Showing papers on "Schiff base published in 2013"
TL;DR: With this simple and moderate methodology, surface-confined 2D covalent organic frameworks (COFs) with few defects and almost entire surface coverage are obtained, which clearly reveals an eclipsed stacking manner.
Abstract: We performed a co-condensation reaction between aromatic aldehyde and aromatic diamine monomers on a highly oriented pyrolytic graphite surface either at a solid/liquid interface at room temperature or in low vacuum with moderate heating. With this simple and moderate methodology, we have obtained surface-confined 2D covalent organic frameworks (COFs) with few defects and almost entire surface coverage. The single crystalline domain can extend to more than 1 μm2. By varying the backbone length of aromatic diamines the pore size of 2D surface COFs is tunable from ∼1.7 to 3.5 nm. In addition, the nature of the surface COF can be modified by introducing functional groups into the aromatic amine precursor, which has been demonstrated by introducing methyl groups to the backbone of the diamine. Formation of small portions of bilayers was observed by both scanning tunneling microscopy (STM) and AFM, which clearly reveals an eclipsed stacking manner.
167 citations
TL;DR: The reaction of a new hexadentate Schiff base hydrazide ligand (LH3) with rare earth(III) chloride salts in the presence of triethylamine as the base afforded two planar tetranuclear neutral complexes, revealing single-molecule magnet (SMM) behavior for complex 1.
Abstract: The reaction of a new hexadentate Schiff base hydrazide ligand (LH3) with rare earth(III) chloride salts in the presence of triethylamine as the base afforded two planar tetranuclear neutral complexes: [{(LH)2Dy4}(μ2-O)4](H2O)8·2CH3OH·8H2O (1) and [{(LH)2Ho4}(μ2-O)4](H2O)8·6CH3OH·4H2O (2). These neutral complexes possess a structure in which all of the lanthanide ions and the donor atoms of the ligand remain in a perfect plane. Each doubly deprotonated ligand holds two Ln(III) ions in its two distinct chelating coordination pockets to form [LH(Ln)2]4+ units. Two such units are connected by four [μ2-O]2– ligands to form a planar tetranuclear assembly with an Ln(III)4 core that possesses a rhombus-shaped structure. Detailed static and dynamic magnetic analysis of 1 and 2 revealed single-molecule magnet (SMM) behavior for complex 1. A peculiar feature of the χM″ versus temperature curve is that two peaks that are frequency-dependent are revealed, indicating the occurrence of two relaxation processes that lea...
132 citations
TL;DR: The prepared complexes bind to DNA via classical intercalative mode and showed a different DNA activity with the sequence: nhi>nari>nali>nasi>nphali.
131 citations
TL;DR: A series of copper (II) complexes of Schiff bases derived from 7H-2,6-diaminopurine and 4H-3,5diamino-1,2,4-triazole with 2-pyridine carbaldehyde, salicylaldehyde, 2,4dihydroxybenzaldehyde and 2-hydroxy-1-naphthaldehyde have been prepared as discussed by the authors.
124 citations
TL;DR: Three novel quadridentate Schiff base complexes, [OIAC, a Schiff base ligand: (([2-oxo-1H-indol-3-ylidene]amino)chitosan)] have been synthesized and catalytic activities have been studied in the oxidation of cyclohexane, using environmental friendly oxidant, hydrogen peroxide.
123 citations
TL;DR: Two series of 4d-4f clusters with novel drum-like structures prepared using a flexible Schiff base ligand determined their NIR luminescence properties.
Abstract: Two series of 4d–4f clusters [Ln8Cd24L12(OAc)48] and [Ln6Cd18L9Cl8(10)(OAc)28(26)] (Ln = Nd, Gd, Er, and Yb) with novel drum-like structures were prepared using a flexible Schiff base ligand. Their NIR luminescence properties were determined.
121 citations
TL;DR: In this article, the spectral, magnetic, molar conductance and thermal analysis of 4-hydroxy-3-(phenyliminomethyl)-phenylazo]benzenesulfonamide compounds were used to identify the pathogenic activities of the synthesized compounds.
112 citations
TL;DR: In this paper, Fe(II) Schiff base amino acid complexes derived from the condensation of o-hydroxynaphthaldehyde with l -alanine, l -phenylalanine and l -aspartic acid were synthesized and characterized by elemental analysis, IR, electronic spectra, and conductance measurements.
107 citations
TL;DR: The title compound was synthesized by the reaction between a manganese(II) carboxylate and the tetradentate Schiff base ligand, 5-Br-salpnH2 [N,N′-bis(5-br-salicylidene)-1,3-diaminopropane] produced in situ as discussed by the authors.
