Showing papers on "Schiff base published in 2018"
TL;DR: A review of the recent developments of unsymmetrically-substituted multidentate Schiff bases whose steric and electronic characteristics are easily manipulated by selecting suitable condensing aldehydes or ketones and primary amines, and on their metal complexes can be found in this article.
250 citations
TL;DR: The metal Schiff base complexes represent a class of compounds that have become a field of immense interest because of their intriguing chemical and physical properties, and their wide-ranging applications in a number of scientific areas as mentioned in this paper.
248 citations
TL;DR: In this paper, a novel aromatic Schiff base called 5-(benzylidene-amino)-isophthalic acid dimethyl ester (BA) has been designed as a self-crosslinking monomer for poly(ethylene terephthalate) (PET) based copolyesters (BAnPETs).
193 citations
TL;DR: The developed Schiff bases might be implemented as antimicrobial contenders to pure chitosan for treatments of wound infections and the cytotoxicity of the developed materials was estimated by MTT assay that substantiated their safety to fibroblast cells.
Abstract: This study intends to develop novel two antimicrobial phenolic chitosan Schiff bases (I) and (II) via coupling of chitosan with Indole-3-carboxaldehyde and 4-dimethylaminobenzaldehyde, respectively, for boosting the antimicrobial activity of native chitosan. The alterations in the chemical structure and morphology of the Schiff bases were verified using FT-IR, electronic spectrum analysis, and SEM, whereas the thermal properties were investigated by TGA and DSC instruments. The results obtained from the potentiometric analysis referred that the degrees of substitution were 1.15 and 12.05% for Schiff bases (I) and (II), respectively. The antimicrobial activities of Schiff base (I) were significantly augmented more than Schiff base (II) and chitosan. Minimum inhibitory concentration (MIC) of Schiff base (I) was perceived at 50 µg/ml against tested microorganisms except for B. cereus and C. albicans. The highest concentration of Schiff base (I) could inhibit the growth of Gram-positive up to 99%. However, Schiff base (II) recorded the maximum inhibition rate versus Gram-positive approximately 82%. The cytotoxicity of the developed materials was estimated by MTT assay that substantiated their safety to fibroblast cells. The findings emphasized that the developed Schiff bases might be implemented as antimicrobial contenders to pure chitosan for treatments of wound infections.
140 citations
TL;DR: A novel series of lanthanide-based SBL metal complexes was successfully synthesized, and their functional groups were elaborately demonstrated using UV–visible, Fourier transform infrared (FT-IR), and fluorescence spectroscopy analyses.
Abstract: A Schiff base ligand (SBL), N2, N3-bis (anthracen-9-ylmethylene) pyridine-2, 3-diamine, was synthesized through the condensation of 2,6-diaminopyridine and anthracene-9-carbaldehyde using a 1:2 ratio. 1H NMR spectra confirmed the observation of non-involvement aromatic carboxylic proton in SBL. A novel series of lanthanide (i.e., praseodymium (Pr), erbium (Er), and ytterbium (Yb))-based SBL metal complexes was successfully synthesized, and their functional groups were elaborately demonstrated using UV–visible, Fourier transform infrared (FT-IR), and fluorescence spectroscopy analyses. FT-IR spectral studies revealed that SBL behaved as a bidentate ligand and it was structured with metal ions by the two azomethine nitrogens. The synthesized SBL-based metal complexes were elaborately performed for cytotoxicity activity versus Vero, human breast cancer (MCF7), and cervical (HeLa) anticancer cell lines.
102 citations
TL;DR: In this paper, a short review compiles examples of the most antiurease Schiff bases (0.23μm) and azomethine-based anti-urease enzymes.
99 citations
TL;DR: In this paper, three new Schiff base ligands were synthesized by the reaction of Salicylaldehyde with semi-aromatic diamines, prepared by the reduction of corresponding dinitro-compounds, and were further used for the formation of complexes with Cu(II) metal ion.
88 citations
Book•
11 Apr 2018
TL;DR: A green chemistry approach for organic synthesis is described in this article, which involves microwave exposure of reactants in presence or absence of solvents, and a novel and simple method has been developed for the synthesis of triazole derivatives under microwave irradiation.
