Acid Schiff Base Research Articles

Fluorescence Sensing of Cu2+ Ion and Some Organic Pollutants by Using Katiragum Dialdehyde‐α‐Amino Acid Schiff Bases in Aqueous Medium

AbstractEfficient and selective fluorescence sensors based on katiragum dialdehyde‐ amino acid Schiff's base is developed for fluorometric sensing to detect vanillin, Cu2+ ions and 4‐nitrophenol (4NP) in their aqueous solution. Two Schiff bases namely katiragum dialdehyde‐ arginine (KGDR) and katiragum dialdehyde‐ tryptophan (KGDT) are developed in the author's laboratory between which KGDR can detect vanillin with a detection limit of 60.29 nM whereas KGDT can detect both Cu2+ ion and 4NP with a detection limit of 72.6 nM and 97.83 nM respectively. KGDR and KGDT show significant quantum yields of 0.47 % and 0.25 % compared to a standard known substance fluorescein (0.97 %). The detection limit of vanillin, Cu2+ ions and 4NP are lower than other reported sensors. The developed Schiff base KGDR and KGDT show excellent recovery percentage and relative standard deviation (RSD) values in real sample analysis.

Synthesis, characterization and biological studies of transition metal complexes of dehydroacetic acid Schiff bases derived from 3-aminomethyl pyridine

The solid metal complexes of Cu (II), Ni (II), Fe (III), Co (II), Mn (II) and Cd (II) with DHA Schiff base ligand derived from DHA and aromatic primary amine 3-aminomethyl pyridine were synthesized and characterized by elemental analysis, spectroscopic techniques (FTIR, UV-VIS, 1HNMR and XRD), magnetic susceptibility measurement, thermogravimetric analysis and differential thermal analysis (TGA/DTA) and investigated for biological activities like anti-bacterial, ant-fungal, antioxidant and anticancer activity. The structure of synthesized DHA Schiff base ligand and all metal complexes were confirmed by spectroscopic methods, stability of complexes was studied by TGA/DTA. DHA Schiff base ligand and all metal complexes were found to be biologically active.

Isatin-based ibuprofen and mefenamic acid Schiff base derivatives as dual inhibitors against urease and α–glucosidase: In vitro, in silico and cytotoxicity studies

α-Glucosidase and urease inhibitors have emerged as crucial for developing therapeutic drugs targeting diabetes and gastrointestinal disorders. This study reports on new series of ibuprofen and mefenamic acid Schiff base derivatives incorporating isatin as dual inhibitors of α-glucosidase and urease enzymes. These synthesized derivatives (7a-r) were structurally characterized by 1H NMR, 13C NMR and HRMS (EI). Biological evaluation (IC50) identified several derivatives i.e.,7a (urease = 17.37 ± 1.37 µM, α-glucosidase = 44.1 ± 1.15 µM), 7j, (urease = 16.61 ± 1.37 µM, α-glucosidase = 81.2 ± 1.33 µM), 7o, (urease = 18.63 ± 1.27 µM, α-glucosidase = 70.3 ± 1.14 µM), 7r (urease = 11.36 ± 1.32 µM, α-glucosidase = 39.3 ± 1.17 µM), as dual inhibitors of urease (thiourea 21.37 ± 1.76 µM) and α–glucosidase (acarbose 375.82 ± 1.76 µM) enzymes. These bioactive derivatives were explored for cell viability studies against mononuclear cells revealing a good cytocompatibility. In silico molecular docking studies were also conducted to predict the binding mode of new derivatives with target enzymes that were found consistent with the results of in vitro research.

