Symmetrical Schiff Base Research Articles

Synthesis and Spectral Characterization of Bis(3(4-dimethylaminophenyl)-2-prop-1-enylydene)-1,2-diaminoethane and Some New Mercury Complexes: An Antibacterial and Antifungal Investigation

Synthesis, physical and spectral characterization of a symmetric N2-donor Schiff base ligand of bis(3(4-dimethylaminophenyl)-2-prop-1-enylydene)-1,2-diaminoethane and its new mercury(II) halide/thiocyanate complexes are reported. The entire compounds were studied by elemental analyses, FT-IR, UV-Visible, 1H and 13NMR spectra, melting point, and molar conductivity measurements. The reasonable red and blue shifts in FT-IR, electronic, and NMR spectroscopic signals of the complexes as compared with ligand proved good coordination of ligand so that a pseudotetrahedral geometry around metal center in the complexes is proposed. At last, in vitro antibacterial and antifungal properties of all compounds were screened against four bacterial strains (gram positive and negative bacteria) and two fungi that the results exhibited more antimicrobial activity of all complexes with respect to free ligand.

DNA interaction and efficient antimicrobial activities of 4N chelating metal complexes

A new series of metal(II) complexes using a symmetric Schiff base ligand, obtained by the condensation reaction of 4-formyl-N,N-dimethylaniline with benzene-1,2-diamine were synthesized and characterized. The various physico-chemical data indicate that the complexes have octahedral geometry. The intrinsic binding constant of the complexes with DNA is explored. The UV–Vis., circular dichorism, fluorescence emission spectral data and the viscosity measurements indicate that the complexes bind to calf thymus DNA (CT DNA) by intercalative mode. The intrinsic binding constants of Cu(II), Ni(II), Co(II) and Zn(II) complexes are found to be 7.1×104, 5.2×104, 1.8×105 and 6.3×104M−1, respectively. The cleavage studies of these complexes are investigated by gel electrophoresis method in the presence of peroxide. The complexes exhibit enhanced biological activities compared to the free ligand.

Solvatochromism and electronic structure of some symmetric Schiff base derivatives

In this present work, we have investigated electronic absorption spectra of three symmetric Schiff bases in fourteen spectroscopic grade solvents which have different polarities. The electronic transitions have been evaluated with regard to solvent polarity. The electronic transition mechanisms and solvatochromic behavior of the investigated molecules are determined by using four different linear solvation energy relationship (LSER) methods, such as the Kamlet–Taft Parameters, the Catalan parameters, the Marcus optical dielectric function and the Reichardt–Dimroth ET solvent parameter. Electronic transitions are found to exhibit four electronic bands. Electronic absorption spectra are observed to display positive solvatochromism with the change of solvent polarity. Enol–keto tautomerism and excited state intramolecular proton transfer are analyzed by means of resonance structures. LSER results indicate that electronic transitions are dominantly controlled by induction–dispersion interactions and that hydrogen bond acceptor capacity is relatively more effective on solvatochromic behavior compared to that of hydrogen bond donor capacity.

Unprecedented reactivity of alkoxo/hydroxide-bridged dinuclear copper(II) complexes as artificial carboxylesterase: Effects of Gemini 16-6-16 micelles and bimetallic synergistic effect