Abstract: A green chemistry approach for organic synthesis is described here, which involves microwave exposure of reactants in presence or absence of solvents. A novel and simple method has been developed for the synthesis of triazole derivatives under microwave irradiation. A new series of Nano complexes of 2-(1,2,4-triazol-3-ylimino)methyl)-6-methoxyphenol under microwave irradiation. The microwave methodology is rapid and gives a better yield (80–98%). The prepared Schiff base was used for further complex formation reaction with different metal ions using Mn(II), Co(II), Ni(II) and Cu(II) complexes by with a molar ratio of ligand: metal as 1:1. The stereochemistry and the mode of bonding of the complexes were achieved based on elemental analysis, FTIR, UV-Vis, 1HNMR, 13CNMR and Mass Spectroscopy as well as Thermo-Gravimetric Analysis (TGA). Structures proposed for geometry of the chelates based on their electronic spectra and magnetic susceptibility. The solid complexes have been synthesized and studied by TGA analysis. The thermal dehydration and decomposition of the complex was studied kinetically using the integral method applying the Coats–Redfern and Horowitz Metzger equation.
76 citations
TL;DR: A novel series of Schiff base has been reported by the reaction of Chitosan with different substituted pyrazole-4-carbaldehydes in acidic media, indicating stronger inhibitory effect of the Schiff bases on these microorganisms compared to ChitOSan and the extent of inhibition varied with the nature of substitution.
74 citations
TL;DR: In this paper, a Schiff base ligand (HL) was prepared via a condensation reaction of quinoline-2-carboxaldhyde with 2-aminophenol in a molar ratio of 1:1.
Abstract: A new Schiff base ligand (HL) was prepared via a condensation reaction of quinoline-2-carboxaldhyde with 2-aminophenol in a molar ratio of 1:1. Its transition metal mixed ligand complexes with 1,10-phenanthroline (1,10-phen) as co-ligand were also synthesized in a 1:1:1 ratio. HL and its mixed ligand complexes were characterized using elemental analysis, infrared, 1H NMR, mass and UV–visible spectroscopies, molar conductance, magnetic measurements, solid reflectance, thermal analysis, electron spin resonance and X-ray diffraction. Molar conductance measurements showed that all complexes have an electrolytic nature, except Cd(II) complex. From elemental and spectral data, the formulae [M(L)(1,10-phen)(H2O)]Clx⋅nH2O (where M = Cr(III) (x = n = 2), Mn(II) and Ni(II) (x = 1, n = 2), Fe(III) (x = n = 2), Co(II), Cu(II) and Zn(II) (x = 1, n = 2)) and [Cd(L)(1,10-phen)Cl]⋅3H2O for the metal complexes have been proposed. The geometric structures of complexes were found to be octahedral. Powder X-ray diffraction reflected the crystalline nature of the complexes; however, the Schiff base is amorphous. HL and its mixed ligand complexes were screened against Gram-positive bacteria (Streptococcus pneumoniae and Bacillus subtilis) and Gram-negative bacteria (Pseudomonas aeruginosa and Escherichia coli). Antifungal activity was determined against Aspergillus fumigatus and Candida albicans, the data showing that most complexes had activity less than that of the Schiff base while Mn(II), Fe(III) and Ni(II) complexes showed no significant antifungal activity. The anticancer activity of HL and its metal complexes was also studied against breast and colon cell lines. The metal complexes showed IC50 higher than that of HL, especially the Cu(II) complex which showed the highest IC50 against breast cell line.
70 citations
TL;DR: In this article, the synthesis and characterization of the Schiff base complexes Fe(II) (2M) and Fe(III)Cl (3M), where M is a K+ or Ba2+ ion incorporated into the ligand, are reported.
Abstract: The synthesis and characterization of the Schiff base complexes Fe(II) (2M) and Fe(III)Cl (3M), where M is a K+ or Ba2+ ion incorporated into the ligand, are reported The Fe(III/II) redox potentials are positively shifted by 440 mV (2K) and 640 mV (2Ba) compared to Fe(salen) (salen = N,N′-bis(salicylidene)ethylenediamine), and by 70 mV (3K) and 230 mV (3Ba) compared to Fe(Cl)(salen), which is likely due to an electrostatic effect (electric field) from the cation The catalytic activity of 3M towards the aerobic oxidation of allylic C–H bonds was explored Prior studies on iron salen complexes modified through conventional electron-donating or withdrawing substituents found that only the most oxidizing derivatives were competent catalysts In contrast, the 3M complexes, which are significantly less oxidizing, are both active Mechanistic studies comparing 3M to Fe(salen) derivatives indicate that the proximal cation contributes to the overall reactivity in the rate determining step The cationic charge also inhibits oxidative deactivation through formation of the corresponding Fe2-μ-oxo complexes, which were isolated and characterized This study demonstrates how non-redox active Lewis acidic cations in the secondary coordination sphere can be used to modify redox catalysts in order to operate at milder potentials with a minimal impact on the reactivity, an effect that was unattainable by tuning the catalyst through traditional substituent effects on the ligand
TL;DR: In this paper, five new Schiff base ligands were synthesized and characterized by 1H NMR, 13C NMR and FT-IR, UV-Vis and elemental analysis (CHN).