Design amino acids Schiff base ligands and their Cu(II) and Zn(II) complexes as potent anticancer agent on human lung carcinoma, efficient CT-DNA binder, antibacterial and mesomorphic properties

A new mesogenic amino acid Schiff base ligands of the type Potassium (E)-4-((4-(hexadecyloxy)-2-hydroxybenzylidene)amino)butanoate (HL1) and Potassium (E)-6-((4-(hexadecyloxy)-2-hydroxybenzylidene)amino)hexanoate (HL2) and their copper(II) and zinc(II) complexes have been successfully synthesized and characterized by various elemental analyses, UV–visible, FT-IR, 1HNMR , 13CNMR , ESI-MS and thermogravimetric analysis (TGA). Both the ligands were found to exhibit mesophase with multiple textures as revealed from the polarizing optical microscope (POM) and differential scanning calorimetry (DSC). The metal complexes were found to exhibit efficient CT-DNA interaction and antibacterial activity against both Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli). The complexes were assessed for their in-vitro anticancer efficacy against A549 cell line and findings indicate notable cytotoxicity effect which is comparable to that of standard drug, cisplatin. The Density Functional Theory (DFT) study of the compounds was carried out by using LanL2DZ and 6–31 G (d, p) basis set with meta-hybrid Truhlar's functional M06–2X in order to obtain the optimized geometry.

Design, synthesis, molecular docking study, and α-glucosidase inhibitory evaluation of novel hydrazide–hydrazone derivatives of 3,4-dihydroxyphenylacetic acid

A series of novel Schiff base derivatives (1–28) of 3,4-dihydroxyphenylacetic acid were synthesized in a multi-step reaction. All the synthesized Schiff bases were obtained in high yields and their structures were determined by 1HNMR, 13CNMR, and HR-ESI–MS spectroscopy. Except for compounds 22, 26, 27, and 28, all derivatives show excellent to moderate α-glucosidase inhibition. Compounds 5 (IC50 = 12.84 ± 0.52 µM), 4 (IC50 = 13.64 ± 0.58 µM), 12 (IC50 = 15.73 ± 0.71 µM), 13 (IC50 = 16.62 ± 0.47 µM), 15 (IC50 = 17.40 ± 0.74 µM), 3 (IC50 = 18.45 ± 1.21 µM), 7 (IC50 = 19.68 ± 0.82 µM), and 2 (IC50 = 20.35 ± 1.27 µM) shows outstanding inhibition as compared to standard acarbose (IC50 = 873.34 ± 1.67 µM). Furthermore, a docking study was performed to find out the interaction between the enzyme and the most active compounds. With this research work, 3,4-dihydroxyphenylacetic acid Schiff base derivatives have been introduced as a potential class of α-glucosidase inhibitors that have remained elusive till now.

Verification of the Inverse Scale Effect Hypothesis on Viscosity and Diffusion by Azo-Amino Acid Schiff Base Copper Complexes

Microdroplets generated in microfluidic devices are attracting attention as a new chemical reaction field and are expected to improve reactivity. One of the effects of microscaling is that the ratio of the force that acts on the diffusion and movement of substances to gravity is different from that of ordinary solvents. Recently, we proposed a hypothesis for determining reaction acceleration through micro-miniaturization: If a reaction is inhibited by setting the volume and viscosity of the solution to conditions that are unfavorable to the reaction on a normal scale, that reaction can be promoted in microfluidics. Therefore, for the purpose of this verification, (1) we used an amino acid Schiff base copper(II) complex with an azobenzene group to demonstrate the polarization-induced orientation in a polymer film (the redirection that is mechanically maintained in a soft matter matrix). Numerical data on optical anisotropy parameters were reported. (2) When the reaction is confirmed to be promoted in laminar flow in a microfluidic device and its azo derivative, a copper(II) complex is used to increase the solvent viscosity or diffusion during synthesis on a normally large scale. We will obtain and discuss data on the investigation of changing the solvent volume as a region. The range of experimental conditions for volume and viscosity did not lead to an improvement in synthetic yield, nor did (3) the comparison of solvents and viscosity for single-crystal growth of amino acid Schiff base copper(II) complexes having azobenzene groups. A solvent whose viscosity was measured was used, but microcrystals were obtained using the diffusion method.

