(6) A3, Z = 8, R1 = 0.0651, and wR2 = 0.1100. The both Zn atoms in I is four-coordinated in a tetrahedral geometry by the NO donor set of the Schiff base ligand, and two Cl ligands. The Zn atom in II is in a tetrahedral geometry by two N and two O atoms from two Schiff base ligands. Crystals of the complexes are stabilized by hydrogen bonds and weak π…π interactions. Fluorescence property of the complexes have been determined.

Tetrazolate bridged dinuclear photo-luminescent zinc(II) Schiff base complex prepared via 1,3-dipolar cycloaddition at ambient condition

A bis(μ-NN′-tetrazolate)-bridged centrosymmetric dinuclear zinc(II) Schiff base complex, [Zn2(L)2(PZTZ)2] (HL is a tridentate Schiff base, 2-(2-(dimethylamino)ethyliminomethyl)-6-ethoxyphenol and HPZTZ is 2-pyrazinyltetrazole), has been synthesized via [3 + 2] cycloaddition of 2-cyanopyrazine and sodium azide in the presence of zinc(II) acetate dihydrate and HL. The structure of the complex is confirmed by single-crystal X-ray diffraction analysis. The complex shows fluorescence.

A novel schiff base zinc coordination compound inhibits proliferation and induces apoptosis of human osteosarcoma cells.

Various kinds of schiff base metal complexes have been proven to induce apoptosis of tumor cells. However, it remains largely unknown whether schiff base zinc complexes induce apoptosis in human cancer cells. Here, we synthesized a novel schiff base zinc coordination compound (SBZCC) and investigated its effects on the growth, proliferation and apoptosis of human osteosarcoma MG-63 cells. A novel SBZCC was synthesized by chemical processes and used to treat MG-63 cells. The cell viability was determined by CCK-8 assay. The cell cycle progression, mitochondrial membrane potential and apoptotic cells were analyzed by flow cytometry. The apoptosis-related proteins levels were determined by immunoblotting. Treatment of MG-63 cells with SBZCC resulted in inhibition of cell proliferation and cell cycle arrest at G1 phase. Moreover, SBZCC significantly reduced the mitochondrial membrane potential and induced apoptosis, accompanied with increased Bax/Bcl-2 and FlasL/Fas expression as well as caspase-3/8/9 cleavage. Our results demonstrated that the synthesized novel SBZCC could inhibit the proliferation and induce apoptosis of MG-63 cells via activating both the mitochondrial and cell death receptor apoptosis pathways, suggesting that SBZCC is a promising agent for the development as anticancer drugs.

Characterization and luminescent properties of zinc–Schiff base complexes for organic white light emitting devices

AbstractZinc complexes with Schiff base ligands bis(salicylidene)ethylene-1,2-diamine (salen), bis(salicylidene)propylene-1,3-diamine (salpen), bis(salicylidene)butylene-1,4-diamine (salbutene), bis(salicylidene)hexylene-1,6-diamine (salhexene), bis(salicylidene)heptylene-1,7-diamine (salheptene) were synthesized and characterized. All these metal complexes exhibited high thermal stability. The photo-physical properties of zinc complexes were investigated by taking their UV–vis absorption and photoluminescent spectra. The complexes of Schiff bases with zinc gave blue luminescence (430–450 nm) under excitation of ultraviolet energy source which can be efficiently used for the generation of white light for display applications.

Synthesis and characterization of Ni and Zn Schiff base complexes supported on modified MCM-41 as reusable catalysts for various oxidation reactions

Using post grafting method, two hybrids composite materials were prepared by anchoring Nickel and Zinc Schiff base complexes onto amino-modified MCM-41(Ni-MCM-41 and Zn-MCM-41). The prepared catalysts have been characterized by FT-IR spectroscopy, thermogravimetric analysis, and transmission electron microscopy, powder X-ray diffraction and N2 adsorption–desorption isotherms. The catalysts showed excellent catalytic efficiency in oxidation reaction of sulfides to sulfoxides and oxidative coupling of thiols to their corresponding disulfides using urea hydrogen peroxide as oxidant under mild reaction conditions. The supported Schiff base complexes can be recovered easily and reused many times without significant loss in catalytic activity and selectivity.

Synthesis and Characterization of Zn (II), Cu (II), Ni (II) and Co(II), Biphenyl Schiff base Complexes

The Biphenyl Schiff base ligand and its divalent metal complexes have been prepared. Solubility, melting point decomposition temperature and elemental analysis, magnetic susceptibility, molar conductance measurement, infrared (IR) and UV-Visible spectrophotometric studies was used in characterizing the complex compounds. The melting point of the Schiff base is 185.03°C, and the decomposition temperatures of the Schiff base Zinc (II), Copper (II), Nickel (II), and Cobalt (II) complex compounds were found to be 323°C, 304°C, 317°C and 311°C respectively. The molar conductance values determined for the complexes are within the range 20–26 ohm−1cm2mol−1. The spectrophotometric analysis of the complex compounds revealed 1:1 (Schiff base: metal ion) stoichiometry.

