Schiff-based Research Articles

Coumarin Schiff base derivatives with terminal cyano group: Synthesis, Mesomorphic properties and DFT investigation

Coumarin Schiff base derivatives with terminal cyano group were synthesized and analysed for their mesomorphic behaviour. The homologous series CN6–16 (n = 6,8,10,12,14,14,16) with 4-cyano benzaldehyde, lower member (n = 6,8) exhibited enantiotropic nematic mesophase, while smectic A mesophase started appearing with n = 8 during cooling process. Enantiotropic smectic A mesophase was observed with higher chain length n = 10,12,14,16. Similar trend of mesomorphic properties was exhibited by Schiff base derivatives BPCN8–14. Introduction of cyano biphenyl at aldehyde end of the molecule has led to formation of stable smectic A mesophase as compared to that by compounds CN8–14. Introduction of ester linkage in Schiff based derivatives, compounds ECN10–12 and RECN10–12 showed smectic A mesophase with high clearing temperature. VT-XRD analysis of two compounds has confirmed orthogonal smectic A mesophase. Additionally, DFT calculations were carried out for all the newly synthesized compounds and compared with similar literature molecules for various structural and electronic parameters followed by their correlation with the mesophase type and stability.

In vitro anti-microbial, DNA-binding, In silico pharmacokinetics and molecular docking studies of Schiff-based Cu(II), Zn(II) and Pd(II) complexes

Synthesis of salen type Schiff base ligand by the condensation of butane 1,4-diamine with 5-bromosalicyaldehyde has been done. Further, three new mononuclear Schiff based complexes of Cu(II), Zn(II) and Pd(II) have been prepared by the reaction of the Schiff base ligand with appropriate metal salts. The developed Schiff base ligand and metal complexes of Cu(II), Zn(II) and Pd(II) have been well characterized by various spectroscopic techniques like UV–Vis, FT-IR, 1H-NMR, 13C-NMR, EPR, Mass and powder XRD. All the synthesized Schiff base compounds have been tested for antibacterial, antifungal, hemolysis assay and DNA binding activities. The zone inhibition measurements revealed the supremacy and enhanced efficiency of metal complexes as compared to free ligand. The molecular modelling studies were carried to analyze the bonding affinity and inhibition probability of the synthesized complexes with the S. aureus nucleoside diphosphate kinase receptor. The in-silico pharmacokinetics studies such as Lipinski's rule, Veber's rule, drug-likeness score and physiochemical parameters analysis predicted the drug-likeness of the synthesized compounds.

A novel isatin Schiff based cerium complex: synthesis, characterization, antimicrobial activity and molecular docking studies

In this work, a novel isatin-Schiff base L2 had been synthesized through a simple reaction between isatin and 2-amino-5-methylthio-1,3,4-thiadiazole. The produced Schiff base L2 was then subjected to a hydrothermal reaction with cerium chloride to produce the cerium (III)-Schiff base complex C2. Several spectroscopic methods, including mass spectra, FT-IR, elemental analysis, UV–vis, 13C-NMR, 1H-NMR, Thermogravimetric Analysis, HR-TEM, and FE-SEM/EDX, were used to completely characterize the produced L2 and C2. A computer simulation was performed using the MOE software program to find out the probable biological resistance of studied compounds against the proteins in some types of bacteria or fungi. To investigate the interaction between the ligand and its complex, we conducted molecular docking simulations using the molecular operating environment (MOE). The docking simulation findings revealed that the complex displayed greater efficacy and demonstrated a stronger affinity for Avr2 effector protein from the fungal plant pathogen Fusarium oxysporum (code 5OD4) than the original ligand. The antibacterial activity of the ligand and its Ce3+ complex were applied in vitro tests against different microorganism. The study showed that the complex was found to be more effective than the ligand.

