Synthesis, characterization and antimicrobial studies of Schiff base complexes

Comparison study (experimental and theoretical), hydrogen bond interaction through water, donor acceptor investigation and molecular docking study of 3,3-((1,2-phenylenebis (azaneylylidene)) bis (methaneylylidene)) diphenol

The novel Schiff's base (CS6) was synthesized and confirmed by various studies. The B3LYP/cc-pVDZ basis set was used for theoretical study and the results indicated that both the theoretical and experimental studies correlated well. The interaction energy of CS6-water complex calculated by using the local energy decomposition analysis was found to be -7.28 kcal/mol. The TD-TFT method was used for the calculation of electronic absorption spectrum. This study confirmed that the observed wavelength and the simulated wavelength in the electronic spectra were almost similar. The electrophilic and nucleophilic attacking sites of the titled compound were identified by using FMO and MEP studies. The highest stabilization energy (30.19 kcal/mol) formed by LP (2) O24 to anti-bonding σ*(C18-C19) was confirmed by the NBO study. The localized and delocalized electrons were confirmed by ELF and LOL studies. The hydrogen bond interaction as well as the physical and chemical properties of CS6 indicated that it showed a moderate similarity to the drugs. The docking study confirmed that the dehydro-L-gulonate decarboxylase inhibitor (1Q6O) could interact with CS6 compound with the binding energy of -5.26 kcal/mol.Communicated by Ramaswamy H. Sarma.

Synthesis, Characterization, and Anticancer Potency of Branched Poly (p-Hydroxy Styrene) Schiff-Bases

A significant issue in cancer biology is finding anticancer therapies that effectively kill cancer cells. Through the use of several aldehydes, Schiff bases based on branched poly (p-hydroxy styrene) are created. The branched polymer is first chloroacetylated, then aminated with 1,4-phenylenediamine, and finally, aldehydes are reacted with the aminated polymer to produce the Schiff base compounds. Through the utilization of FTIR, TGA, XRD, NMR, and elemental analysis, all synthesized Schiff-bases are identified and characterized. Further, the antineoplastic potential of all Schiff bases is evaluated against different cancer cell lines. The results gained from this study indicate that the Schiff base polymers have cytotoxic power against cancer cells depending on cancer cell type and this antiproliferation potency is dose-concentration dependent. Importantly, the prepared S1 Schiff-base polymer shows potent cytotoxicity and is able to trigger the apoptosis and reactive oxygen species (ROS) in MCF-7 cells. Further, it downregulates VEGFR protein expression. The Schiff base polymers would have extensive applications in the biological disciplines.

Synthesis, biological and molecular docking studies of pyrimidine-derived bioactive Schiff bases

Pyrimidine which is an important constituent of the genetic material of deoxyribonucleic acid, is identified with a large number of biological activities. Based on this, pyrimidine-derived Schiff bases (1-6) of hydroxy-1-naphthaldehyde were synthesized by using the condensation method. In addition, the molecular docking studies against topoisomerase II DNA gyrase, human hematopoietic cell kinase, urate oxidase from Aspergillus flavus, and cyclin-dependent kinase 8 to explore the antibacterial, antioxidant, antifungal, and anticancer properties respectively and binding affinities through bioinformatics approaches to determine the interaction among active molecules with the receptor. Hence, the computational docking analyses identified that all synthesized pyrimidine Schiff bases (1-6) are active and exhibited better binding affinities as compared to the standard drugs. Furthermore, all the prepared materials were characterized by using nuclear magnetic resonance, infrared, and elemental analysis. Additionally, the phase-transition and thermal decomposition temperatures were determined by differential scanning calorimetry and thermo-gravimetric analysis measurements. Moreover, the structures of pyrimidine-derived Schiff bases 1, 2, 3, 4, and 5 were also confirmed by the X-ray single-crystal diffraction technique. The pyrimidine-derived Schiff bases 5 possess significant antibacterial, antioxidant, antifungal, and anticancer agent properties which confirms its promising biological activities over standard drugs.

