The Schiff bases are a class of compounds formed by the condensation of primary amines with aldehydes and ketones to form the azomethine (C=N) group. Due to their ease of preparation, flexibility of chemical structure, and high coordination ability with metal ions, Schiff bases have gained increasing attention in many fields, including coordination chemistry, medicinal chemistry, and materials science. The formation of chelate rings is an important property of Schiff bases that makes them effective building blocks for the synthesis of diverse stable complexes with square-planar, tetrahedral, and octahedral geometries, which are more stable than the corresponding ligands. Apart from these properties, metal complexes of Schiff bases have been proven to be potential candidates for various scientific fields, including antimicrobial, antioxidant, anticancer, catalytic, sensing, and environmental fields. With the advent of modern experimental and computational methods, the Schiff base systems are now better known than ever. Single-crystal X-ray diffraction, Hirshfeld surface analysis, cyclic voltammetry, electron paramagnetic resonance (EPR), and X-ray absorption spectroscopy have been used successfully in such investigations. On the other hand, computational methods like density functional theory (DFT), molecular docking, molecular dynamics simulation, and ADMET studies can be employed to study electronic structures, predict reactivity, and examine biological interactions. However, despite the progress made in all the above-mentioned fields, no unified method to understand the electronic structures, chemical reactivity, and biological interaction properties has been developed as of yet. In particular, most studies tend to explore one aspect of Schiff bases only, which results in a lack of understanding of how to link specific structures with particular biological effects in order to achieve desired functions. Hence, this review provides a critical and comprehensive overview of the recent advances in the design of Schiff base ligands and their metal complexes by highlighting their synthesis and structure, biological activities, and mechanistic behavior, and structure-activity relationship studies using a computational approach.
The preparation of secondary phosphines in an easily implemented and safe way is a challenging task. Herein, we report on the suitability of phthalimide-substituted phosphines as starting materials for the photo-catalytic production of such secondary phosphines in the presence of an IrIII photocatalyst and sacrificial electron donors. While diarylphosphines could be prepared, dialiphatic phthalimide derivatives showed a fundamentally different reactivity. They were found to undergo rearrangement of the phthalimide group, followed by cleavage, to give oxides of the secondary phosphines. Although achieving high-yielding transformations remained a challenge, unexpected mechanistic insights into the fate of the one-electron-reduced phthalimidophosphines formed as intermediates could be obtained. This knowledge is valuable for developing future benign routes to secondary phosphines.
In this work, adsorptions of As2, As4, and AsH3 molecules on the M12O12 (M = Be, Mg, Ca) nanocages were inspected at the D3-LC-ωPBE/6–311G(d,p) level of theory. Energetic and thermochemical parameters of the adsorption reaction were calculated. The interactions between two fragments were analyzed using energy decomposition analysis (EDA). Molecular electrostatic potential (MEP) surfaces were considered to explore interactions between two fragments. Electronic spatial extent (ESE) and molecular orbital analyses of these systems were presented. Charge transfer between nanocages and molecules was exemplified using charge decomposition analysis (CDA). TAIM and Mayer bond order results were used to explore the interaction between fragments.
Waste-derived hydroxyapatite (HAp) represents a sustainable functional material platform for investigating interfacial adsorption phenomena. In this study, HAp synthesized from bonefish waste via calcination was employed to examine the adsorption behavior and underlying mechanisms of divalent metal ions (Cu2+, Ni2+, and Co2+). Structural characterization using X-ray diffraction, Fourier-transform infrared spectroscopy, and electron microscopy confirmed the formation of crystalline HAp with well-defined morphology and surface features. Batch adsorption experiments conducted at pH 5.5 and ambient temperature revealed ion-specific performance, with removal efficiencies of approximately 62% for Cu2+, 31% for Ni2+, and 23% for Co2+ at an initial concentration of 50 mg L−1. Kinetic analysis followed a pseudo-second-order model, indicating surface-controlled adsorption processes. At the same time, equilibrium data were best described by the Langmuir model for Cu2+ and the Freundlich model for Ni2+ and Co2+, reflecting differences in surface homogeneity and interaction strength. Mechanistic interpretation indicates that Cu2+ adsorption proceeds via coupled Ca2+ ion exchange and inner-sphere complexation, suggesting strong interfacial binding and localized charge redistribution. In contrast, Ni2+ and Co2+ adsorption is governed by weaker, heterogeneous interactions consistent with outer-sphere complexation. These findings establish clear structure–property relationships and demonstrate the potential of waste-derived HAp as an efficient functional material for metal ion capture.