A designer Schiff based motif offered dual dynamic exchangeable bonds, faster curing and closed‐loop circularity in epoxy vitrimers

AbstractA fast‐curing epoxy with improved mechanical properties, self‐healing and re‐processability was designed using a tailored Schiff based motif that offered dual covalent adaptable network (CAN) in epoxy. The designer motif is a dynamic hardener with both acetal linkage and a Schiff base motif in the same molecule which allowed us to gain a mechanistic insight into the evolving transient network in epoxy vitrimers. The dynamic hardener besides offering a cross‐linked network in epoxy can facilitate rapid exchange reactions, resulting in a material with high tensile strength (74 MPa), high glass transition temperature (121°C), and that can be re‐purposed through solvent induced degradation. The proposed dynamic curing agent is suitable to be employed as a coating material on substrates to ensure excellent self‐healing and re‐processability ensuring chemical recyclability. Few carbon fiber‐based laminates were prepared using the epoxy vitrimer and the recovery of CF post laminate preparation clearly demonstrates the closed‐loop circularity in epoxy vitrimers.Highlights A unique dynamic curing agent is designed consisting of an aldehyde (salicylaldehyde) and an amine and acetal containing species (amino acetaldehyde dimethyl acetal). It facilitates imine and acetal exchange that can bond at temperatures <60°C and break at temperatures >105°C as evidenced by the vitrimer transition temperature. Epoxies show high tensile strength (74 MPa), exceptional Tg (121°C), fast stress relaxation and an activation energy of 96.2 KJ/mol. The imine‐acetal exchange system rendered the epoxies re‐processable, malleable and re‐usable.

Synthesis, spectroscopic elucidation, density functional theory calculation, and molecular docking studies of a novel series of tetradentate macrocyclic Schiff base ligands and their Zn(II) complexes and investigations of their antimicrobial, anti‐inflammatory, and anticancer activities

In the present work, novel Schiff base macrocyclic Zn(II) complexes [Zn(N8O4MacL1)Cl2–Zn(N8O4MacL3)Cl2] were synthesized by the reaction of ZnCl2 and macrocyclic ligands (N8O4MacL1–N8O4MacL3) derived from the condensation of ligand (L) and dicarboxylic acids [HOOC‐(CH2)n‐COOH]. The structural confirmation of the newly synthesized compounds was accomplished through various analytical techniques, including elemental analysis, infrared (IR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, mass spectrometry (MS), UV–visible spectroscopy, and powder X‐ray diffraction (XRD) studies. The spectral data provided evidence that the macrocyclic ligands acted as tetradentate ligands, forming coordination bonds with Zn(II) ions through the nitrogen atom of the imine (>C=N) group. The coordination complexes exhibited an octahedral geometry around the zinc ion, with two chloro groups covalently attached. Density functional theory (DFT) studies of the synthesized Schiff base macrocyclic compounds were carried out to determine their structural and electronic properties. The antimicrobial potential of the macrocyclic compounds was examined against a panel of pathogenic microbes, including four bacterial strains (Staphylococcus aureus, Bacillus subtilis, Escherichia coli, and Xanthomonas campestris) and two fungal strains (Fusarium oxysporum and Candida albicans). Then, the newly synthesized Schiff based macrocyclic compounds were evaluated for their anti‐inflammatory activity using an egg albumin method. The synthesized compounds were subjected to further evaluation to assess their potential as anticancer agents against MCF‐7 (human breast adenocarcinoma cell line), HCT‐116 (human colon cancer cell line), and A549 (human alveolar adenocarcinoma epithelial cell line). In addition, molecular docking studies were conducted to explore the potential interactions between the synthesized compounds and the target proteins VEGFR2 (PDB ID 1YWN), EGFR (PDB ID 1M17), and DNA gyrase B (PDB ID 4URO). It was found that there was a high correlation between the experimental results and the docking calculations.

Design, Synthesis, Drug-Likeness and In Silico Prediction of Polycyclic Aromatic Schiff base Tethered Organosilatranes

The present article includes the generation of aromatic Schiff base tethered organosilatranes via two step synthetic pathways starting from anthracene-10-carbaldehyde and 1H-indole-3-carbaldehyde. The synthesis was achieved by employing condensation reaction followed by transesterification methodology. The prepared organosilatranes containing aromatic schiff based ligands were structurally authenticated using spectroscopic techniques such as FT-IR, NMR and mass analysis. The prepared compounds were also scrutinized for in silico physiochemical properties via Molininspiration and ADMET software and the results revealed their good biological potential for drug discovery.