Abstract: The title compound was synthesized by the reaction between a manganese(II) carboxylate and the tetradentate Schiff base ligand, 5-Br-salpnH2 [N,N′-bis(5-Br-salicylidene)-1,3-diaminopropane] produced in situ. The complex crystallizes in the P21/c space group with unit cell dimensions (10), (10), (3), , (10), and . The manganese(III) ion is in a distorted octahedral environment with longer axial bonds.
105 citations
TL;DR: In this article, six transition metal complexes derived from the reaction of 4(4-(dimethylamino) benzylideneamino) benzoic acid and Mn(II), Fe, Co, Ni, Cu, and Zn(II) cations were prepared, isolated and characterized by a range of spectral and analytical methods including UV/Vis, FT IR, NMR, MS, powder XRD, TGA and SEM.
104 citations
TL;DR: The aim of this review is to highlight specific characteristics of Schiff-based compounds capable of chelating metal ions and their antioxidant activity.
Abstract: The search for metal-derived antioxidants has received much attention and effort in order to identify the compounds having high capacity in scavenging free radicals related to various disorders and diseases associated with oxidative damage, caused by reactive oxygen species (ROS). Presently, synthetic antioxidants are widely used because they are effective and cheaper than natural antioxidants. Currently a number of Schiff-base metal complexes have been investigated as effective scavengers of ROS, acting as antioxidants. The aim of this review is to highlight specific characteristics of Schiff-based compounds capable of chelating metal ions and their antioxidant activity. Schiff bases form an important class of organic compounds with a wide variety of biological properties. Schiff bases have often been used as chelating ligands in the field of coordination chemistry, and their metal complexes have been of great interest to researchers for many years. The activity is usually increased by complexation therefore to understand the properties of both ligands and metal can lead to the synthesis of highly active compounds. The influence of certain metals on the biological activity of these compounds and their intrinsic chemical interest as multidentate ligands has prompted a considerable increase in the study of their coordination behavior. Development of a new chemotherapeutic Schiff bases and their metal complexes is now attracting the attention of medicinal chemists.
TL;DR: Results showed that the Cu(II) complex could quench the intrinsic fluorescence of bovine serum albumin (BSA) remarkably through a static quenching process, and induce a conformational change with the loss of helical stability of protein.
Abstract: The DNA-binding properties and DNA-cleavage activities of a Cu(II) complex, [Cu(sal-tau(phen)]·1.5H2O (sal-tau=a Schiff base derived from salicylaldehyde and taurine, phen=1,10-phenanthroline), have been investigated by using UV-Vis absorption, fluorescence, circular dichroism (CD) spectra and agarose gel electrophoresis. Results indicated that this Cu(II) complex can bind to calf thymus DNA (CT-DNA) via an intercalative mode and shows efficient cleavage activity in the absence and presence of reducer. Its intrinsic binding constant Kb (1.66×10(4)M(-1)) was calculated by absorption spectra and its linear Stern-Volmer quenching constant K(sq) (3.05) was obtained from florescence spectroscopy, as well as the cleaving reaction rate constant k1 (2.0×10(-4)s(-1)) was acquired from agarose gel electrophoresis. Meanwhile, the interactions of the complex with BSA have also been studied by spectroscopy. Results showed that the complex could quench the intrinsic fluorescence of bovine serum albumin (BSA) remarkably through a static quenching process, and induce a conformational change with the loss of helical stability of protein.
TL;DR: A new Schiff base bidentate ligand (L), 5-methyl thiophene-2-carboxaldehyde-carbohydrazone and its metal complexes with general stoichiometry [M(L)2X2] (where X=Cl) were synthesized and showed that copper complex exhibited higher activity than the other complexes.
TL;DR: The immobilized complex did not leach or decompose during the catalytic reactions, showing practical advantages over the homogeneous catalysis, and has shown high activity toward the Suzuki and Stille cross-coupling reaction in 20% H2O/EtOH and EtOH medium, respectively.
Abstract: An ecofriendly solid catalyst has been synthesized by anchoring palladium(II) into post synthetically modified metal organic framework IRMOF-3. The pore of IRMOF-3 was first modified with pyridine-2-aldehyde. The amine group of IRMOF-3 upon condensation with pyridine-2-aldehyde afforded a bidentate Schiff base moiety in the porous matrix. The Schiff base moieties were used to anchor palladium(II) ions. The prepared catalyst has been characterized by UV–vis, IR spectroscopy, X-ray powder diffraction, and nitrogen sorption measurements. Framework structure of the catalyst is not being destroyed in the multistep synthesis procedure as evidenced in X-ray powder diffraction studies. The catalyst has shown high activity toward the Suzuki and Stille cross-coupling reaction in 20% H2O/EtOH and EtOH medium, respectively, at 80 °C. The immobilized complex did not leach or decompose during the catalytic reactions, showing practical advantages over the homogeneous catalysis.
