Showing papers on "Schiff base published in 2017"
TL;DR: A total of five new metal complex derivatives of 2N-salicylidene-5-(p-nitro phenyl)-1,3,4-thiadiazole, HL with the metal ions Vo(II), Co(II, Rh(III), Pd(II) and Au(III) have been successfully prepared in alcoholic medium as discussed by the authors.
165 citations
TL;DR: A direct and highly stereoselective synthesis of small peptides with enantiopure α-alkyl or α,α-dialkyl α-amino acids residues incorporated at specific sites was accomplished using this dual catalyst system.
Abstract: We report a stereoselective and site-specific allylic alkylation of Schiff base activated amino acids and small peptides via a Pd/Cu dual catalysis. A range of noncoded α,α-dialkyl α-amino acids were easily synthesized in high yields and with excellent enantioselectivities (up to >99% ee). Furthermore, a direct and highly stereoselective synthesis of small peptides with enantiopure α-alkyl or α,α-dialkyl α-amino acids residues incorporated at specific sites was accomplished using this dual catalyst system.
162 citations
TL;DR: It is expected that the addendum of the imine based COF would not only enrich the structural variety but also help to understand the electrochemical behavior of these class of materials.
Abstract: A [2 + 2] Schiff base type condensation between 5,10,15,20-tetrakis(4-aminophenyl)porphyrin (TAP) and 1,3,6,8-tetrakis (4-formylphenyl) pyrene (TFFPy) under solvothermal condition yields a crystalline, quasi-two-dimensional covalent organic framework (SB-PORPy-COF). The porphyrin and pyrene units are alternatively occupied in the vertex of 3D triclinic crystal having permanent microporosity with moderately high surface area (∼869 m2 g–1) and promising chemical stability. The AA stacking of the monolayers give a pyrene bridged conducting channel. SB-PORPy-COF has been exploited for metal free hydrogen production to understand the electrochemical behavior using the imine based docking site in acidic media. SB-PORPy-COF has shown the onset potential of 50 mV and the Tafel slope of 116 mV dec–1. We expect that the addendum of the imine based COF would not only enrich the structural variety but also help to understand the electrochemical behavior of these class of materials.
153 citations
TL;DR: A tetradentate ONNO Schiff base ligand (HNDAP) was synthesized from 1:2-M ratio condensation of 2, 3-diaminopyridine and 2- hydroxy-1-naphthaldhyde, respectively.
138 citations
15 Sep 2017
TL;DR: The investigation results indicate that the Schiff Bases compounds with an average efficiency of 92% at 1.0mM of additive concentration have fairly effective inhibiting properties for mild steel in hydrochloric acid, and acts as mixed type inhibitor character.
Abstract: The inhibitory effect of two Schiff bases 3-(5-methoxy-2-hydroxybenzylideneamino)-2-(-5-methoxy-2-hydroxyphenyl)-2,3-dihydroquinazoline-4(1H)-one (MMDQ), and 3-(5-nitro-2-hydroxybenzylideneamino)-2(5-nitro-2-hydroxyphenyl)-2,3-dihydroquinazoline-4(1H)-one (NNDQ) on the corrosion of mild steel in 1M hydrochloric acid were studied using mass loss, potentiodynamic polarization technique and electrochemical impedance spectroscopy measurements at ambient temperature. The investigation results indicate that the Schiff Bases compounds with an average efficiency of 92% at 1.0mM of additive concentration have fairly effective inhibiting properties for mild steel in hydrochloric acid, and acts as mixed type inhibitor character. The inhibition efficiencies measured by all measurements show that the inhibition efficiencies increase with increase in inhibitor concentration. This reveals that the inhibitive mechanism of inhibitors were primarily due to adsorption on mild steel surface, and follow Langmuir adsorption isotherm. The temperature effect on the inhibition process in 1MHCl with the addition of investigated Schiff bases was studied at a temperature range of 30-60°C, and the activation parameters (Ea, ΔH and ΔS) were calculated to elaborate the corrosion mechanism. The differences in efficiency for two investigated inhibitors are associated with their chemical structures.
130 citations
TL;DR: In this article, a novel Schiff base was synthesized from the condensation of 2-hydroxy-1-naphthaldehyde and isatin with 4-nitro-o-phenylenediamine.