Synthesis, Characterization and Antifungal Activities, Aspergillus Niger, Aspergillus Flavus, Candida Albicans of Novel Schiff Base and Schiff Based Resin

Synthesis, Characterization and Antifungal Activities, Aspergillus Niger, Aspergillus Flavus, Candida Albicans of Novel Schiff Base and Schiff Based Resin

In silico Study of the Interactions between Schiff Base Polyphenols and HPV 16 E6/E6AP/p53 complex

The rise in the incidence of cervical cancer globally has accentuate attention to the potential role of polyphenols as anticancer agents. Different studies have demonstrated the role of some polyphenols in altering Human Papillomavirus (HPV) carcinogenesis. Thus, this study was aimed at establishing the potentials of Schiff-based polyphenols from imesatin and satin as anticancer agents through in silico analysis. The polyphenols were synthesized and characterized using elemental analyses, spectroscopic analyses, UV-visible, Infrared, and Nuclear Magnetic Resonance (1H NMR and 13C, NMR). Molecular docking study of the polyphenols was carried out using Auto Dock Vina. The oncogenic E6 protein structure of HPV 16 was obtained from the protein bank (ID: 4XR8). The E6 proteins were prepared using AutoDock tools. Water molecules were removed from the protein molecules while hydrogen atoms were added. Also, the structures of Curcumin and Isomericitrin were obtained from PubChem. Results showed that three different Schiff based polyphenols were obtained from the synthesis; 3-(2’,4’-dimethoxy benzylidene hydrazono) indoline-2-one (DMBH), 3-(2’-hydroxy-4’-methoxy benzylidene hydrazono) indoline-2-one (HMBD), and 3-((4-4’-((2’’, 4’’-dimethoxy benzylidene amino) benzyl)phenyl)imino) indoline-2-one (DMBP). Higher ability of the docked polyphenols to bind to the E6/E6AP/p53 complex when compared to Curcumin was revealed. Also, results showed that the binding energy of Curcumin and Isomericitrin were -7.1kcal/mol and -8.4kcal/mol respectively while that of the polyphenols ranged from -7.4kcal/mol to -7.9kcal/mol. The molecular docking results of the polyphenols used in this study further confirm their potentials as strong anti-cancer agents.

Exploration the effect of metal and electron withdrawing groups on charge transport and optoelectronic nature of schiff base Ni(II), Cu(II) and Zn(II) complexes at molecular and solid-state bulk scales

The charge transport and optoelectronic nature of semiconductor materials are important to understand their potential use in numerous semiconductor device applications. Here, diverse functional properties of Schiff base Ni(II), Cu(II) and Zn(II) complexes at molecular and solid-state bulk scales have been explored. The effect of metal substitution in Schiff based complexes has been studied at bulk level with respect to optoelectronic properties, and at isolated molecular level (frontier molecular orbitals, electron affinity, ionization potential, reorganization energy, and transfer integrals). The Zn+2 metal substitution in place of Ni+2 or Cu+2 lead to decrease the electron and hole reorganization energy values ultimately boost the hole intrinsic mobility two times higher magnitude while one and four times higher magnitude electron intrinsic mobility for Zn-comple×3 than Ni-complex1, and Cu-complex2, respectively. The effect of –COOH, –CN and –NO2 on the frontier molecular orbitals, energy gap, reorganization energy, ionization potential, and electron affinity has been explored on isolated molecules of Ni-complex1, Cu-complex2 and Zn-complex3 as well. The intrinsic mobility and electro-optical properties explored that Ni-complex1, Cu-complex2 and Zn-complex3 as well as their derivatives would be proficient contenders for semiconductor and optoelectronic devices applications.

