bis-Schiff Base Research Articles

A hetero trinuclear manganese(III)-iron(II) complex derived from N,N′-bis(5-chlorosalicylidene)-1,2-diaminoethane: Synthesis, crystal structure, and antimicrobial activity

A new hetero trinuclear manganese(III)-iron(II) complex, [Mn(ClSalen)(H2O)]2[Fe(CN)5(NO)] · CH3OH · H2O, where ClSalen is the dianionic form of N,N′-bis(5-chlorosalicylidene)-1,2-diaminoethane, has been prepared and characterized by elemental analyses, IR, and single crystal X-ray crystallographic determination (CIF file CCDC no. 1024666). The crystal of the complex is orthorhombic: space group Pca21, a = 27.784(2), b = 10.8876(6), c = 15.1755(8) A, V = 4590.5(4) A3, Z = 2, R1 = 0.0596, wR2 = 0.1406. The bis-Schiff base ligand coordinates to the Mn atom through two phenolate O and two imine N atoms. Each Mn atom in the complex is in octahedral coordination, with the equatorial donor atoms come from the Schiff base ligand, and with the axial donor atoms come from a water O atom and a cyanide N atom. The effects of the complex on the antimicrobial activity against Staphylococcus aureus, Escherichia coli, and Candida albicans were studied.

Aggregation of a Zn(II)-salen complex: Theoretical study of structure and spectra

A theoretical study of the dimerization of amphiphilic Schiff-base bis(salicylaldiminato)Zinc(II) complex (1) in dichloromethane with and without pyridine, is reported in this paper. A comparative investigation between experimental and calculated 1H NMR and UV–vis spectra was performed to evaluate the percentage contribute of each conformer in non-coordinating solvent. DFT calculations and a detailed analysis of the rotational barrier were carried out to study various dimer aggregate. Gibbs free energy related to the dimerization process, in presence of pyridine, was also estimated.Results highlight that in solution of non-coordinating solvent are mainly present three different conformers (D1, D2 and D3) which can convert each other at room temperature. Moreover, it was confirmed that dimerization is a favored process in the non-coordinating solvent. Without a doubt, best fit procedure demonstrates that the greater contribute to the dimers distribution in solution, is due to conformer D3. UV–vis bands were also assigned to the corresponding electronic transitions.Finally the dimerization process is, thermodynamically, not favored in presence of pyridine. In this case the stable complex monomer–pyridine is formed.

Synthesis, characterization, and crystal structure of a novel cyanide-bridged heteronuclear Co(III)-Mn(III) complex derived from N,N′-ethylene-bis(chlorosalicylideneimine)

With a bis-Schiff base N,N′-ethylene-bis(5-chlorosalicylideneimine) (H2L) and K3[Co(CN)6], a novel cyanide-bridged heteronuclear Co(III)-Mn(III) complex was prepared and characterized by elemental analysis, IR spectroscopy and X-ray structure determination (CIF file CCDC no. 1029225). The complex crystallizes in the monoclinic space group P21/c with unit cell dimensions a = 10.741(2), b = 14.015(3), c = 15.074(3) A, β = 94.237(2)°, V = 2263.0(8) A3, Z = 2, R 1 = 0.0441, and wR 2 = 0.0999. Single crystal X-ray diffraction analysis reveals that two [Mn(L)(OH2)]+ units are linked through a [Co(CN)6]3− bridge, forming a trinuclear Mn-Co-Mn moiety. The Mn-Co-Mn moieties are further linked through K atoms to form a 1D chain. The chains are stacked through π⋯π interactions. The Mn and Co atoms are in octahedral coordination, and the K atom is in square planar geometry.

Synthesis, Characterization, Crystal Structure, and Antimicrobial Activity of a Novel Dinuclear Zinc(II) Complex Derived From N,N′-Bis(5-Fluoro-2-Hydroxybenzylidene)-1,3-Diaminopropane

A new dinuclear zinc(II) complex derived from the bis-Schiff base ligand N,N'-bis(5-fluoro-2-hydroxybenzylidene)-1,3-diaminopropane (H2L) was prepared and characterized by elemental analysis, IR spectra, and single-crystal X-ray diffraction. The complex crystallizes in the monoclinic space group P21/c, with a = 10.100(1), b = 8.953(1), c = 27.664(1) Å, β = 106.406(2)°, V = 2399.8(3) Å3, Z = 4, R1 = 0.0785, wR2 = 0.1336, S = 1.067. The ZnZn distance is 3.106(1) Å. The inner Zn atom is in a square pyramidal coordination, with two imino N and two phenolate O atoms of the Schiff base ligand defining the basal plane, and with one methanol O atom locating at the apical position. The outer Zn atom is coordinated by two phenolate O atoms and two Br atoms, forming a tetrahedral coordination. The molecules are linked through O–HO and O–HBr hydrogen bonds, forming 1D chains along the b axis. The free Schiff base and the zinc complex were evaluated for their antibacterial (Bacillus subtilis, Staphylococcus aureus, Escherichia coli, and Pseudomonas fluorescens) and antifungal (Candida albicans and Aspergillus niger) activities by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) method.