Abstract: A novel Schiff base, namely Z-3-((2-((E)-(2-hydroxynaphthyl)methylene)amino)-5-nitrophenylimino)-1,3-dihydroindin-2-one, was synthesized from the condensation of 2-hydroxy-1-naphthaldehyde and isatin with 4-nitro-o-phenylenediamine. It was structurally characterized on the basis of 1H NMR, 13C NMR and infrared spectra and elemental analyses. In addition, Ni(II) and Cu(II) complexes of the Schiff base ligand were prepared. The nature of bonding and the stereochemistry of the investigated complexes were elucidated using several techniques, including elemental analysis (C, H, N), Fourier transform infrared and electronic spectroscopies and molar conductivity. The thermal behaviours of the complexes were studied and kinetic–thermodynamic parameters were determined using the Coats–Redfern method. Density functional theory calculations at the B3LYP/6-311G++ (d, p) level of theory were carried out to explain the equilibrium geometry of the ligand. The optimized geometry parameters of the complexes were evaluated using LANL2DZ basis set. The total energy of highest occupied and lowest unoccupied molecular orbitals, Mullikan atomic charges, dipole moment and orientation are discussed. Moreover, the interaction of the metal complexes with calf thymus DNA (CT-DNA) was explored using electronic spectra, viscosity measurements and gel electrophoresis. The experimental evidence indicated that the two complexes could strongly bind to CT-DNA via an intercalation mechanism. The intrinsic binding constants of the investigated Ni(II) and Cu(II) complexes with CT-DNA were 1.02 × 106 and 2.15 × 106 M−1, respectively, which are higher than that of the standard ethidium bromide. Furthermore, the bio-efficacy of the ligand and its complexes was examined in vitro against the growth of bacteria and fungi to evaluate the antimicrobial potential. Based on the obtained results, the prepared complexes have promise for use as drugs. Copyright © 2016 John Wiley & Sons, Ltd.
113 citations
TL;DR: The mechanisms of these biomimetic oxidase reactions are proposed for the first time involving any heterometallic catalyst on the basis of mass spectral analysis, EPR spectroscopy, and cyclic voltammetry.
Abstract: A new Cu(II) complex of an asymmetrically dicondensed Schiff base (H2L = N-(2-hydroxyacetophenylidene)-N′-salicylidene-1,3-propanediamine) derived from 1,3-propanediamine, salicylaldehyde, and o-hydroxyacetophenone has been synthesized. Using this complex, [CuL] (1), as a metalloligand, two new trinuclear Cu-Mn complexes, [(CuL)2Mn(N3)(H2O)](ClO4)·H2O (2) and [(CuL)2Mn(NCS)2] (3), have been prepared. Single-crystal structural analyses reveal that complexes 2 and 3 both have the same bent trinuclear {(CuL)2Mn}2+ structural unit in which two terminal bidentate square-planar (CuL) units are chelated to the central octahedral Mn(II) ion. This structural similarity is also evident from the variable-temperature magnetic susceptibility measurements, which suggest that compounds 2 and 3 are both antiferromagnetically coupled with comparable exchange coupling constants (−21.8 and −22.3 cm–1, respectively). The only difference between 2 and 3 lies in the coordination around the central Mn(II) ion; in 3, two SCN– gr...
110 citations
TL;DR: In this paper, a series of transition metal complexes of Schiff base derived from 4-aminoantipyrine and quinoline-2-carbaldehyde to give 4-((quinolin-2yl)methyleneamino)-1,2-dihydro-2,3-dimethyl-1-phenylpyrazol-5-one (QMP).
96 citations
TL;DR: Result indicates that metal complexes shows increase cytotoxicity in proliferation to cell lines as compared to free ligand.
93 citations
TL;DR: In this article, five new organotin(IV) complexes were synthesized and characterized using 1H NMR, 13C NMR, 119Sn NMR and infrared spectroscopic techniques, and the results demonstrate that the compounds containing Sn-Ph ligands are more effective than those with Sn-Bz ligands.