One μ-alkoxo/hydroxide-bridged dinuclear copper(II) complex (Cu2L) and a mononuclear analogue (CuL) with symmetric Schiff base compound were employed as carboxylesterase models to promote the hydrolysis of a carboxylic acid ester, p-nitrophenyl picolinate (PNPP). Also the introducing of a Gemini surfactant, bis(hexadecyldimethylammonium)hexane bromide (16-6-16, 2Br−), gave interested observations relative to those controlled trials preformed in buffer and a micellar solution of traditional single-chain surfactant, CTAB (cetyltrimethylammonium bromide). The results indicated that the dinuclear Cu2L efficiently accelerated PNPP hydrolysis with 18,096- and 49,569.6-fold rate enhancement under moderate conditions (pH 7.00, 25°C) in buffer and 16-6-16 micellar solution, respectively. Much greater rate enhancement was observed in 16-6-16 micelles in contrast with CTAB micelles, launching 1.6–2.6 folds difference in hydrolysis rate of PNPP at pH 7.00. Additionally, the Cu2L-induced PNPP hydrolysis showed a bell-shaped rate-pH profile, which is an enzyme-like behaviour. Interestingly, rate–pH curves could provide the direct evidence for the interfacial effects of Gemini 16-6-16 micelles on the deprotonation of coordinated water, indicating about 0.2 unit pKa1 difference of the Cu2L-bound H2O between in micellar phase and bulk phase. Cu2L was found to be approximately 199.3- and 288.7-fold reactive than CuL in buffer and 16-6-16 micellar solution, respectively. Significant activity difference between both complexes probably results from the bimetallic coorperation of the two catalytic copper sites and more open binding site of Cu2L.

Supramolecular Interactions Involved in the Solid State Structure of N,N'-[bis(pyridin-2-yl)formylidene]ethane-1,2-diamine

The structure of the symmetrical Schiff base, N,N'-(bis(pyridin-2-yl)formylidene)ethane-1,2- diamine (bpfd) has been characterized by single crystal X-ray diffraction. The non-covalent supramolecular chemistry involved in the crystal structure of this ligand has been carefully investigated. The structure adopted different motifs of nitrogen-hydrogen interactions that led to the formation of centrosymmetric dimers. In addition, edge-edge and face-face nitrogen-nitrogen interactions were ob- served and reported. The Schiff base (bpfd) ligand crystallizes in a monoclinic space group C12/c1 with a

Synthesis, spectral characterization, molecular modeling and antimicrobial activity of new potentially N2O2 Schiff base complexes

Metal complexes of a new potentially tetradentate symmetrical Schiff base ligand (H2L) with Cu(II), Ni(II), Co(II), VO(IV), Zn(II), Cd(II), Ce(III), Fe(III) and UO2(VI) metal ions have been synthesized and characterized based on their elemental analyses, spectral (IR, UV–Vis, 1H NMR and mass spectra), magnetic and molar conductance studies as well as thermal gravimetric analysis (TGA). The synthesized complexes have the general formula [MHxL(H2O)yXn]: x=0–1, y=0–4 and n=0–1; where: L=dianion of 6-hydroxy-5-[N-(2-{[(1E)-1-(6-hydroxy-2,4-dioxo-3,4-dihydro-2H-1,3-thiazin-5-yl)ethylidene]amino}ethyl) ethanimidoyl]-2H-1,3-thiazine-2,4(3H)-dione and X=nitrate or sulphate anion. The ligand behaves as diabasic tetradentate N2O2 sites, except in cases of Co(II), VO(IV) and UO2(VI) metal ions, it behaves as monobasic tetradentate Schiff base ligand. The metal complexes exhibited square planar, square-pyramidal and octahedral geometrical arrangements except for Ce(III) and UO2(VI) complexes, they are octa-coordinated. The Coats-Redfern equation was used to calculate the kinetic and thermodynamic parameters for the different thermal decomposition stages of some complexes. Structural parameters of the ligand and its metal complexes have been theoretically computed on the basis of semiemperical PM3 level, and the results were correlated with their experimental data. The antimicrobial activities of the ligand and its metal complexes were tested against some Gram-positive and Gram-negative bacteria; and fungus strain and the results were discussed.