Synthesis, Crystallographic, Monoclinic, Inflexible, Antifungal Assessment of Schiff based resin

The present study investigates the preparation of a newly prepared Schiff base BHNMXD and Schiff based resin PMBHNMXD via polymerization. The condensation or polymerization procedure was used with formaldehyde (HCHO) at temperature 70 to 80 ˚C for 2-3 h. The prepared Schiff base BHNMXD and its respective resinPMBHNMXD were recrystallized from methanol to attain pure resin. After successful synthesis of Schiff base and resin was characterized by different instrumental techniques such as; CHN, elemental microanalysis, thermogravimetric analysis (TGA) studies of Schiff based resin, energy- dispersive x-ray spectroscopy EDS mass spectrometry, E.I-MS (electron impact ionization), 1HNMR spectroscopy and MALDI-TOF mass spectrometry clearly investigated the molecular weight and structural information of synthesized compounds. The FT-IR spectra of resin PMBHNMXD showed stronger absorption band at 1632 cm-1 of azomethine >C=NH confirming the compound formation. The SEM analysis showed the morphology of Schiff base and resin showing, longitudinal spherical rough, inflexible and rigid structure. The structures and components were carefully investigated by X-ray diffraction .The crystallographic evaluation of Schiff base and its resin, aproved the monoclinic sharp crystalline structure. These active materials have shown high efficiency against the antifungal growth of Aspergillus Flavus (G-ve), Candida albicans (G-ve) and Aspergillus Niger (G-ve),by agar well diffusion method.

In vivo evaluation of wound healing improvement of a new Schiff base derived bromine compound (CNBP) in rats

BackgroundThe effect of delivered bromine vapor and also bromine substitutions are shown to play an important role in anti-inflammatory activity. The present study encompasses a broad in vivo study to size up healing activity of a novel dibromide substituted Schiff based compound against cutaneous wound model in Sprague Dawley (SD) rats. Methodology/principal findings2, 2′-[1, 2-Cyclohexanediylbis(nitriloethylidyne)] bis[4-bromophenol], CNBP, is synthesized through a Schiff base reaction applying the related ketone and diamine as the initiators. Four groups of six in each male SD rats are divided as negative group which are treated with gum acacia, positive control animals which are treated with topical dosage of Intrasite gel, and testing groups treated with low (10 mg/kg) and high (20 mg/kg) doses of CNBP. The excisional wounds are created on the posterior neck area of each group and the wound closure percentage was measured in the two separated days of the experiment. Moreover, the histopathological evaluation and determination of activities of superoxide dismutase (SOD), catalase (CAT), peroxidase (GPx), and malondialdehyde (MDA) of the skin sections are performed. Furthermore, the immunohistochemistry consists of the evaluation of Hsp70 and BAX proteins. Conclusions/significanceThe wound closure percentage showed a significant increase in high dose CNBP-treated group compared to the negative control. Histopathological evaluation of the skin sections showed that granulation tissue contained more proliferating fibroblast, collagen deposition, angiogenesis, and also less inflammatory cells in the high dose CNBP-treated group compared to the normal rats. In the treated groups with CNBP, SOD, CAT, and GPx activities were found significantly higher, however, the MDA level was shown to be lower (*P < 0.05; **P < 0.01; ***P < 0.001) than the negative control. At the molecular level, CNBP (20 mg/ml, HD) improved wound-healing process via down and up regulation of Bax and Hsp70 protein, respectively at the wound site.

Schiff Based Silatranyl Compounds Exhibiting ‘Fe3+ and Mn2+ Fluorescence Dual Ion Sensing and Antibacterial Activity’

The synthesis of different Schiff base substituted silatranes (1c–4c) was carried out from the corresponding organotrimethoxysilanes (OTMS) (1b–4b) under anhydrous atmospheric conditions. The title compounds were scanned by spectroscopic analytical studies like NMR (1H, 13C) and IR which confirm their formation. The fluorescence studies performed indicate that two of the silatranes (1c and 4c) can act as ‘dual–ion fluorescent sensors’ selectively for Mn2+ and Fe3+ cations. The structural arrangement of these silatranes allowed the metals to bind and form five/six membered stable ring which is not possible in non-active silatranes (2c and 3c). Antibacterial studies of silatranes were also performed which produced much better results than already reported cefepime.