Oxovanadium (IV) Complexes of α-Amino Acid Schiff Bases and 2,2'-Bipyridine Ligands: Synthesis, Characterization and Investigation of their Biological Potency

Five new oxovanadium(IV) complexes of the type [VO(L)(bpy)], [where L= 3-hydroxybenzaldehyde-α-alanine (hb-ala), 3-hydroxybenzaldehyde-DL-phenylalanine (hb-pheala), 3-hydroxybenzaldehyde-leucine (hb-leu), 3-hydroxybenzaldehyde-glycine (hb-gly) and 3-hydroxybenzaldehyde-DL-methionine (hb-met) and bpy = 2,2´-bipyridine] have been synthesized and characterized by some physicochemical properties, molar conductance, magnetic susceptibilities measurements, elemental analysis, UV-Visible and FTIR and ESI-MS spectral studies. The molar conductance values showed that the complexes are non-electrolytic in nature. The magnetic moment values of the complexes are in accordance with the d1 electronic configuration of the VIVO2+ moiety and indicates the paramagnetic nature of the complexes. IR spectral data indicates the coordination of tridentate amino acid Schiff base ligands to the vanadyl (VO2+) ion through O, N, O-donor. ESI-MS spectral studies supports the proposed structure of the complexes. The magnetic moment value coupled with electronic spectral data suggested the distorted octahedral geometry of the complexes. All the complexes were screened for their antibacterial activity against three human pathogenic bacteria- Escherichia coli, Staphylococcus aureus and Bacillus cereus with Kanamycin (K-30) standard. The result shows that all the complexes possess to have moderate to strong potential antibacterial activity against all the tested pathogens.

Photocatalytic dye degradation and hydrogen peroxide sensing by a novel copper-Schiff base complex prepared via mechanochemical method

ABSTRACT Water pollution, primarily caused due to hazardous organic and inorganic substances, is a cause of concern for human health and development, for it manifests adverse repercussions across health, economic, and social dimensions. The footprints of its adverse effects are also left on aquatic/marine life forms. In the light of the negative impacts of such substances, the development of efficient remediation techniques becomes pertinent. In this article, we report a water-soluble glutamic acid Schiff base copper complex (Cu-GSb) that has been synthesised by taking recourse to a mechanochemical approach, relying upon solid-state reagent interactions in a benign environmental setting, eluding a rigorous refluxing condition and overuse of solvents. The experimental results revealed that the ligand coordinates to the metal centre in a bidentate fashion through the imine nitrogen and carboxylate oxygen, respectively, adopting a distorted square planar geometry. Further, the complex’s utility in mitigating chemical hazards has been demonstrated through the studies involving degradation of organic dyes like methylene blue and bromocresol green, and decomposition/sensing of H2O2. Notably, as a photocatalyst towards the degradation of above-mentioned dyes under visible light irradiation, our study showed the photocatalytic efficiency of Cu-GSb to be ~95% in 50–60 min. The rate of degradation reaction has been found to follow first-order kinetics with rate constant values of 6 × 10−2 and 5.66 × 10−2 min−1 for MB and BCG, respectively. Furthermore, the results of H2O2 sensing evaluation revealed that the complex is capable of potentially decomposing H2O2 in about 20–30 min. The compounds have been routinely characterised by UV–visible spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, and proton nuclear magnetic resonance (1H NMR).

Oxovanadium (IV) Complexes of α-Amino Acid Schiff Bases and Polypyridyl Ligands: Synthesis, Characterization and Antimicrobial Activity

Oxovanadium(IV) complexes of the type [VO(L)(bpy)] (V-1 to V-5) have been synthesized and characterized by FTIR and UV-Vis spectra, molar conductance, melting points, and magnetic susceptibilities measurements, where L= N-salicylidene-β-alanine (sal-ala), N-salicylidene-glycine (sal-gly), N-salicylidene-DL-β-phenylalanine (sal-pheala), N-salicylidene-leucine (sal-leu), and N-salicylidene-DL-methionine (sal-met), and bpy is 2,2´-bipyridine. The infrared spectral data reveals that the tridentate nature of the amino acid-based Schiff base ligand and the coordination of the ligand through azomethine nitrogen, phenolic oxygen and carboxylate oxygen with vanadyl (VO2+) ion. All of these complexes were determined to be non-electrolyte in nature, according to conductivity measurements. The magnetic moment measurements have been attributed that these complexes are paramagnetic and have d1 configuration of vanadium (IV) ion. In Virto antimicrobial activity of the synthesized complexes was evaluated against two gram-positive (Bacillus subtilis and Staphylococcus aureus) and two gram-negative (Escherichia coli, Proteus vulgaris) bacterial strains.