Sw uobaghdad edu iqSynthesis and Characterization of Mn(II), Co(II), Ni(II), Cu(II), Zn(II), and Hg(II) Complexes with Symmetrical Schiff base

New binuclear Mn(II), Co(II), Ni(II), Cu(II), Zn(II), and Hg(II) Complexes of N2S2 tetradentate or N4S2 hexadentate symmetric Schiff base were prepared by the condensation of butane-1,4-diylbis(2-amino ethylcarbamodithioate) with 3-acetyl pyridine. The complexes having the general formula [M2LCl4] (where L=butane-1,4-diyl bis (2-(z)-1-(pyridine-3-ylethylidene amino))ethyl carbamodithioate, M= Mn(II), Co(II), Ni(II), Cu(II), Zn(II), and Hg(II)), were prepared by the reaction of the mentioned metal salts and the ligand. The resulting binuclear complexes were characterized by molar conductance, magnetic susceptibility ,infrared and electronic spectral measurements. This study indicated that Mn(II), Ni(II) and Cu(II) complexes have octahedral geometry, while Co(II) Zn(II) and Hg(II) complexes are proposed to be tetrahedral structure .K

Sw uobaghdad edu iqSynthesis and Characterization of Mn(II), Co(II), Ni(II), Cu(II), Zn(II), and Hg(II) Complexes with Symmetrical Schiff base

New binuclear Mn(II), Co(II), Ni(II), Cu(II), Zn(II), and Hg(II) Complexes of N2S2 tetradentate or N4S2 hexadentate symmetric Schiff base were prepared by the condensation of butane-1,4-diylbis(2-amino ethylcarbamodithioate) with 3-acetyl pyridine. The complexes having the general formula [M2LCl4] (where L=butane-1,4-diyl bis (2-(z)-1-(pyridine-3-ylethylidene amino))ethyl carbamodithioate, M= Mn(II), Co(II), Ni(II), Cu(II), Zn(II), and Hg(II)), were prepared by the reaction of the mentioned metal salts and the ligand. The resulting binuclear complexes were characterized by molar conductance, magnetic susceptibility ,infrared and electronic spectral measurements. This study indicated that Mn(II), Ni(II) and Cu(II) complexes have octahedral geometry, while Co(II) Zn(II) and Hg(II) complexes are proposed to be tetrahedral structure .K

Synthesis, characterization and computational studies of zinc(II)-halide complexes with a bidentate schiff base ligand (2,5-MeO-ba)2En: The crystal structure of (2,5-MeO-ba)2En

In this study four coordinated complexes of zinc(II) halides with a new symmetrical bidentate Schiff base ligand (2,5-MeO-ba)2En are synthesized and characterized. The metal to ligand ratio of the complexes is found to be 1:1 with the formula of Zn((2,5-MeO-ba)2En)X2 (X = Cl (1), Br (2), I (3)). The crystal structure of the Schiff base ligand (2,5-MeO-ba)2En is determined by X-ray crystallography from single crystal data. Also, the optimized geometries of the Schiff base ligand (2,5-MeO-ba)2En and its zinc(II) complexes are calculated using the density functional theory method (B3LYP/6-31G). The obtained structural parameters of (2,5-MeO-ba)2En are in agreement with the experimental data.

Silver(I) complexes with symmetrical Schiff bases: Synthesis, structural characterization, DFT studies and antimycobacterial assays

Synthesis, structural and spectroscopic characterizations, molecular modeling and antimycobacterial assays of new silver(I) complexes with two Schiff bases – MBDA and MBDB – are reported. The complexes [Ag(MBDA)2]NO3, or AgMBDA, and [Ag(MBDB)NO3] or AgMBDB, were obtained by the reaction of the respective ligands with silver(I) nitrate in methanol. The Schiff bases were previously obtained by mixing ethylenediamine or 1,3-diaminopropane with p-anisaldehyde. The characterizations of the complexes were based on elemental (C, H and N) and thermal (TG-DTA) analyses and 13C and 1H NMR and FT-IR spectroscopic measurements, as well as X-ray structure determination for AgMBDA. Spectroscopic data predicted by DFT calculations are in agreement with the experimental data for the AgMBDA complex. The AgMBDA complex has a monomeric structure with a molar proportion 1:2 Ag/ligand, while AgMBDB presents a 1:1 proportion. The complexes AgMBDA and AgMBDB showed to be more effective against Mycobacterium tuberculosis than antibacterial agent silver sulfadiazine – SSD.

