Coordination chemistry of thiazoles, isothiazoles and thiadiazoles

Structural diversity of photoluminescent lanthanide(III) coordination compounds with an isothiazole derivative

Two different series of europium(III), terbium(III) and gadolinium(III) complexes with 4,5-dichloroisothiazole-3-carboxylic acid (HL) were obtained. According to the data obtained from various analysis methods, the first type of coordination compounds with the general formula of [Ln(H2O)L2(OAc)]n was polymer chains, and the second type with the general formula of [Ln6(H2O)10L18] was hexanuclear complexes, with central atoms arranged similar to octahedrons. DFT calculations were used to determine the location of the electron density in HOMO/LUMO and the value of the triplet state energy of the ligand molecule. The highest luminescence quantum yield was observed in the case of the hexanuclear terbium(III) complex (24%) with a millisecond luminescence lifetime, while the hexanuclear europium(III) compound (96%) exhibited the highest value of color purity.

Structural tuning of tetrazole-BODIPY Ag(i) coordination compounds via co-ligand addition and counterion variation

The coordination properties of a previously described fluorescence active ligand (L), consisting of a coordinating unit (1H-tetrazol-1-yl) and a fluorophore (4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) derivative) towards Ag(i) were investigated. Additionally, the influence of different anions (BF4 -, PF6 -, PF2O2 -, ClO4 -, ReO4 - and NO3 -) and a co-ligand (CH3CN) on the crystal structure formation and intramolecular interactions of the Ag(i) coordination compounds was studied. Beside structural investigations via single crystal X-ray diffraction, bulk characterization of the coordination compounds was conducted in both solution and solid-state, including NMR (1H, 11B, 19F, 31P and 13C), ATR-IR, UV-vis and photoluminescence spectroscopy as well as PXRD. Eleven distinct coordination compounds are reported, each falling into one of four classes: the first group (I) comprises of a mononuclear complex, whereas group (II) consists of dinuclear complexes with ligand bridged metal centers (Ag(i)) and weak intermetallic interactions (∼4 Å). Group (III) likewise includes dinuclear complexes, but the bridging mode was prevented and the Ag-Ag distance was reduced (∼3.2 Å) upon the addition of a co-ligand. Group (IV), a structurally diverse category consists of coordination polymers, which in some cases show even shorter intermetallic contacts (<3.1 Å). All investigated coordination compounds exhibit photoluminescence in the solid state, with structurally dependent emission maxima distinct from those of the ligand.

From Donor-Acceptor Ligands to Smart Coordination Polymers: Cyanothiazole-Cu(I) Complexes for Multifunctional Electronic Devices

Cyanothiazoles, small and quite overlooked molecules, possess remarkable optical properties that can be fine-tuned through coordination with transition metals. In this study, we investigate a promising application of cyanothiazoles, where their combination with copper(I) iodide forms a new class of complexes exhibiting outstanding optical properties. X-ray crystallography of copper(I) iodide complexes with isomeric cyanothiazoles revealed key structural features, such as π─π stacking, hydrogen bonding, and rare halogen⋅⋅⋅chalcogen I⋅⋅⋅S interactions, enhancing stability and reactivity. Advanced spectroscopy and computational modeling allowed precise identification of spectral signatures in Fourier-transform infrared (FTIR), nuclear magnetic resonance (NMR), and ultraviolet-visible (UV-Vis) spectra. Fluorescence studies, along with X-ray absorption near edge structure (XANES) synchrotron analyses, highlighted their unique thermal and electronic properties, providing a solid foundation for further research in the field.

Advances in Π-Conjugated Benzothiazole and Benzoxazole-Boron Complexes: Exploring Optical and Biomaterial Applications

This mini-review highlights the transformative potential of benzothiazole (BTz)- and benzoxazole (BOz)-based boron-complexed dyes. It represents an innovative evolution of the classic boron-dipyrromethene (BODIPY) structure, which is well established for its superior photophysical properties. Incorporating BTz- or BOz-ligands into the borane (-BR2) component, originates more electron-deficient architecture, enabling novel modes of complexation and addressing limitations such as spectral overlap and self-quenching in traditional BODIPY dyes. The review focuses on the remarkable versatility of boron-benzothiazole (BOBTz)- and boron-benzoxazole (BOBOz)-based complexes, particularly in three rapidly advancing fields: organic light emitting diode (LED) technology, bioimaging, and mechanochromic luminescence (MCL). Over the past 15 years, these complexes have demonstrated exceptional adaptability, showcasing enhanced properties like high fluorescence quantum yields, large molar extinction coefficients, and tunable emissions across visible and near-infrared spectra. The insights described in this review highlight the major role of BOBTz- and BOBOz-complexes in shaping innovative, and sustainable advanced materials while addressing emerging challenges in modern materials science. Besides, the refining of both BOBTz- and BOBOz-complexes offers exciting prospects for technological challenges such as energy-efficient lighting, non-invasive imaging, and creating stimuli-responsive materials for next-generation sensors. Moreover, the environmental sustainability of these materials, including green synthesis approaches and recyclable components represents an important frontier for future exploration.