Pyrene-based fluorescent chemosensor for rapid detection of water and its applications

This manuscript introduces a pyrene-based Schiff base L by reacting pyrenecarboxaldehyde with 2-aminothiazole in equimolar ratio. The ligand L was characterized by various spectral data and single crystal. The water sensing ability of L was examined in different organic solvents. The weakly emissive L in DMSO showed a fluorescence enhancement upon the addition of water. The water-induced fluorescence enhancement of L was occurred due to the combined effect of aggregation-induced emission (AIE) phenomenon and suppression of photo-induced electron transfer (PET) process. Using L, the water in DMSO can be detected down to 0.50 wt% with a quantification limit of 1.52 wt%. The analytical novelty of the developed sensor L was validated by detecting moisture in a variety of raw food products.

Experimental and Theoretical Biological Probing of Schiff Bases as Esterase Inhibitors: Structural, Spectral and Molecular Insights

The present study was designed to evaluate the in vitro and in silico potential of the Schiff bases (Z)-4-ethoxy-N-((5-nitrothiophen-2-yl)methylene)benzenamine (1) and (Z)-2,4-diiodo-6-((2-methyl-3-nitrophenylimino)methyl)phenol (2). These Schiff bases were synthesized according to a reported method using ethanol as a solvent, and each reaction was monitored on a TLC until completion of the reaction. The structures of both compounds were elucidated using spectroscopic techniques such as UV-Vis, FTIR, 1H NMR and 13C NMR. Molecular structure was determined using single-crystal XRD, which revealed that compounds 1 and 2 were monoclinic and triclinic, respectively. Hirshfeld surface analysis (HS) and 2D fingerprint plots were used to determine the intermolecular interactions along the contact contribution in the crystalline molecules. The structures of both compounds were optimized through a hybrid functional method B3LYP using the 6-31G(d,p) basis set, and various structural parameters were studied. The experimental and theoretical parameters (bond angle and bond length) of the compounds were compared with each other and are in close agreement. The in vitro esterase potential of the synthesized compounds was checked using a spectrophotometric model, while in silico molecular docking studies were performed with AutoDock against two enzymes of the esterase family. The docking studies and the in vitro assessment predicted that such molecules could be used as enzyme inhibitors against the tested enzymes: acetylcholine esterase (AChE) and butyrylcholine esterase (BChE).

Investigating the biological actions of some Schiff bases using density functional theory study

Schiff base ligands have wide varieties of application in several fields. One of which is the biological actions they possess such as anti-fungal, anti-bacterial, anti-malarial, and anti-viral characteristics. In this study, some synthesized phenylimino-based Schiff bases were investigated using density functional theory (DFT) to unravel their biological descriptors. The gas-phase quantum chemical calculation was done on the Schiff base 3-((E)-(phenylimino)methyl)benzene-1,2-diol and other synthesized analogues to evaluate their reactivity and stability properties including the substituent effect on the basic molecule. The Coulomb-attenuating method (CAM-B3LYP) functional was employed for the theoretical calculations. The Nuclear Magnetic Resonance (NMR), Fourier Transform-Infrared (FT-IR), Ultraviolet/visible spectroscopies calculated agrees with the experimental values. The obtained charge transfer and electronic features provide useful information regarding the active sites for biological application in the compounds.

Lewis Acid Promoted, One-Pot Synthesis of Fluoroquinolone Clubbed 1,3,4-Thiadiazole Motifs under Microwave Irradiation: Their Biological Activities

Background:

A Lewis acid promoted efficient and facile procedure for one-pot synthesis of a novel series of fluoroquinolone clubbed with thiadiazoles motifs under microwave irradiation is described here. This technique has more advantages such as high yield, a clean procedure, low reaction time, simple work-up and use of Lewis acid catalyst.

Objective:

Our aim is to generate a biologically active 1,3,4- thiadiazole ring system by using a onepot synthesis method and microwave-assisted heating. High yield and low reaction time were the main purposes to synthesize bioactive fluoroquinolone clubbed 1,3,4- thiadiazole moiety.

