Showing papers on "Schiff base published in 2009"
TL;DR: Melamine has been reacted with various di- and trivalent aldehydes to form a series of highly cross-linked microporous aminal networks with BET surface areas as high as 1377 m(2)/g and a NLDFT micropore volume of up to 0.41 cm(3)/g, which are promising candidates for large-scale applications in gas storage, gas separation, catalysis, and sensing.
Abstract: Recently, the synthesis of organic materials with high porosity has received considerable scientific interest, and various chemical approaches have been applied to the build-up of microporous polymer networks. In a novel catalyst-free process using Schiff base chemistry, melamine has been reacted with various di- and trivalent aldehydes to form a series of highly cross-linked microporous aminal networks with BET surface areas as high as 1377 m(2)/g and a NLDFT micropore volume of up to 0.41 cm(3)/g. It was shown that through the proper choice of the starting compounds the porosity of the final material can be fine-tuned. The materials contain up to 40 wt % of nitrogen and were also found to exhibit high thermal stability. Owing to the cheap and abundant monomers used in this study these networks are promising candidates for large-scale applications in gas storage, gas separation, catalysis, and sensing.
555 citations
TL;DR: In this paper, the catalytic activity of different types of Schiff base was analyzed and presented in a review, showing that polymer-supported Schiff base complexes of metal ions show high catalytic performance in comparison to their unsupported analogues.
345 citations
TL;DR: Two novel 2-oxo-quinoline-3-carbaldehyde (4'-hydroxybenzoyl) hydrazone, thiosemicarbazone ligands and its corresponding Cu(2+) complexes were synthesized, and the two complexes' structures were determined by X-ray single crystal diffraction.
252 citations
TL;DR: The antimicrobial activity study revealed that all the compounds screened showed good or moderate activity except compounds 3, 5c, 7, 9c, 9e, 9g, 9h, 11, and 13.
241 citations
TL;DR: The in vitro and in vivo anti- cancer efficacy, as well as the anti-cancer mechanisms of the most potent gold(III) porphyrin compound [Au III (TPP)]Cl ( 1a) are detailed.
221 citations
TL;DR: A macrocyclic hydrazone Schiff base was synthesized by reacting 1,4-dicarbonyl phenyl dihydrazide with 2,6-diformyl-4-methyl phenol and a series of metal complexes with this new Schiff base were synthesised by reaction with Co(II), Ni(II) and Cu(II).
220 citations
TL;DR: The covalency factor (β) and orbital reduction factor (k) suggest the covalent nature of the complexes and the ligand and its complexes have been screened for their antifungal and antibacterial activities against three fungi and two bacteria.
Abstract: Transition metal complexes of Co(II), Ni(II) and Cu(II) metal ions with general stoichiometry [M(L)X]X and [M(L)SO(4)], where M = Co(II), Ni(II) and Cu(II), L = 3,3'-thiodipropionic acid bis(4-amino-5-ethylimino-2,3-dimethyl-1-phenyl-3-pyrazoline) and X = NO(3)(-), Cl(-) and OAc(-), have been synthesized and structurally characterized by elemental analyses, molar conductance measurements, magnetic susceptibility measurements and spectral techniques like IR, UV and EPR. The nickel(II) complexes were found to have octahedral geometry, whereas cobalt(II) and copper(II) complexes were of tetragonal geometry. The covalency factor (beta) and orbital reduction factor (k) suggest the covalent nature of the complexes. The ligand and its complexes have been screened for their antifungal and antibacterial activities against three fungi, i.e. Alternaria brassicae, Aspergillus niger and Fusarium oxysporum and two bacteria, i.e. Xanthomonas compestris and Pseudomonas aeruginosa.
182 citations
TL;DR: In this article, structural properties and biological studies of transition metal complexes derived from 4-aminoantipyrine are discussed. But the most important results of extensive studies (syntheses, spectral, magnetic, redox, structural characteristics, antimicrobial and DNA cleavage) of the metal complexes with heterocyclic Schiff bases of 4-AMINOANTipyrines with some aldehydes and oximes are reviewed.
Abstract: The survey highlights structural properties and biological studies of transition metal complexes derived from 4-aminoantipyrine. The most important results of extensive studies (syntheses, spectral, magnetic, redox, structural characteristics, antimicrobial and DNA cleavage) of the metal complexes with heterocyclic Schiff bases of 4-aminoantipyrine with some aldehydes and oximes are reviewed.