Visible-Light-Induced Annulation of Benzothioamides with Sulfoxonium Ylides To Construct Thiazole Derivatives

Herein, visible-light-induced annulation of benzothioamides with sulfoxonium ylides to furnish thiazole derivatives is developed under transition-metal-, photocatalyst-, and oxidant-free conditions. This protocol exhibits good substrate scope, affording the desired products with satisfied yields in a mild and green manner. Detailed mechanistic studies suggest that the benzothioamide substrate plays a dual role in this reaction. Under visible-light irradiation, excited benzothioamide, in its triplet state, could undergo S attack to the C═S moiety of the sulfoxonium ylide followed by the dissociation of dimethyl sulfoxide and H migration to give a key adduct. In addition, benzothioamide could act as an organocatalyst to facilitate the intramolecular cyclization of the adduct and proton transfer steps. After the dehydration of the cyclized intermediate, the desired thiazole derivatives can be produced.

Thiazole and Isothiazole Chemistry in Crop Protection

Thiazole and isothiazole are types of five-membered heterocycles that contain both sulfur and nitrogen atoms. They have gained attention in the field of green pesticide research due to their low toxicity, strong biological activity, and ability to undergo diverse structural modifications. By incorporating thiazole and isothiazole groups into various compounds, researchers have been able to create a wide range of pesticides with broad-spectrum effectiveness. Understanding the relationship between the structure of these compounds and their activities is crucial for the development of new and highly potent pesticides. This review highlights thiazole and isothiazole derivatives with various biological activities and aims to inspire the development of innovative pesticide based on these structures.

Synthesis, crystal structure, Hirshfeld surface analysis and DFT calculations of the coordination compound tetra-aqua-bis-{2-[(5-methyl-1,3,4-thia-diazol-2-yl)sulfan-yl]acetato-κO}cobalt(II)

A novel coordination compound, [Co(L)2(H2O)4], was synthesized from aqueous solutions of Co(NO3)2 and the ligand 2-[(5-methyl-1,3,4-thia-diazol-2-yl)sulfan-yl]acetic acid (HL, C5H6N2O2S2). In the monoclinic crystals (space group P21/c), the cobalt(II) ion is located about a centre of symmetry and is octa-hedrally coordinated by two L- anions in a monodentate fashion through carboxyl O atoms and by four water mol-ecules. A relatively strong hydrogen bond between one of the water mol-ecules and the non-coordinating carboxyl-ate O atom consolidates the conformation. In the crystal, inter-molecular hydrogen bonds lead to the formation of a complex tri-periodic structure. Hirshfeld surface analysis revealed that 30.1% of the inter-molecular inter-actions are from H⋯H contacts and 20.8% are from N⋯H/H⋯N contacts. DFT calculations were performed to assess the stability and chemical reactivity of the compound by determining the energy differences between the HOMO and LUMO.

Copper-Catalyzed One-Pot Synthesis of N,N-4-Triphenylthiazol-2-amines

Herein, we reported an efficient copper-catalyzed strategy for the synthesis of N,N-4-triphenylthiazol-2-amines from bromoacetophenone, phenylthiourea and iodobenzene. This method features good functional group tolerance, easy availability of starting materials and simplicity of operation, which provides an alternative method for the synthesis of 2-aminothiazoles.

Discovery of quaternized pyridine-thiazole-ruthenium complexes as potent anti-Staphylococcus aureus agents

Quaternization of ruthenium complexes may be a promising strategy for the development of new antibiotics. In response to the increasing bacterial resistance, we integrated the quaternary amine structure into the design of ruthenium complexes and evaluated their antibacterial activity. All the ruthenium complexes showed good antibacterial activity against the tested Staphylococcus aureus (S. aureus). Ru-8 was the most effective antibacterial agent that displayed excellent antibacterial activity against S. aureus (MIC = 0.78-1.56 μg/mL). In vitro experiments showed that all nine ruthenium complexes had low hemolytic toxicity to rabbit erythrocytes. Notably, Ru-8 was found to disrupt bacterial cell membranes, alter their permeability, and induce ROS production in bacteria, all the above leading to the death of bacteria without inducing drug resistance. To further explore the antibacterial activity of Ru-8in vivo, we established a mouse skin wound infection model and a G. mellonella larvae infection model. Ru-8 exhibited significant antibacterial efficacy against S. aureus in vivo and low toxicity to mouse tissues. The Ru-8 showed low toxicity to Raw264.7 cells (mouse monocyte macrophage leukemia cells). This study indicates that the ruthenium complex ruthenium quaternary was a promising strategy for the development of new antibacterial agents.

