Schiff Base Derivatives Research Articles

Corrosion Inhibition of Mild Steel in 1.0 M HCl from Thiadiazole Derivative Schiff Bases and Their Complexes with Co(II) and Ni(II): Synthesis, Characterization, DFT Study, and Monte Carlo Simulation

Corrosion Inhibition of Mild Steel in 1.0 M HCl from Thiadiazole Derivative Schiff Bases and Their Complexes with Co(II) and Ni(II): Synthesis, Characterization, DFT Study, and Monte Carlo Simulation

Recent development and strategies towards target interactions: Synthesis, characterization and in silico analysis of benzimidazole based thiadiazole as potential anti-Alzheimer agents

In the current research study, we aim to design and synthesize highly potent hybrid analogs of benzimidazole derived thiadiazole based Schiff base derivatives which can combat the cholinesterase enzymes (acetylcholinesterase and butyrylcholinesterase) accountable for developing Alzheimer's disease. In this context, we have synthesized 15 analogs of benzimidazole based thiadiazole derivatives, which were subsequently confirmed through spectroscopic techniques including 1H NMR, 13C NMR and HREI-MS. Biological investigation of all the analogs revealed their varied acetylcholinesterase inhibitory potency covering a range between 3.20 ± 0.10 μM to 20.50 ± 0.20 μM as well as butyrylcholinesterase inhibitory potential with a range of 4.30 ± 0.50 μM to 20.70 ± 0.50 μM when compared with the standard drug Donepezil having IC50 = 6.70 ± 0.20 μM for AChE and 7.90 ± 0.10 μM for BuChE. The promising inhibition by the analogs was evaluated in SAR analysis, where analog-1 (IC50 = 3.20 ± 0.10 μM for AChE and 4.30 ± 0.50 μM for BuChE), analog-4 (IC50 = 4.30 ± 0.30 μM for AChE and 5.50 ± 0.20 μM for BuChE) and analog-5 (IC50 = 4.10 ± 0.30 μM for AChE and 4.60 ± 0.40 μM for BuChE) were found as the lead candidates. Moreover, molecular docking and ADME analysis were conducted to explore the better binding interactions and drugs likeness respectively.

Synthesis of Some New Schiff Base Derivatives of Simazine and Atrazine for In Vitro Antimycobacterial Activity

Synthesis of Some New Schiff Base Derivatives of Simazine and Atrazine for In Vitro Antimycobacterial Activity

Design, Synthesis, in vitro biological evaluation and in silico molecular docking study of chloro substituted Benzimidazole-Thiazole hybrid derivatives as potential Anti-Alzheimer’s agents

In order to explore new acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) inhibitors, a series of benzimidazole-fused-thiazole bearing Schiff base derivatives (1–16) were designed and synthesized and further their precise structures were elucidated using various spectroscopic tools including 1H NMR, 13C NMR and HREI-MS. All the synthesized derivatives demonstrated better acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) inhibitory potential with IC50 values ranging from 0.10 ± 0.10 µM to 11.60 ± 0.40 µM (against AChE) and 0.90 ± 0.10 µM to 22.10 ± 0.60 µM (BuChE) when the results were compared with Donepezil (IC50 = 2.16 ± 0.12 µM (against AChE) & 4.5 ± 0.11 µM (against BuChE) as standard inhibitor. Specifically, the analogues 4, 5, 11, 14 and 15 were identified to be significant potent, even more active than standard drug having IC50 values of 0.80 ± 0.10, 0.50 ± 0.10, 0.60 ± 0.10, 0.10 ± 0.10, 0.10 ± 0.10 µM (against AChE) and 2.40 ± 0.10, 1.10 ± 0.10, 1.30 ± 0.10, 0.90 ± 0.10 & 0.80 ± 0.10 µM (against BuChE) respectively. The structure–activity relationship (SAR) studies were carried out for all synthesized derivatives based on substitution pattern around aryl ring. Furthermore, the molecular docking approach was developed to explore the binding mode of interactions between most active scaffolds and active sites of targeted acetylcholinesterase and butyrylcholinesterase enzymes.