180 citations
TL;DR: New Schiff base (H(2)L) ligand is prepared via condensation of o-phthaldehyde and 2-aminophenol and is coordinated to the metal ions in a bi-negatively tetradentate manner with ONNO donor sites of the azomethine N and deprotonated phenolic-OH.
172 citations
TL;DR: Metal complexes of novel Schiff base (HL) ligand, prepared via condensation of 4-aminoantipyrine and 2-aminophenol, are prepared and are screened for its antibacterial activity against bacterial species.
159 citations
TL;DR: In this paper, three novel Schiff base ligands containing the azo group were synthesized from the reaction of p-aminoazobenzene with salicylaldehyde.
TL;DR: The measured molar conductance values indicate that, the complexes are non-electrolytes in nature.
TL;DR: Experimental results indicate that the reactivity of [LMg(mu-OBn)](2) (1-8) is dramatically affected by the electronic effect of the substituents on the Schiff-base ligands, and 4 has the highest activity among them.
Abstract: A series of magnesium benzyl alkoxides, [LMg(mu-OBn)](2) (1-8), supported by NNO-tridentate Schiff-base ligands are prepared by the reactions of Mg(OBn)(2) with one molar equivalent of related Schiff-base ligands (L(1)H-L(8)H) in toluene. The molecular structures of compounds 2, 3, 7, and 8 are characterized by X-ray structure determination. All of these compounds are crystallized as penta-coordinated dimers, and the central magnesium atoms are bridged by the oxygen atoms of benzyl alkoxides. The catalytic activities of complexes 1-8 toward the ring-opening polymerization of l-lactide are investigated. Experimental results indicate that the reactivity of [LMg(mu-OBn)](2) (1-8) is dramatically affected by the electronic effect of the substituents on the Schiff-base ligands, and 4 has the highest activity among them.
TL;DR: The results confirmed that amino groups on chitosan reacted with citral to form the Schiff base, and it was found that the antimicrobial activity of the Schiffbase was stronger than that of chitOSan.
TL;DR: In this article, a tridentate Schiff base ligand was used to synthesize five new nickel(II) complexes, namely, [Ni2L2N3]2(H2O)2] (1), [Ni 2L2(NO3)2], [Ni3L2O2CPh)(CH3OH)2 ]ClO4.0.5CH3H2.
Abstract: Five new nickel(II) complexes [Ni2L2(N3)2(H2O)2] (1), [Ni2L2(NO3)2] (2), [Ni2L2(O2CPh)(CH3OH)2]ClO4.0.5CH3OH (3), [Ni3L2(O2CPh)4] (4), and [Ni2L2(NO2)2]n (5) have been synthesized by using a tridentate Schiff base ligand, HL (2-[(3-Methylamino-propylimino)-methyl]-phenol), and the polyatomic monoanions N3−, NO3−, PhCOO−, or NO2−. The complexes have been structurally and magnetically characterized. The structural analysis reveals that in all five complexes, the Ni(II) ions possess a distorted octahedral geometry. Complexes 1 and 2 are dinuclear with di-μ-1,1-azido and di-μ2-phenoxo bridges, respectively. Complex 3 is also a di-μ2-phenoxo-bridged dinuclear Ni(II) complex but has an additional syn−syn benzoate bridge. Compound 4 possesses a linear trinuclear structure with the tridentate Schiff base ligand coordinated to the terminal nickel atoms which are linked to the central Ni(II) by phenoxo and carboxylate bridges. Complex 5 consists of a dinuclear entity, bridged by di-μ2-phenoxo together with a cis-(μ...
TL;DR: A colorimetric anion sensor was developed using the Schiff base formed from the condensation of salicylaldehyde and 2-amino-4-nitrophenol under microwave irradiation as discussed by the authors.
Abstract: A colorimetric anion sensor was developed using the Schiff base formed from the condensation of salicylaldehyde and 2-amino-4-nitrophenol under microwave irradiation. The Schiff base portrayed a color change upon addition of fluoride, acetate and dihydrogen phosphate (DHP) ions with a substantial bathochromic shift from 342 to 450 nm. No significant color change was observed upon addition of other anions such as chloride, bromide, perchlorate, and hydrogen sulfate. The binding constants showed the binding order AcO − ≈ F − ≫ H 2 PO 4 − . Job plots indicated the formation of a (1:1) complex (receptor:anion) with fluoride, acetate and DHP. Single crystal X-ray structure of the Schiff base indicated that the compound exists in the keto-amine tautomer in the solid state.