Synthesis of hydroxy-thiazoline substituted pyridine derivatives via [3 + 2] annulation of 1,4-dithiane-2,5-diol with cyanopyridine

A series of hydroxy-thiazoline substituted pyridine compounds were synthesized via the annulation of 1,4-dithiane-2,5-diol with cyanopyridine catalyzed by organic bases. The yields could reach up to 95%. The reaction required no solvent, and the products were obtained from raw materials and catalysts simply by grinding the mixture at room temperature for 10 min. The reaction could be well tolerated by variously substituted cyanide compounds. The universal applicability of this method was proven by gram-scale reaction and product derivatization.

Efficient extraction of nickel from chloride system using a cleaner extractant: Taking the example of processing nickel-aluminum slag remaining from spent hydroprocessing catalysts

The efficient recovery of nickel from chloride systems has long presented a challenge in the field. While solvent extraction is a viable approach, conventional extractants have been associated with drawbacks such as a high requirement for chloride ions and substantial consumption of acids and alkalis. In response to these challenges, this investigation developed and synthesized a novel thiazole-based extractant, N, N-Bis(4-thiazolylmethyl)octylamine (NNBT), tailored for the selective extraction of nickel from chloride systems. Findings from the study indicate that the nitrogen atom situated on the benzylamine framework within NNBT can interact synergistically with the chelating thiazole ring, facilitating effective nickel extraction and notably reducing the need for chloride ions. Furthermore, the extractant can be regenerated using deionized water, thereby obviating the necessity for additional consumption of acids and alkalis. Following the validation of NNBT as an environmentally sustainable and efficient nickel extractant within the chloride ion system, it was successfully employed to selectively and effectively extract nickel from the nickel-aluminum slag of spent HDP catalyst. The extracted nickel and aluminum were subsequently processed into electroplated nickel chloride and polyaluminum chloride, respectively, meeting the national standards of China. These outcomes underscore the eco-friendliness and promise of NNBT for nickel extraction from chloride systems.

Investigation of Ln3+ complexation by a DOTA derivative substituted by an imidazothiadiazole: synthesis, solution structure, luminescence and relaxation properties

We investigated the coordination properties of original macrocyclic Ln3+ complexes comprising an imidazothiadiazole heterocycle. The thermodynamic stability of the Gd3+ complex was determined by a combination of potentiometric and photophysical measurements. The kinetic inertness was assessed in highly acidic media. The solution structure of the Ln3+ complex was unambiguously determined by a set of photophysical measurements and 1H, 13C, 89Y NMR data in combination with DFT calculations, which proved coordination of the heterocycle to Ln3+. The ability of the imidazothiadiazole moiety to sensitize Tb3+ luminescence was investigated. Finally, the relaxation properties were investigated by recording 1H nuclear magnetic relaxation dispersion (NMRD) profiles and 17O measurements. The water exchange rate is similar to that of GdDOTA as the less negative charge of the ligand is compensated for by the presence of a bulky heterocycle. Relaxivity is constant over a large range of pH values, demonstrating the favorable properties of the complex for imaging purposes.

Cascade Rearrangement: Nitro Group-Participating Syntheses of 1,2,5-Thiadiazoles and 1,2,4-Thiadiazolones

A trifluoroacetic anhydride-mediated cascade process for the synthesis of thiadiazole derivatives is described. 1,2,5-Thiadiazoles and 1,2,4-thiadiazolones could be obtained by variation of the reaction conditions. A group of functionalized thiadiazole derivatives were synthesized in moderate to good yields from nitro-group-containing N-tert-butanesulfinamides. The reactions involved in this tandem process are a Pummerer-like rearrangement of the tert-butanesulfinamide unit, a nitrile oxide formation via nitro group rearrangement, addition of oxygenated nucleophiles, and an N-S bond forming cyclization followed by concomitant elimination.

Phenanthroline and Schiff Base associated Cu(II)-coordinated compounds containing N, O as donor atoms for potent anticancer activity

As an inherent metal ion, copper has been the subject of investigation for developing a novel antitumoral compound that exhibits fewer adverse effects. Copper serves as a cofactor in multiple enzymes, generates reactive oxygen species (ROS), facilitates tumour evolution, metastasis and angiogenesis and has been detected at elevated concentrations in the serum and tissues of various human cancer types. In the given setting, utilising two methodologies in developing novel Copper-based pharmaceuticals for anti-cancer applications is standard practice. These approaches involve either the sequestration of unbound Copper ions or the synthesis of Copper complexes that induce cellular apoptosis. In the past four decades, the latter system has been used, leading to numerous reviews that have examined the anticancer characteristics of a wide range of Copper complexes. These analyses have consistently demonstrated that multiple factors frequently influence the efficacy of these compounds. This review examines the possible anticancer properties of copper and Cu(II) complexes that incorporate Schiff base ligands containing 1,10-phenanthroline. The present study will comprehensively analyse the examined cell lines and mechanistic research associated with each complex.