New oxidation catalysts based on copper complexes with salicylidene-amino acids Schiff bases onto SBA-15 support

New mononuclear Cu(II) complexes with Schiff base derived from salicylaldehyde condensed with alanine (Ala), phenylalanine (Fen), glycine (Gli) and histidine (His) amino acids were synthesized and covalently anchored onto an amino-functionalized SBA-15 mesoporous silica in order to obtain efficient heterogeneous catalysts. The elemental, structural, textural and morphological characterization confirmed the structure of the synthesized complexes and their successful immobilization into the inner pore surface of the NH2-functionalized support without the loss of the mesoporous structure. The catalytic activity of the free or immobilized Cu(II) complexes was tested in oxidation of styrene with H2O2 under mild conditions with very good results.

Desymmetrization of Geminal Difluoromethylenes using a Palladium/Copper/Lithium Ternary System for the Stereodivergent Synthesis of Fluorinated Amino Acids

AbstractFluorinated amino acids and related peptides/proteins have been found widespread applications in pharmaceutical and agricultural compounds. However, strategies for introducing a C−F bond into amino acids in an enantioselective manner are still limited and no such asymmetric catalysis strategy has been reported. Herein, we have successfully developed a Pd/Cu/Li ternary system for stereodivergent synthesis of chiral fluorinated amino acids. This method involves a sequential desymmetrization of geminal difluoromethylenes and allylic substitution with amino acid Schiff bases via Pd/Li and Pd/Cu dual activation, respectively. A series of non‐natural amino acids bearing a chiral allylic/benzylic fluorine motif are easily synthesized in high yields with excellent regio‐, diastereo‐, and enantioselectivities (up to >20 : 1 dr and >99 % ee). A density functional theory (DFT) study revealed the F−Cu interaction of the allylic substrate and the Cu catalyst significantly influence the stereoselectivity.

Desymmetrization of Geminal Difluoromethylenes using a Palladium/Copper/Lithium Ternary System for the Stereodivergent Synthesis of Fluorinated Amino Acids.

Fluorinated amino acids and related peptides/proteins have been found widespread applications in pharmaceutical and agricultural compounds. However, strategies for introducing a C-F bond into amino acids in an enantioselective manner are still limited and no such asymmetric catalysis strategy has been reported. Herein, we have successfully developed a Pd/Cu/Li ternary system for stereodivergent synthesis of chiral fluorinated amino acids. This method involves a sequential desymmetrization of geminal difluoromethylenes and allylic substitution with amino acid Schiff bases via Pd/Li and Pd/Cu dual activation, respectively. A series of non-natural amino acids bearing a chiral allylic/benzylic fluorine motif are easily synthesized in high yields with excellent regio-, diastereo-, and enantioselectivities (up to >20 : 1 dr and >99 % ee). A density functional theory (DFT) study revealed the F-Cu interaction of the allylic substrate and the Cu catalyst significantly influence the stereoselectivity.

Anti-carcinoma and anti -microbial behavioral studies for octahedral synthesized Schiff base metal complexes

