Schiff base

A series of novel N-(substituted)-2-[4-oxo-2-phenylquinazolin-3(4H)-yl] acetohydrazide derivatives were designed and synthesized, and their structures were characterized by 1H, 13C NMR, IR and Mass Spectral analysis. Their antimicrobial activity against bacterial strains and unicellular and multicellular pathogenic fungal strains were evaluated, and the results of in vitro antimicrobial evaluations of all newly synthesized compounds revealed that compounds 4(a-g) found to possess varied degree of antibacterial and antifungal activities Therefore, it can be inferred that presence of Schiff base nucleus in newly synthesized compounds can act as better system for antimicrobial activity. Lipinski rule were evident that all synthesized compounds have a good potential for development as an oral agent and can be potentially active drug candidate.

Schiff bases and their complexes are playing very important role in medicinal chemistry from ancient period because of their broad range of biological activities such as antibacterial, antifungal, antimalarial and antiviral etc. In this research project several Schiff bases have been synthesized from p-toluidine and derivatives of benzaldehyde to investigate the antibacterial activity. The synthesized Schiff bases have been characterized by IR and 1H-NMR spectral analysis. All the synthesized compounds have been screened for their in vitro antibacterial activity against gram (+) and gram (–) bacterial strains by disc diffusion method. Among the synthesized compounds, the compound 5 showed strong efficacy against E. coli and the others showed moderate activity against bacterial strains.

A new series of azetidinone derivatives have been synthesized due to the growing resistance of bacteria towards the â-lactam antibiotics. In our present study Oxadiazole is synthesized from semicarbazide is on condensation with substituted aldehyde to form Schiff base. The schiff bases are cyclized with chloroacetylchloride in triethylamine to yield the corresponding 2-azetidinones. Structures of synthesized compounds are confirmed by physical & spectral analysis. The compounds have screened for antimicrobial activity.

Fe (III) and Cu (II) metal complexes of Schiff base derived from ethylenediamine, succinic acid and formaldehyd. The newly synthesized Schiff base complexes were characterized by elemental analysis, Melting point, conductivity, IR and UV-VIS spectral methods. The absorption spectrum of CrL displayed only one low energy transition centered at 488 nm, which was attributed to 2A1g→2Eg transition indicating its square planer geometry.

Catalysis is an area of research which still continues to be a premier area of chemistry. It plays a key role in modern chemical technology. There are a large number of important organic transformations such as oxidation, hydrogenation, hydroformylation, carbonylation, polymerization and various coupling reactions. The majority of these novel catalysts are based on silica, primarily since silica displays many advantageous properties excellent stability (chemical and thermal), high surface area, good accessibility, and organic groups can be robustly anchored to the surface, to provide catalytic centers. However, it does have drawbacks it has limited stability in aqueous especially basic conditions, and it cannot easily be formed into membranes or into other forms which could be attached to novel reactors for use in intensive processing applications.

Tuberculosis is a serious threat to public health throughout the world. Schiff bases are compounds carrying the imine or azomethine (–C=N–) functional group. Recent studies report that benzimidazole based Schiff bases possess antibacterial, antimicrobial, anti-tubercular, and anti-inflammatory activities. 1,2 Further it has been known that fluoroaniline moiety can have profound and unexpected results in biological activity 19. A series of benzimidazole and fluroaniline based Schiff bases were designed and docked against crucial mtb enzyme target Glutamine synthetase1. The molecules with good docking-score and multiple interactions were chosen for synthesis. Compounds (BE1, BE2, FA-1, FA-2, and FA-3) were synthesized by reflux condensation reaction with good yield. The newly synthesized compounds were characterized by spectral methods and evaluated for anti- mycobacterial activity against tuberculosis H37RV strain. Anti-tubercular activity was carried out by using Microplate Alamar Blue Assay (MABA) method. The experimental results revealed that Compounds (BE1& BE2) showed promising anti-tubercular activity with an MIC below 0.8 mcg/mL while (FA-1, FA-2, and FA-3) showed moderate anti tubercular activity with an MIC below 6.25 and 12.5 mcg/mL. Key words: Benzimidazole, Schiff base, Fluoroaniline, Docking, Anti-tubercular.