Selective capture of palladium from acid wastewater by thiazole-modified activated carbon: Performance and mechanism

As a kind of scarce metal, palladium is widely used in many chemical industries. It essential to recover palladium from secondary resources, especially acidic media, owing to high content of palladium in secondary wastes and widespread extraction of palladium via strong acids. Chemically modified carbon materials not only have the advantage of activated carbon but also achieve the precise removal of specific pollutants, which is a kind of adsorption material with broad application prospects. In this direction, we report a solid carbon material named AT-C, which is obtained by one-step synthesis of 2-aminothiazoles grafted to the carbon surface by amidation. The present adsorbent delivers a high palladium adsorption capacity of 178.9 mg g-1, and desirable thermal and chemical stability. The uniform presence of abundant sulfur atoms and CO in the porous network enables AT-C to achieve selective absorption and rapid adsorption kinetics of Pd2+ in the complex water mixture containing many competing ions in the acidic pH range. For the strongly acidic leachates of catalysts, AT-C exhibits outstanding stability in cyclic experiments. Meanwhile, the fixed-bed column test indicates that 1076 bed volumes of the feeding streams can be effectively treated. In addition, AT-C exhibits superior adsorption selectivity, and the recovery efficiency of Pd2+ in actual industrial wastewater is 96.6%. This work realizes an efficient, rapid, and selective removal of palladium under acidic conditions, and provides a reference for complex industrial water treatment and resource recovery of precious metals.

Synthesis, Structure, and Magnetic and Biological Properties of Copper(II) Complexes with 1,3,4-Thiadiazole Derivatives

New coordination compounds of copper(II) with 2,5-bis(ethylthio)-1,3,4-thiadiazole (L1) and 2,5-bis(pyridylmethylthio)-1,3,4-thiadiazole (L2) with compositions Cu(L1)2Br2, Cu(L1)(C2N3)2, Cu(L2)Cl2, and Cu(L2)Br2 were prepared. The complexes were identified and studied by CHN analysis, infrared (IR) spectroscopy, powder X-Ray diffraction (XRD), and static magnetic susceptibility. The crystal structures of Cu(II) complexes with L1 were determined. The structures of the coordination core of complexes Cu(L2)Cl2 and Cu(L2)Br2 were determined by Extended X-ray absorption fine structure (EXAFS) spectroscopy. Magnetization measurements have revealed various magnetic states in the studied complexes, ranging from an almost ideal paramagnet in Cu(L1)2Br2 to alternating-exchange antiferromagnetic chains in Cu(L1)(C2N3)2, where double dicyanamide bridges provide an unusually strong exchange interaction (J1/kB ≈ -23.5 K; J2/kB ≈ -20.2 K) between Cu(II) ions. The cytotoxic activity of copper(II) complexes with L2 was estimated on the human cell lines of breast adenocarcinoma (MCF-7) and hepatocellular carcinoma (HepG2).

Discovery of a new potent oxindole multi-kinase inhibitor among a series of designed 3-alkenyl-oxindoles with ancillary carbonic anhydrase inhibitory activity as antiproliferative agents

An optimization strategy was adopted for designing and synthesizing new series of 2-oxindole conjugates. Selected compounds were evaluated for their antiproliferative effect in vitro against NCI-60 cell lines panel, inhibitory effect on carbonic anhydrase (CA) isoforms (hCAI, II, IX and XII), and protein kinases. Compounds 5 and 7 showed promising inhibitory effects on hCA XII, whereas compound 4d was the most potent inhibitor with low nanomolar CA inhibition against all tested isoforms. These results were rationalized by using molecular docking. Despite its lack of CA inhibitory activity, compound 15c was the most active antiproliferative candidate against most of the 60 cell lines with mean growth inhibition 61.83% and with IC₅₀ values of 4.39, 1.06, and 0.34 nM against MCT-7, DU 145, and HCT-116 cell lines, respectively. To uncover the mechanism of action behind its antiproliferative activity, compound 15c was assessed against a panel of protein kinases (RET, KIT, cMet, VEGFR1,2, FGFR1, PDFGR and BRAF) showing % inhibition of 74%, 31%, 62%, 40%, 73%, 74%, 59%, and 69%, respectively, and IC₅₀ of 1.287, 0.117 and 1.185 μM against FGFR1, VEGFR, and RET kinases, respectively. These results were also explained through molecular docking.

