Showing papers on "Schiff base published in 2010"
TL;DR: In this article, the inhibition effect of 5-((E)-4-phenylbuta-1, 3-dienylideneamino)-1,3,4-thiadiazole-2-thiol (PDTT) Schiff base on mild steel corrosion in 0.5 M HCl was studied for both short and long immersion time.
302 citations
TL;DR: High-performance yellow to red organic light-emitting devices (OLEDs) using these platinum(II) Schiff base complexes have been fabricated with the best efficiency up to 31 cd A(-1) and a device lifetime up to 77 000 h at 500 cd m(-2).
Abstract: The syntheses, crystal structures, and detailed investigations of the photophysical properties of phosphorescent platinum(II) Schiff base complexes are presented. All of these complexes exhibit intense absorption bands with lambda(max) in the range 417-546 nm, which are assigned to states of metal-to-ligand charge-transfer ((1)MLCT) (1)[Pt(5d)-->pi*(Schiff base)] character mixed with (1)[lone pair(phenoxide)-->pi*(imine)] charge-transfer character. The platinum(II) Schiff base complexes are thermally stable, with decomposition temperatures up to 495 degrees C, and show emission lambda(max) at 541-649 nm in acetonitrile, with emission quantum yields up to 0.27. Measurements of the emission decay times in the temperature range from 130 to 1.5 K give total zero-field splitting parameters of the emitting triplet state of 14-28 cm(-1). High-performance yellow to red organic light-emitting devices (OLEDs) using these platinum(II) Schiff base complexes have been fabricated with the best efficiency up to 31 cd A(-1) and a device lifetime up to 77 000 h at 500 cd m(-2).
279 citations
TL;DR: Chemodosimeter FS1 demonstrated selective and sensitive detection of intracellular Fe(3+) in hepatocytes and its fluorescence properties and application to an iron-overloaded cell line demonstrated.
249 citations
TL;DR: Multi-spectroscopic experiments reveal that the binding modes of Co( II) complex in comparison with SF are different; SF may be intercalating between DNA base pairs while its Co(II) complex most likely interact with DNA in an electrostatic binding mode.
239 citations
TL;DR: A series of mononuclear lanthanide complexes with chiral Schiff base ligands displaying single-ion magnet behavior and ferroelectricity are synthesized and characterized.
234 citations
TL;DR: A highly enantioselective catalytic asymmetric access to 3-aminooxindoles with a tetrasubstituted carbon stereocenter and transformation of the products into an optically active oxindole with a spiro-beta-lactam unit and a known key intermediate for AG-041R synthesis is described.
Abstract: A highly enantioselective catalytic asymmetric access to 3-aminooxindoles with a tetrasubstituted carbon stereocenter is described. 1−2 mol % of homobimetallic (R)-Ni2−Schiff base 1 catalyzed the asymmetric amination of 3-substituted oxindoles with azodicarboxylates to give (R)-products in 99−89% yield and 99−87% ee. Reversal of enantiofacial selectivity was observed between bimetallic and monometallic Schiff base complexes, and monometallic (R)-Ni−Schiff base 2c gave (S)-products in 98−80% ee. Transformation of the products into an optically active oxindole with a spiro-β-lactam unit and a known key intermediate for AG-041R synthesis is also described.
229 citations
TL;DR: The full details of a catalytic asymmetric syn-selective nitro-Mannich reaction promoted by heterobimetallic Cu/Sm/dinucleating Schiff base complexes are described, demonstrating the effectiveness of the heterobetimetallic transition metal/rare earth metal bifunctional catalysis.