Journal Article•
TL;DR: In this paper, the effect of Schiff base S1 and S2 on mild steel with two different microstructures resulted from two different heat treatments (annealed (A) and quenched and tempered (Q&T) by ac impedance spectroscopy.
TL;DR: A series of aluminum ethyls and isopropoxides based on a bis(pyrrolidene) Schiff base ligand framework has been prepared and characterized in this article.
Abstract: A series of aluminum ethyls and isopropoxides based on a bis(pyrrolidene) Schiff base ligand framework has been prepared and characterized. NMR studies of the dissolved complexes indicate that they adopt a symmetric structure with a monomeric, five-coordinated aluminum center core. The aluminum ethyls used as catalysts in the presence of 2-propanol as initiator and the aluminum isopropoxides were applied for lactide polymerization in toluene to test their activities and stereoselectivities. All polymerizations are living, as evidenced by the narrow polydispersities and the good fit between calculated and found number-average molecular weights of the isolated polymers. All of these aluminum complexes polymerized (S,S)-lactide to highly isotactic PLA without epimerization of the monomer, furnished isotactic-biased polymer from rac-lactide, and gave atactic polymer from meso-lactide. The study of kinetics indicated that the activity of the bis(pyrrolidene) Schiff base aluminum initiator systems toward lactid...
TL;DR: In this article, the effect of Schiff base S1 and S2 on mild steel with two different microstructures resulted from two different heat treatments (annealed (A) and quenched and tempered (Q&T) by ac impedance spectroscopy.
TL;DR: The Ga(O-iPr)(3)/Yb(OTf)(3/Schiff base 2d complex promoted asymmetric alpha-additions of alpha-isocyanoacetamides to aryl, heteroaryl, alkenyl, and alkyl aldehydes in good to excellent enantioselectivity (88-98% ee).
Abstract: Development of a new heterobimetallic Ga(O-iPr)3/Yb(OTf)3/Schiff base 2d complex for catalytic asymmetric α-additions of isocyanides to aldehydes is described. Schiff base 2d derived from o-vanillin was suitable to utilize cationic rare earth metal triflates with good Lewis acidity in bimetallic Schiff base catalysis. The Ga(O-iPr)3/Yb(OTf)3/Schiff base 2d complex promoted asymmetric α-additions of α-isocyanoacetamides to aryl, heteroaryl, alkenyl, and alkyl aldehydes in good to excellent enantioselectivity (88−98% ee).
TL;DR: All the macrocycles and macrocyclic Ru(II) complexes along with existing antibacterial drugs were screened for antibacterial activity against Gram +ve (Bacillus subtilis, Staphylococcus aureus) and Gram -ve (Escherichia coli, Klebsiella pneumonia) bacteria and were found to be more active when compared to streptomycin and ampicillin.
TL;DR: The coordination chemistry of the new unsymmetrical Schiff base ligand {(3,5-tBu2-1-OC6H4)CH═N(trans-1,2-cyclo-C6H10)N═C(Me)CH2C(CF3)2O} 2− ({ArONCyNOCF3}2−) onto Al (III) and Y(III) centers has been studied as discussed by the authors.
TL;DR: In this article, a new dioxo-molybdenum (VI) complex [MoO2(L)(CH3OH)] has been synthesized, using 2-[(2-hydroxypropylimino)methyl]phenol as tridentate ONO donor Schiff base ligand (H2L) and MoO 2(acac)2.
TL;DR: Fluorescent dinuclear chiral zinc complexes were synthesized in a "one-pot" method in which the lysine-based Schiff base ligand was generated in situ.
Abstract: Fluorescent dinuclear chiral zinc complexes were synthesized in a "one-pot" method in which the lysine-based Schiff base ligand was generated in situ This complex acts as a highly sensitive and selective fluorescent ON-OFF probe for Cu(2+) in water at physiological pH Other metal ions such as Hg(2+), Cd(2+), and Pb(2+) gave little fluorescence change
TL;DR: The reactions proceeded without air or moisture sensitivity in high yields and with high enantioselectivities at room temperature under highly concentrated conditions (neat-20 M) with 0.1-2.5 mol % catalyst loading.