Synthesis, characterization, electrochemical behavior, thermal study and antibacterial/antifungal properties of some new zinc(II) coordination compounds

A novel symmetrical Schiff base ligand was prepared by condensation reaction of 2,2-dimethyl-1.3-diaminopropane and (E)3-(2nitrophenyl)acrylaldehyde. The ligand and its Zn(II) coordination compounds were well characterized by the elemental analysis, FTIR, 1H, 13C NMR, UV–vis spectra and molar conductance. Thermal behaviors of all compounds were investigated from the room temperature to 600°C with a heating rate of 10°C/min. Furthermore some decomposition thermo-kinetic parameters were evaluated by Coats–Redfern equation at each decomposition step. Electrochemical properties of ligand and its complexes were studied by cyclic voltammetry technique. Also antibacterial/antifungal activities of the ligand and its complexes were tested against three Gram-negative bacteria Escherichia coli (ATCC 25922), Salmonella spp. and Pseudomonas aeruginosa (ATCC 9027) and two Gram-positive bacteria Staphylococcus aureus (ATCC 6538) and Corynebacterium renale and also three fungi (Aspergillus niger, Penicillium chrysogenum and Candida albicans). The results exhibited suitable antibacterial/antifungal properties for ligand and Zn(II) complexes. The study has shown that the complexation of ligand to zinc center lead to enhancement of antibacterial/antifungal activity.

Spectroscopic, electrochemical and biological studies of the metal complexes of the Schiff base derived from pyrrole-2-carbaldehyde and ethylenediamine

The new symmetrical Schiff base N,N′bis(pyrrole-2-carbaldehyde)ethylenediamine and its Mn(II), Co(II), Ni(II) and Cu(II) complexes were synthesized and characterized by spectral, magnetic and electrochemical studies. The spectral studies of the complexes reveal that the ligand has coordination through the azomethine nitrogen atoms, pyrrole nitrogen atoms and anions, supported by octahedral geometry. Mass spectrum explains the successive degradation of the molecular species in solution and justifies ML complexes. The electrochemical study indicates that the pyrrole ring stabilizes the metal ion, makes the complex more positively charged, and causes it to be more easily reduced. The molecular structure of the complexes has been optimized by MM2 calculations and suggests an octahedral geometry. Powder X-ray diffraction allows us to determine the cell parameters of the complexes. The bio-efficacy of the ligand and their complexes has been examined against the growth of bacteria in vitro to evaluate their anti-microbial potential.

Syntheses, studies and crystal structures of coordination polymers and dinuclear complexes of mercury(II) halides and thiocyanate with a symmetrical Schiff base ligand

A series of mercury(II) compounds, [Hg2(μ-L)(SCN)4]n (1), [Hg2(μ-L)(μ-Cl)2Cl2]n (2), [Hg2(μ-L)Br4].[Hg2(μ-L)(μ-Br)2Br2]n (3) and [Hg2(μ-L)I4] (4) {L=N,N′-(bis-(pyridin-2-yl)benzylidene)-1,2-ethanediamine} have been prepared and characterized by using microanalytical, spectroscopic, thermal and X-ray crystallographic results. In solid states 1 and 2 have 2D and 1D coordination polymer structure, respectively. Solid state 3 consists of both 1D coordination polymers and dinuclear units. Solid state 4 is only composed of dinuclear units. In the polymeric structures, each mercury(II) center is five coordinated with trigonal bipyramidal geometry in 1D and square pyramidal environment in 2D coordination polymers. Coordination geometry around Hg centers in dinuclear units is tetrahedral. HOMO and LUMO of the title compounds and also the energy gap among them have been studied by using the density functional theory (DFT/B3LYP) method with the LANL2DZ pseudo-potential.