The rhodanine core or 2-thioxothiazolidin-4-one, a five-membered heterocyclic ring system, has garnered significant interest in drug discovery, owing to its diverse biological activities. Derivatization of rhodamine has yielded many clinically useful therapeutic compounds for various ailments due to the presence of both nitrogen and sulfur heteroatoms within its ring system. Its broad-spectrum activities are facilitated by its two key electrophilic binding groups, ketone and thioketone, which enable interactions with various biological targets. Significant advances have been made toward its efficient synthetic strategies for drug discovery and development. This comprehensive review discusses rational design strategies for rhodanine-based heterocycles and their therapeutic potential as antibacterial, anti-diabetes, anti-Alzheimer’s, anticancer, anthelmintic, anti-obesity, and against COVID-19. The article also sheds light on the synthetic strategies used to develop rhodamine derivatives and drug design supported with detailed structure-activity relationships (SAR). Further molecular docking providing mechanistic insights into their binding modes within receptors are also presented. These structural insights could help in further rational design of potent rhodamine derivatives as newer and safer therapeutic agents.
This study reports, for the first time, the green synthesis of copper oxide nanoparticles (CuONPs) using a sulfur-containing inorganic salt and Buchanania lanzan Spreng (BLS) bark extract under ultrasonic irradiation. UV–Vis spectroscopy confirmed the formation of CuONPs by an absorption peak at 292 nm. FESEM images revealed irregular, flake-like, and granular nanoparticles, while EDX analysis confirmed the presence of copper and oxygen. XRD analysis indicated a monoclinic crystal structure with an average crystallite size of 6.9 nm. FTIR spectroscopy showed that the surface of the CuONPs was modified by organic compounds originating from the plant extract, with characteristic absorption bands at 3337 cm−1 (N–H stretching) and 1068 cm−1 (C–O stretching). The observed shifts in the FTIR absorption bands indicated the involvement of these functional groups in the formation and stabilization of the CuONPs. The use of dried BLS bark biomass provides a simple, environmentally friendly, and cost-effective approach for the synthesis of CuONPs. The synthesized nanoparticles exhibited antibacterial activity against both Gram-positive and Gram-negative bacteria, including Staphylococcus aureus (NCIM 5021), Streptococcus mutans (MTCC 497), Bacillus cereus (NCIM 2703), Bacillus subtilis (NCIM 2063), Escherichia coli (NCIM 2832), Salmonella typhi (NCIM 2501), Pseudomonas aeruginosa (NCIM 9027), and Proteus vulgaris (NCIM 2813). The CuONPs showed greater inhibitory activity against Gram-negative bacteria than against Gram-positive bacteria. Furthermore, the nanoparticles exhibited antituberculosis activity against Mycobacterium tuberculosis with an IC50 value of 83.11 µg/mL, compared with 78.94 µg/mL for rifampicin. Overall, the synthesized CuONPs demonstrated significant antimicrobial activity and represent promising broad-spectrum antimicrobial agents.
A series of novel 5,6-dimethylthieno[2,3-d]pyrimidine-piperazine hybrids was rationally designed, synthesized, and evaluated to explore their potential as multifunctional bioactive agents. The target compounds were synthesized via nucleophilic substitution of 4-chloro-5,6-dimethylthieno[2,3-d]pyrimidine with structurally diverse substituted piperazines, affording the desired derivatives in good yields. Structural confirmation was achieved through elemental analysis and comprehensive spectroscopic techniques, which were consistent with the proposed molecular frameworks. Derivatives 4h and 4i showed the most potent antimicrobial activity, while 4f and 4g exhibited superior antioxidant effects. Compounds 4g, 4j, and 4k demonstrated comparatively higher anti-inflammatory activity. Structure–activity relationship (SAR) analysis revealed that electron-withdrawing groups enhance antimicrobial activity, whereas aromatic and electron-rich substituents favor antioxidant and anti-inflammatory responses. Although the activity was lower than that of standard drugs, several compounds displayed meaningful biological potential. These results suggest that the thienopyrimidine–piperazine scaffold is a promising framework for the development of multifunctional therapeutic agents.