Abstract: The full details of a catalytic asymmetric syn-selective nitro-Mannich reaction promoted by heterobimetallic Cu/Sm/dinucleating Schiff base complexes are described, demonstrating the effectiveness of the heterobimetallic transition metal/rare earth metal bifunctional catalysis. The first-generation system prepared from Cu(OAc)(2)/Sm(O-iPr)(3)/Schiff base 1a = 1:1:1 with an achiral phenol additive was partially successful for achieving the syn-selective catalytic asymmetric nitro-Mannich reaction. The substrate scope and limitations of the first-generation system remained problematic. After mechanistic studies on the catalyst prepared from Sm(O-iPr)(3), we reoptimized the catalyst preparation method, and a catalyst derived from Sm(5)O(O-iPr)(13) showed broader substrate generality as well as higher reactivity and stereoselectivity compared to Sm(O-iPr)(3). The optimal system with Sm(5)O(O-iPr)(13) was applicable to various aromatic, heteroaromatic, and isomerizable aliphatic N-Boc imines, giving products in 66-99% ee and syn/anti = >20:1-13:1. Catalytic asymmetric synthesis of nemonapride is also demonstrated using the catalyst derived from Sm(5)O(O-iPr)(13).
190 citations
TL;DR: All zinc complexes were shown to be very effective catalysts for the ring-opening polymerization (ROP) of lactides at ambient temperature, producing polymers with controlled and narrow molecular weight distributions.
Abstract: A series of chiral NNO-tridentate Schiff base ligands derived from natural amino acids were reacted with zinc(bis-trimethylsilylamide)2 to provide metal complexes which have been fully characterized. One of these derivatives was further reacted with p-fluorophenol to yield a phenoxide complex. X-ray crystallographic studies reveal the zinc Schiff base amide complexes to be monomeric, whereas, the p-fluorophenolate complex was shown to be dimeric with bridging phenoxide ligands. All zinc complexes were shown to be very effective catalysts for the ring-opening polymerization (ROP) of lactides at ambient temperature, producing polymers with controlled and narrow molecular weight distributions. These enantiomerically pure zinc complexes did not show selectivity toward either l- or d-lactide, that is, kd(obsd)/kl(obsd) ≈ 1. However, steric substituents on the Schiff base ligands exhibited moderate to excellent stereocontrol for the ROP of rac-lactide. Heterotactic polylactides were produced from rac-lactide wi...
180 citations
TL;DR: In this paper, a new Schiff base, 3-ethoxy salicylidene amino benzoic acid (ETSAN), has been synthesized from 3-ethylsalicylaldehyde and 2-amino benzosic acid.
Abstract: A new Schiff base, 3-ethoxy salicylidene amino benzoic acid (ETSAN), has been synthesized from 3-ethoxy salicylaldehyde and 2-amino benzoic acid. Metal complexes of the Schiff base were prepared from nitrate/chloride salts of Ni(II), Co(II) Cu(II) and Zn(II) in an alcoholic medium. The complexes were non-electrolytes in dimethyl sulfoxide solvent (DMSO). The chemical structures of the Schiff-base ligand and its metal complexes were confirmed by various spectroscopic studies like IR, UV-VIS, 1 H NMR, 13 C NMR, ESI-mass spectra, elemental analysis, molar conductance, thermogravimetric studies and magnetic susceptibility measurements. On the basis of elemental and spectral studies, six-coordinated geometry was assigned to these complexes. In the light of these results, it is suggested that this ligand acts as neutral and tridentate and coordinates to each metal atom by azomethine nitrogen and oxygen atoms of hydroxyl group of the 3-ethoxy salicylaldehyde, besides the hydroxyl group of the carboxyl group of 2-amino benzoic acid. The mass spectral data confirm s the monomeric structure of the metal complexes while the TGA studies confirm the presence of water molecules in the complex. The free Schiff base and its complexes have been tested for their antibacterial as well as antifungal activity by using disc diffusion method and the results discussed. Keywords: Schiff base; 3-ethoxy salicylaldehyde; 2-amino benzoic acid; Metal complexes; Antibacterial activity; Antifungal activity. © 2010 JSR Publications. ISSN: 2070-0237 (Print); 2070-0245 (Online). All rights reserved. DOI: 10.3329/jsr.v2i3.4899 J. Sci. Res. 2 (3), 513-524 (2010)
170 citations
TL;DR: Two series of cationic Schiff base surfactants, namely 2-(benzylideneamino)-3-(2-oxo-2-alkoxyethyl)1,3-benzothiazol-3-ium bromide and 2-[(4-methoxybenzylonidene)amino]-3-(1.5 M HCl solution using gravimetric and polarization measurements were evaluated as corrosion inhibitors for carbon steel as mentioned in this paper.