Bis-Schiff base as a donor–acceptor fluorescent probe: Recognition of Al3+ ions in near 100% aqueous solution

Abstract In this paper, a novel bis-Schiff base fluorescent probe (HL) for Al3+ has been designed and synthesized on the basis of the mechanism of internal charge transfer (ICT). Compared with the free receptor, the fluorescence intensity of HL shows significant fluorescence enhancement accompany with about 40 nm blue shift in the presence of Al3+. More importantly, the lowest detection limit for Al3+ can reach at 10−7 M level in near 100% aqueous solution.

Coordination behavior of new bis Schiff base ligand derived from 2-furan carboxaldehyde and propane-1,3-diamine. Spectroscopic, thermal, anticancer and antibacterial activity studies

Novel bis Schiff base ligand, [N1,N3-bis(furan-2-ylmethylene)propane-1,3-diamine], was prepared by the condensation of furan-2-carboxaldehyde with propane-1,3-diamine. Its conformational changes on complexation with transition metal ions [Co(II), Ni(II), Cu(II), Mn(II), Cd(II), Zn(II) and Fe(III)] have been studied on the basis of elemental analysis, conductivity measurements, spectral (infrared, 1H NMR, electronic), magnetic and thermogravimetric studies. The conductance data of the complexes revealed their electrolytic nature suggesting them as 1:2 (for bivalent metal ions) and 1:3 (for Fe(III) ion) electrolytes. The complexes were found to have octahedral geometry based on magnetic moment and solid reflectance measurements. Thermal analysis data revealed the decomposition of the complexes in successive steps with the removal of anions, coordinated water and bis Schiff base ligand. The thermodynamic parameters were calculated using Coats–Redfern equation. The Anticancer screening studies were performed on human colorectal cancer (HCT), hepatic cancer (HepG2) and breast cancer (MCF-7) cell lines. The antimicrobial activity of all the compounds was studied against Gram negative (Escherichia coli and Proteus vulgaris) and Gram positive (Bacillus vulgaris and Staphylococcus pyogones) bacteria. It was observed that the coordination of metal ion has a pronounced effect on the microbial activities of the bis Schiff base ligand. All the metal complexes have shown higher antimicrobial effect than the free bis Schiff base ligand.

Gadolinium(III) and dysprosium(III) complexes with a Schiff base bis(N-salicylidene)-3-oxapentane-1,5-diamine: synthesis, characterization, antioxidation, and DNA-binding studies

A pentadentate Schiff base bis(N-salicylidene)-3-oxapentane-1,5-diamine (H2L) and its lanthanide(III) complexes, [GdL(NO3)(DMF)(H2O)] (1) and [Dy2L2(NO3)2]·2H2O (2), have been synthesized and characterized by physical, chemical, and spectroscopic methods. Single crystal X-ray structure reveals that 1 is a discrete mononuclear species with nine-coordinate Gd(III) in a distorted mono-capped square antiprism geometry. Complex 2 is a centrosymmetric binuclear neutral entity, in which Dy(III) is eight-coordinate in a distorted square antiprism. Electronic absorption titration spectra, ethidium bromide competitive experiments, and viscosity measurements indicate that both the ligand and complexes bind calf thymus DNA, presumably via groove binding. Investigations of antioxidant activities show that both complexes have some scavenging effects for hydroxyl and superoxide radicals.