Synthesis and characterization of indazole derived Schiff base ligands and their metal complexes: Biological and computational studies

Indazoles represent one of the most important heterocycles in drug molecules. Therefore, in the pursuit of potent biological agents, a series of ligands (HL1-HL4) and their corresponding transition metal complexes [M(L1-L4)2(H2O)2] were synthesized by the condensation reaction of 6-aminoindazole with various derivatives of salicylaldehyde. Further, the compounds underwent characterization through several physicochemical (TGA, powder XRD, SEM, EDAX) and spectroscopic techniques (FT-IR, UV–Vis, NMR, mass spectrometry, ESR). These techniques suggested hexacoordinated stereochemistry of the metal complexes, where ligands chelate via oxygen atom of phenolic ring, azomethine nitrogen and oxygen atom of water molecules in 1:2 (M:L) molar ratio. The thermal stability of the complexes was demonstrated by thermal analysis revealing three step decompositions leaving behind metal oxide as an end residue. The surface morphology of the ligands was distinct from metal complexes as revealed by SEM analysis, while mapping images demonstrated the simultaneously existence of the elements. While, to ascertain the nature of the obtained compounds (crystalline or amorphous), powder X-ray investigation was conducted by utilizing a wavelength of 1.54 Å. The compound’s antioxidant potential was assessed through DPPH assays and anti-inflammatory activity was evaluated using BSA denaturation inhibition assay, while their antimicrobial potential was evaluated against six microbial strains (E. coli, S. aureus, P. aeruginosa, B. subtilis, C. albicans, A. niger) by serial dilution approach. The performed biological evaluations revealed that the complexes are more efficient in controlling infectious ailment in comparison of ligands. HL2 (2) and its Cu(II), Zn(II) complexes (11, 12) exhibited potent antimicrobial activity (MIC value: 0.0047, 0.0048 µmol/mL against B. subtilis) and potent anti-inflammatory efficacy (IC50 value: 6.7 ± 0.044, 6.9 ± 0.036 µM). All the complexes exhibited potent antioxidant activity and their is enhancement in the activity of Schiff base ligands upon complexation, complex (19) demonstrated the greatest activity with IC50 value 2.1 ± 0.059. Additionally, the ADMET score provided a robust indication of the compounds’ drug-like behaviour. Furthermore, the biological effectiveness of the highly microbial potent ligand HL2 (2) and its complexes (9–12) was demonstrated through computational studies. The binding studies exposed that complexes (11, 12) exhibited lowest binding energy at −7.8, −7.9 kcal/mol. While, DFT study emphasized that complex (12) exhibits the highest electrophilicity index value (6.359), suggesting its affinity for binding with biological molecules and also revealed that complexes exhibit greater potency compared to the ligands and could potentially be utilized as drugs for combatting pathogen-induced malformations.

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.

Synthesis of Schiff‐Base Allied Silanes for the Photophysical Detection of Cr(III) Ion And In‐Silico Staphylococcus Aureus Inhibiting Activity

AbstractChromium is known to play an important role in various metabolic pathways; however, its excessive use can result in negative impact on mankind, this necessitates the development of sensors for Cr(III) ion. The current study has incorporated the synthesis of ether derived Schiff base allied silanes 4 a–4 d, which have been characterized using 1H NMR, 13C NMR and mass spectrometry. The spectroscopic technique of UV‐visible has been utilized to study the sensing behaviour of probe 4 a, resulting in a good sensing ability towards Cr(III) ion, yielding a detection limit of 4.2×10−7 M and an association constant value of 2.25×106 M−1. In order to study the stoichiometric binding between probe and metal ion, Job's plot method has been employed which shows 1 : 1 binding ratio. The mechanism of binding has been studied via 1H NMR, UV‐visible, FT‐IR spectroscopy and mass spectrometry. The binding has been further supported by DFT. The real sample analysis has been performed to validate the utility of the synthesized sensor in practical applications. The theoretical tool of molecular docking has been considered to study the protein‐ligand interaction between S. aureus bacterial protein and ligand 4 a, yielding a value of −7.63 kcal/mol for binding energy.