Methods:

Fluoroquinolone Clubbed 1,3,4-Thiadiazole Motifs was prepared by Lewis acid promoted, one-pot synthesis, under microwave irradiation. All the synthesized molecules were determined by IR, 1H NMR, 13C NMR, and Mass spectra. The antimicrobial activity of synthesized compounds was examined against two Gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa), two Gram-positive bacteria (Staphylococcus aureus, Streptococcus pyogenes), and three fungi (Candida albicans, Aspergillus niger, Aspergillus clavatus) using the MIC (Minimal Inhibitory Concentration) method and antitubercular activity H37Rv using L. J. Slope Method.

Results:

Lewis acid promoted, one-pot synthesis of Fluoroquinolone clubbed 1,3,4-Thiadiazole motifs under microwave irradiation is an extremely beneficial method because of its low reaction time and good yield. Some of these novel derivatives showed moderate to good in vitro antibacterial, antifungal, and antitubercular activity.

Conclusion:

One-pot synthesis of 1,3,4-Thiadiazole by using Lewis acid catalyst gives a good result for saving time and also getting more production of novel heterocyclic compounds with good antimicrobial properties via microwave heating method.

Synthesis, DNA Binding, and Molecular Docking Studies of Dimethylaminobenzaldehyde-Based Bioactive Schiff Bases

A new series of p-dimethylaminobenzaldehyde derivatives were tested for therapeutic potential by exploring their properties through characterization. The derivatives were synthesized by 1 : 1 condensation reaction of p-dimethylaminobenzaldehyde and substituted amines. The synthesized compounds 1–8 were characterized by different characterization techniques including IR, mass, 1H NMR, and 13C NMR spectroscopy, elemental analysis, and mass spectrometry. Furthermore, binding of these Schiff bases to Ct-DNA was examined by absorption spectroscopy, fluorescence quenching, circular dichroic, viscosity measurement, molecular docking, and molecular dynamics simulation methods. Schiff bases were tested for antimicrobial activity against bacterial species Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Staphylococcus aureus by the disc diffusion method. The pharmacological treatment of Schiff bases showed that 1–8 have promising potential against tested bacterial strains. The molecular docking study of the target compounds was also carried out against B-DNA dodecamer d(CGCGAATTCGCG)2, and it has been found that 1–8 can bind to Ct-DNA via an intercalative mode. DPPH free radical and hydrogen peroxide scavenging assays were employed to assess the antioxidant potential of synthesized Schiff bases.

Experimental and molecular topology-based biological implications of Schiff base complexes: a concise review

This review is a gentle introduction toward Schiff bases with special attention to bioinorganic aspects. Depending on the nature of condensation moieties (ketonic or aldehydic) with primary amine, a large number of novel compounds are reported every year with applicability in various material science aspects. Herein, a burgeoning literature overview is presented to provide a salient discussion of the current status of these molecular systems. Schiff bases are designed depending on the particular desirable properties. For instance, to enlighten a biologically relevant molecule, it is always appreciated when a prepared compound shows biological membrane crossing and nucleic acid linking potential. Under such purview, the Schiff base functional group can serve as an enhancer of biomembrane traversing capability. In addition to various other catalytic aspects, the type of disease to be encountered also matters. Nowadays, theoretical chemistry is applied before synthesizing a compound of this sort and fruitful results are first depicted and, if found feasible, a suitable synthetic route is followed to synthesize Schiff base compounds. Molecular charge topology analysis under theoretical expression is analyzed generally to predict the biological relevance of a molecule.