TL;DR: An evaluation of the transition metal ion-induced modification of the fluorophore-receptor communication reveals a promising prospect for the title compound to function as a fluorosensor for Cu(2+) and Zn( 2+) ions selectively, through remarkable fluorescence enhancement.
Abstract: A new Schiff base compound 2-((benzylimino)-methyl)-naphthalen-1-ol (2BIMN1O) has been synthesized and characterized by 1H NMR, 13C NMR, DEPT, FT-IR and mass spectroscopic techniques. The significantly low fluorescence yield of the compound has been rationalized in connection with photo-induced electron transfer (PET) from the imine receptor moiety to the naphthalene fluorophore unit. Subsequently, an evaluation of the transition metal ion-induced modification of the fluorophore–receptor communication reveals a promising prospect for the title compound to function as a fluorosensor for Cu2+ and Zn2+ ions selectively, through remarkable fluorescence enhancement. While perturbation of the PET process in 2BIMN1O has been argued to be the responsible mechanism behind the fluorescence enhancement, the selectivity for these two metal ions has been interpreted on the grounds of an appreciably strong binding interaction. Particularly notable aspects regarding the chemosensory activity of the compound are its ability to detect the aforesaid transition metal ions down to the level of micromolar concentration (detection limit being 0.82 and 0.35 μM respectively), along with a simple and efficient synthetic procedure. Also the spectral modulation of 2BIMN1O in the presence of the transition metal ions paves the way for the construction of a calibration curve in the context of its fluorescence signaling potential.
TL;DR: The literature survey as discussed by the authors highlights spectra and biological activity of transition metal complexes derived from Schiff bases of quinoxaline and discusses the extensive studies of synthesis, spectral, structural characterization, and biological activities of the metal complexes with heterocyclic Schiff bases.
Abstract: The literature survey highlights spectra and biological activity of transition metal complexes derived from Schiff bases of quinoxaline. The extensive studies of synthesis, spectral, structural characterization, and biological activities of the metal complexes with heterocyclic Schiff bases of quinoxaline are reviewed.
TL;DR: Magnetic susceptibility measurements show that the spin states of the complexes are related to the substituents of H2L(x), and that spin transition occurs only in complexes 1 and 2, which are derived from a bulky ligand, whereas complex 3 is diamagnetic.
Abstract: Two bis(tridentate) Schiff base ligands H2Lx were used to construct three 2×2 grid-type tetranuclear Fe(II) complexes 1–3 to obtain polynuclear spin-crossover materials. Magnetic susceptibility mea...
TL;DR: In this article, a review of the structural and supramolecular features of the metal complexes derived from chiral N-salicyl-β-amino alcohol Schiff base ligands is presented.
TL;DR: In this article, the corrosion inhibition and adsorption of N,N′-bis( n -hydroxybenzaldehyde)-1,3-propandiimine ( n -HBP) Schiff bases has been investigated on steel electrode in 1-M HCl by using electrochemical techniques.
TL;DR: In this article, metal ions coordinate in a tetradentate or hexadentate features with these O2N donor ligand, which are characterized by elemental analyses, magnetic moments, infrared, Raman laser, electronic, and 1H NMR spectral studies.
TL;DR: It has been shown that all the synthesized compounds showed moderate to significant antibacterial activity against one or more bacterial strains and against six fungal strains by using agar-well diffusion method.
TL;DR: In this paper, a new class of bidentate (N, O) Schiff base ligand (L) has been derived from the functional biopolymer (chitosan) and 1,2-diphenylethanedione in 1:1-M ratio.
TL;DR: A series of new organotin(IV) complexes of the types R2SnL, R is Me (1), Ph (2), o-Cl-C6H4CH2 (3); and [R3SnL]∞, R = n-Bu (4) (H2L = 2-hydroxy-1-naphthaldehyde 5-chloro-2-hydroxbenzoylhydrazone) have been synthesized and structurally characterized by means of elemental analysis, FT-IR, UV-vis spectroscopy,
TL;DR: The air-moisture stable and recyclable palladium(II) Schiff base complex anchored to multi-walled carbon nanotubes (Pd-Schiff base@MWCNTs) behaves as a very efficient heterogeneous catalyst in the Suzuki-Miyaura coupling of arylboronic acids and aryls halides as discussed by the authors.
TL;DR: Zinc ( II) complexes 6 and 13 of both the ligands and copper (II) complexes 9 of the HL(2) were observed to be the most active against all bacterial strains, antifungal activity was overall enhanced after complexation of the ligand.
TL;DR: The antioxidative properties showed that the copper(I) complex has a strong radical-scavenging potency than ligands, and the cytotoxic effect of the compounds examined on cancerous cell lines show that the complex exhibited substantial anticancer activity.