Coumarin Schiff base derivatives with alkyl 4’-formyl-biphenyl-4-carboxylate: design, synthesis, mesomorphic studies and DFT calculations

ABSTRACT Symmetric and unsymmetric homologous series of coumarin Schiff base derivatives with alkyl 4’-formyl-biphenyl-4-carboxylate have been synthesised and studied for their mesomorphic behaviour. In the symmetric homologous series of Schiff base derivatives BPES(6–16), alkoxy chain length was varied at both ends of the molecules with n = 6,8,10,12,14,16, while in the unsymmetric homologous series of Schiff base derivatives 10BPEU(2–12), chain length was varied at coumarin end only (n = 2–8,10,12). In symmetric homologous series, compounds BPES(6–10) (n = 6,8,10) exhibited enantiotropic smectic A (SmA) mesophase, while smectic C (SmC) mesophase in cooling cycle only. SmC mesophase became prominent on increasing the chain length n = 12,14,16 in BPES(12–16). In the unsymmetric homologous series 10BPEU(2–12), compound with n = 2 showed monotropic nematic mesophase and highly stable (~165 °C) SmA mesophase. Higher analogues in unsymmetric series were turned biphasic and showed SmA as well as SmC mesophase during cooling scan only. Compound with n = 12 showed stable enantiotropic SmC mesophase (~92 °C). VT-XRD analysis of symmetric compound with n = 12, showed the tilted SmC mesophase. Further DFT calculations were investigated for un/symmetric series along with the literature molecules with similar variations and compared for various structural (length, aspect ratio) and electronic (dipole moment, polarisability) parameters to establish correlation with observed mesomorphic behaviour.

Schiff base derivative flame-retardant endowing epoxy resin with toughness, transparency, and high flame retardancy

In this study, a novel phosphorus-containing flame retardant, SMAE, was prepared through a nucleophilic addition of N,N'-bis(salicylidene)ethylenediamine (SAED) and phenyl hypophosphite. SMAE can dissolve well in epoxy resin and provides molecular-level flame retardancy. By using SMAE as a co-curing agent and DDM to cure epoxy resin, EP/SMAE composites with excellent flame retardancy and good mechanical properties were obtained. As the dosage gradually increases, the limited oxygen index (LOI) values continue to rise. At a 5 % dosage, the Limiting Oxygen Index (LOI) value can reach 39.7 % and meet the UL 94 V-0 standard. It is observed that SMAE mainly exerts a blowing-out effect in EP. In addition, the use of SMAE as a co-curing agent can improve the impact strength of EP. The impact strength of 5 % SMAE/EP can reach 14.15 kJ/m2, which is 25 % higher than that of pure EP.

Synthesis and Crystal Structure Studies of a New Complex of Co (III)-Schiff Base Derivative Derived from Isonicotinohydrazide

A new Co(III) complex prepared by the reaction of N'–(1–(pyridin–2 yl)ethylidene) isonicotinohydrazide (H2L) with Co(II) ion is reported in this paper. The H2L ligand is structurally characterized by elemental analysis, NMR, and infrared spectroscopies. The mononuclear complex [Co(HL)2]·Cl·3H2O (1), is characterized by infrared spectroscopy, elemental analysis, conductance, magnetic room temperature measurement and single X-ray diffraction. The complex crystallizes in the monoclinic system with space group P21/c. The parameters of the unit cell are a = 9.6818(3) Å; b = 25.1587(6) Å; c = 11.5481(3) Å; β = 101.797(3) °; Z = 4; Rint = 0.0313 and wR(F2) = 0.0812. The asymmetric unit of the compound contains a discrete [Co(HL)2]+ cation one free chloride anion and three uncoordinated water molecules. In the discrete cation one Co3+ ion two organic ligand molecules are present. The coordination polyhedron around the Co3+ center is best described as a distorted octahedral with CoN4O2 chromophore. The crystal structure of the complex is stabilized by intramolecular and intermolecular hydrogen bonds.

Synthesis and characterization of a new eco-friendly dopamine derivative schiff base as an effective corrosion inhibitor for mild steel in acidic environment