Abstract: Five new organotin(IV) complexes of composition [Bz2SnL1]n (), [Bz3SnL1H⋅H2O] (), [Me2SnL2⋅H2O] (), [Me2SnL3] () and [Bz3SnL3H]n () (where L1 = (2S)-2-{[(E)-(4-hydroxypentan-2-ylidene)]amino}-4-methylpentanoate, L2 = (rac)-2-{[(E)-1-(2-hydroxyphenyl)methylidene]amino}-4-methylpentanoate and L3 = (2S)- or (rac)-2-{[(E)-1-(2-hydroxyphenyl)ethylidene]amino}-4-methylpentanoate) were synthesized and characterized using 1H NMR, 13C NMR, 119Sn NMR and infrared spectroscopic techniques. The crystal structure of reveals a distorted trigonal-bipyramidal geometry around the tin atom where the oxygen atoms of the carboxylate ligand and a water ligand occupy the axial positions, while the three benzyl ligands are located at the equatorial positions. On the other hand, the analogous derivative of enantiopure L3H () consists of polymeric chains, in which the ligand-bridged tin atoms adopt the same trans-Bz3SnO2 trigonal-bipyramidal configuration and are now coordinated to a phenolic oxygen atom instead of H2O. In , the OH hydrogen of the ketoimine substituent has moved to the nearby nitrogen atom while in the salicylidene derivative , the OH is located almost midway between the phenolic oxygen atom and the nitrogen atom of the C[DOUBLE BOND]N group. For the dibenzyltin derivative , a polymeric chain structure is observed as a result of a long intermolecular Sn⋅⋅⋅O bond involving the exocyclic carbonyl oxygen atom from the tridentate ligand of a neighbouring tin-complex unit. The tin atom in this complex has distorted octahedral coordination geometry. In contrast, the racemic dimethyltin(IV) complexes and display discrete monomeric structures with a distorted octahedral- and trigonal-bipyramidal geometry, respectively. The structures show that the coordination mode of the Schiff base ligand depends primarily on the number of bulky benzyl ligands (R) at the tin atom, as indeed found in the structures of related complexes where R = phenyl. With three bulky R groups, the tridentate chelating O,N,O coordination mode is preferred, whereas with fewer or less bulky R ligands, only the carboxylate and hydroxy groups are involved, which leads to polymers. Larvicidal efficacies of two of the new tribenzyltin(IV) complexes ( and ) were assessed on the second larval instar of Anopheles stephensi mosquito larvae and compared with two triphenyltin(IV) analogues, [Ph3SnL1H]n and [Ph3SnL3H]n. The results demonstrate that the compounds containing Sn–Ph ligands are more effective than those with Sn–Bz ligands. Copyright © 2016 John Wiley & Sons, Ltd.
92 citations
TL;DR: In this paper, a metal-organic framework (MOFs) UiO-66-Schiff base was successfully synthesized by post-synthetic modification to investigate the cobalt sorption behavior in simulated wastewater.
TL;DR: Schiff bases and their complexes are good candidates as versatile compounds which are synthesized by the condensation of a primary amino compound with either aldehydes or ketones for a variety of industrial applications.
Abstract: Schiff bases and their complexes are good candidates as versatile compounds which are synthesized by the condensation of a primary amino compound with either aldehydes or ketones for a variety of industrial applications. They can act as catalysts in the catalytic oxidation of organic compounds. Recent researches in oxidation catalysis have focused on how to employ the metal-catalyzed oxidation of organic substrates. This review summarizes the current developments of the last few decades for the oxidations of organic compounds that proceed through Schiff base complexes. The chemical syntheses of Schiff bases and their complexes are outlined.
TL;DR: In this paper, six novel Co(II) and Ni(II)-triazole Schiff base complexes have been successfully synthesized by refluxing the prepared triazole bases with CoCl 2 ·6H 2 O or NiCl 2·6H2 O. On the basis of conductance results, it was concluded that all the prepared complexes are nonelectrolytes.
TL;DR: Mechanistic studies showed that C2 effectively induced DNA damage and thus led to cell cycle arrest at the G2/M phase, and also stimulated mitochondrial dysfunction mediated by reactive oxygen species and caspase-dependent apoptosis.
TL;DR: Electrophoresis observations revealed that these copper complexes (1–4) could efficiently induce single-strand breakage of pUC18 plasmid DNA in the presence of ascorbic acid.
Abstract: A series of four new mixed-ligand copper(II) complexes (1–4) of the type [Cu(L)(diimine)] (ClO4) [where L is 2-((1H-imidazol-2-yl)methylene)-N-phenylhydrazinecarbothioamide and the diimines are 1,10-phenanthroline (phen, 1), 2,2′-bipyridine (bpy, 2), 4,4′-dimethyl-2,2′-bipyridyl (dmbpy, 3), and 2,2′-dipyridylamine (dpa, 4)] have been successfully synthesized and characterized by various spectral techniques. The Kb values were calculated from electronic absorption spectral titration of these complexes with herring sperm DNA, and these varied in the order phen (1) > dmbpy (3) > bpy (2) > dpa (4). Electrophoresis observations revealed that these complexes (1–4) could efficiently induce single-strand breakage of pUC18 plasmid DNA in the presence of ascorbic acid. These copper complexes underwent a static quenching process with BSA. Moreover, their potential free-radical scavenging and anti-inflammatory properties were also determined using DPPH and protein denaturation techniques. These complexes showed efficient antibacterial activities against Staphylococcus aureus (Gram positive) and Pseudomonas aeruginosa (Gram negative). Furthermore, studies of their in vitro cytotoxicity against AGS cancer cells indicated promising antitumor activity with significant IC50 values.