Design of a new method for one-pot synthesis of 2-amino thiazoles using trichloroisocyanuric acid in the presence of a novel multi-functional and magnetically catalytic nanosystem: Ca/4-MePy-IL@ZY-Fe3O4

In this study, an effective approach was developed to synthesize a novel, multifunctional ionic liquid nanocatalyst based on zeolite-Y with 4-methylpyridinium chloride (4-MePy-Cl) and calcium ions (Ca/4-MePy-IL@ZY). Then, Fe₃O₄ nanoparticles were produced inside the zeolite pores with the use of ultrasonic waves. XRD, FESEM, FT-IR, EDX-Map, TGA-DTA, VSM, BET, and atomic absorption techniques were used to identify the structure of the magnetic nanocomposite. Then, its catalytic activity in the one-pot synthesis of 2-aminothiazoles using trichloroisocyanuric acid (TCCA) as a green supplier of halogen ions for intermediates was studied. To provide ideal conditions for the preparation of pure products, first, the one-pot reaction of acetophenone and thiourea in various solvents, different temperatures, and the presence of different amounts of nanocatalysts and the molar amount of TCCA was used. Next, the reaction was investigated in the one-pot preparation of 2-aminothiazole derivatives under optimal conditions. This method replaces iodine (I₂), a toxic reagent, for the first time with TCCA, a safe and sustainable source of halogen. The use of non-toxic solvent and a cheap, safe, recyclable nanocatalyst, quick reaction times, high efficiency, and ease of nanocatalyst separation with the aid of a magnet are additional benefits of this method. This has led to this procedure being classified as "green chemistry".

Detection of Glucose Based on Noble Metal Nanozymes: Mechanism, Activity Regulation, and Enantioselective Recognition

Glucose monitoring is essential to evaluate the degree of glucose metabolism disorders. The enzymatic determination has been the most widely used method in glucose detection because of its high efficiency, accuracy, and sensitivity. Noble metal nanomaterials (NMs, i.e., Au, Ag, Pt, and Pd), inheriting their excellent electronic, optical, and enzyme-like properties, are classified as noble metal nanozymes (NMNZs). As the NMNZs are often involved in two series of reactions, the oxidation of glucose and the chromogenic reaction of peroxide, here the chemical mechanism by employing NMNZs with glucose oxidase (GOx) and peroxidase (POD) mimicking activities is briefly summarized first. Subsequently, the regulation strategies of the GOx-like, POD-like and tandem enzyme-like activities of NMNZs are presented in detail, including the materials, size, morphology, composition, and the reaction condition of the representative NMs. In addition, in order to further mimic the enantioselectivity of enzyme, the design of NMNZs with enantioselective recognition of d-glucose and l-glucose by using different chiral compounds (DNA, amino acids, and cyclodextrins) and molecular imprinting is further described in this review. Finally, the feasible solutions to the existing challenges and a vision for future development possibilities are discussed.

Synthesis and Characterization of New Mixed-Ligand Complexes; Density Functional Theory, Hirshfeld, and In Silico Assays Strengthen the Bioactivity Performed In Vitro

N'-Acetyl-2-cyanoacetohydrazide (H₂L¹) and 2-cyano-N-(6-ethoxybenzo thiazol-2-yl) acetamide (HL²) ligands were used to synthesize [Cr(OAc)(H₂L¹)(HL²)]·2(OAc) and [Mn(H₂L¹)(HL²)]·Cl₂·2H₂O as mixed ligand complexes. All new compounds were analyzed by analytical, spectral, and computational techniques to elucidate their chemical formulae. The bidentate nature was suggested for each coordinating ligand via ON donors. The electronic transitions recorded are attributing to ⁴A₂g(F) → ⁴T₂g(F)(υ₂) and ⁴A₂g(F) → ⁴T₁g(F)(υ₃) types in the octahedral Cr(III) complex, while ⁶A₁ → ⁴T₂(G) and ⁶A₁ → ⁴T₁(G) transitions are attributing to the tetrahedral Mn(II) complex. These complexes were optimized by the density functional theory method to verify the bonding mode which was suggested via N(3), O(8), N(9), and N(10) donors from the mixed-ligands. Hirshfeld crystal models were demonstrated for the two ligands to indicate the distance between the functional groups within the two ligands and supporting the exclusion of self-interaction in between. Finally, the biological activity of the two mixed ligand complexes was tested by in silico ways as well as in vitro ways for confirmation. Three advanced programs were applied to measure the magnitude of biological efficiency of the two complexes toward kinase enzyme (3nzs) and breast cancer proliferation (3hy3). All in silico data suggest the superiority of the Mn(II) complex. Moreover, the in vitro assays for the two complexes that measure their antioxidant and cytotoxic activity support the distinguished activity of the Mn(II) complex.