The natural corrosion inhibitor behaviour of a newly synthesized dopamine derivative Schiff base (4-DBAB) has been inspected on mild steel in aggressive 1 M HCl using linear polarization, electrochemical impedance spectroscopy and potentiodynamic polarization techniques. The Schiff base was synthesized by eco-friendly pathway. Characterization of the synthesized new non-toxic inhibitor was performed using FT-IR and 1H-NMR spectroscopy techniques. The anti-corrosive efficiencies at optimum concentration of 4-DBAB inhibitor was 87.4% after 1 h and 98.4% after 120 h by impedance technique in acidic solution. The potential of zero charge of mild steel was also determined to elucidate the inhibition mechanism in the presence of the highest 4-DBAB solution. The atomic force microscopy and field emission scanning electron microscopy researches performed on surface morphology to provide additional support on the interaction between the mild steel surface and 4-DBAB molecules. Adsorption behaviour of the inhibitor was also studied at different durations by experimental inhibition results and showed the Langmuir isotherm involving chemisorption. Highlights A new dopamine-derived Schiff base (4-DBAB) with natural and environmentally friendly corrosion inhibition properties was synthesized. (Synthesis of eco-friendly compound). 4-DBAB demonstrated a high anti-corrosive efficiency after 120 hours in aggressive 1M HCl, as determined by impedance technique. (Exceptional corrosion inhibition). The determination of the potential of zero charge of mild steel provided insights into the inhibition mechanism in the presence of the highest 4-DBAB solution. (Mechanism elucidation). AFM and FE-SEM studies on surface morphology supported the interaction between the mild steel and 4-DBAB molecules, affirming its corrosion inhibition properties. (Surface interaction analysis).

Coumarin Schiff base derivatives with 4′-alkoxy biphenyl-4-carboxaldehyde: Synthesis, mesomorphic studies and DFT calculations

Two homologous series of coumarin Schiff base derivatives with 4′-alkoxy biphenyl-4-carboxaldehyde have been designed and synthesized. All the compounds were analyzed IR, 1H NMR, 13C NMR, ESI-MS and CHN analysis followed by mesomorphic properties polarizing optical microscopy (POM) and differential scanning calorimetry (DSC) analysis. In the first homologous series BPS(6–16), Schiff base of 7-alkoxy-3-aminocoumarin with 4′-alkoxy biphenyl-4-carboxaldehyde, alkoxy chain length was varied systematically at both end of the molecules such as n = 6,8,10,12,14,16. In this series, BPS(6–10) (n = 6,8,10) exhibited enantiotropic nematic(N) and smectic C (SmC) mesophase and turned to monophasic on increasing the chain length n = 12,14,16 in BPS(12–16) with stable SmC mesophase. While in the second homologous series 10BPU(2–16), systemic variation of alkoxy chain length was carried out at coumarin end only (n = 2–18) and 4′-decyloxy-biphenyl-4-carboxaldehyde was used for Schiff base formation. In the this series, early member of the series with n = 2,3 showed enantiotropic very stable (∼ 145 °C) nematic mesophase, while N as well as SmC mesophase were observed for n = 4–8 at, whereas with increase of chain length stability of nematic mesophase was decreased and that of SmC was increased. Higher membered analogous 10BPU(12–16) exhibited SmC mesophase with stability in the rage of 130–160 °C. VT-XRD analysis was also confirmed the tilted SmC mesophase in this class of compounds. For both the series, all compounds were studied for the DFT calculations as well as literature molecules with similar variations. Based on the calculated structural (length, aspect ratio) and electronic (dipole moment, polarizability) parameters were correlated with mesomorphic behaviour observed for literature compounds and compounds from both the series followed by the detailed discussion.

Synthesis and Antimicrobial Evaluation of Some Schiff Base Derivatives

Schiff bases are the nitrogen analogs of ketones or aldehydes, with the carbonyl functional group replaced by an imine or azomethine group. They are formed by the condensation reaction of a primary amine and a carbonyl group, and they are widely employed in industry and have a variety of biological activities. Four Schiff base derivatives were successfully synthesized from benzaldehyde (PC1), anisaldehyde (PC2), 4-nitrobenzaldehyde (PC 2), and cinnamaldehyde (PC4) and tested for their antibacterial capabilities were evaluated against bacteria and fungi. The Schiff base had a high percentage yield of 98.28% (PC1), 95.7% (PC2), 91.6% (PC3), and 98% (PC4), with melting points ranging from 178 -187°C, 183-191°C, 160-164°C, and 195-205°C respectively. All Schiff bases showed activity against Escherichia coli with a Minimum Inhibitory Concentration (MIC) of 62.5ug/ml (PC1, PC4) and 250ug/ml (PC2, PC3). The Minimum Bactericidal Concentrations (MBC) were 125ug/ml, 500ug/ml, and 250ug/ml for PC1, PC2 and PC4 respectively. PC3 showed no bactericidal activity against Escherichia coli. Schiff bases PC1, PC2, and PC3 showed activity against Staphylococcus aureus with MIC of 62.5ug/ml. The MBC obtained was 125ug/ml for PC1 and PC2, while 125ug/ml, and 250ug/ml for PC3. PC4 showed no bacteriostatic and bactericidal activity against Staphylococcus aureus. Schiff bases showed fungistatic activity against Candida albican with MIC of 250ug/ml, 62.5ug/ml, and 125ug/ml for PC1, PC2/PC3, and PC4 respectively. However, none showed fungicidal activity.