162 citations
TL;DR: The paper presents the synthesis of complex combinations of Cu(II), V(IV) and Ni(II) with Schiff bases obtained through the condensation of 4-amino-1,5-dimethyl-2-phenyl-1H-3-pyrazol-3(2H)-one (antipyrine) with 2-hydroxybenzaldehyde, 4-Hydroxy-5-methoxyisophthalaldehyde and 4-dihydroxy
TL;DR: In this paper, a series of aluminum half-salen complexes have been synthesized from either chiral or achiral tridentate Schiff base ligands derived from amino alcohols or amino acids.
TL;DR: A rationalization of the structural, electronic, and redox properties of the title compounds is provided, based on a theoretical investigation at the density functional theory (DFT) level.
Abstract: The synthesis, spectroscopic and structural characterization, linear and nonlinear optical properties, as well as the electrochemical behavior of a series of robust neutral binuclear M[Fc-C(O)CH=C(CH(3))N-X-N=CH-(2-O,5-R-C(6)H(3))] (M = Ni (4), Cu (5), X = o-C(6)H(4), R = H; M = Ni (9), X = CH(2)CH(2), R = OH), and their corresponding ionic trinuclear [M{Fc-C(O)CH=C(CH(3))N-X-N=CH-(eta(6)-2-O,5-R-C(6)H(3))RuCp*}][PF(6)] (6, 7, 10), M[ONNO]-type unsymmetrical Salophen and salen complexes featuring ferrocenyl (Fc) donor and the mixed sandwich acceptor [Cp*Ru(eta(6)- salicylidene)](+) as a push-pull moiety are reported in this paper (Fc = CpFe(eta(5)-C(5)H(4)); Cp = eta(5)-C(5)H(5); Cp* = eta(5)-C(5)Me(5)). The single-crystal X-ray structure of the bimetallic iron-nickel derivative 4 indicates a bowed structure of the unsymmetrical Schiff base skeleton. The Ni(II) ion is tetracoordinated in a square planar environment, with two nitrogen atoms and two oxygen atoms as donors. The new metalloligand [Fc-C(O)CH=C(CH(3))N(H)CH(2)CH(2)N=CH-(2,5-(OH)(2)C(6)H(3))] (8) obtained from the Schiff base condensation of 2,5-dihydroxobenzaldehyde with the half-unit precursor, Fc-C(O)CH=C(CH(3))N(H)CH(2)CH(2)NH(2) (2), is reported with its crystal structure showing partial delocalization of the heteroconjugated [O-C-C-C-N] frameworks with a dihedral angle between the respective planes of 60.76 degrees. Second order nonlinear optical (NLO) measurements were achieved using the Harmonic Light Scattering technique to probe the role of the M[ONNO] chromophores and of the pi-complexation of the salicylidene ring in the nonlinearity. All the complexes exhibit a second-order nonlinear response increasing with the nuclearity, the hyperpolarizability (beta) value of the trinuclear complex 10 being 1.5 time larger than that of the metalloligand 8 (beta = 155 x 10(-30) esu). A rationalization of the structural, electronic, and redox properties of the title compounds is provided, based on a theoretical investigation at the density functional theory (DFT) level. Their UV-visible spectra has been assigned with the help of time-dependent (TD) DFT calculations. They are dominated by LMCT, MLCT, and pi-pi* transitions.
TL;DR: A new Pd(II) bounded 2D-hexagonally ordered functionalized MCM-41 type material (IV) has been synthesized and was found that this catalyst is highly efficient and recyclable towards Suzuki-Miyaura reaction with high turn over frequencies.