Synthesis, Characterization, In-Vitro Antimicrobial and Antioxidant Activities of Co+2, Ni+2, Cu+2 and Zn+2 Complexes of 3-(2-(2-hydroxy-3-methoxybenzylidene)hydrazono)indolin-2-one

Four novel complexes of “3-(2-(2-hydroxy-3-methoxybenzylidene)hydrazono)indolin-2-one” have been synthesized with Co+2, Ni+2, Cu+2 and Zn+2. Physical and analytical techniques including CHN, IR, UV-Vis, AAS, molar conductivity values and magnetic susceptibility data were used to characterize all complexes. The bis Schiff base ligand i.e. 3-(2-(2-hydroxy-3-methoxybenzylidene)hydrazono)indolin-2-one, acted as a tridentate ligand and coordinated through phenolic oxygen, azomethine nitrogen and carbonyl group. Low values of molar conductance suggested the non-electrolyte nature of all complexes. Elemental analysis of complexes indicated the 1:1 metal to ligand mole ratios for [Cu(Inh)(OAc)] and [Zn(Inh)(OAc)] metal complexes and 1:2 metal to ligand mole ratios for [Co(Inh)2] and [Ni(Inh)2] metal complexes. Square planner geometry is proposed for [Cu(Inh)(OAc)] and distorted tetrahedral geometry is proposed for [Zn(Inh)(OAc)] while octahedral geometries are proposed for [Co(Inh)2] and [Ni(Inh)2] metal complexes. Antimicrobial and antioxidant studies were performed for all compounds and it was discovered that the complexes are more potent antibacterial and antifungal agents while the ligand exhibited comparatively more DPPH (1,1-diphenyl-2-picryl-hydrazil) radical scavenging activity than the complexes.

Linearly, circularly, or non-polarized light induced supramolecular arrangement of diastereomer Schiff base Ni (II), Cu (II), and Zn (II) complexes by azobenzene in PMMA matrix

Three pairs of diastereomers of Schiff base bis(N-2-hydroxy-1-isopropyl-3,5-dibromosalicydenaminato)nickel(II), copper(II), and zinc(II) complexes and their organic/inorganic hybrid materials with azobenzene (AZ) in PMMA cast thin films have been investigated by means of polarized electronic and IR spectra and CD (circular dichroism) spectra. Due to Weigert effect for AZ, not only AZ but also metal complexes dispersed separately increased optical anisotropy after linearly polarized UV light irradiation, while supramolecular chirality after circularly polarized UV light irradiation. Besides control results by non-polarized light, optical anisotropy and supramolecular chirality were confirmed by polarized spectra (overlapped π-π* and n-π* bands and d-d bands for electronic or C=N bands for IR) and CD spectra, respectively. Degree of induced optical anisotropy mainly depends on flexibility of central metal ions (less depends on diastereomers about ligands), while degree of induced supramolecular chirality mainly depends on chilarity of ligands. In other words, optical active complexes are easy to form chiral supramolecular arrangement after circularly polarized UV light irradiation.

A ‘chromogenic’ and ‘fluorogenic’ bis-Schiff base sensor for rapid detection of hydrazine both in solution and vapour phases

A simple, cost effective Schiff base ligand has been exploited as a fluorescent-colorimetric probe for rapid detection of hydrazine both in liquid and gas phase based on hydrogen bonding recognition. It has good practical applicability in different environmental and biological samples.

Electrochemical and structural analysis of a novel symmetrical bis-Schiff base with herringbone packing motif

A novel symmetrical bis-Schiff base was synthesized and characterized by means of single crystal X-ray diffraction, FT-IR and NMR spectroscopy, elemental, TG/DSC and electrochemical analysis. The synthesized molecule represents a rare example of symmetrical bis-Schiff base with uncondensed primary amino group as the final reaction product. The molecule is planar, with largest deviation of aminophenyl benzene ring from the plane calculated through the aliphatic chain in the amount of 4.93(1)°. In the crystal, the molecules are primarily linked by hydrogen bonds involving primary amino groups and weak CH⋯π interactions. Consequently, these interactions are arranging molecules into herringbone packing motif. The FT-IR and NMR spectra indicated presence of both imino and amino groups in dissolved and solid state, therefore confirming consistency of the studied material and also molecular structure determined by X-ray diffraction. Electrochemical study has shown that the oxidation of the investigated Schiff base is irreversible, diffusion controlled process and that the oxidation products are adsorbed on the glassy carbon electrode surface.