Synthesis and Characterization of some new heterocyclic derivatives from aromatic carbonyl ‎compounds and carboxylic acids with Evaluation some of them for biological activity

In this research investigation, a total of eighteen diverse tetra- and penta-lateral cyclic compounds were synthesized. These included 1,3,4-thiadiazole, thiazolidin-4-one (via an alternative method), 1,2,4-triazole, carbothioamide, thiazole-4-one, azetidin-2-one, and oxazole. The synthesis procedure entailed a sequence of reactions. The thiazolidine-4-one 1 was obtained by reaction p-aminobenzoic acid with thiosemicarbazide, followed by treatment with p-tolualdehyde to produce Schiff base 2. Reaction Schiff base 2 with mercaptoacetic acid in dry benzene was carried out to produce thiazolidine-4-one 3. In another synthesis pathway, the esterification of p-nitro benzoic acid with ethanol in the presence of sulfuric acid was obtained to formation of compound 4. Compound 4 was subsequently reacted with thiosemicarbazide, yielding compound 5. Cyclization of compound 5 was then achieved using 4% sodium hydroxide solution. This formed the 1,2,4-triazole heterocycle, designated compound 6. Thiosemicarbazone 7-9 were prepared by reaction of thiosemicarbazide with different aldehydes. Additionally, 2-substituted-1,3-thiazolidine-4-one derivatives 10-12 were synthesized through the reaction of thiosemicarbazone with chloroacetic acid in the presence of anhydrous sodium acetate. The Oxazole derivative 15 was obtained through a series of reactions starting with the reaction of p-amino benzoic acid with ethyl chloroacetate, resulting in compound 13. Compound 13 was then treated with urea to obtain compound 14, followed by a reaction with 4-phenyl phenacyl bromide to yield the final product, the Oxazole derivative 15. The 2-aminooxadiazole derivative 16 was synthesized by reaction urea with 4-bromoacetophenone which was reacted with 4-bromobenzaldehyde to produce Schiff base derivative 17. Finally, β-lactam 18 is obtained through reaction Schiff base with chloroacetyl chloride in the presence of triethyl amine. FT-IR, 1H-NMR, and 13C-NMR spectroscopy were used to confirm their proposed structures. Moreover, the antibacterial and antifungal activities of certain synthesized compounds, specifically 2,3,6,11,13,15,17, and 18, were assessed against Staphylococcus aureus, Escherichia coli, and Candida albicans, demonstrating encouraging outcomes.Keywords: Antibacterial, antifungal activity, oxadaizole, heterocyclic derivatives, Oxazole.

Synthesis and Characterization of Propofol‐Like Compounds, Anticancer Activities and Investigation of Their Anesthetic Effects by Molecular Docking

AbstractThis study was designed to synthesize hybrid molecules starting from 2,6‐diisopropyl aniline (1), which is similar to Propofol (2,6‐diisopropyl phenol), by increasing its biological activity with other heterocycles and to determine the anesthetic activity of the obtained compounds. For this purpose, commercially available 2,6‐diisopropylaniline (1) was used as a starting compound. Then, ester (2), hydrazide (3), carbothioamide (5, 6) and Schiff bases derivatives (4 a–f) were synthesized, respectively. To achieve the etomidate‐like target compound 8, compound 7 containing chloroacetamide group was firstly synthesized from starting compound 1, and this compound reacted with ethyl‐1H‐imidazole‐5‐carboxylate. The structures of the newyl synthesized 12 compounds were characterized and confirmed by FT‐IR, MALDI‐TOF/MS, 1H NMR, 13C NMR.Within the scope of in silico study, ligand binding status of all compounds on the GABAA receptor was revealed. Molecular docking studies of them with GABAA found out that the interaction modes, including van der Waals interactions, hydrogen bonds, and pi‐pi interactions, are similar to that of the cocrystalline ligand Propofol. For the compounds 1, 2, 3, 4 d, 5, 7 have micromolar (μM) level, for the compounds 4 a, 4 b, 4 c, 4 e, 4 f, 6 and 8 have nanomolar (nM) level of inhibition has been estimated. When all data such as active localization, interacting residues, bond types formed, estimated Ki values, docking scores are evaluated together, compounds 1, 2, 3 and 7 which can be considered as synthesis starting or intermediate material, may be less effective.On the other hand the anticancer activities of the synthesized compounds were investigated against A549 (non‐small cell lung carcinoma) and BEAS‐2B cell line (normal bronchial epithelial) cell lines using Resazurin cell viability assay. It has been revealed that the compounds 4, 5, 6 and 8 may be more active in terms of anesthetic activity, whereas only compound 6 showed anti‐cancer activity.