TL;DR: Three new tetranuclear copper(II) complexes have been synthesized using three different hydrazone Schiff base ligands derived from the condensation of the aromatic acid hydrazides 2-hydroxybenzo-, 2-aminobenzo- or benzo-hydrazide with 2,3-dihydroxybenzaldehyde.
Abstract: Three new tetranuclear copper(II) complexes [Cu(HL1)]4·4EtOH (1·4EtOH), [Cu(HL2)]4 (2) and [Cu(H2L3)]4(NO3)4·2H2O (3·2H2O) have been synthesized using three different hydrazone Schiff base ligands derived from the condensation of the aromatic acid hydrazides 2-hydroxybenzo-, 2-aminobenzo- or benzo-hydrazide, with 2,3-dihydroxybenzaldehyde. Complexes 1 and 3 have been characterized by single crystal X-ray diffraction analysis. The coordinating behaviour of the ligand depends on the nature of the ortho substituent present in the hydrazide moiety. The ligands bearing a strong electron donating group (by resonance) in the ortho position undergo complexation via enolization and deprotonation, whereas the absence of such an effect leads to complexation via the keto form, and two different types of tetranuclear Cu(II) clusters, viz. open-cubane and cubane, are obtained. Variable temperature magnetic susceptibility measurements of complexes 1 and 3 have been carried out to examine the nature of magnetic interaction between the Cu(II) centres. All the three complexes (1–3) act as good catalyst precursors towards mild hydrocarboxylation of linear and cyclic alkanes into carboxylic acids in water–acetonitrile medium.
TL;DR: In this paper, a 2,5-diformylfuran with two primary amines was used for polymerization in acetonitrile and ethanol at room temperature.
Abstract: Polymerization of 2,5-diformylfuran with two primary amines was carried out in acetonitrile and ethanol at room temperature. the reaction was characterized using a combination of mass spectroscopy and nmr spectroscopy, which revealed the clean formation of the imine -ch n-functional group. although some cyclic products were detected from mass spectroscopy, the ring size was limited to products that have the -ch n-group only in anti-geometry. the furan schiff bases exhibit good thermal stability. while mass spectra evidenced oligomers of different lengths, cross-polarization magic angle spinning 13c nmr spectra of the insoluble polymer revealed the linear structure as proposed. (c) 2013 society of chemical industry
TL;DR: In this article, a multimetallic salen and related Schiff base complexes designed for cooperative asymmetric catalysis are introduced, and studies to design dinuclear Schiff base catalysts that exhibit unique intramolecular cooperative functions of two distinct metals are discussed in detail.
Abstract: Multimetallic salen and related Schiff base complexes designed for cooperative asymmetric catalysis are introduced. First, studies to enhance the cooperative function of two distinct metal–salen units using covalently linked metal–salen complexes, supramolecular bimetallic salens as well as μ-oxo-bridged metal salens are described. Then, studies to design dinuclear Schiff base catalysts that exhibit unique intramolecular cooperative functions of two distinct metals are discussed in detail. 1 Introduction 2 Covalently Linked Metal Salens 3 Supramolecular Bimetallic Salens 4 μ-Oxo-Bridged Metal Salens 5 Heterodinuclear Schiff Base Complexes 6 Homodinuclear Schiff Base Complexes 7 Summary
TL;DR: Density functional theory calculations have been performed on the complexes 1-3 to provide a qualitative theoretical interpretation of their overall magnetic behavior.
Abstract: Three new copper–azido complexes [Cu4(N3)8(L1)2]n (1), [Cu4(N3)6(L2)2(H2O)2] (2), and [Cu4(N3)6(L3)2]n (3) [L1 is the imine resulting from the condensation of pyridine-2-carboxaldehyde with N-methylethylenediamine, HL2 and HL3 are the condensation products of 2-hydroxy-3-methoxybenzaldehyde with N,N-diethylethylenediamine and N-ethylethylenediamine respectively] have been synthesized by using 0.5 molar equivalents of the Schiff base ligands with Cu(NO3)2·3H2O and an excess of NaN3. Single crystal X-ray structures show that the basic unit of these complexes contains very similar CuII4 building blocks. While 1 and 3 have overall 1D structures, 2 forms discrete tetranuclear clusters due to blocking of two coordination sites on the tetranuclear cluster by water molecules. Magnetic susceptibility measurements over a wide range of temperatures exhibit the presence of both antiferromagnetic and ferromagnetic exchanges within the tetranuclear unit structures. Density functional theory calculations (using B3LYP functional and two different basis sets) have been performed on the complexes 1–3 to provide a qualitative theoretical interpretation of their overall magnetic behavior.