2,2′-((1Z-1′Z) (1,3-diphenylpropane-1,3-diylidene) bis (azanylylidene)) dibenzoic acid (H2L) Schiff base ligand, derived from condensation reaction in a molar ratio 2:1 between anthranilic acid and dibenzoyl methane, respectively. Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) complexes were obtained from 1:1 (ligand: metal salt) reaction. Elemental analyses, IR, 1H NMR, UV–Vis, ESR, mass spectra, conductivity, and magnetic susceptibility measurements as well as thermal (TG/DTG) analyses have been used to conclude the molecular structure of the prepared complexes. From the analytical and spectroscopic tools, the stoichiometry of the complexes was found to be of ML type with octahedral geometry. The conductivity values supported the electrolytic nature of Cr(III) and Fe(III) complexes and non- electrolytic nature of the remaining complexes. From IR studies, the involvement of two azomethine nitrogen atoms and two carboxylate oxygen has been proved as tetradendate binding sites of the ligand. Screening Schiff base and its complexes for their antimicrobial activity against Streptococcus pneumoniae and Bacillus subtilis as G + bacteria; Pseudomonas aeruginosa and Escherichia coli as G− bacteria) and fungi (Aspergillus fumigatus; Syncephalastrum racemosum; Geotricum candidum and Candida albicans) has been conducted by disk diffusion method. The Comparison between the antimicrobial activity of the metal complexes and the free ligand showed the advancement of the metal complexes. Unfortunately, no promising anti-tumor activity has been detected for the ligand and its metal complexes as they were evaluated against human cancer (MCF-7 cells viability).

Synthesis, Characterization, DFT calculations and molecular Docking study of Novel Copper mixed ligands complex on Drosophila melanogaster for insecticidal properties

In this study, the novel mixed ligand complex of copper is prepared from (Z)-N’-((E)-2-hydroxy-3,5-diiodobenzylidene)-N,N-dimethylcarbamohydrazono-thioic acid schiff base(H2L)and 2,2’-bypyridine. The characterization has been done by NMR, elemental analysis, IR and HRMS. Computation calculations based on DFT showed that the HOMO-LUMO energy gap is -5.81 eV for ligand and -5.53 eV for the Cu(II) complex and the [Cu(L)(bipy)] is having square pyramidal geometry. The binding energy values obtained from the molecular docking with acetylcholinesterase enzymes of Drosophila melanogaster for ligand (H2L) and [Cu(L)(bipy)] are -6.8 and -7.4 (kcal/mol) respectively. These values showed that the ligand (H2L) and [Cu(L)(bipy)] are having affinity for the target enzyme.

Synthesis, Characterization, and Toxicity Studies on Three Amino Acid Schiff-Base Ligands and Their Potential Binding Sites to Ni(II) ion: Comparison with Computational Density Functional Theory (DFT) Studies

Synthesis, Characterization, and Toxicity Studies on Three Amino Acid Schiff-Base Ligands and Their Potential Binding Sites to Ni(II) ion: Comparison with Computational Density Functional Theory (DFT) Studies

Amino acid Schiff bases as efficient corrosion inhibitor for mild steel in aqueous H2SO4: a comparative study

Amino acid Schiff bases as efficient corrosion inhibitor for mild steel in aqueous H2SO4: a comparative study

Glycine methyl ester based Schiff base bearing long alkoxy arm and its zinc(II) and copper(II) complexes: Synthesis, mesomorphism, photoluminescence, CT-DNA interaction and DFT study

A new photoluminescent mesogenic glycine methyl ester based Schiff base ligand and its zinc(II) and copper(II) complexes have been synthesised. The compounds were characterized by elemental analyses, Fourier transform infrared spectroscopy (FT-IR), 1H, 13C nuclear magnetic resonance (NMR), ultraviolet–visible spectroscopy (UV–Vis), ESI-MS, MALDI-TOF, EDX and thermogravimetric analysis (TGA). The polarizing optical microscopy (POM) and differential scanning calorimetry (DSC) study revealed that the ligand and zinc(II) complex possess SmecticA mesophase on heating but copper(II) complex is non-mesogenic. The optical absorption and fluorescence spectroscopy studies of zinc(II) complex indicate the existence of aggregation/ de-aggregation species in the presence of non-coordinating and coordinating solvents. The Density Functional Theory (DFT) study was carried out using LanL2DZ and 6–31 G (d, p) basis set with meta-hybrid Truhlar's functional M06–2X to obtain a stable, optimized structure, HOMO-LUMO energy gap and chemical hardness. As designed, the combination of both the –CN- and -COO- linkages plays significant role to influence the mesomorphic behaviour as well as biogenic properties of the compounds. The in vitro interactions of the compounds with CT-DNA has been investigated using UV–Vis and fluorescence spectroscopy. To the best of our knowledge, this is one of the few report on DNA binding studies of mesogenic amino acid Schiff base, which is having binding constant in the same range with the gold standard compound, ethidium bromide.