In the present study, a novel quinone-substituted piperazine compound (3) was synthesized and characterized using various spectroscopic techniques including FT-IR,1H NMR,13C NMR, UV-Vis, and MS analyses. The conformational preferences of compound (3) were investigated using the semi-empirical PM3 method, and the lowest-energy conformer was then optimized using the Density Functional Theory (DFT) at the wb97xd/6-311++G(d,p) level to determine its optimized structure. Molecular electrostatic potential (MEP) and frontier molecular orbitals (HOMO, LUMO) analyses were performed on the optimized structure using the same level of theory. Molecular docking studies revealed that compound (3) binds strongly to DNA and to Escherichia coli DNA gyrase B. Molecular dynamics (MD) simulations over 200 ns indicated that the (3)-DNA and (3)-6F86 complexes remained stable under the simulated conditions. These in silico results provide preliminary insights into the potential biological activities of compound (3), but experimental studies are needed to confirm these findings. The antibacterial and antifungal activities of (3) were evaluated using the disk diffusion method against various Gram-positive and Gram-negative bacterial strains, including Staphylococcus aureus, Listeria monocytogenes, Bacillus cereus, and Escherichia coli. The results showed that compound (3) exhibited greater antimicrobial activity than its precursor (1), particularly against Enterococcus faecalis and Micrococcus luteus. Additionally, (3) demonstrated significant antifungal activity against Aspergillus niger and Alternaria alternata.
Three new sulfur-rich “scorpionate” ligands containing thione groups have been prepared: potassium hydrobis(pyrazolyl)-N-(2,6-dimethoxyphenyl)-2-thioimidazolylborate (KN2S), potassium hydro{bis-[N-(2,6-dimethoxyphenyl)-2-thioimidazol-1-yl]-[5-phenyl-3-methyl-pyrazol-1-yl]}borate (KNS2), and potassium hydrotris[N-(2,6-dimethoxyphenyl)-2-thioimidazolyl]borate (KS3). These ligands offer progressively higher sulfur content (N2S, NS2, S3 donor sets), which is known to strongly influence zinc–thiolate reactivity in biomimetic systems. Each ligand has been fully characterized by elemental analysis, Fourier-transform infrared (FT-IR), and 1H-13C NMR spectroscopes. To probe their functional behavior, the alkylation reactivity of zinc(II)-benzylthiolato complex S3Zn–SBz as a representative example was evaluated using methyl iodide. Methylation initiated an intramolecular nucleophilic attack by the coordinated thiolate on the methyl group, followed by iodide binding at zinc, cleanly converting S3Zn–SBz into the corresponding zinc(II) iodide complex, S3Zn–I, and the benzyl methyl. Thioether kinetic measurements show that this transformation follows a second-order rate law – first order in zinc complex and first order in methyl iodide – with a rate constant of 5.9 × 10−2 M−1 s−1. This value is in the range reported for intramolecular SN2-type alkylation at zinc-bound thiolates in related tripod systems, underscoring the strong activating effect of an S3 donor environment on sulfur nucleophilicity.