Abstract: Two metal cooperation: A homodinuclear Co(2)-Schiff base complex Co(2)(OAc)(2)-1 promoted the asymmetric 1,4-addition of beta-keto esters to alkynones under solvent-free conditions in air (see scheme). The reactions proceeded without air or moisture sensitivity in high yields and with high enantioselectivities (99-91% ee) at room temperature under highly concentrated conditions (neat-20 M) with 0.1-2.5 mol % catalyst loading.
TL;DR: In this paper, the fine structure of Schiff-base ligand systems (metallocycle sizes and their number, nature of donor centers, aldehyde and amine fragments, co-ligands) are examined.
Abstract: Data on molecular design of various types of mononuclear complexes of Schiff bases are generalized. Factors for variation of fine structure of Schiff-base ligand systems (metallocycle sizes and their number, nature of donor centers, aldehyde and amine fragments, co-ligands) are examined. A systematization of Salen complexes is offered. Electronic configurations of p- and d-metals in the coordination and organometallic compounds are taken into account in a series of chelate structures. Non-standard structures are emphasized, including various ligand chelates and molecular complexes.
TL;DR: The crystal structure of 2 presents a polymorph (dimorph) to a previously reported structure (2b, CSD refcode SCLIRB10) and can crystallize as the enantiomorph 3S in the tetragonal, chiral space group P41 in a spontaneous resolution of the racemic mixture into homo-chiral helix-enantiomers.
Abstract: The dimeric complex acetato(η4-cycloocta-1,5-diene)rhodium(I), [Rh(O2CMe)(η4-cod)]2 (cod = cycloocta-1,5-diene) reacts with N,O-chelating Schiff-base ligands or with N-phenylglycine to afford the diminato- or aminocarboxylato(η4-cycloocta-1,5-diene)rhodium(I) complexes [{Rh(η4-cod)}2(salen)] (1), [{Rh(η4-cod)}2(salophen)] (2), [Rh((S)-N-phenylglycinato)(η4-cod)] (3S), [Rh(rac-N-phenylglycinato)(η4-cod)] (3rac), [Rh((R)-N-(4-methoxphenyl)ethyl-2-oxo-1-naphthaldiminato)(η4-cod)] (4) and [Rh(N-(o-tolyl)-2-oxo-1-naphthaldiminato)(η4-cod)] (5) [salen2− = N,N′-ethylene-bis(salicylaldiminato), salophen2− = N,N′-(1,2-phenylene)-bis(salicylaldiminato)]. The complexes are characterized by IR-, UV/Vis-, 1H/13C-NMR- and mass-spectroscopy. Complexes 1, 2, 4 and 5 contain six-membered metallaaromatic Rh–(N–CCC–O)-chelate rings which accept C–H⋯π contacts. The crystal structure of 2 presents a polymorph (dimorph) (2a) to a previously reported structure (2b, CSD refcode SCLIRB10). Polymorphic forms 2a and 2b are traced to a different interlocking of adjacent dinuclear molecules with their corrugated van der Waals surface. The achiral N-phenylglycine ligand gives a chiral N-phenylglycinato complex [Rh(O2C–CH2–NHPh)(η4-cod)] (3) with the nitrogen atom becoming the stereogenic center upon metal coordination. Complex 3 can crystallize as the enantiomorph 3S in the tetragonal, chiral space groupP41 in a spontaneous resolution of the racemic mixture into homo-chiral helix-enantiomers due to inter-molecular N–H⋯O hydrogen bonding which connects only molecules of the same (S-) configuration into (right-handed or P-) 41-helical chains. Variation of the crystallization conditions gives 3 as a racemic polymorphic 3rac. R- and S-complexes 3 assemble in the polymorph 3rac in parallel chains along the 21-axes through N–H⋯O hydrogen bonding. Again, only molecules of the same configuration are combined into a chain, albeit neighboring chains have complexes of opposite configuration. The chiral enantiomeric naphthaldiminato complex 4 displays a herring-bone arrangement. Achiral compound 5 crystallizes in the non-centrosymmetric polar space groupCc where all molecules show the same orientation.