Role of the kinetic template effect in the syntheses of non symmetric Schiff base complexes

The template effect involves two main effects, first the “kinetic template effect”, in which a metal ion is able to hold two reactive functions in a position that allows a reaction to occur, followed by the “thermodynamic template effect” that favours the formation of a thermodynamically more stable product resulting from the reaction. Through the preparation of a non symmetric Schiff base, we highlight the primordial role of the “kinetic template effect”. Very often, this kinetic effect is not easy to evidence, the resulting complex being too reactive to be isolated. In the present example, the use of an ambidentate ligand, pyrrole carboxaldehyde, has been quite interesting. Reaction of a cationic copper complex possessing a primary amine function coordinated to the copper ion with pyrrole carboxaldehyde can yield two different complexes, depending on the reaction conditions. In absence of a base, the structural determination shows that the copper ion is linked in apical position to the carbonyl oxygen atom of pyrrole carboxaldehyde and the two reactive aldehyde and amine functions are unable to react, as a consequence of their mutual coordination to copper. On the contrary, addition of a base to the reaction mixture induces deprotonation of the pyrrole function followed by its coordination to copper ion, leaving free the carbonyl carbon atom that can be positioned in the vicinity of the primary amine function, thus facilitating the formation of a new imine function. The resulting thermodynamically stable complex is characterized by X-ray diffraction.

Synthesis, characterization, and DNA damaging of bivalent metal complexes incorporating tetradentate dinitrogen–dioxygen ligand as potential biocidal agents

A new symmetrical tetradentate Schiff base was prepared by the condensation of 5-nitro-o-vanillin and diaminoethane. Its complexes were synthesized and characterized by elemental analysis, magnetic moment, molar conductance, UV-Vis, IR, 1H NMR, ESI-mass, and EPR spectra. The DNA-binding behavior of these complexes was investigated by absorption spectra, cyclic voltammetry, and viscosity measurements. The DNA-binding constants for Co(II), Ni(II), Cu(II), and Zn(II) complexes were 1.58 × 104, 1.65 × 104, 2.71 × 104, and 1.83 × 104 (mol L−1)−1, respectively. The results suggest that the complexes intercalate between DNA base pairs. Further, all these complexes exhibit moderate to high ability to cleave pUC19 DNA. The ligand and its complexes have been screened for antimicrobial activities using the disc diffusion method against selected bacteria and fungi. Antibacterial activity was greater against Gram-positive than Gram-negative bacteria for Cu(II) complex and antifungal activity was greater against Aspergillus niger and Candida albicans for the Cu(II) complex.

Solid Phase Extraction of Ultra Trace Copper Using Octadecyl Silica Bonded Phase Membrane Disks Modified by a New Symmetric Schiff Base Ionophore Prior to FAAS Determination

A very selective, reliable and precise method for rapid separation of the trace amounts of copper in aqueous samples using octadecyl silica bonded phase membrane disks modified by N,N-ethylene-bis-(3-formyl-5-methyl salicyl aldymine) combined with flame atomic absorption spectrometric determination has been established. All the affecting experimental variables such as pH, amount of modifier, eluent type, sample and eluent flow-rate, foreign ions and disk capacity were also investigated. The target analyte (trace copper) was quantitatively retained at pH=4, and eluted with 8 mL of HCl (1M) and HNO3 0.5 M each containing 2.0% (v/v) methanol applying flow rates of 50 mL min-1 and 15 mL min-1 for sample introduction and elution steps, respectively. The proposed method exhibits a wide linear dynamic range over 5- 150 ng mL-1 and reproducibility at the most 3%. It also permits an enrichment factor of about 400 or higher and a detection limit of 0.005 ng mL-1. The method has been successfully applied for isolation and determination of copper in different aqueous, real samples, peppers and standard alloys. Keywords: Copper(II), Flame atomic absorption spectrometry, Modifier, N,N'-ethylene bis-(3-formyl-5-methyl salicyl aldymine) (EFMA), Solid phase extraction, Schiff Base Ionophore, Total reflection X-ray fluorescence (TXRF) spectrometry, Inductively coupled plasma optical emission spectrometry (ICP-OES), Atomic fluorescence spectrometry (AFS), Environmental samples

Synthesis, Characterization, and Spectroscopic Properties of a Symmetrical Schiff Base Ligand and its Bimetallic Complexes

This article presents the synthesis of new Schiff base ligand and preparation of its transition metal complexes with copper (II), nickel (II), zinc (II), and cobalt (II). Furthermore, absorption and fluorescence properties of ligand and its metal complexes are investigated. The effect of the solvents, such as N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), ethanol, methanol, 1,4-dioxane on fluorescence properties of metal complexes, are performed and obtained results are summarized. All of the structures were characterized by using spectroscopic techniques.