TL;DR: In this article, a new series of Co(II, Ni(II), Cu(II and Zn(II) metal complexes of a novel ligand 3-(2-(1-(2,4- D ihydroxy P henyl) e thylidene) h ydrazinyl)-2H-b enzo[b][1,4]oxazin-2-O ne, (DPE-HBO) were prepared and characterized.
TL;DR: In this paper, a series of zirconium (IV) Schiff-base complexes formulated as [Zr (L x ) 2 ] and Zr(L x ′) 2 ] were synthesized by reaction of tetradentate salicylaldimine Schiff base ligands with Zr (acac) 4 ] in methanol, and the new complexes have been characterized using FT-IR, l H NMR, 13 C{ 1 H} NMR spectroscopic techniques, elemental analyses (CHN) and the crystal structure of Z
TL;DR: In this article, a green cellulose Schiff base supported Pd(II) catalyst (CL-Sc-Pd) for the synthesis of different biaryls under microwave irradiation without the use of any organic solvent is reported.
Abstract: Bio-supported catalysts, due to their green nature, are promising materials for coupling reactions. In this paper, the design and application of a new green cellulose Schiff base supported Pd(II) catalyst (CL-Sc-Pd) for the synthesis of different biaryls under microwave irradiation without the use of any organic solvent is reported. Firstly, a silane-modified cellulose Schiff base (CL-Sc) was synthesized as a support material, and then its heterogonous Pd(II) catalyst was easily prepared in water for the Suzuki coupling reaction. The synthesized materials were then characterized with various analytical tools. Finally, the catalytic performance of the green catalyst was investigated towards various C C reactions using a green, simple and fast microwave technique. The catalyst indicated excellent selectivity and activity in a very short time (6 min) under a solvent-free media. In addition, outstanding TON (19,800) and TOF (198,000) values were obtained with the green Pd(II) catalyst. The longevity of the green Pd(II) catalyst was studied and it was found to be reusable for at least eight runs. CL-Sc-Pd catalyst showed perfect catalytic efficiency for the Suzuki C C reaction when it was compared to commercial palladium catalysts.
TL;DR: In this paper, five imine-linked ligands (H2L1, H4L2, and L3L5) were synthesized in two step reactions and final products were fully characterized with spectroscopic techniques.
Abstract: Five new imine-linked ligands (H2L1, H4L2, and L3–L5) were synthesize in two step reactions and final products were fully characterized with spectroscopic techniques The binding behavior of these ligands was evaluated with the library of metal ions However, substantial photophysical modulations were observed with the coordination of [Ni2+] ion to the ligand pocket The fact that Ni2+ induced remarkable modulation in photophysical studies encouraged us to prepare the nickel complexes of respective ligands The resultant coordination complexes offered interesting properties like tunable coordination geometry, variable stereochemistry, and possibility of electrostatic interactions which are important for biomolecular recognition These properties of coordination complexes encouraged us to evaluate the antimicrobial activity of nickel complexes All nickel complexes have shown appreciable antibacterial activity against Staphylococcus aureus and methicillin-resistant S aureus (MRSA) The SEM imaging studies
TL;DR: Electronic absorption and infrared spectra indicate that the Lewis acid cations have a minor effect on the electronic structure of the Co(II) ion, which suggests the shifts in redox potential are primarily a result of electrostatic effects due to the cationic charge.
Abstract: Redox inactive Lewis acidic cations are thought to facilitate the reactivity of metalloenzymes and their synthetic analogues by tuning the redox potential and electronic structure of the redox active site. To explore and quantify this effect, we report the synthesis and characterization of a series of tetradentate Schiff base ligands appended with a crown-like cavity incorporating a series of alkali and alkaline earth Lewis acidic cations (1M, where M = Na+, K+, Ca2+, Sr2+, and Ba2+) and their corresponding Co(II) complexes (2M). Cyclic voltammetry of the 2M complexes revealed that the Co(II/I) redox potentials are 130 mV more positive for M = Na+ and K+ and 230–270 mV more positive for M = Ca2+, Sr2+, and Ba2+compared to Co(salen–OMe) (salen–OMe = N,N′-bis(3-methoxysalicylidene)-1,2-diaminoethane), which lacks a proximal cation. The Co(II/I) redox potentials for the dicationic compounds also correlate with the ionic size and Lewis acidity of the alkaline metal. Electronic absorption and infrared spectra ...