Filling two needs with one deed: Differential sensing of anthrax biomarker dipicolinic acid and bovine serum albumin using binary ensemble based on 1,8-naphthalimide Schiff base and cationic surfactant

Keeping in mind the severities of anthrax disease caused by bacteria Bacillus anthracis and side effects of abnormal levels of a nonmetalloprotein bovine serum albumin (BSA), their early diagnosis was highly required. The existing lanthanide based sensors for their detection are not up to the mark due to their potential disadvantages of genetic toxicity, bio-migration, supply shortages, low atom utilization and poor stability. To address these issues, a binary ensemble OHNP@CTAB was fabricated in aqueous medium by encapsulation of 1,8-naphthalimide derived Schiff base (OHNP) in the micelles of a cationic surfactant CTAB. Significant changes were observed in the absorption and emission spectrum of OHNP@CTAB in the presence of DPA and BSA mainly due to electrostatic interaction among positively charged receptor and negatively charged guest species. Limit of detection (LOD) values of OHNP@CTAB towards DPA and BSA were calculated to be 1.19 and 0.11 µM, respectively from fluorescence spectral titration data. Moreover, the binary ensemble OHNP@CTAB efficiently detected BSA and DPA in real samples viz. packaged milk, gulkand and candy.

Synthesis and characterization of catalytic active oxazolidine/Schiff complexes using 2-quinoline formaldehyde and tris-base for carbon dioxide chemical fixation

Catalytic chemical fixation of carbon dioxide to high value-added chemicals has attracted extensive attention and the discovery of new catalytic system has always been a research hotspot in carbon dioxide chemistry. Three complexes were synthesized by using 2-quinoline formaldehyde and tris-base precursor through Schiff base reaction and characterized. Compound Co[L1]2Cl2·2H2O (1) and compound Ni[L1]2Cl2·2H2O (2) are two mononuclear complex with derived schiff base ligand (L1 = 2-(hydroxymethyl)-2-((quinolin-2-ylmethylene)amino)propane-1,3-diol), while compound Cu2[L2]2Cl2∙2CH3OH (3) is a dinuclear complex containing derived deprontonated ligand (L2 = (2-(quinolin-2-yl)oxazolidine-4,4-diyl)dimethanol) The self-assembly process of these complexes were monitored by ESI-MS. The catalytic explore for the cycloaddition of CO2 and different reaction substrates and preliminary kinetic studies shows that all complexes are active and the reaction is an intramolecular Lewis acid-base catalytic mechanism. This is the first report of oxazolidine complex/ tetrabutylammonium halide catalyst in for cycloaddition of epoxides and CO2 reaction and the complex 3 is more active than the other two complexes, which provides new notions for the design and solicitation of Schiff base/oxazolidine catalysts.