Syntheses and characterizations of 2-nitrobenzaldehyde amino acid Schiff base reductive amination compounds

Condensation of 2-nitrobenzaldehyde with five amino acid compounds (valine, glycine, leucine, aspartic acid, and glutamic acid) gives the corresponding Schiff bases, which upon treatment with sodium borohydride afford the reductive amination products 1−5. Compounds 1−5 have been well characterized by FT-IR and 1H NMR spectroscopic techniques, in addition to X-ray crystallography, from which the structure of compound 2 has been established. Compound 2 crystallizes in monoclinic space group P21/c, with a = 12.215(8), b = 8.096(5), c = 10.608(7) Å, β = 115.324(7), and Z = 4.

Design of Y-Shaped Trimers of Chiral Phase-Transfer Catalysts for the Asymmetric Alkylation of Amino Acid Derivatives

AbstractA series of soluble Y-shaped trimers of chiral phase-transfer catalysts were synthesized and utilized in the asymmetric alkylation of amino acid Schiff bases. The length of the linker between the ammonium cation of the simplified Maruoka catalyst and a phloroglucinol moiety was varied and excellent yields and enantioselectivity were observed when using the Y-shaped trimer of chiral phase-transfer catalyst with an octamethylene linker. A theoretical study of the most efficient Y-shaped trimer of chiral phase-transfer catalyst suggests the chiral ammonium center of the catalyst is more exposed and thus more available in the reaction.

Experimental and Insilico Evaluations of Transition Metal Complexes with L-Histidine (N, N Donor) Schiff Base Ligand and Its Biological Applications in Ovarian and Melanoma Cancer Cell Lines

Schiff base metal complexes are essential in modern coordination chemistry. It owns modern structural features and finds several uses in various fields, including pharmaceuticals, agriculture, dyeing, polymer science, food packaging, O2 detection, various biological systems, catalysis, and birth control. The Chemistry of Schiff base ligands and their metal complex increased, encompassing a wide range of organometallic compounds and bio-inorganic chemistry. Schiff bases belong to the class of organic compounds regarded as particularly significant. They have been investigated extensively in the past few years and have attracted much attention due to their appealing chemical and physical features. They are versatile and have a broader range of applications, such as anti-cancer, anti-fungal, anti-microbial, antiulcer, anti-tumor, anti-diabetic, herbicidal, anti-proliferative, and anti-inflammatory actions. The aim and objective of our research are to synthesize a series of five new Zn (II), Ni (II), Cu (II), Mn (II), and Co (III) of bis-3-(4.5-Dihydro-3 H-imidazol-4-yl)-2-[(4-methoxy-benzylidine)-amino]- propionic acid Schiff base metal complexes and to characterize those complexes by elemental analysis, UV-Visible, FT- IR, and Mass spectral studies. Bis-3-(4.5-Dihydro-3 H-imidazol-4-yl)-2-[(4-methoxy-benzylidine)-amino]-propionic acid ligand coordinates to metal ions as bidentate N and O donors. Biological studies of the synthesized Schiff base complex have also been investigated by anti-microbial, radical scavenging, docking study, anticancer analysis, and cytotoxic studies. Based on the analytical and spectral results, tetrahedral geometry has been tentatively proposed for all complexes except that of cobalt. The antioxidant studies of the Schiff base ligand and Schiff base complexes exhibit significant free radical scavenging activity against DPPH. Invitro cytotoxic activity of the Schiff complexes was evaluated against the over3 (ovarian) and melanoma cell lines (MCF14). The docking studies have been carried out using BSA protein and DNA biomolecules with synthesized metal complexes. Antimicrobial studies demonstrated the effectiveness against gram-positive and gram-negative bacteria.