TL;DR: In this article, the new Schiff base 1-[(2-{1]-1-[dicyclohexylamino)-methyl]-1H-indol-3-yl]--ethylimino]-naphthalen-2-ol (HL) was prepared from 1-{[2-( 1H-Indol- 3-yl)-ethylimin] methyl] methyl and dicycloenyl amine, and the results showed that the geometrical structural were octahedral geometries for the Cr(III and Fe(
TL;DR: Findings indicate that pyrazolo[3,4-d-d]pyrimidine derivatives containing a Schiff base may be potential antiviral agents.
TL;DR: In this article, the authors demonstrate a new route to fabricate hybrid nanomaterial by encapsulating Schiff base molecules into sulfonate groups charged polystyrene beads (PS), which showed more preferable Cu(II) ion removal capacity in the presence of Mg2+ and Ca2+ co-ions in solutions.
TL;DR: In this article, a Sulfadiazine-Ortho-Vanillin Schiff base namely (E)-4-((2-hydroxy-3-methoxybenzylidene)amino) N-(pyrimidin-2-yl)benzene-sulfonamide (BS) was synthesized.
TL;DR: The Fe3O4@La-MOF-Schiff base-Pd ensemble showed very active, quite stable, magnetically recoverable and reusable in coupling of bromo- or iodoaryls with arylboronic acids, affording practically quantitative yields of biaryls (>99%) and high TONs and TOFs as discussed by the authors.
TL;DR: A schiff base H2L derived from simple condensation of 2-hydroxy-6-isopropyl-3-methyl benzaldehyde and 1,2-diaminopropane in 2:1-M ratio and its [MnL], [CoL] and [NiL]2 complexes have been prepared and characterized by spectroscopic technique, elemental analysis, SEM-EDX analysis, and cyclic voltammetry as discussed by the authors.
TL;DR: Two types of drum-like 30- and 32-metal Cd-Ln nanoclusters were constructed using a designed Schiff base ligand built around a flexible (CH2)7 chain this paper.
Abstract: Two types of drum-like 30- and 32-metal Cd–Ln nanoclusters [Ln8Cd24L12(OAc)48] (Ln = Sm (1), Yb (2), Er (3)) and [Er8Cd22L12(OAc)38(OH)6] (4) were constructed using a designed Schiff base ligand built around a flexible (CH2)7 chain. Hydroxide (OH−) anions are found in the structure of 4, indicating that the basic environment favors the formation of the 30-metal cluster. The chromogenic Cd/L components in these clusters can act as efficient sensitizers for lanthanide luminescence. With the Ln(III) centers enclosed within the drum-like structures, 1–4 display the typical emission spectra of lanthanide ions. For the Cd–Er clusters, 3 exhibits better NIR luminescence properties than 4. The long-chain Schiff base ligands show “linear” configurations in these clusters, resulting in the large sizes of 1–4. The drum-like structures of 1–4 have inner cavities with the internal sizes approximately 6 × 11 × 11 A, and some solvent molecules such as H2O, MeOH and EtOH are enclosed in the drums. Interestingly, the Cd–Sm cluster 1 shows visible and NIR luminescent sensing of metal cations and exhibits high selectivity to Zn2+ and Fe3+ ions.
TL;DR: A new coumarin-thiazole based Schiff base (Ligand, L) and its Pd(II), Pt(II) complexes; ([Pd( L)2] and [Pt(L)2]), were synthesized and characterized using spectrophotometric techniques, and the reaction mechanisms of L with CN-, F- and AcO- ions showed that the reaction of L was due to the deprotonation and addition mechanisms at the same time.