Abstract: A new Pd(II) bounded 2D-hexagonally ordered functionalized MCM-41 type material (IV) has been synthesized. Functionalization was carried out by the anchoring of 3-aminopropyltriethoxysilane in the MCM-41 type mesoporous material, followed by grafting with 2,6-diacetylpyridine (DAP) to give a N3-type Schiff base chelating attachment for the Pd(II) species. Fourier transform infrared (FTIR), powder X-ray diffraction (PXRD) and high resolution transmission electron microscopy (HRTEM) studies have been used to characterize the material. Material IV behaves as a highly active catalyst towards Suzuki–Miyaura cross-coupling reaction for the synthesis of biaryl organics. In addition, IV acts as a true heterogeneous catalyst in coupling reaction. It was found that this catalyst is highly efficient and recyclable towards Suzuki–Miyaura reaction with high turn over frequencies. X-Ray photoelectron spectroscopic (XPS) analysis was employed to understand the oxidation state of the palladium atom in the catalyst (IV) and its loading in the material.
TL;DR: Newly synthesized phenol based novel Schiff base polydentate symmetric ligand and two complexes showed good biological activity against all tested bacteria and yeast strains.
TL;DR: In this paper, three mono oxovanadium(V) complexes of tridentate Schiff base ligands were obtained by monocondensation of 3-hydroxy-2-naphthohydrazide and aromatic o-hydroxaldehydes, and the catalytic potential of these complexes was tested for the oxidation of cyclooctene using H2O2 as the terminal oxidant.
TL;DR: A Schiff-based fluorescence probe benzene-1,2-dicarbaldehyde bis-benzoyl hydrazide (L) was designed and synthesized as mentioned in this paper.
TL;DR: Four new Cu(II)-azido complexes have been synthesized using the same tridentate Schiff base ligand HL (2-[1-(2-dimethylaminoethylimino)ethyl]phenol, the condensation product of dmen and 2-hydroxyacetophenone) and can be obtained in pure form by carefully controlling the conditions.
Abstract: Four new Cu(II)-azido complexes of formula [CuL(N(3))] (1), [CuL(N(3))](2) (2), [Cu(7)L(2)(N(3))(12)](n) (3), and [Cu(2)L(dmen)(N(3))(3)](n) (4) (dmen = N,N-dimethylethylenediamine) have been synthesized using the same tridentate Schiff base ligand HL (2-[1-(2-dimethylaminoethylimino)ethyl]phenol, the condensation product of dmen and 2-hydroxyacetophenone). The four compounds have been characterized by X-ray structural analyses and variable-temperature magnetic susceptibility measurements. Complex 1 is mononuclear, whereas 2 is a single mu-1,1 azido-bridged dinuclear compound. The polymeric compound 3 possesses a 2D structure in which the Cu(II) ions are linked by phenoxo oxygen atoms and two different azide bridges (mu-1,1 and mu-1,1,3). The structure of complex 4 is a double helix in which two mu-1,3-azido-bridged alternating one-dimensional helical chains of CuL(N(3)) and Cu(dmen)(N(3))(2) are joined together by weak mu-1,1 azido bridges and H-bonds. The complexes interconvert in solution and can be obtained in pure form by carefully controlling the conditions. The magnetic properties of compounds 1 and 2 show the presence of very weak antiferromagnetic exchange interactions mediated by a ligand pi overlap (J = -1.77) and by an asymmetric 1,1-N(3) bridge (J = -1.97 cm(-1)), respectively. Compound 3 presents, from the magnetic point of view, a decorated chain structure with both ferro- and antiferromagnetic interactions. Compound 4 is an alternating helicoidal chain with two weak antiferromagnetic exchange interactions (J = -1.35 and -2.64 cm(-1)).
TL;DR: A binucleating new Schiff-base ligand with a phenylene spacer, afforded by the condensation of glycyl-glycine and o-phthalaldehyde has been served as an octadentate N₂O₄ ligand in designing some binuclear complexes of cobalt(II), nickel(II, copper( II), and palladium(II).
01 Jan 2010
TL;DR: This review summarizes the synthesis and biological activities of Schiff bases and its complexes.
Abstract: Schiff bases are versatile ligands which are synthesized from the condensation of primary amines with carbonyl groups. These compounds are very important in medicinal and pharmaceutical fields because of their wide spectrum of biological activities. Most of them show biological activities such as antibacterial, antifungal as well as antitumor activity. Transition metal complexes derived from the Schiff base ligands with biological activity have been widely studied. This review summarizes the synthesis and biological activities of Schiff bases and its complexes.