Novel Schiff base derivatives containing 4,5-disubstituted thiazole as potential antibiofilm, anti-inflammatory and antioxidant agents: Green synthesis, molecular docking and ADME analysis

We report the microwave-assisted (MW) green synthesis of some novel 4,5 disubstituted thiazole-containing Schiff base derivatives (SBs) as antibiofilm, anti-inflammatory, and antioxidant agents. Spectroscopic techniques were used to confirm the formation of synthesized compounds. In-vitro antibiofilm and antifungal activity of synthesized molecules were evaluated against the Candida albicans strain (MTCC 227) by broth dilution method. Among the tested molecules, 3a showed excellent inhibition of both biofilm formation and planktonic growth at much lower MIC50 values (5.56 μg/mL and 1.20 μg/mL respectively) than other derivatives. Moreover, the spot assay of compound 3a showed fungicidal activity (100% cell death) for biofilm formation and planktonic growth at the lowest MFC values (10 μg/mL and 3.12 μg/mL respectively) compared to the standard drug fluconazole. In addition, the biofilm inhibition was further confirmed by morphological study through FESEM analysis. The anti-inflammatory study of SBs by protein denaturation method indicates that compound 3a (63.19%) was the most active anti-inflammatory agent at a lower concentration of 100 μg/mL in the series than the standard ibuprofen (42.36%). Whereas, the antioxidant study of SBs by the DPPH scavenging method shows compound 3j (IC50 = 436.10 μg/mL) was the more potent antioxidant agent as compared to other tested compounds and standard drug ascorbic acid (IC50 = 626.99 μg/mL). Furthermore, the molecular docking study of SBs with the active sites of sterol 14-α demethylase CYP51 enzyme of (PDB:5TZ1) C. albicans shows strong binding properties, supporting the experimental results of inhibition of biofilm formation. Additionally, the ADME characteristic of SBs demonstrates their potential for development as oral medication candidates.

Biphenyl based schiff base derivatives of 6-aminocoumarin: Design, synthesis, mesomorphic properties and DFT studies

The study focused on synthesizing two series of coumarin Schiff base liquid crystals. These series involved molecules with variations in alkoxy chains at aldehyde ends: one being the Schiff base with 4′‑hydroxy-[1,1′]-biphenyl-4-carbaldehyde (ASBP series) and the other being alkyl 4-formyl-[1,1′]-biphenyl-4-carboxylate (AEBP series). The compounds were characterized using FTIR, NMR, and Mass spectral analyses. All the compounds were studied for their mesomorphic properties, differential scanning calorimetry (DSC) and polarized optical microscopy (POM). In both the homologous series, variation of alkyl chain length showed intriguing phase transitions. In the first homologous series ASBP, compound with hexyloxy chain displayed an enantiotropic nematic (N) phase, while those with chain lengths n = 8–16 exhibited enantiotropic smectic A (SmA) mesophase. Similarly, in the AEBP series, compounds with n = 6,8 chain length showed an enantiotropic nematic (N) phase, while those with higher chain lengths n = 10–16 exhibited enantiotropic smectic A (SmA) phases. SmA mesophase was further confirmed by powdered XRD analysis. The study included DFT theoretical calculations to comprehend the compounds' mesomorphic behavior, comparing them with analogous reported compounds. Additionally, the investigation correlated experimental findings of individual compounds with calculated parameters like polarizability, dipole moment, and aspect ratio. Molecular electrostatic potential projections and analysis of frontier molecular orbitals were also employed to elucidate how polarity variations in terminal chains and mesogenic cores influenced the energy gap of FMOs and the distribution of electrostatic charges on these compounds. It has been found that the ASBP series has lower energy gap and higher dipole moment than the AEBP series.

Synthesis and Characterization of Piano-Stool Ruthenium(II)-Arene Complexes of Isatin Schiff Bases: Cytotoxicity and DNA Intercalation.

A series of aryl-isatin Schiff base derivatives (3a-d) and their piano-stool ruthenium complexes (4a-d) were synthesized and characterized via 1H and 13C NMR and Fourier transform infrared (FTIR) spectroscopy. In addition, the purity of all of the compounds (3a-c and 4a-d) was determined via elemental analysis. Complex 4d was analyzed using X-ray crystallography. An in vitro antiproliferative study of the compounds (3a-c and 4a-d) against human hepatocellular carcinoma (HEPG2), human breast cancer (MCF-7), human prostate cancer (PC-3), and human embryonic kidney (HEK-293) cells exhibited their considerable antiproliferative activity. 4d exhibited effective cytotoxicity against HEPG2 and MCF-7. It displayed higher cytotoxicity than the reference metallo-drug cisplatin. Moreover, the stability of 4d was studied via 1H NMR spectroscopy, and the binding model between 4d and DNA was investigated via ultraviolet-visible spectroscopy. The lipophilicity of the synthesized complexes was determined using an extraction method.