The apoptotic, cytotoxic and genotoxic effect of novel binuclear boron-fluoride complex on endometrial cancer.

Endometrial cancer (EC) is one of the most common types of gynecologic cancer of the female genital tract; it considered being the fourth leading death factor among other types of cancer. Therefore, developing new anti-cancer agents are crucial for cancer treatment. Based on the potential of Schiff based complexes for the induction of apoptosis, Schiff base compounds, and their metal complexes displayed excellent anticancer properties. In this current study, antiproliferative activity of [L(BF2)2] as a novel binuclear boron-fluoride complex was examined to preliminary research in eight different cell lines, HELA, DU-145, PC3, DLD-1, ECC-1, PNT1-A, HT-29, and MCF-7, it was found to have a potent, suppressive effect on human endometrial adenocarcinoma cell line ECC-1. Based on this data, later investigated its apoptotic, cytotoxic, and genotoxic properties on human endometrial adenocarcinoma cell line ECC-1 in different concentrations. Apoptotic and cytotoxic tests such as single cell gel electrophoresis assay (comet assay), DNA fragmentation laddering, acridine orange test for DNA damage, and ELISA for apoptotic measurement was performed. We also gauged the oxidative status by evaluating total antioxidant status (TAS) and total oxidant status (TOS). Oxidative stress index (OSI) was calculated too. As a result [L(BF2)2] has been found to have a marvelous effect on ECC-1 cells, especially in damaging their DNA and cause a series of reactions lead to apoptosis. Taken together, it suggests that the [L(BF2)2] complex can induce the apoptotic pathway of endometrial cancer cells and is a possible candidate for future cancer treatment studies.

Synthesis, Characterization and Antimicrobial Activity of Transition Metal Complexes of [NN] Donor Benzenesulfonamide Based Schiff Bases

The new sulfonamide Schiff based ligands have been prepared by refluxing 7-Methylquinoline-3-carbaldehyde and Halobenzenesulfonamide in methanol for 46 hours. The transition metal complexes of Cu, Co, Ni and Zn are synthesized and characterized on the basis of physical characteristics, micro-analytical data, 1H-NMR, FT-IR spectrum and electronic spectrum data. The FT-IR spectrum data suggest that Schiff base ligand behave in bidentate manner as coordinated with transition metals through nitrogen of azomethine group and of nitrogen of quinolone group. 1H-NMR data confirmed the formation of the complexes. The biological screening effect of Schiff base and their metal complexes are studied against gram positive and gram negative bacteria by disc diffusion technique. While electronic spectrum data confirmed the octahedral geometry of complexes. The biological activity show that complex exhibit higher antibacterial activity than that of Schiff base against tested

Schiff based ligand containing nano-composite adsorbent for optical copper(II) ions removal from aqueous solutions

A novel Schiff base ligand based nano-composite adsorbent (NCA) was prepared for the detection and removal of copper (Cu(II)) ions in wastewater samples. Upon the addition of Cu(II) ions to NCA at optimum conditions, the clear color was visible to the naked-eye in the detection system. This NCA exhibited an obvious color change from yellowish to dark green in the presence of Cu(II) ions in aqueous solution. The limit of detection was found to be 0.16μg/L by optical detection. The NCA could detect the Cu(II) ions over other foreign ions with high sensitivity and selectivity. For adsorption behavior, influences several factors such as solution pH, contact time, concentration for Cu(II) ion adsorption was investigated by batch experiment in detail. The results showed that neutral solution pH was suitable to get optimum Cu(II) ions adsorption. Also an extending contact time was favorable for improving adsorption efficiency. The adsorption process of Cu(II) ions by the NCA was followed the Langmuir adsorption isotherm model. The maximum adsorption capacity of Cu(II) ions by the NCA from the Langmuir isotherm model was 173.62mg/g. The mesoporous NCA exhibited higher adsorption capacity compared with some other reported diverse materials. In the multi-component system, the competing ions did not significantly interfere in the adsorption of Cu(II) ions. The adsorbed Cu(II) ions was effectively eluted with 0.25M HCl and remain the almost same functionality for many cycles use. Even in seven consecutive cycles, the NCA showed great potential in the optical Cu(II) ions removal from wastewater. Then the proposed NCA could be used a promising adsorbent for the clean-up of Cu(II) ions in wastewater treatment.