New thiadiazole modified chitosan derivative to control the growth of human pathogenic microbes and cancer cell lines

The emergence of multidrug-resistant microbes and the propagation of cancer cells are global health issues. The unique properties of chitosan and its derivatives make it an important candidate for therapeutic applications. Herein, a new thiadiazole derivative, 4-((5-(butylthio)-1,3,4-thiadiazol-2-yl) amino)-4-oxo butanoic acid (BuTD-COOH) was synthesized and used to modify the chitosan through amide linkages, forming a new thiadiazole chitosan derivative (BuTD-CH). The formation of thiadiazole and the chitosan derivative was confirmed by FT-IR, ¹H/¹³C-NMR, GC-MS, TGA, Elemental analysis, and XPS. The BuTD-CH showed a high antimicrobial effect against human pathogens Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis, Staphylococcus aureus, and Candida albicans with low MIC values of 25-50 μg ml^-1 compared to unmodified chitosan. The in-vitro cytotoxicity of BuTD-CH was evaluated against two cancer cell lines (MCF-7 and HepG2) and one normal cell (HFB4) using the MTT method. The newly synthesized derivatives showed high efficacy against cancerous cells and targeted them at low concentrations (IC₅₀ was 178.9 ± 9.1 and 147.8 ± 10.5 μg ml^-1 for MCF-7 and HepG2, respectively) compared with normal HFB4 cells (IC₅₀ was 335.7 ± 11.4 μg ml^-1). Thus, low concentrations of newly synthesized BuTD-CH could be safely used as an antimicrobial and pharmacological agent for inhibiting the growth of human pathogenic microbes and hepatocellular and adenocarcinoma therapy.

Design, Spectroscopy, and Assessment of Cholinesterase Inhibition and Antimicrobial Activities of Novel Coumarin–Thiadiazole Hybrids

A novel series of coumarin–thiadiazole hybrids, derived from substituted coumarin-3-carboxylic acids was isolated and fully characterized with the use of a number of spectroscopic techniques and XRD crystallography. Several of the novel compounds showed intensive fluorescence in the visible region, comparable to that of known coumarin-based fluorescence standards. Moreover, the new compounds were tested as potential antineurodegenerative agents via their ability to act as acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) inhibitors. Compared to the commercial standards, only a few compounds demonstrated moderate AChE and BuChE activities. Moreover, the novel derivatives were tested for their antimicrobial activity against a panel of pathogenic bacterial and fungal species. Their lack of activity and toxicity across a broad range of biochemical assays, together with the exceptional emission of some hybrid molecules, highlights the possible use of a number of the novel hybrids as potential fluorescence standards or fluorescence imaging agents.

Design and synthesis of five-membered heterocyclic derivatives of istradefylline with comparable pharmacological activity

Parkinson's disease (PD) is a common degenerative disease of the central nervous system among the elderly. Istradefylline, an FDA-approved adenosine A_2A receptor antagonist (anti-PD drug), has good efficacy. However, it has been reported that the double bond of istradefylline is easily converted into cis-configuration when exposed to an indoor environment or direct light in a dilute solution. In order to find more stable adenosine A_2A receptor antagonists with similar pharmacological efficacy to istradefylline, the compounds series I-1 (12 compounds) was designed by maintaining the xanthine skeleton of istradefylline unchanged and replacing the trans-double bond with thiazole or benzothiazole and other biologically active heterocyclic compounds. These compounds were synthesized via multi-step experiment and successfully confirmed through different characterization techniques for their ability to inhibit cAMP formation in A_2A AR overexpressing cells. The thiazole derivative of istradefylline (Compound I-1-11, I-1-12) exhibited significant activity (IC₅₀  = 16.74 ± 4.11 μM, 10.36 ± 3.09 μM), as compared to istradefylline (IC₅₀  = 5.05 ± 1.32 μM). In addition, the molecular docking of benzothiazole derivatives I-1-11 and thiazole derivatives I-1-12 with higher inhibition rate were carried out and compared with istradefylline. The molecular docking results showed that I-1-11 and I-1-12 anchored in the same site as that of XAC (3REY) with predicted affinity binding energy -6.63 kcal/mol and - 6.75 kcal/mol, respectively. Validation through dynamics simulation also showed stable interactions, with fluctuations <3 Å and MM/GBSA energy <-20 kcal/mol. Hence, this study could provide a basis for the rational design of adenosine A_2A receptor antagonists with better potency.