TL;DR: The (51)V NMR spectra recorded for solutions in methanol confirm that complex 4, on treatment with H(2)O(2), is able to generate peroxo-vanadium(V) complexes, including quite stable protonated peroxO-V(V), and an outline of the mechanism is proposed.
Abstract: The Schiff base (Hfsal-dmen) derived from 3-formylsalicylic acid and N,N-dimethyl ethylenediamine has been covalently bonded to chloromethylated polystyrene to give the polymer-bound ligand, PS-Hfsal-dmen (I). Treatment of PS-Hfsal-dmen with [VIVO(acac)2] in the presence of MeOH gave the oxidovanadium(IV) complex PS-[VIVO(fsal-dmen)(MeO)] (1). On aerial oxidation in methanol, complex 1 was oxidized to PS-[VVO2(fsal-dmen)] (2). The corresponding neat complexes, [VIVO(sal-dmen)(acac)] (3) and [VVO2(sal-dmen)] (4) were similarly prepared. All these complexes are characterized by various spectroscopic techniques (IR, electronic, NMR, and electron paramagnetic resonance (EPR)) and thermal as well as field-emission scanning electron micrographs (FE-SEM) studies, and the molecular structures of 3 and 4 were determined by single crystal X-ray diffraction. The EPR spectrum of the polymer supported VIVO-complex 1 is characteristic of magnetically diluted VIVO-complexes, the resolved EPR pattern indicating that the ...
TL;DR: Two functionalized copper(II) and oxovanadium(IV) Schiff base complexes of type [M(N 2 O 2 ), M = Cu, VO] bearing chloromethyl groups were respectively synthesized, directly anchored onto amino-modified SBA-15 materials and examined as catalysts for styrene oxidation as discussed by the authors.
Abstract: Two functionalized copper(II) and oxovanadium(IV) Schiff base complexes of type [M(N 2 O 2 ), M = Cu, VO] bearing chloromethyl groups were respectively synthesized, directly anchored onto amino-modified SBA-15 materials and examined as catalysts for styrene oxidation. The purity of each ligand was confirmed by 1 H NMR, FT-IR and elemental analysis. XRD, N 2 adsorption/desorption and TEM results indicated that the mesoporous structure of SBA-15 remained intact throughout the grafting procedure. FT-IR, UV–vis spectroscopy plus TG–DTA data demonstrated the incorporation of copper(II) and oxovanadium(IV) complexes on amino-modified SBA-15. ICP-AES, SEM-EDX combined with XPS data further showed the different anchorage status of copper(II) and oxovanadium(IV) species on amino-modified SBA-15. The copper(II) Schiff base complex was anchored through the coordination of copper atom with the nitrogen atom of the amino group modified on the SBA-15 external surface. The oxovanadium(IV) Schiff base complex, however, was covalently anchored on SBA-15 via the condensation reaction of the chloromethyl group of the Schiff base with the amino group from the modified SBA-15 matrix. The catalytic properties of supported copper(II) and oxovanadium(IV) complexes in the oxidation of styrene with air or H 2 O 2 as oxidant were investigated and compared with the properties of their homogeneous analogues. It was found that both heterogeneous copper(II) and oxovanadium(IV) catalysts were more active than their homogeneous analogues and that the product selectivity varied in cases of different oxidants. The supported oxovanadium(IV) complex showed high yield of styrene oxide (56.0%) and good recoverability when using air as oxidant.
TL;DR: In this article, a review of the most important discoveries and achievements accomplished in this field is presented, along with a short overview of conformational differences between free Schiff bases and Schiff bases bonded to metal ions as well as some structural characteristics of Schiff base metal complexes.