This research work experimentally studied the mechanical characteristics and Electrical Discharge machining (EDM) machinability of in-situ synthesized A356-TiB2 composites using Box–Behnken based RSM. The composite exhibited an average tensile strength (TS) of 251 MPa (248–254 MPa), impact strength of 6.93 J (6.8–7.1 J), and microhardness of 120 HV (118–122 HV), confirming enhanced strength and hardness due to uniform distribution of TiB2 particles. EDM of A356-TiB2 composite was conducted by varying discharge current (Dc):4–12 A, pulse-on time (Pon): 40–80 µs, and pulse-off time (Poff):10–30 µs, The maximum material removal rate (MRR) of 60.18 mg/min was attained at 12 A, 60 µs, and 10 µs, while surface roughness (Ra) ranged from 3.73 µm to 6.93 µm, with the lowest Ra at 4 A and 40 µs. The developed quadratic models demonstrated high statistical significance with R2 values of 99.46% for MRR and 99.55% for Ra. ANOVA identified Dc as the most dominant factor, contributing F-values of 711.39 for MRR and 823.76 for Ra (p < 0.001). SEM examination revealed enlarged crater, microcracks, resolidified globules, and TiB2 at higher discharge settings. The study established empirical relationship for predicting EDM performance and identified optimal parametric level.
The study investigates the synthesis of fused pyridine and pyrimidine derivatives, valued for their varied biological activities and structural adaptability, rendering them essential in organic synthesis. We prepared substituted cyanamide derivatives (4a–m) using a three-component cyclo-condensation method in one pot. 4-chlorobenzaldehyde (1), malononitrile (2), and a variety of primary amines (3a–m) that were rich in electrons and had either aromatic or heterocyclic structures were used in this method. Some synthetic methods, like grinding, microwave irradiation (MWI), and constant reflux, used ethanol as a solvent. Pyridine, pyrimidine, pyrazine, thiazole, and tetrazole are all types of heterocyclic amines that make up the molecule. We used infrared (IR),1H, and 1³C NMR spectroscopy to identify the new compounds. Knoevenagel condensation, Michael addition, and intramolecular cyclization are the three main steps in the chemical process. Prepared compounds displayed anticancer activity on the (HepG2) hepatocarcinoma cell line with reference to doxorubicin (DOX). Compound 4b worked really well against the HepG2 hepatocarcinoma cell line. The rest are fine to good. The suggested method has many advantages, such as a simple one-pot cascade condensation process, easy product isolation, quick reaction times, and yields of 85–94% (excellent to good).
In this paper, a comparative computational study has been conducted on two sets of chalcogen-fused acene molecules. This study aims to provide evidence that the effect of optical and charge transport properties varies with the variation of fused heteroacenes. Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) are employed to calculate absorption and charge transport properties of the designed molecules. Other parameters like ionization potential and electron affinity, along with hole and electron reorganization energies of the designed molecules, are also reported as they affect the charge transport properties of the molecules. Our results reveal that modifications in five-membered heterocycles and increases in molecular size led to significant changes in both optical absorption and charge transport characteristics. These findings provide new insights into the design of heteroacene-based materials with tailored electronic and optoelectronic properties.
Scandium is extensively utilized in advanced technologies, including aerospace materials, electronic information, and nuclear technology, and is considered a strategic resource. At present, low-grade associated minerals and secondary resources serve as the primary sources of scandium. This paper provides an overview of recent research progress in China. It reviews the extraction processes for scandium from various scandium-containing raw materials, analyses the extraction mechanisms and performance of different extractant systems currently employed, and discusses the existing problems and challenges in scandium extraction.
The green synthesis of copper oxide nanoparticles (CuONPs) using mushroom extracts offers a promising alternative for developing antimicrobial agents to combat drug resistance. This study investigated the synthesis of CuONPs from aqueous extract of Pleurotus ostreatus mycelia with copper nitrate as a precursor. Biosynthesis parameters were optimized using response surface methodology (RSM) based on a central composite design (CCD). The CuONPs were characterized using UV–Visible analysis with a peak at 335 nm, and X-ray diffraction (XRD) revealed the characteristic pattern. The resulting NPs had an average diameter of 45.9 nm and a zeta potential of about −10 mV, indicating good stability. The CuONPs exhibited notable antibacterial (with minimum inhibitory concentration against Escherichia coli 72 ± 1.78 mg/L, Klebsiella pneumoniae 81 ± 2.21 mg/L, Bacillus subtilis 95 ± 1.72 mg/L, and Streptomyces sp. 102 ± 0.83 mg/L) and antifungal activity (ED50 value 199.41 mg/L against Fusarium oxysporum). The antibacterial effect was further confirmed by observations of morphological alterations, compromised membrane integrity, reduced motility, and ROS production. In addition, CuONPs showed antioxidant activity, and the ED50 dose did not show any toxic effect when applied to the chili plant. Thus, CuONPs synthesized using the mushroom extract might be applied for curing bacterial and fungal diseases.