Syntheses, Characterization, and Crystal Structures of Bromido-Coordinated Zinc(II) Complexes With Multidentate Schiff Bases

A new dinuclear bromido-coordinated Schiff base zinc(II) complex, [Zn2Br2L1(MeOH)]·MeOH (1), and a new mononuclear bromido-coordinated Schiff base zinc(II) complex, [ZnBr2L2] (2), where L1 is the dianionic form of N,N’-bis(5-fluoro-2-hydroxybenzylidene)propane-1,3-diamine (H2L1), and L2 is the zwitterionic form of 2-[(3-dimethylammoniopropylimino)methyl]-4-fluorophenol, have been preprared and characterized mainly by single-crystal X-ray diffraction. Complex 1 crystallizes in the monoclinic space group P21/n with unit cell dimensions a = 10.0876(9) Å, b = 8.9549(8) Å, c = 26.586(2) Å, β = 95.134(2)º, V = 2391.9(4) Ǻ3, Z = 4, R1 = 0.0547, and wR2 = 0.1025. Complex 2 crystallizes in the monoclinic space group P21/c with unit cell dimensions a = 7.359(1) Å, b = 13.798(2) Å, c = 17.676(2) Å, β = 114.602(2)º, V = 1631.8(4) Ǻ3, Z = 4, R1 = 0.0877, and wR2 = 0.2197. The inner Zn atom in 1 is five-coordinated in a square pyramidal geometry. The outer Zn atom in 1 and the Zn atom in 2 are four-coordinated in tetrahedral geometry. The crystals of the complexes are stabilized by intermolecular hydrogen bonds.

A new zinc–Schiff base complex as an electroluminescent material

A Schiff base bis(salicylidene)propylene-1,3-diamine (salpen)2 and its complex with zinc metal as bis(salicylidene)propylene-1,3-diaminatozinc(II) [Zn(salpen)2] were prepared and characterised by various spectral techniques. The zinc complex had high thermal stability (>300°C) as well as high glass transition temperature (>150°C). Optical properties of the metal complex were studied by UV–visible absorption and photoluminescence emission spectroscopy. Multilayered organic electroluminescent devices were fabricated with a structure ITO/α -NPD/Zinc(salpen)2/BCP/Alq 3/LiF/Al, using the zinc complex as an emissive material. The electroluminescence peak emission was centred at 513 nm with colour chromaticity having Commission Internationale d'Eclairage (CIE) coordinates x=0.26 and y=0.50. A bright blue-green emission with a luminance of 1990 Cd/m2 was recorded at 15 V as an optimum voltage.

Some new nano-structure zinc(II) coordination compounds of an imidazolidine Schiff base: Spectral, thermal, antimicrobial properties and DNA interaction

Some novel nano-sized structure zinc complexes of a new Schiff base ligand entitled as (3-nitro-benzylidene)-{2-[2-(3-nitro-phenyl)-imidazolidine-1-yl]-ethyl}-amine(L) with general formula of ZnLX2 wherein X=Cl−, Br−, I−, SCN− and N3− have been synthesized under ultrasonic conditions. The ligand and its complexes have been characterized by elemental analysis, molar conductance measurements, FT-IR, 1H and 13C NMR and UV–Visible spectroscopy. The resulting data from spectral investigation especially 1H and 13C NMR well confirmed formation of an imidazolidine ring in the ligand structure. Transmission electron microscopy (TEM) showed nano-size structures with average particle sizes of 21.80–78.10nm for the zinc(II) Schiff base complexes. The free Schiff base and its Zn(II) complexes have been screened in vitro both for antibacterial activity against some gram-positive and gram-negative bacteria and also for antifungal activity. The metal complexes were found to be more active than the free Schiff base ligand. The results showed that ZnL(N3)2 is the most effective inhibitor against Escherichia coli, Pseudomonas aereuguinosa, Staphylococcus aureus and Candida albicans while ZnLBr2 was found to be more effective against Bacillus subtillis than other compounds. Moreover, DNA cleavage potential of all compounds with plasmid DNA was investigated. The results showed that the ligand and ZnLCl2 complex cleave DNA more efficiently than others. In final, thermal analysis of ligand and its complexes revealed that they are decomposed via 2–3 thermal steps in the range of room temperature to 1000°C. Furthermore some activation kinetic parameters such as A, E*, ΔH*, ΔS* and ΔG* were calculated based on TG/DTA plots by use of coats – Redfern relation. Positive values of activation energy evaluated for the compounds confirmed the thermal stability of them. In addition to, the positive ΔH*, and ΔG* values suggested endothermic character for the thermal decomposition steps.