SYNTHESIS, STRUCTURAL CHARACTERIZATION AND CATALYTIC OXIDATION PROPERTY OF SCHIFF BASE COPPER(II) COMPLEXES

ABSTRACT Two new square planar mononuclear copper(II) complexes, [CuL 1 ] ( 1 ) and [CuL 2 (NCS)] ( 2 ), where L 1 is the dianionic form of the bis-Schiff base N,N’ -bis(2-hydroxynaphthylmethylidene)-1,3-pentanediamine (H 2 L 1 ), and L 2 is the monoanionic form of 1-[(2-diethylaminoethylimino)methyl]naphthalen-2-ol (HL ), have been synthesized and characterized by physico-chemical methods and single-crystal X-ray diffraction. Complex ( 1 ) (C 27 H 24 CuN 2 O 2 ) crystallizes as the orthorhombic space group Pbca , with unit cell dimensions a = 18.284(1) A, b = 12.2373(7) A, c = 19.775(1) A, V = 4424.6(4) A 3 , Z = 8, R 1 = 0.0421, wR 2 = 0.0975, S = 1.054. Complex ( 2 ) (C 18 H 21 CuN 3 OS) crystallizes as the monoclinic space group P 2 1 / c , with unit cell dimensions a = 12.776(1) A, b = 24.181(2) A, c = 11.743(1) A, β = 98.621(1)o, V = 3586.7(7) A 3 , Z = 8, R 1 = 0.0520, wR 2 = 0.1183, S = 1.012. X-ray analysis indicates that the Cu atoms in the complexes are in square planar coordination. The complexes were evaluated for their catalytic oxidation of cyclooctene and styrene with

Ring-opening copolymerization of epoxide and dianhydride in the presence of manganese(III) asymmetrical bis-Schiff base catalysts

Based on a series of asymmetrical bis-Schiff base H2Ln (n = 1–4) ligands with different electronic and steric effects, a series of [Mn(Ln)Cl] complexes 1–4 are obtained and shown to be effective catalysts in ring-opening copolymerization of epoxides and dianhydrides. Through the structure design, the input of electron-withdrawing bromine substituent para to the phenoxide group of the complexes is considerately beneficial to the improved activities. Moreover, steric and electronic effects of the suitable MeO substituent at the ortho orientation on the phenoxide group may both play a role in the formation of alternating ring-opening copolymers under the identical reaction conditions. In three cocatalysts tested, n-Bu4NBr is positive to monomer conversion and chain growth of polymer.

Electronic Spectrum of different Bis-Schiff bases of Isatin and its Solvatochromism

Electronic Spectrum of different Bis-Schiff bases of Isatin and its Solvatochromism

Manganese(III) complexes derived from bis-Schiff bases: Synthesis, structures, and antimicrobial activity

Manganese(III) complexes derived from the bis-Schiff bases N,N′-bis(5-fluorosalicylidene)-1,2-diaminoethane (H2La) and 3,4-bis(2-hydroxybenzylideneamino)pyridine (H2Lb), respectively, have been prepared and characterized by elemental analyses, IR, and single crystal X-ray crystallographic determination (CIF files CCDC nos. 997243 (I), 995896 (II)). The crystal of [MnLa(μ1,3-N3)]n (I) is orthorhombic: space group Pca21, a = 10.723(1), b = 13.430(1), c = 11.112(1) A, V = 1600.2(2) A3, Z = 4, R1 = 0.0264, wR2 = 0.0649. The crystal of [MnLb(N3)(CH3OH)] (II) is monoclinic: space group C2/c, a = 22.792(1), b = 14.4442(7), c = 12.8637(6) A, β = 119.262(1)°, V = 3694.5(3) A3, Z = 8, R1 = 0.0367, wR2 = 0.0776. The bis-Schiff base ligands coordinate to the metal atoms through phenolate O and imine N atoms. Each metal atom in the complexes is in octahedral coordination. The effects of the complexes on the antimicrobial activity against Staphylococcus aureus, Escherichia coli, and Candida albicans were studied.

Synthesis, crystal structure, antioxidation and DNA-binding properties of a dinuclear copper(II) complex with bis(N-salicylidene)-3-oxapentane-1,5-diamine

A Schiff base bis(N-salicylidene)-3-oxapentane-1,5-diamine (H2L) and its Cu(II) complex, [Cu2(L)2]∙CHCl3, have been synthesized and characterized by physicochemical and spectroscopic methods. Single-crystal X-ray analysis revealed that the complex is a centrosymmetric binuclear neutral entity, in which Cu(II) is a five-coordinate in a distorted trigonal bipyramidal geometry. The DNA-binding properties of the free ligand and the complex have been investigated by electronic absorption, fluorescence, and viscosity measurements. The results suggest that the H2L and the complex to DNA via the intercalation mode and the binding affinity of the complex were higher than that of the H2L. The intrinsic binding constants Kb of the ligand and the complex are 2.2 × 104 and 2.7 × 104 M−1, respectively. Antioxidant assay in vitro shows the Cu(II) complex possesses significant antioxidant activities and better scavenging activity than the H2L and other antioxidants.