Application of Heterocycles as an Alternative for the Discovery of New Anti-ulcer Compounds: A Mini-Review

Peptic ulcer is a lesion located in the esophagus, stomach, and upper intestine, caused by an imbalance between acid secretion and the release of protective mucus. This pathology is prevalent in approximately 14% of the world population and is commonly treated with proton pump inhibitors and type 2 histaminergic receptor antagonists, however, these drugs present concerning side effects that may lead to gastric cancer. In this sense, this research aimed to present the main heterocyclics studied in recent years. The screening method for the choice of articles was based on the selection of publications between 2000 and 2021 present in the Science Direct, Web of Science, Capes, and Scielo databases, by using the descriptors ''new derivatives'', "heterocyclics" "antiulcerogenic", "gastroprotective" and "antisecretor". This research showed that the most used rings in the development of antiulcer drugs were benzimidazole, quinazoline, thiazole, and thiadiazole. The results also portray several types of modern in silico, in vitro and in vivo assays, as well as the investigation of different mechanisms of action, with emphasis on proton pump inhibition, type 2 histaminergic receptor blockers, potassium competitive acid blockers, type E prostaglandin agonism, anti-secretory activity and antioxidant action. Additionally, the review evidenced the presence of the nitrogen atom in the heterocyclic ring as a determinant of the potential of the compound. This research suggests new alternatives for the treatment of gastric lesions, which may be more potent and cause fewer side effects than the currently used, and tend to evolve into more advanced studies in the coming years.

Zn(ii) complexes with thiazolyl–hydrazones: structure, intermolecular interactions, photophysical properties, computational study and anticancer activity

Title ligands and their symmetrical octahedral complexes are not photoluminescent, contrary to other synthesized asymmetrical complexes. In comparison to the ligands, the complexes showed improved antiproliferative activity and lower toxicity.

Carbon-Sulfur Bond Formation: Tandem Process for the Synthesis of Functionalized Isothiazoles

In this paper, we report a new process for the construction of 3,4,5-substituted isothiazoles via reaction cascades including Pummerer-like rearrangement, nucleophilic condensation, and sulfenamide cyclization followed by concomitant elimination and dehydration under mild reaction conditions. This process provides isothiazoles bearing fluorine and other functional groups in good to excellent yields from readily available starting materials.

Synthesis of Isothiazoles through N-Propargylsulfinylamide: TFA-Promoted Sulfinyl Group-Involved Intramolecular Cyclization

A new reactivity mode of tert-butanesulfinamide has been developed, which proceeds through C-S and O-S bond cleavage of N-propargyl tert-butanesulfinylamide allowing rapid assembly of poly functionalized isothiazoles. This intramolecular cyclization reaction could be conducted under mild and convenient conditions and tolerates several fluoroalkyl and substituted phenyl groups with good chemical yields. This reaction not only represents a new reactivity of tert-butanesulfinamide but also provides an easy strategy for the synthesis of isothiazoles.

1,2,5-Thiadiazole 1,1-dioxides and Their Radical Anions: Structure, Properties, Reactivity, and Potential Use in the Construction of Functional Molecular Materials

This work provides a summary of the preparation, structure, reactivity, physicochemical properties, and main uses of 1,2,5-thiadiazole 1,1-dioxides in chemistry and material sciences. An overview of all currently known structures containing the 1,2,5-thiadiazole 1,1-dioxide motif (including the anions radical species) is provided according to the Cambridge Structural Database search. The analysis of the bond lengths typical for neutral and anion radical species is performed, providing a useful tool for unambiguous assessment of the valence state of the dioxothiadiazole-based compounds based solely on the structural data. Theoretical methodologies used in the literature to describe the dioxothiadiazoles are also shortly discussed, together with the typical 'fingerprint' of the dioxothiadiazole ring reported by means of various spectroscopic techniques (NMR, IR, UV-Vis). The second part describes the synthetic strategies leading to 1,2,5-thiadiazole 1,1-dioxides followed by the discussion of their electrochemistry and reactivity including mainly the chemical methods for the successful reduction of dioxothiadiazoles to their anion radical forms and the ability to form coordination compounds. Finally, the magnetic properties of dioxothiadiazole radical anions and the metal complexes involving dioxothiadiazoles as ligands are discussed, including simple alkali metal salts and d-block coordination compounds. The last section is a prospect of other uses of dioxothiadiazole-containing molecules reported in the literature followed by the perspectives and possible future research directions involving these compounds.

Synthesis, structure and computational study of 5-[(prop-2-en-1-yl)sulfanyl]-1,3,4-thiadiazol-2-amine (Pesta) and its heterometallic π,σ-complex [Cu2FeCl2(Pesta)4][FeCl4]