Growing numbers of antibiotic-resistant bacteria are putting this golden era of medicine at risk and stresses the need for regular monitoring of antibiotic susceptibility, and developing a new design being active against resist pathogens. In this view seven Schiff base ligands of Cephalosporin group antibiotics were synthesized by their condensation with salicylaldehyde in equimolar ratio. Complexes of these Schiff bases with Pd (II) metal were synthesized in 1:2 stoichiometric ratio. The complexes were formulated as [Pd(L)2].3H2O, where L is Schiff base of seven different cephalosporin antibiotics. Complexes were characterized by elemental analyses, molar conductance, UV-Visible, FT-IR, 1H-NMR, 13C{1H}-NMR, 2D-NMR and ESI-Mass spectrometry. Schiff bases were coordinated with metal through phenolic oxygen and azomethine-N, giving simple square planar geometry to complexes. Complexes were tested for antibacterial activity and MIC against gram-negative bacteria E. coli and gram positive bacteria S. aureus and were found more potent than Schiff bases and precursor antibiotics.

A pestle and mortar-assisted solvent-free condensation of salicylaldehyde and 2-aminopyridine efficiently afforded a NO donor Schiff base ligand in high yield. This is an environmentally benign method, as satisfactory results were obtained in solvent free conditions with excellent yields, short reaction time, and operational simplicity in the experimental procedure. Copper(II) complex of this ligand were synthesized. Schiff base ligand and its complex were characterized by their melting point, elemental analysis, IR and 1H NMR spectra. In addition, DNA-binding properties of the metal complex were investigated using absorption spectroscopy, viscosity measurements and thermal denaturation methods. The DNA photoclevage experiment shows that, the complex act as effective DNA cleavage agent.

There has been an extensive effort all over the world to develop inorganic complexes which can withstand severe conditions of temperature, oxidation and hydrolysis. While there has been no breakthrough, considerable progress has been made in this direction. Many of these complexes show thermal stability much higher than that of the organic substrate, employed as ligands in the synthesis of metal complexes. These complexes offer academic interest and at the same time provide materials of desired and superior qualities which promise a variety of applications. The Schiff base complexes have been synthesized from 1-(5-chloro-2-hydroxyphenyl) ethanone with 1, 3-diaminopropane using Mn(II), Co(II), Cr(II), Ni(II), Cu(II), Zn(II) and Cd(II) ions and characterized by elemental, spectral and thermogravimetric analysis. The ligand acts as tetradentade molecule coordinating through deprotonated phenolic oxygen atoms and azomethine nitrogen atoms. The isolated products are colored solids and are soluble in DMF and DMSO. The thermogravimetric study indicates all the complexes are stable up to 60-700 C. All the complexes show half decomposition temperature (Table-3) and various kinetic and thermodynamics parameters have been evaluated from thermal data. The similarity in the values of kinetic parameters indicates a common decomposition reaction mode in all the complexes. The thermal activation energy of all the complexes has been calculated by Freeman-Carroll and Sharp-Wentworth methods.

A new series of novel substituted Gallic acid derivatives were synthesized by reacting methylated Gallic acid with hydrazine hydrate and then with various substituted aromatic aldehyde in mild and facile synthetic route to form various Schiff base derivatives.  Melting points of the synthesized compounds were determined by open capillary and are uncorrected. The purity of the compounds was checked using precoated TLC plates (MERCK, 60F) using chloroform: methanol (8:2) solvent system. The developed chromatographic plates were visualized under UV at 254nm. IR spectra were recorded using KBr on Josco FTIR model 8400 spectrophotometer, 1H NMR spectra in DMSO on a BRUKER FT-NMR instrument using TMS as internal standard. FAB mass spectra were recorded on JEOL SX 102 (DA-6000 mass Spectrometer) Data system using Argon (6KV.10MA) as the FAB gas. The designed compounds were screened for Antibacterial activity against Staphylococcus aureus and Escherichia coli and Antifungal activity against Aspergillus Niger in comparison with Ofloxacin and Fluconazole as standard to reveal the potency of synthesized derivatives. In accordance with the data obtained from antimicrobial activity, all the synthesized Schiff bases of substituted gallic acid have shown good activity against the tested microbes. Among these Schiff bases, compound bearing p-chloro group, o-chloro group, p-nitro group and m-nitro group has shown good activity against all the tested bacteria and fungi.