Syntheses and Structures of a Pair of Isologous Complexes: ZnLCl2 and ZnLBr2

A pair of mononuclear Schiff base zinc(II) complexes, [ZnLCl2] (1) and [ZnLBr2] (2), have been prepared by the reaction of equimolar quantities of a new Schiff base ligand 2-[(2-dimethylammonioethylimino)methyl]-4-methylphenolate with ZnCl2 and ZnBr2, respectively, in methanol. The structures of the complexes have been characterized by single-crystal X-ray diffraction. Complex 1 crystallizes as orthorhombic space group P212121, with unit cell dimensions a = 7.518(1) Å, b = 13.518(2) Å, c = 14.766(2) Å, V = 1500.7(3) Å3, Z = 4, R 1 = 0.0301, wR 2 = 0.0780, S = 1.028. Complex 2 crystallizes as orthorhombic space group P212121, with unit cell dimensions a = 7.731(1) Å, b = 13.761(1) Å, c = 14.705(1) Å, V = 1564.4(1) Å3, Z = 4, R 1 = 0.0230, wR 2 = 0.0488, S = 1.031. The Zn atom in each of the complexes is four-coordinated in a tetrahedral geometry by the phenolate O and imine N atoms of the Schiff base ligand, and two halide anions. Single crystals of the complexes are stabilized by hydrogen bonds.

Synthesis and Characterization of a Novel o-Vanillin Schiff Base Derivatives and Their Complexes With Zn(II)

A Schiff base compound (H2L) was synthesized using o-vanillin and o-phenylenediamine, and then the zinc Schiff base complex was obtained by the reaction of zinc acetate. They were characterized by elemental analysis, the infrared spectroscopy (IR), thermogravimetric analysis (TG), fluorescence spectrometer (PL), and antioxidative activity. For Zn(II) complex, fluorescence spectrum shows that excitation of solid sample at 380 nm produces a strong emission with the peak maximum at 596 nm, the ligands display their characteristic emission peaks at 550 nm. The results illustrate that the complex and the ligand inhibition rate were up to 42.55%, 37.27%, respectively, when the concentrations were 10 mg mL−1.

Activities comparison of Schiff base zinc and tri-zinc complexes for alternating copolymerization of CO2 and epoxides

A series of salicylaldiminato-zinc and -tri-zinc complexes containing various Schiff base ligands were prepared using quick methods and then well identified by full characterization. All zinc complexes were examined as catalysts for the copolymerization of CO2 and cyclohexene oxide. Many factors such as electron-donating or -withdrawing substituents on the benzene rings of the ligands, as well as chloride anions or acetate groups bound to the zinc centers, are found to greatly influence on the insertion of CO2 and ring-opening of epoxides. Tri-metallic complexes 2a and 2b exhibited excellent catalytic activities, and thus the copolymerization conditions such as temperature, pressure and reaction time were optimized. The molecular weights of the resulting copolymers determined by gel permeation chromatography display a bimodal distribution with relatively wide polydispersities. The results of the investigation indicate that the catalytic activities of zinc complexes are highly dependent on the electronic density and steric environment around the Zn metal centers.

Synthesis, characterization, optical absorption/fluorescence spectroscopy, and second-order nonlinear optical properties of aggregate molecular architectures of unsymmetrical Schiff-base zinc(ii) complexes

This paper reports the synthesis and a detailed investigation in solution, through (1)H NMR, optical absorption, fluorescence spectroscopy and second-order nonlinear optical studies, on the structure and photophysical properties of a series of unsymmetrical alkoxy-derivatized Schiff-base Zn(II) species bearing on one side an alkyl ammonium bromide as a Lewis base. Overall results suggest that these complexes are present in solution of dichloromethane as dimeric aggregates in which each molecular unit mutually interacts with another unit through intermolecular Zn···Br(-) interactions. This represents an alternative approach to control the supramolecular architecture of Lewis acidic, Schiff-base Zn(II) complexes.

Gastroprotection Studies of Schiff Base Zinc (II) Derivative Complex against Acute Superficial Hemorrhagic Mucosal Lesions in Rats

BackgroundThe study was carried out to assess the gastroprotective effect of the zinc (II) complex against ethanol-induced acute hemorrhagic lesions in rats.Methodology/Principal FindingThe animals received their respective pre-treatments dissolved in tween 20 (5% v/v), orally. Ethanol (95% v/v) was orally administrated to induce superficial hemorrhagic mucosal lesions. Omeprazole (5.790×10−5 M/kg) was used as a reference medicine. The pre-treatment with the zinc (II) complex (2.181×10−5 and 4.362×10−5 M/kg) protected the gastric mucosa similar to the reference control. They significantly increased the activity levels of nitric oxide, catalase, superoxide dismutase, glutathione and prostaglandin E2, and decreased the level of malondialdehyde. The histology assessments confirmed the protection through remarkable reduction of mucosal lesions and increased the production of gastric mucosa. Immunohistochemistry and western blot analysis indicated that the complex might induced Hsp70 up-regulation and Bax down-regulation. The complex moderately increased the gastroprotectiveness in fine fettle. The acute toxicity approved the non-toxic characteristic of the complex (<87.241×10−5 M/kg).Conclusion/SignificanceThe gastroprotective effect of the zinc (II) complex was mainly through its antioxidant activity, enzymatic stimulation of prostaglandins E2, and up-regulation of Hsp70. The gastric wall mucus was also a remarkable protective mechanism.

