Amino 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.

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.

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.

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.

Formation of Ketimines from Aldimines in Schiff Base Condensation of Amino Acids and Imidazole-2-Carboxaldehydes: Tautomerization of Schiff Bases of Amino Acids Resulting in the Loss of Stereogenic Center

The Schiff base reaction of imidazole-2-carboxaldehydes with the anion of alanine, leucine and phenylalanine in the presence of nickel(II) ion gives the neutral NiL2 complexes. The Schiff base ligand, L, binds through an imidazole nitrogen, NIm, the amino acid nitrogen, NAA, and a carboxylate oxygen, O, atom. The two N2O ligands bind to the nickel(II) in a meridional fashion with the NIm and O of each ligand in trans positions. These ligands can exist as the anticipated aldimine, Im − CH = NAA − CH(R) − CO2−, or the ketimine, Im − CH2NAA = C(R) − CO2−, tautomer. Tautomerization of the initially formed aldimine Schiff base results in movement of the hydrogen atom of the alpha carbon of the amino acid to the aldehyde carbon, CAld, atom of the imidazole carboxaldehyde with resultant relocation of the imine double bond in the reverse direction. Ten structures of the structurally unprecedented ketimine tautomer, prepared from imidazole-2-carboxaldehydes and a pyrazole-3-carboxaldehyde, were presented. The structural data supported the formation of the ketimines in each case, while the aldimine tautomer was observed with imidazole-4-carboxaldehydes. A rationale of this can be explained on the basis of charge distribution in the likely intermediate in the tautomerization.

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.

Efficient Synthesis of a Schiff Base Copper(II) Complex Using a Microfluidic Device

The efficient synthesis of amino acid Schiff base copper(II) complexes using a microfluidic device was successfully achieved. Schiff bases and their complexes are remarkable compounds due to their high biological activity and catalytic function. Conventionally, products are synthesized under reaction conditions of 40 °C for 4 h using a beaker-based method. However, in this paper, we propose using a microfluidic channel to enable quasi-instantaneous synthesis at room temperature (23 °C). The products were characterized using UV–Vis, FT–IR, and MS spectroscopy. The efficient generation of compounds using microfluidic channels has the potential to significantly contribute to the efficiency of drug discovery and material development due to high reactivity.

Preferential Enrichment of Enantiomer from Amino Acid Schiff Bases by Coordination Interaction and Crystallization.

In this paper, preferential enrichment (PE) is described for three pairs of novel amino acid Schiff base Cu(II)/Cu(I) complexes. Single crystal X-ray diffraction indicated that 1-S/R are one-dimensional coordination polymers (CPs) with helical structures, and 2-S/R and 3-S/R are one-dimensional CPs with auxiliary ligands. By tuning the pH, the solvent and second ligands, the 1-S/R, 3-S/R underwent polymorphic transitions, resulting in enantioselective liberation of excess enantiomers into solution, until the deposited crystals were slightly enriched with the opposite enantiomer, thereby successfully exhibiting PE. However, under the effects of Cu(II), the solvent and low pH, 2-S/R did not exhibit PE and resulted in enrichment of racemic compounds, which was attributed to amino acid Schiff base chiral complex mechanisms of PE. The three pairs of Cu complex structures were characterized by UV-vis, MS and X-ray photoelectron spectroscopy (XPS). All chiral properties were studied by circular dichroism (CD) in the solid and liquid.

Synthesis, Identification and Antibacterial Activities of Amino Acid Schiff Base Cu(II) Complexes with Chlorinated Aromatic Moieties

Amino acid Schiff base Cu(II) complexes were synthesized under microwave irradiation using methanol as a solvent, to maximize the best conditions to obtain the attained compounds, containing aromatics possessing no, one or two chlorine atoms. The compounds’ antibacterial activities were tested against Gram-positive and Gram-negative bacteria, and the most active were tested for their antioxidant activities, and as E. coli, in particular, was found to be sensitive to these compounds, their interaction with this bacterium was investigated. It was found that, depending on the amino acid used for the formation of the Schiff base ligand, its LogPo/w mono-chlorinated or bis-chlorinated compounds are the most efficient against the tested bacteria.

Anti-tumor effect of novel amino acid Schiff base nickel (II) complexes on oral squamous cell carcinoma cells (CAL-27) in vitro

Anti-tumor effect of novel amino acid Schiff base nickel (II) complexes on oral squamous cell carcinoma cells (CAL-27) in vitro

Catalytic Dehydrogenative β-Alkylation of Amino Acid Schiff Bases with Hydrocarbon.