TL;DR: The antioxidant activity experiments show that these compounds also exhibit good antioxidant activities against (*)OH and O(2)(-).
TL;DR: A series of Schiff base-modified ordered mesoporous silica materials impregnated with the transition metal-monosubstituted Keggin-type polyoxometalates (mono-TMSPs), K 10− n X n + MW 11 O 39 -Schiff-SBA-15, (X = P/Si, M = Co/Ni/Cu/Mn), was prepared using successive grafting procedures of SBA15 silica with 3-aminopropyl-trimethoxysilane, benzaldehyde, and
Abstract: A series of Schiff base-modified ordered mesoporous silica materials impregnated with the transition metal-monosubstituted Keggin-type polyoxometalates (mono-TMSPs), K 10− n X n + MW 11 O 39 -Schiff-SBA-15, (X = P/Si, M = Co/Ni/Cu/Mn), was prepared using successive grafting procedures of SBA-15 silica with 3-aminopropyl-trimethoxysilane, benzaldehyde, and mono-TMSP. The composite materials were well-characterized by spectroscopy methods, X-ray diffraction analysis, transmission electron microscopy, and nitrogen sorption analysis to confirm the structure integrities of the Keggin unit and Schiff base ligand after the incorporation, to evidence formation of the coordination binding between the starting Keggin units and the Schiff base-modified silica matrix, and to investigate the morphology and surface textural properties of the composite catalysts. These materials were subsequently utilized as efficient and selective catalysts in the reaction of oxidation of styrene to benzaldehyde using H 2 O 2 as an oxidant. For comparison, an amine-modified SBA-15 silica material impregnated with mono-TMSP (K 10− n X n + MW 11 O 39 -NH 2 -SBA-15) and the neat Keggin unit (K 10− n [X n + M(H 2 O)W 11 O 39 ]) was also tested. The influences of key reaction parameters, including the molar ratios of H 2 O 2 to styrene, compositions and loadings of the neat mono-TMSPs, solvents, the catalyst amount, and reaction temperatures on the reactivity and selectivity, were also studied. Finally, the reusability of the catalysts was evaluated.
TL;DR: Interestingly, the [VIVO(SAA)(bpy)] complex selectively inhibits PTP1B over the other two phosphatases (approximate ninefold selectivity against SHP-1 and about twofold selectivities against TCPTP).
Abstract: A series of oxovanadium complexes with mixed ligands, a tridentate ONO-donor Schiff base ligand [viz., salicylidene anthranilic acid (SAA)], and a bidentate NN ligand [viz., 2,2'-bipyridine (bpy), 1,10-phenanthroline (phen), dipyrido[3,2-d:2',3'-f]quinoxaline (dpq), dipyrido[3,2-a:2',3'-c]phenazine (dppz), or 7-methyldipyrido[3,2-a:2',3'-c]phenazine (dppm)], have been synthesized and characterized by elemental analysis, electrospray ionization mass spectrometry, UV-vis spectroscopy, Fourier transform IR spectroscopy, EPR spectroscopy, and X-ray crystallography. Crystal structures of both complexes, [V(IV)O(SAA)(bpy)].0.25bpy and [V(IV)O(SAA)(phen)].0.33H(2)O, reveal that oxovanadium(IV) is coordinated with one nitrogen and two oxygen atoms from the Schiff base and two nitrogen atoms from the bidentate planar ligands, in a distorted octahedral geometry (VO(3)N(3)). The oxidation state of V(IV) with d(1) configuration was confirmed by EPR spectroscopy. The speciation of VO-SAA-bpy in aqueous solution was investigated by potentiomtreic pH titrations, and the results revealed that the main species are two ternary complexes at a pH range of 7.0-7.4, and one is the isolated crystalline complex. The complexes have been found to be potent inhibitors against human protein tyrosine phosphatase 1B (PTP1B) (IC(50) approximately 30-61 nM), T-cell protein tyrosine phosphatase (TCPTP), and Src homology phosphatase 1 (SHP-1) in vitro. Interestingly, the [V(IV)O(SAA)(bpy)] complex selectively inhibits PTP1B over the other two phosphatases (approximate ninefold selectivity against SHP-1 and about twofold selectivity against TCPTP). Kinetics assays suggest that the complexes inhibit PTP1B in a competitive and reversible manner. These suggest that the complexes may be promising candidates as novel antidiabetic agents.