Synthesis, Characterization, Crystal Structures, and Antimicrobial Activities of N,N’-Bis(3-Bromo-2-Hydroxybenzylidene)-1,3-Diaminopropane and Its Dinuclear Copper(II) Complex

A new bis-Schiff base N,N’-bis(3-bromo-2-hydroxybenzylidene)-1,3-diaminopropane (H2L) was prepared by reaction of 3-bromosalicylaldehyde and propane-1,3-diamine in methanol. The Schiff base reacting with copper bromide in methanol afforded a new dinuclear copper(II) complex [Cu2L2]. The Schiff base and the complex were characterized by elemental analysis, 1H NMR and IR spectra, and single-crystal X-ray diffraction. H2L crystallizes in the monoclinic space group P21/c, with a = 12.8003(13), b = 10.2011(10), c = 14.3747(13) Å, β = 113.633(3)°, V = 1719.6(3) Å3, Z = 4, R1 = 0.0509, wR2 = 0.1091, GOOF = 1.038. The complex crystallizes in the monoclinic space group P21/n, with a = 11.086(2), b = 10.5881(19), c = 15.0889(17) Å, β = 110.827(2)°, V = 1655.5(5) Å3, Z = 2, R1 = 0.0470, wR2 = 0.1087, GOOF = 1.025. The coordination mode of H2L to Cu atom has been studied. The Schiff base and the complex 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.

Synthesis and thermal behavior study of complexes of the type [Pd(μ-X)(4-eb-p-phen)]2 (X = Cl, Br, I, N3, NCO, SCN) and 4-eb-p-phen [bis(4-ethylbenzyl)p-phenylenediimine

The Schiff base bis(4-ethylbenzyl) p-phenylenediimine, 4-eb-p-phen (1), and six new dimeric Pd(II) complexes of the type [Pd(μ-X)(4-eb-p-phen)]2 {X = Cl (2), Br (3), I (4), N3 (5), NCO (6), SCN (7)} have been synthesized and characterized by elemental analysis, IR spectroscopy, and 1H and 13C{1H}-NMR experiments. The thermal behavior of the complexes 2–7 has been investigated by means of thermogravimetry and differential thermal analysis. From the final decomposition temperatures, the thermal stability of the complexes can be ordered in the following sequence: 3 > 4 > 7 > 2 ≈ 5 > 6. The final products of the thermal decompositions were characterized as metallic palladium by X-ray powder diffraction (XRD).

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.

ChemInform Abstract: Iodine Promoted Simple Synthesis of Benzimidazole Acyclonucleosides.

In nature, 5,6-dimethyl-1-(α-D-ribofuranosyl)benzimidazole exists as a moiety of vitamin B12 (Ref 1). The furanosyl benzimidazole can be considered as Cnucleoside mimic. Due to its structural similarity to purine, benzimidazole is also an important chemical entity in pharmaceuticals 2 . In one approach, aldobenzimimdazoles are prepared by the condensation of aldonic acid or aldonic δ-lactones with o-phenylenediamine 3 . The condensation reactions are often conducted in strong acidic conditions at elevated temperature (e.g.135°C) 4 . The teritol-1-yl benzimidazoles can be further converted to furanosyl benzimidazoles by Lewis acid promoted dehydrative cyclization 5 . In another approach, aldoses are subjected to oxidative condensation with o-phenylenediamine to give aldobenzimidazoles in a direct manner 6 . This approach mitigates the laborious work in the prior preparation of aldonic acids from the corresponding aldoses 7 . For example, Moore and Link 4 have previously applied this approach to synthesize two monosaccharides benzimidazoles, D-gluco and Dgalactobenzimidazoles, in 24% and 50% yields from D-glucose and D-galactose, respectively, by heating with cupric acetate (2 equiv) at 53°C for 14 hr in aqueous acetic acid solution. Some saccharide bisSchiff bases and quinaxolines also form as side products under such reaction conditions 4-6 . However using catalytic amounts of CuSO4 or replacing the AcOH solvent with MeOH does not give any desired aldo-benzimidazoles 8 . Considering the acid-sesitive internal glycosidic bonds in disaccharides and higher saccharides, it is questionable that the corresponding aldo-benimidazoles can be obtained by the above mentioned reactions involving acidic conditions at high reaction temperature. In continuation of our study, the novel transformation of aldehyde and aldoses by use of amines and iodine 9-12 , we describe herein an improved protocol for the synthesis of various aldo-benzimidazoles by direct oxidative condensation of aldoses, including different mono-saccharides with substituted ophenylenediamine in the presence of iodine.