A synthetic method for the synthesis of a highly congested α,β-dehydroamino acid through the β-C-H bond activation of an amino acid Schiff base is described. Abundant hydrocarbon feedstock could be used as an alkylating reagent to afford an α,β-dehydroamino acid bearing a quaternary carbon at the γ-position with an exclusively (Z)-geometry. Notably, a tetrasubstituted olefin could be constructed from saturated starting materials. The transformation of the synthesized α,β-dehydroamino acid into unnatural α-amino acid derivatives was also demonstrated.

Spectroscopic study, theoretical calculations, and optical nonlinear properties of amino acid (glycine)-4-nitro benzaldeyhyde-derived Schiff base

Schiff base of amino acid salt: potassium 2-((4-nitrobenzylidene)amino)acetate 4 (C 9 H 7 KN 2 O 4 ), derived from the condensation reaction of amino acid (glycine) 1 and 4-nitro benzaldeyhyde 3 is synthesized and fully characterized by magnetic nuclear resonance ( 1 H and 13 C NMR), infrared (IR), mass, UV–visible spectroscopies and melting point. The optical nonlinear (ONL) properties of amino acid Schiff base salt 4 are studied using continuous wave (cw), visible, single transverse fundamental mode, low power, 473 nm laser beam. Ring diffraction patterns (RDPs) and Z-scan techniques are adopted to calculate the nonlinear index of refraction (NIR) together with testing the sample property of optical limiting (OLg). RDPs are simulated numerically using the integral of Fresnel-Kirchhoff and compared with experimental findings. • The Schiff base compound was synthesized and characterized by magnetic nuclear resonance ( 1 H and 13 C NMR). • We studied the nonlinear optical properties of Schiff base compound. • The nonlinear refractive index of this sample is determined using diffraction ring patterns and Z-scan techniques. . • Optical limiting threshold of Schiff base compound is found to be 9 mW.

Novel amino acid Schiff base Zn(II) complexes as new therapeutic approaches in diabetes and Alzheimer's disease: Synthesis, characterization, biological evaluation, and molecular docking studies.

Schiff bases are compounds that have gained importance in the paint industry due to their colorful nature and in the field of chemistry and biochemistry due to their biological activities. Various biological applications of Schiff bases, such as antitumor, antifungal, antibacterial, antioxidant, antituberculosis, and anthelmintic, have been widely studied. Within the scope of the study, 5-bromo-2-hydroxybenzaldehyde and amino acid methyl esters (isoleucine, phenylalanine, and methionine) and amino acid Schiff bases were synthesized first. The synthesis of the new Zn(II) complexes of these Schiff bases was carried out by the reaction of synthesized Schiff bases and Zn(OAc)2 ·2H2 O. The structures of the synthesized complexes were elucidated using elemental analysis, Fourier transform infrared, nuclear magnetic resonance, UV-visible, and thermal analysis spectroscopy techniques. These synthesized salts were found to be effective inhibitor compounds for the α-glycosidase, and acetylcholinesterase enzyme with Ki values in the range of 30.50 ± 3.82-38.17 ± 6.26 µM for α-glycosidase, 3.68 ± 0.54-10.27 ± 1.68 µM for butyrylcholinesterase, and 6.26 ± 0.83-15.73 ± 4.73 µM for acetylcholinesterase, respectively.

Antimicrobial Activities of Schiff Base Metal Complexes of First Transition Series

The correlative antimicrobial analysis of amino acid Schiff base and derivatized tren metal complexes: A= [MLCl2], B= [ML(CH3OH)2], respectively, against fungal strains, Candida parapsilosis, Candida albicans, Candida krusei, and Cryptococcus neoformans and (Gram-negative) P. aeruginosa, E. coli, S. typhimurium, and S. pyogenes, Methicillin-resistant Staphylococcus aureus (MRSA), S. mutans (Gram-positive) bacterial strains had been done by disk diffusion method following McFarland protocol. [CuLCl2] and [Cu (CH3OH)2] manifest overwhelming activity against microbes than other metal complexes of cobalt, nickel and zinc. Minimum inhibition concentration data also shows that copper complexes have the lowest MIC values against these tested microorganisms. The significance of this investigation is to uncover shielding and constructive therapeutic agents that wield against bacterial and fungal infection.