Synthesis, thermal behavior and optical characterizations of thin films of a novel thiazole azo dye and its copper complexes

In the present paper, a novel dye of 4-methyl-5-(4-acetylphenyldiazenyl)thiazol-2-amine (L) and its corresponding copper complexes are synthesized and characterized using different techniques including elemental analysis, thermal analysis, ¹H NMR, Mass, and FT-IR spectra. The thermal behavior of L and its complexes is carried out and discussed using thermogravimetric analysis, and it observed that the type of copper substituent affects the thermal decomposition of complexes. Homogenous thin films of L and its complexes are successfully grown onto quartz substrates using spin coating technique. Optical features and spectral phenomena of the thin films are studied using spectrophotometric measurements of absorbance, transmittance and reflectance. The optical constants such as refractive index, extinction coefficient, optical conductivity and energy loss functions of the thin films of L and its complexes are calculated. The refractive index curves for all films show a normal dispersion behavior in the non-absorbing region of spectra, from which the dispersion parameters can be calculated using Wemple-DiDomenico model. The type of optical transition bands shows indirect allowed. The values of the optical energy gap are calculated in the range from 2.13 to 2.33 eV, depending on the nature of Cu(II) substituent. Indeed, the present results show that the complexes as organic semiconductors acquired good characterizations better than metal free ligand (L) such as more thermal stability, reducing in the optical band gap and increasing in the absorption coefficient that refers to light harvesting capacity.

Heterocyclic Schiff base transition metal complexes in antimicrobial and anticancer chemotherapy

In recent years, the number of people suffering from cancer and multidrug-resistant infections has sharply increased, leaving humanity without any choice but to search for new treatment options and strategies. Although cancer is considered the leading cause of death worldwide, it also paves the way many microbial infections and thus increases this burden manifold. Development of small molecules as anticancer and anti-microbial agents has great potential and a plethora of drugs are already available to combat these diseases. However, the wide occurrence of multidrug resistance in both cancer and microbial infections necessitates the development of new and potential molecules with desired properties that could circumvent the multidrug resistance problem. A successful strategy in anticancer chemotherapy has been the use of metallo-drugs and this strategy has the potential to be used for treating multidrug-resistant infections more efficiently. As a class of molecules, Schiff bases have been the topic of considerable interest, owing to their versatile metal chelating properties, inherent biological activities and flexibility to modify the structure to fine-tune it for a particular biological application. Schiff base-based metallo-drugs are being researched to develop new anticancer and anti-microbial chemotherapies and because both anticancer and anti-microbial targets are different, heterocyclic Schiff bases can be structurally modified to achieve the desired molecule, targeting a particular disease. In this review, we collect the most recent and relevant literature concerning the synthesis of heterocyclic Schiff base metal complexes as anticancer and anti-microbial agents and discuss the potential and future of this class of metallo-drugs as either anticancer or anti-microbial agents.

Novel bio-essential metal based complexes linked by heterocyclic ligand: Synthesis, structural elucidation, biological investigation and docking analysis

New series of bio-essential metal based complexes linked by Schiff base ligand (L) and 2,2'-bipyridine (bpy) have been synthesized and characterized by diverse spectral techniques such as elemental analysis, magnetic susceptibility, molar conductivity measurements, FT-IR, UV-Vis., (1)H NMR, (13)C NMR, EPR and Mass. The spectral data suggest that the metal complexes espouse octahedral geometry around the metal ions. Interactions of the complexes with CT DNA have been explored by electronic absorption, ethidium bromide displacement assay, viscosity measurements, cyclic voltammetry and differential pulse voltammetry in order to evaluate the possible DNA-binding mode and to calculate the corresponding DNA-binding constants. The DNA interaction studies propose that the intercalative mode of interaction and the complexes exhibit oxidative cleavage of pUC19 DNA in the presence of hydrogen peroxide as activator. The synthesized Schiff base ligand and its metal complexes have been screened for anti-microbial activity by micro dilution method against two Gram-positive bacteria (Staphylococcus aureus and Bacillus subtilis), two Gram-negative bacteria (Escherichia coli and Salmonella typhi) and three fungi strains (Fusarium solani, Aspergillus niger and Candida albicans) revealing that the complexes are good anti-pathogenic agents than the ligand. Moreover, molecular docking analysis has been performed to confirm the nature of binding of the complexes with DNA.