Abstract: During the last 50 years a vast number of structural studies on Schiff bases derived from hydroxyaryl aldehydes and their coordination compounds have been undertaken. In this review we present a systematic and brief overview of the most important discoveries and achievements accomplished in this field. The occurrence of Schiff bases (and their complexes) derived from nine most commonly used hydroxyaryl aldehydes in the Cambridge Structural Database (CSD) has been investigated. Keto-enol tautomerism and intramolecular hydrogen bonding in salicylaldimines and naphthaldimines is discussed, with a comment of the most common errors in determining the correct tautomeric form. Also, the interrelationship of crystal packing and the substituents on the Schiff base is studied. Finally, we give a short overview of conformational differences between free Schiff bases and Schiff bases bonded to metal ions as well as some structural characteristics of Schiff base metal complexes.
TL;DR: In this article, a chemosensor based on the Schiff base is easily prepared by reacting tryptophan and 2-hydroxy-1-naphthaldehyde in methanol, which displays specific recognition to Zn2+, and especially avoids the interference of Cd2+ when 1 is tested against a range of physiological and environmentally relevant metal ions.
TL;DR: Syntheses, characterization, and magnetic properties of a series of diphenoxo-bridged discrete dinuclear M(II)Ln(III) complexes derived from the compartmental Schiff base ligand, H(2)L, obtained on condensation of 3-ethoxysalicylaldehyde with trans-1,2-diaminocyclohexane, are described.
Abstract: Syntheses, characterization, and magnetic properties of a series of diphenoxo-bridged discrete dinuclear MIILnIII complexes (M = Cu or Ni, Ln = Ce−Yb) derived from the compartmental Schiff base lig...
TL;DR: In this article, the crystal structure of 1-phenyl-2,3-dimethyl-4-(N-3-formyl-6-methyl-chromone)-3-pyrazolin-5-one (HL) has been determined by X-ray diffraction studies, as well as the one of its copper(II) complex [CuL(OAc)]·CH3OH which contains an anionic ligand and an acetate in the coordination sphere of the metal.
TL;DR: The isolated compounds were characterized by their physical properties, elemental analysis, IR-, MS (EI)- and NMR-spectroscopy and the cytotoxic effect of these complexes against the fast growing head and neck squamous carcinoma cells SQ20B and SCC-25 has been studied.
TL;DR: In this paper, the structure of the dibasic Schiff base ligand was elucidated by analytical and spectroscopic tools (IR, 1 H and 13 C NMR spectra) which indicated that the coordinating sites are oxygen atoms of the phenolic OH groups, nitrogen atoms of azomethine groups and the oxygen atom of the ketonic group.
TL;DR: In this article, the tetradentate asymmetric Schiff base ligand HL5 has been synthesized using cadmium(II) chloride and asymmetric base ligands under different pH conditions at room temperature.
Abstract: Six cadmium(II) complexes containing the N2O2 donor tetradentate asymmetrical Schiff base ligand 2-{[2-(dimethylamino)ethylimino]methyl}-6-methoxyphenol (HL5), namely, [(Cd3L52Cl4)2]·CH3OH·H2O (1), [Cd(L5)Cl]2·CH3OH (2), [Cd2(HL5)Cl4]n (3), {[Cd3(H2L5)2Cl8]·2H2O}n (4), [(H2L5)2]2+·[CdCl4]2−·H2O (5), and [(H2L5)2]2+·[CdCl4]2− (6), have been synthesized using cadmium(II) chloride and the asymmetrical Schiff base ligand HL5 under different pH conditions at room temperature. The diverse structures show the marked sensitivity of the structural chemistry of the tetradentate asymmetrical Schiff base ligand HL5. Complex 1 formed at pH = 10 exhibits a rare zero-dimensional structure of trinuclear cadmium(II). At pH = 8−9, a dinuclear cadmium(II) complex 2 is formed. The reaction at pH = 5−7 leads to two one-dimensional structures of 3 and 4. A further decrease of the pH to 3−5 results in a zero-dimensional structure 5. Owing to the departure of lattice water molecules in the crystal, complex 5 at room temperature ...
TL;DR: In this paper, a Schiff base ligand derived from indole-3-carboxaldehyde (indal) and glycylglycine(glygly) was synthesized and characterized by elemental analysis, IR, electronic spectrum, 1 H NMR and mass spectrum.