Novel thiophene symmetrical Schiff base compounds as corrosion inhibitor for mild steel in acidic media

The inhibiting effect of two Schiff bases on the corrosion of the mild steel (MS) in 1 M HCl has been studied by electrochemical impedance spectroscopy (EIS) and Tafel polarisation measurements. The Schiff bases, 4,4′-bis(3-carboxaldehyde thiophene) diphenyl diimino ether ( L 1) and 4,4′-bis(3-carboxaldehyde thiophene) diphenyl diimino ethane ( L 2), were synthesized using 3-carboxaldehydethiophene and its corresponding amine. Polarisation curves reveal that both compounds are mixed type (cathodic/anodic) inhibitors and inhibition efficiency (% IE) increases with increasing concentration of compounds. It is suggested that their effects depend on their concentrations and the molecular structures. Adsorption of compounds on mild steel surface is spontaneous and obeys Langmuir’s isotherm.

Synthesis, Structural, and Insulin-Enhancing Studies of Oxovanadium(IV) Complexes

Oxovanadium(iv) complexes with Schiff bases derived from substituted salicylaldehyde and diamine have been prepared and characterized. 1H NMR and IR spectral data revealed that the symmetrical Schiff base was isolated, and elemental analysis confirmed the purity of all the compounds as formulated. The room-temperature magnetic moments of 1.6–1.8 Bohr magneton for the complexes confirmed that the complexes are VIV complexes, with d1 configuration. Cyclic voltammetry revealed only one quasi-reversible wave for each complex and they all showed redox couples with peak-to-peak separation values (ΔEp) ranging from 76 to 84 mV, indicating a single-step one-electron transfer process. An oral administration of these complexes supplied at a dose of 0.2 mmol kg–1 to streptozotocin-induced diabetic rats elicited a progressive reduction in plasma glucose over 6-h periods. Two of the complexes produced significant and consistent reduction in fasting blood glucose levels over a 6-h monitoring period.

Isolation of a novel intermediate during unsymmetrical to symmetrical rearrangement of a tetradentate Schiff base ligand in a manganese(III) complex: Catalytic activity of the rearranged product towards alkene epoxidation

An attempt for the synthesis of a Mn III complex with unsymmetrical tetradentate Schiff base ligand uspen (1:1:1 condensate of salicylaldehyde, 2,4-pentanedione and 1,2-ethanediamine) resulted in the isolation of a novel complex, {[{Mn(salen)}{Mn(uspen)}(HCOO)]·ClO 4} n ( 1) as an intermediate species that contains both the unsymmetrical and symmetrical tetradentate ligand uspen and salen (2:1 condensate of salicylaldehyde and 1,2-ethanediamine) respectively. The structure of the complex shows that half of the unsymmetrical Schiff base, uspen rearranged to its symmetrical analogue, salen. A phenoxo bridged dinuclear Mn III complex [Mn(salen)(sal)] 2·2H 2O ( 2) with only the symmetrical Schiff base was also obtained. Compound 1 that contains both unsymmetrical and symmetrical Schiff base ligands in one molecule is unprecedented and provides an insight into the unsymmetrical to symmetrical rearrangement of tetradentate Schiff base ligand. Complex 2 acts as an efficient catalyst in the alkene (( E)-stilbene, styrene) epoxidation reaction in presence of two terminal oxidants PhIO and NaOCl in solvents CH 3CN and CH 2Cl 2 independently and it retains its reactivity with high efficiency for a long time.