Near-Infrared Emitting Heterobinuclear Zn-Ln (Ln = Nd, Yb, Er,and Gd) Complexes Based on a Novel Asymmetric Schiff-Base Ligand

With the asymmetric Schiff-base zinc complex ZnL (H2L = N-(5-bromo-3-methoxysalicylidene)-N'-(5-(4-cyanophenyl)-3-methoxysalicylidene) phenylene-1,2-diamine) as the precursor, a series of heterobinuclear Zn-Ln complexes [ZnLnL(NO3)3(CH3CN)] (Ln = Nd, 1; Ln = Yb, 2; Ln = Er, 3; Ln = Gd, 4) are synthesized by the further reaction with Ln (NO3)3·6H2O, and characterized by FT-IR, FAB-MS and elementary analysis. Photophysical studies of these complexes show that the strong and characteristic NIR luminescence of Nd3+, Yb3+and Er3+ with emissive lifetimes in the microsecond range has been sensitized from the excited state of the asymmetric Schiff-base ligand due to effective intramolecular energy transfer.

Insights into mechanisms and proteomic characterisation of Pseudomonas aeruginosa adaptation to a novel antimicrobial substance.

Antibiotic resistance has been reported since the introduction of synthetic antibiotics. Bacteria, such as one of the most common nosocomial pathogens P. aeruginosa, adapt quickly to changing environmental conditions, due to their short generation time. Thus microevolutional changes can be monitored in situ. In this study, the microevolutional process of Pseudomonas aeruginosa PAO1 resistance against a recently developed novel antibacterial zinc Schiff-base (ZSB) was investigated at the proteome level. After extended exposure to ZSB the passaged strain differed in tolerance against ZSB, with the adapted P. aeruginosa PAO1 exhibiting 1.6 times higher minimal inhibitory concentration. Using Two-dimensional Difference Gel Electrophoresis, the changes in the proteome of ZSB adapted P. aeruginosa PAO1 were examined by comparison with the non-adapted P. aeruginosa PAO1. The proteome of the adapted P. aeruginosa PAO1 strain differed significantly from the non-adapted in the abundance of two proteins when both strains were grown under stressing conditions. One protein could be identified as the outer membrane protein D that plays a role in uptake of basic amino acids as well as in carbapeneme resistance. The second protein has been identified as alkyl peroxide reductase subunit F. Our data indicated a slight increase in abundance of alkyl peroxide reductase F (AhpF) in the case of ZSB passaged P. aeruginosa PAO1. Higher abundance of Ahp has been discussed in the literature as a promoter of accelerated detoxification of benzene derivatives. The observed up-regulated AhpF thus appears to be connected to an increased tolerance against ZSB. Changes in the abundance of proteins connected to oxidative stress were also found after short-time exposure of P. aeruginosa PAO1 to the ZSB. Furthermore, adapted P. aeruginosa PAO1 showed increased tolerance against hydrogen peroxide and, in addition, showed accelerated degradation of ZSB, as determined by HPLC measurements.

Microwave-assisted Decomposition of two Simple Zinc(II) Schiff Base Complexes: A Facile and Fast Route to Synthesize ZnO Nanostructures

ZnO nanorods and nanoparticles have been easily prepared via the decomposition of two simple Schiff base zinc (II) complexes, namely (N,N'–disalicylalethylenediamine)zince(II) and (N,N'–disalicylalphenylenediamine)zince(II) under microwave irradiation. The decomposition products of the complexes were characterized by FT-IR, XRD, SEM, EDX and UV-visible spectroscopy. FT-IR, XRD and EDX results confirmed that as-prepared products are pure and single-phase ZnO. SEM images show that the product of each complex was made up of ZnO nanoparticles average diameter size of 50 nm and ZnO nanorods with diameter of 70–100 nm and length up to 3.5 μm .ZnO nanostructures prepared by present method could be appropriate photocatalytic materials due to a red shift in their band gaps (2.80 and 2.95 eV) compared with the bulk sample (3.37 eV). This method is simple, fast, safe, low-cost and also it is suitable for large-scale preparation of high purity ZnO nanostructures for applied purposes.