Among five-membered nitrogen-rich heterocycles, 1,2,4-triazoles are known for their coordination and significant biological activity. It is observed that triazole-based Schiff bases exhibit enhanced antimicrobial, antifungal, anticancer, and other medicinal properties upon coordination with metal ions. Strong metal-binding ability of these heterocycles also led to wide-range applications in materials science, medicine and agriculture. These metal complexes display remarkable structural diversity, from the variable coordination modes of the ligands and the multiple oxidation states of the metal ions, which govern their geometry, nuclearity, and reactivity. Owing to their stability and versatile coordination behavior, these complexes are promising candidates for functional materials, catalysts, as well as biological and environmental applications. In this context, the present review focuses on the structural diversity and practical applications of metal complexes derived from 1,2,4-triazole Schiff bases reported over the past 15 years, highlighting their unique coordination features and multifunctional applications.
A series of novel sulfonamide derivatives of 6-(aminothiazole) flavones have been designed, synthesized and evaluated in MTT cell proliferation assay against three human cell lines, HeLa (Cervical carcinoma), Hep3B (Hepatocytic carcinoma) and MCF-7 (Breast carcinoma). All the compounds were analyzed by spectroscopic methods. Compound 10c IC50 of 21.93 µM is the good inhibitor of MCF-7 cell line. In sulfonamide series 10h with IC50 values 20.32 µM and 17.23 µM against HeLa and HeP3B cell lines is showing activity comparable with methotrexate. Docking results also have supported above observations by indicating that compounds are held in the active pocket by combination of various hydrogen and hydrophobic interactions.
Coumarin Schiff-base metal complexes have garnered significant interest in medicinal chemistry due to the coumarin scaffold’s synthetic accessibility, low molecular weight, and high biocompatibility. Structural diversification of this core through the incorporation of heterocycles (e.g., pyridine, pyrimidine, thiazole, indole, quinoline) or specific functional groups has proven highly effective in enhancing biological potency. This review underscores the rationale for studying this subclass, highlighting its potential as a versatile pharmacophore with efficient metal chelation and low toxicity. Therefore, we have undertaken a review of coumarin Schiff base metal complexes reported over the past two decades, examining their biomedical applications and highlighting the outcomes of various structural modifications. We elucidate how strategic structural modifications augment bioactivity by fine-tuning lipophilicity, electronic properties, and target selectivity. Surveyed literature demonstrates that metal coordination markedly enhances antimicrobial, anticancer, and antioxidant capabilities compared to the free ligands. These improvements are often attributed to mechanisms such as increased cell permeability and optimized enzyme binding. Furthermore, computational studies, including DFT and Docking, provide critical insights into electronic structures, binding modes, and structure–activity relationships, thereby guiding rational drug design. This review aims to bridge existing research gaps and serve as a foundational resource for advancing these complexes toward therapeutic applications.
Multicomponent reactions (MCRs) have emerged as efficient and sustainable approaches for the synthesis of diverse heterocyclic compounds. Among them, pyrano[2,3-c]pyrazole derivatives have attracted considerable attention due to their wide range of biological and pharmacological activities. One-pot multicomponent strategies provide a simple, rapid, and environmentally friendly method for constructing these heterocyclic frameworks through the reaction of aldehydes, malononitrile, ethyl acetoacetate, and hydrazine derivatives. These reactions generally proceed under mild conditions and often offer high yields with minimal purification steps. The use of various catalysts such as organic bases, metal nanoparticles, ionic liquids, and green solvents has further improved the efficiency and sustainability of these methods. This review summarizes recent developments in one-pot multicomponent synthetic approaches for pyrano[2,3-c]pyrazole derivatives, highlighting reaction mechanisms, catalytic systems, and their advantages in terms of efficiency, selectivity, and eco-friendly synthesis. The review aims to provide a comprehensive overview of current strategies and future perspectives in this field.