Copper(I) π-coordination compounds with allyl derivatives of azoles are an interesting subject of current research, but Cu^I π-complexes with other transition-metal ions incorporated in the structure have been virtually uninvestigated. The present work is directed toward the synthesis and structural characterization of the novel heterometallic Cu^I/Fe^II π-complex di-μ₂-chlorido-1:2κ²Cl;2:3κ²Cl-tetrakis[μ₂-5-(prop-2-en-1-ylsulfanyl)-1,3,4-thiadiazol-2-amine]-1:2κ²N⁴:N³;1(η²),κN⁴:2κN³;2:3κ²N³:N⁴;2κN³:3(η²),κN⁴-dicopper(I)iron(II) tetrachloridoferrate(II), [Cu₂FeCl₂(C₅H₇N₃S₂)₄][FeCl₄] (1). The structure of the 5-[(prop-2-en-1-yl)sulfanyl]-1,3,4-thiadiazol-2-amine (Pesta, C₅H₇N₃S₂) ligand is also presented. The cationic substructure in 1 consists of one Fe^II and two Cu^I ions bridged by two chloride ions along with two σ,σ- and two π,σ-coordinated ligands, whereas the anionic part is built of isolated tetrahedral [FeCl₄]^2- ions. π-Coordination of the Pesta allyl group to the Cu^I ions prevents agglomeration of the inorganic Cu-Cl-Fe-Cl-Cu part into infinate chains. An energy framework computational analysis was performed for Pesta.

Cross-coupling of [11C]methyllithium for 11C-labelled PET tracer synthesis

The cross-coupling of aryl bromides with [¹¹C]CH₃Li for the labelling of a variety of tracers for positron emission tomography (PET) is presented. The radiolabelled products were obtained in excellent yields, at rt and after short reaction times (3-5 min) compatible with the half-life of ¹¹C (20.4 min). The automation of the protocol on a synthesis module is investigated, representing an important step towards a fast method for the synthesis of ¹¹C-labelled compounds for PET imaging.

Anticancer activity, DNA binding and docking study of M(ii)-complexes (M = Zn, Cu and Ni) derived from a new pyrazine–thiazole ligand: synthesis, structure and DFT

A series of structurally related Zn(ii), Cu(ii) and Ni(ii) complexes of 4-(2-(2-(1-(pyrazin-2-yl)ethylidene)hydrazinyl)-thiazol-4-yl)-benzonitrile (PyztbH) have been synthesized and characterized by spectroscopy, single crystal X-ray crystallography and density functional theory (DFT).

Synthesis of Isoselenazoles and Isothiazoles from Demethoxylative Cycloaddition of Alkynyl Oxime Ethers

A general method for the synthesis of isoselenazoles and isothiazoles has been developed by the base-promoted demethoxylative cycloaddition of alkynyl oxime ethers using the cheap and inactive Se powder and Na₂S as selenium and sulfur sources. This transformation features the direct construction of N-, Se-, and S-containing heterocycles through the formation of N-Se/S and C-Se/S bonds in one-pot reactions with excellent functional group tolerance.

Synthesis, characterization, HSA/DNA interactions and antitumor activity of new [Ru(η6-p-cymene)Cl2(L)] complexes

Three new ruthenium(II) complexes were synthesized from different substituted isothiazole ligands 5-(methylamino)-3-pyrrolidine-1-ylisothiazole-4-carbonitrile (1), 5-(methylamino)-3-(4-methylpiperazine-1-yl)isothiazole-4-carbonitrile (2) and 5-(methylamino)-3-morpholine-4-ylisothiazole-4-carbonitrile (3): [Ru(η⁶-p-cymene)Cl₂(L1)]·H₂O (4), [Ru(η⁶-p-cymene)Cl₂(L2)] (5) and [Ru(η⁶-p-cymene)Cl₂(L3)] (6). All complexes were characterized by IR, UV-Vis, NMR spectroscopy, and elemental analysis. The molecular structures of all ligands and complexes 4 and 6 were determined by an X-ray. The results of the interactions of CT-DNA (calf thymus deoxyribonucleic acid) and HSA (human serum albumin) with ruthenium (II) complexes reveal that complex 4 binds well to CT-DNA and HSA. Kinetic and thermodynamic parameters for the reaction between complex and HSA confirmed the associative mode of interaction. The results of Quantum mechanics (QM) modelling and docking experiments toward DNA dodecamer and HSA support the strongest binding of the complex 4 to DNA major groove, as well as its binding to IIa domain of HSA with the lowest ΔG energy, which agrees with the solution studies. The modified GOLD docking results are indicative for Ru(p-cymene)LCl··(HSA··GLU292) binding and GOLD/MOPAC(QM) docking/modelling of DNA/Ligand (Ru(II)-N(7)dG7) covalent binding. The cytotoxic activity of compounds was evaluated by MTT (3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide) assay. Neither of the tested compounds shows activity against a healthy MRC-5 cell line while the MCF-7 cell line is the most sensitive to all. Compounds 3, 4 and 5 were about two times more active than cisplatin, while the antiproliferative activity of 6 was almost the same as with cisplatin. Flow cytometry analysis showed the apoptotic death of the cells with a cell cycle arrest in the subG1 phase.