Abstract: A new coumarin-thiazole based Schiff base (Ligand, L) and its Pd(II), Pt(II) complexes; ([Pd(L)2] and [Pt(L)2]), were synthesized and characterized using spectrophotometric techniques (NMR, IR, UV-vis, LC-MS), magnetic moment, and conductivity measurements. A single crystal X-ray analysis for only L was done. The crystals of L have monoclinic crystal system and P21/c space group. To gain insight into the structure of L and its complexes, we used density functional theory (DFT) method to optimize the molecules. The photophysical properties changes were observed after deprotonation of L with CN- via intermolecular charge transfer (ICT). Additionally, as the sensor is a colorimetric and fluorimetric cyanide probe containing active sites such as coumarin-thiazole and imine (CH=N), it showed fast color change from yellow to deep red in the visible region, and yellow fluorescence after CN- addition to the imine bond, in DMSO. The reaction mechanisms of L with CN-, F- and AcO- ions were evaluated using 1H NMR shifts. The results showed that, the reaction of L with CN- ion was due to the deprotonation and addition mechanisms at the same time. The anti-cancer activity of L and its Pd(II) and Pt(II) complexes were evaluated in vitro using MTT assay on the human cancer lines MCF-7 (human breast adenocarcinoma), LS174T (human colon carcinoma), and LNCAP (human prostate adenocarcinoma). The anti-cancer effects of L and its complexes, on human cells, were determined by comparing the half maximal inhibitory concentration (IC50) values. The activity results showed that, the Pd(II) complex of L has higher anti-tumor effect than L and its Pt(II) complex against the tested human breast adenocarcinoma (MCF-7), human prostate adenocarcinoma (LNCAP), and human colon carcinoma (LS174T) cell lines.
TL;DR: In this article, three heteronuclear cobalt(III)/sodium Schiff base complexes have been synthesized and characterized by elemental and spectral analysis, and the structures of all three complexes were confirmed by single crystal X-ray analyses.
Abstract: Three heteronuclear cobalt(III)/sodium Schiff base complexes have been synthesized and characterized by elemental and spectral analysis. The structures of all three complexes have been confirmed by single crystal X-ray analyses. Each of these three complexes crystallizes in monoclinic space group P21/c. In each complex, cobalt(III) is placed in the inner N2O2 compartment and sodium is placed in the outer O2O′2 compartment (O and O′ denote the phenolic and ethoxy/methoxy oxygen atoms, respectively) of the Schiff bases. With decrease in steric hindrance around the O2O′2 compartment by the replacement of ethyl groups with methyl groups, tetranuclear complexes resulted instead of dinuclear ones. Interesting carbon bonding interactions in the solid state of the complexes have been studied by means of DFT calculations using several computational tools such as “atoms-in-molecules” (AIM) and natural bond orbital (NBO) analyses.
TL;DR: In this article, a new mono cationic Schiff base complexes were designed and synthesized from salicylalidene-4-imino-2,3-dimethyl-1-phenyl-3-pyrazolin-5-one and 2-aminothiazole.
TL;DR: Two types of Zn-Ln nanoclusters were prepared using one long Schiff base ligand (H2L) with a naphthyl backbone and two short polydentate ligands (H 2L′ and H2L′).
Abstract: Two types of Zn–Ln nanoclusters [Nd2Zn2L2(L′)2(OAc)2(NO3)2(H2O)2] (1) and [Ln6Zn6L2(L′′)2O2(OAc)18] (Ln = Nd (2) and Sm (3)) were prepared using one long Schiff base ligand (H2L) with a naphthyl backbone and two short polydentate ligands (H2L′ and H2L′′). 1 and 2–3 show linear and planar structures with sizes of approximately 10 × 10 × 30 A and 10 × 15 × 22 A, respectively. The chromogenic Zn/ligand components can act as efficient sensitizers for lanthanide luminescence, and thus 1–3 show visible and NIR emissions. In these clusters, the Schiff base ligands display a “U-shaped” configuration, which is suitable to form π⋯π interactions and hydrogen bonds with nitro aromatic compounds. Interestingly, Zn–Sm cluster 3 shows visible and NIR luminescence sensing of nitro explosives and exhibits high sensitivity to 1,4-DNB and TNT at the ppb level.
TL;DR: In this paper, the design and synthesis of two Co2+ and Zn2+ phthalocyanine (PC)-based redox active metal-organic conjugated microporous polymers (MO-CMP), CoCMP and znCMP, respectively, obtained by a Schiff base condensation reaction.
TL;DR: In this article, nanosized Schiff-base Cu/Ni complexes and their oxides showed remarkable catalytic activity towards the selective oxidation of benzyl alcohol (BzOH) in aqueous H2O2/dimethylsulfoxide (DMSO) solution.