TL;DR: In this article, metal complexes of dithiocarbazate Schiff bases were synthesized and characterized using several techniques; Fourier transforms infrared spectroscopy, nuclear magnetic resonance, 1H NMR and 13C NMR.
TL;DR: In this article, three new mononuclear cobalt(III) complexes, [Co(L1)2]ClO4·2H2O (1) {HL1= 2((2(2-hydroxyethylamino)ethylimino)methyl)-6-methoxyphenol}, [Co (L2)(acna)(N3)] (2)
TL;DR: In this article, a new heterogeneous palladium (II) catalyst that contains O-carboxymethyl chitosan Schiff base has been designed for Suzuki coupling reactions, and the chemical structures of the synthesized catalyst were characterized with the FTIR, TG/DTG, ICP-OES, SEM/EDAX, 1 H NMR, 13 C NMR and GC/MS.
TL;DR: In this paper, four new organotin(IV) complexes Me 2 SnL 1, Ph 2 NLL 1, Me 2 SNL 2 and Ph 2 Snl 2 have been synthesized and characterized by elemental analyses, FT-IR, NMR ( 1 H, 13 C and 119 Sn) and single crystal X-ray diffraction techniques.
TL;DR: Schiff bases synthesised from the condensation of 2-(hydroxy)naphthaldehyde and sulfonamides (sufathiazole (STZ), sulfapyridine (SPY), sulfadiazine (SDZ) and sulfaguanidine (SGN)) are characterized by different spectroscopic data (FTIR, UV-Vis, Mass, NMR) and two of them, (E)-4-(((2-hydroxynaphthalen-1-yl)methylene)amino)- N -(thiaz
TL;DR: In this paper, metal complexes of dithiocarbazate Schiff bases were synthesized and characterized using techniques including Fourier transform infrared spectroscopy, nuclear magnetic resonance, 1 H NMR, 13 C NMR and magnetic susceptibility measurements.
TL;DR: In this paper, a Schiff base-modified silver catalyst was developed for the direct carboxylation of terminal alkynes with CO2, enabling an efficient and green synthesis of valuable alkynyl carboxylic acids.
TL;DR: In this article, Salen-Zr(IV)-Sal Schiff base complex incorporated into amino-functionalized MIL-101(Cr) framework by salicylaldehyde condensing to amino group, and coordinating Zr (IV) ion have been successfully synthesized.
TL;DR: Complex 1-4 showed highly intense electrochemical luminescence (ECL) in DMF solution and high thermal stability and C-HX (X = Br, Cl) interactions play a crucial role in stabilizing the self-assembly process among adjacent 2-D networks for both complexes.
Abstract: Four coordination polymers, formulated as [Zn(L1)2]n (1), [Cd(L1)2]n (2), [Zn(L2)2]n (3) and [Cd(L2)2]n (4) (HL1 is (E)-2-(((4H-1,2,4-triazol-4-yl)imino)methyl)-4,6-dibromophenol; HL2 is (E)-2-(((4H-1,2,4-triazol-4-yl)imino)methyl)-4,6-dichlorophenol) have been synthesized through vial reactions. The four compounds were structurally characterized by single crystal X-ray diffraction, elemental analysis, PXRD, and fluorescence spectroscopy. For 1–4, a detailed analysis of Hirshfeld surfaces and fingerprint plots facilitates a comparison of intermolecular interactions, which are crucial in building different supramolecular architectures. C–H⋯X (X = Br, Cl) interactions play a crucial role in stabilizing the self-assembly process among adjacent 2-D networks for both complexes. Above all, complexes 1–4 showed highly intense electrochemical luminescence (ECL) in DMF solution and high thermal stability.
TL;DR: The proposed GO derivative that was functionalized with a primary amine derivative bearing a positively charged quaternary ammonium group, GO-S, demonstrated good dispersion stability in aqueous medium and exhibited better adsorption performance than GO for Th(IV) and U(VI), suggesting a great potential for the application of graphene oxide-based materials for facilitating the removal of Th( IV) andU(VI) from nuclear waste solutions.