Self-stratifying coatings based on Schiff base epoxy resins

Schiff base epoxy resin was used as a component of self-stratifying compositions, in which different acrylic resins were used. The degree of stratification was determined using the ATR FTIR spectroscopy and microscopy technique. Results were compared with those for commercial epoxy resins with a comparable epoxy number. A determination was made of the mechanical properties of the coatings obtained. Based on the previous studies, it was concluded that Schiff base epoxy resin in a film-forming composition behaves in a similar manner to BPA-based epoxy resins. The best mechanical properties and a high degree of stratification were achieved using a Schiff base epoxy resin/poly(isobutyl methacrylate) composition. Use of a self-stratifying composition not only reduces the time and cost of preparing a multilayer coating system, thanks to the formation of two layers in one application, but also causes the Schiff based epoxy coatings to become more flexible.

Schiff based injectable hydrogel for in situ pH-triggered delivery of doxorubicin for breast tumor treatment

In this study, we report a facile approach to develop an injectable hydrogel with an in situ and pH sensitive drug delivery system for cancer treatment. The hydrogel was based on modified chitosan and alginate. We conjugated doxorubicin (DOX) to succinated chitosan (S-chi) via a Schiff base between a ketone group in the DOX and an amine group in the S-chi, which led to a pH sensitive release of DOX upon the stimulus of an acidic tumor microenvironment. Hydrogel formed in minutes while DOX conjugated S-chi was mixed with oxidized alginate. The hydrogel structure was characterized by cryo-imaging, FTIR and a rheology test. The DOX release profiles were tested in response to different pH values. The MTT assay showed a low toxicity of the hydrogel. The gel in turn inhibited the growth of tumor cells MCF-7 effectively when loaded with DOX. Finally, the DOX laden hydrogel was injected into the xenograft breast tumor model and significantly inhibited tumor growth.

Synthesis and characterization of oligo‐2‐hydroxy‐1‐naphthaldehyde and its Schiff base oligomers

AbstractIn this study, oligo‐2‐hydroxy‐1‐naphthaldehyde (OHNA) was synthesized from the oxidative polycondensation of 2‐hydroxy‐1‐naphthaldehyde (HNA) with air oxygen, NaOCl, and H2O2 in an aqueous alkaline medium at 50–95°C. We determined the products and the oxidative polycondensation reaction conditions of HNA with oxidants such as air oxygen, NaOCl, and H2O2. In these reactions, H2O2 was more active than air oxygen and NaOCl and their optimum reaction conditions were studied. The products were characterized by 1H‐NMR, FTIR, UV–visible, and elemental analysis. The respective number‐average molecular weight, mass‐average molecular weight, and polydispersity index values of OHNA and its Schiff base oligomers (compounds 1, 2, and 3) were found to be 500 g mol−1, 1880 g mol−1, and 3.75 for OHNA; 670 g mol−1, 2490 g mol−1, and 3.71 for compound 1; 390 g mol−1, 1080 g mol−1, and 2.77 for compound 2; and 320 g mol−1, 670 g mol−1, and 1.85 for compound 3. At the optimum reaction conditions, the yields of the reaction products were found to be 77.0% O2, 78.0% H2O2, and 75.4% NaOCl. About 80% of the HNA was converted into OHNA. In addition, new Schiff based oligomers were synthesized from the condensation reaction of OHNA with p‐aminophenol, triethyleneglycol bis(4‐aminophenyl ether), and aniline and their structures and properties were determined. Thermogravimetric and dynamic thermal analyses showed OHNA and its Schiff base oligomers to be stable against thermooxidative decomposition. The weight losses of OHNA and its Schiff base oligomer compounds 1, 2, and 3 were found to be 5% at 175, 225, 190, and 230°C, respectively; 50% at 900, 590, 650, and 620°C, respectively; and 60, 80, 85, and 82%, respectively, at 1000°C. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 442–450, 2003