Abstract: In this work, nanosized Cu and Ni Schiff-base complexes, namely ahpvCu, ahpnbCu, and ahpvNi, incorporating imine ligands derived from the condensation of 2-amino-3-hydroxypyridine, with either 3-methoxysalicylaldehyde (ahpv) or 4-nitrobenzaldehyde (ahpnb), were synthesized using sonochemical approach. The structure and properties of the new ligands and their complexes with Ni(II) and Cu(II) were determined via infrared (IR), nuclear magnetic resonance (NMR), electronic spectra (UV-Vis), elemental analysis (CHN), thermal gravimetric analysis (TGA), molar conductivity (Λm), and magnetic moment (μeff). The combined results revealed the formation of 1:1 (metal: ligand) complexes for ahpvCu and ahpvNi and 1:2 for ahpnbCu. Additionally, CuO and NiO nanoparticles were prepared by calcination of the respective nanosized Cu/Ni complexes at 500 °C, and characterized by powder X-ray diffraction (XRD) and transmission electron microscopy (TEM). Significantly, the as-prepared nanosized Schiff-base Cu/Ni complexes and their oxides showed remarkable catalytic activity towards the selective oxidation of benzyl alcohol (BzOH) in aqueous H2O2/ dimethylsulfoxide (DMSO) solution. Thus, catalytic oxidation of BzOH to benzaldehyde (BzH) using both ahpvCu complex and CuO nanoparticles in H2O2/DMSO media at 70 °C for 2 h yielded 94% and 98% BzH, respectively, with 100% selectivity.
TL;DR: It is found that solvent-free catalytic reaction conditions offer good catalytic conversion in the case of cyclic carbonates, and for sulfoxide, good conversion and selectivity are achieved in the presence of DCM as a solvent medium under ambient reaction conditions.
Abstract: Herein, a zinc(ii)-based 3D mixed ligand metal organic framework (MOF) was synthesized via versatile routes including green mechanochemical synthesis. The MOF {[Zn(ATA)(L)·H2O]}n (ZnMOF-1-NH2) has been characterized by various physico-chemical techniques, including SCXRD, and composed of the bipyridyl-based Schiff base (E)-N'-(pyridin-4-ylmethylene)isonicotinohydrazide (L) and 2-aminoterephthalic acid (H2ATA) ligands as linkers. The MOF material has been explored as a multifunctional heterogeneous catalyst for the cycloaddition of alkyl and aryl epoxides with CO2 and sulfoxidation reactions of aryl sulfides. The influence of various reaction parameters is examined to optimize the performance of the catalytic reactions. It is found that solvent-free catalytic reaction conditions offer good catalytic conversion in the case of cyclic carbonates, and for sulfoxide, good conversion and selectivity are achieved in the presence of DCM as a solvent medium under ambient reaction conditions. The chemical and thermal stability of the catalyst are excellent and it is active for up to four catalytic cycles without significant loss in activity. Furthermore, based on the catalytic activity and structural evidence, a plausible mechanism for both catalytic reactions is proposed.
TL;DR: In this paper, mesoporous silica nanoparticles (MSNs) were prepared by sol-gel method and functionalized with 3-aminopropyltriethoxysilane.
TL;DR: In this paper, the first systematic study of solvent effect on reductive amination of ketones with ammonia and dihydrogen (H2) over Ru/C, Rh/C and Pd/C catalysts was performed.
TL;DR: In this paper, four new Schiff base ester liquid crystal compounds, 4-((4ʹ-substituted phenylimino) methyl)phenyl-4″-alkoxybenzoates, Ina-d, were prepared and investigated for their mesophase formation and stability.
Abstract: Four new groups of Schiff base ester liquid crystal compounds, 4-((4ʹ-substituted phenylimino) methyl)phenyl–4″-alkoxybenzoates, Ina–d, were prepared and investigated for their mesophase formation and stability. Each group constitutes four homologous series that differ from each other by the polar substituent X (CH3O, CH3, H, and Cl). Within each homologous series, the number (n) of carbons in the alkoxy chain varies between 6, 8, 10, and 12. Molecular structures of the prepared compounds were confirmed via FT-IR, 1H NMR, mass spectroscopy, and elemental analysis. The mesomorphic properties were investigated by differential scanning calorimetry and polarised light microscopy. Comparative studies between the present series and previously investigated 4-(4-substituted phenylazo)phenyl 4″-alkoxybenzoates revealed that the phenylimino mesogenic core increases the mesophase stability rather than the azo analogues.
TL;DR: In this paper, a new N4-morpholinyl isatin-3-thiosemicarbazone (HL) has been proposed for antimicrobial activity in the presence of a monobasic tridentate ONS donor.