Search Results (326)

Catalytic transformation of carbon dioxide (CO₂) into high-value-added chemicals represents a promising approach for CO₂ emission reduction and utilization. Herein, single-atom ruthenium (Ru) supported on N-heterocyclic carbene (NHC)-functionalized hypercrosslinked polymers were fabricated and applied as recyclable catalysts for the N-formylation of amines using CO₂ and H₂ as feedstocks. Catalytic evaluations demonstrated that the chemical structure of the NHC ligand had a significant influence on catalytic activity. Specifically, P(PhPy-TPB)-Ru, functionalized with a single pyridine moiety on the NHC ligand, exhibited the optimal catalytic performance, even slightly outperforming its homogeneous counterpart. Furthermore, mechanistic studies indicated that both the base and solvent played pivotal roles in modulating the reaction activity. In particular, the use of methanol as the solvent in the presence of a base significantly enhanced reaction efficiency, which was attributed to the in situ generation of methyl formate as a key intermediate. Notably, the developed catalytic system possessed excellent catalytic efficiency, a broad substrate scope, superior stability, and easy recyclability, allowing the catalyst to be reused for up to eight consecutive cycles without significant loss of catalytic activity. Full article

Visible-light-driven decarboxylative alkylation faces challenges from the inertness of Pd-catalyzed oxidative addition of unactivated alkyl halides and the complexity of dual photoredox/metal systems. In this study, we present the first utilization of unsymmetrical N,C,Se-pincer NHC-Pd(II) complexes as single-component photocatalysts for the coupling of arylacrylic acids with unactivated alkyl bromides under blue light. The reaction is conducted at room temperature with catalyst loading of 0.5 mol%, delivering a wide range of alkenylalkane products in yields ranging from 31% to 88%, exhibiting excellent tolerance to halogens and unprotected phenols. Control studies have revealed that the selenoether donor stabilizes active Pd species and enables a radical-mediated pathway. This work extends the utility of N,C,Se-pincer Pd catalysts to reductive C−C coupling and provides a practical platform for biomass valorization. Full article

Imidazolium salt derivatives (IMSDs) represent a structurally diverse class of compounds that has attracted increasing interest as a source of novel anticancer agents due to their tunable chemical architecture and broad spectrum of biological activities. This review summarizes current advances in the development of organic imidazolium derivatives and metal–N-heterocyclic carbene (NHC) complexes, with particular emphasis on their structure–activity relationships (SARs), mechanisms of action, and therapeutic potential. Numerous IMSDs exhibit significant antiproliferative activity against a wide range of cancer cell lines through multiple mechanisms, including DNA damage, reactive oxygen species generation, mitochondrial dysfunction, thioredoxin reductase inhibition, cell-cycle arrest, and apoptosis induction. Among the reported compounds, Au(I)-, Pt(II)-, and Ag(I)-NHC complexes consistently demonstrate the highest cytotoxic potency, whereas hybrid derivatives incorporating pharmacologically active moieties, such as lithocholic acid, have been investigated as potential approaches to improving selectivity and multitarget activity. Current SAR analyses indicate that metal coordination, bulky aromatic substituents, molecular hybridization, and balanced lipophilicity are key determinants of enhanced biological activity. Despite these encouraging findings, most available evidence is limited to in vitro studies, while comprehensive in vivo evaluation, pharmacokinetic characterization, and systematic toxicological assessment remain insufficient. Consequently, the clinical relevance of these compounds has yet to be established. Future research should focus on rational structural optimization, standardized preclinical evaluation, combination therapies, and advanced drug delivery strategies, including nanomedicine, to facilitate the translation of IMSDs into clinically useful anticancer agents. Full article

The clinical success of cisplatin has significantly spurred the exploration of new organometallic complexes in oncology. In this quest, repurposing of auranofin as an anticancer agent has diverted the research interest from platinum to gold complexes, as gold offers unique chemical features; among them, thioredoxin reductase (TrxR) inhibition is one of the most extensively studied anticancer pathways. In this study, we have compiled the major ligand modifications reported for gold(I) complexes and categorized them into various groups, which include sulfur-based ligands, nitrogen-containing heterocyclic ligands, carbon-derived ligands, and N-heterocyclic carbene-based ligands. Also, a few structurally distinct ligands, including propargyl-, allene-, tricarbene-, and urea-functionalized NHC frameworks, have further extended structural diversity and functional potential. The in vitro evaluation of these newly synthesized gold complexes against various cancer cell lines exhibited enhanced biological potential compared to conventional metal complexes. Comparative evaluation of the reported cytotoxicity data revealed distinct structure–activity relationships among different ligand classes, with phosphine-carbon donor and bis-NHC frameworks emerging as the most promising ligand for achieving potent anticancer activity, highlighting the critical role of ligand design in modulating anticancer activity. In addition, the use of bioactive pharmacophores derived from natural products and active pharmaceuticals has emerged as a promising design strategy for developing multitarget gold(I) complexes with enhanced therapeutic efficacy. Among the reviewed compounds, complex 68 containing a bis-NHC ligand exhibited the highest potency against HL-60 leukemia cells (GI₅₀ = 0.017 μM), while complex 49 bearing a carbon-donor ligand demonstrated remarkable activity against A549 lung cancer cells (IC₅₀ = 0.02 μM). Several other gold(I) complexes also exhibited submicromolar activity against diverse cancer cell lines, further emphasizing the importance of rational ligand engineering in enhancing anticancer efficacy. Collectively, gold(I) complexes have emerged as a promising class of anticancer agents, and the comparative evaluation presented herein provides a valuable framework for identifying potent ligand scaffolds and guiding the rational development of next-generation gold-based therapeutics. Future advances in ligand engineering may facilitate targeted drug delivery, controlled release, and multi-mechanistic therapeutic strategies to overcome toxicity and drug resistance while enhancing therapeutic efficacy. Full article

Thioesterification of (2E,2′E)-3,3′-(1,4-phenylene)diacrylaldehyde with thiols has been performed using a bulky N-heterocyclic carbene (NHC) as an organocatalyst. This metal-free protocol enables efficient synthesis of new mono and difunctional acrolein derivatives in high isolated yields under mild conditions. Importantly, the reaction proceeds in the absence of external additives or oxidants, and requires only low organocatalyst loadings, thereby facilitating the straightforward isolation of structurally defined sulfur-containing acrolein derivatives in both symmetric and asymmetric forms. The resulting functional acrolein derivatives are the hitherto underexplored class of functional building blocks with promising potential for biomedical materials, including drug delivery systems and other biomaterials applications. Full article

Cubane-type iron–sulfur clusters play central roles in biological nitrogen fixation, where precise redox regulation governs multi-electron transfer processes. However, how heterometal centers and terminal ligands cooperatively modulate the electronic structure and redox behavior of such clusters remains insufficiently understood. Herein, we report a systematic study on a series of cubane-type [MoFe₃S₃N] clusters as structural mimics of nitrogenase cofactors. Using [(Tp*)MoFe₃S₃(μ₃-NSiMe₃)Cl₃]⁻ as a common precursor, thiolate (RS⁻; R = Me, Et, Ph) and N-heterocyclic carbene (NHC^R; R = Me, Et, iPr) ligands were introduced to probe ligand effects under an invariant cluster framework. All complexes were fully characterized by single-crystal X-ray diffraction and electrochemical measurements. Combined with previously reported tungsten analogues, a direct comparison reveals that both heterometal identity (Mo vs. W) and terminal ligand environment significantly influence local electron density and intermetallic redox cooperativity. Notably, strong σ-donating NHC ligands and heavier heterometal centers induce distinct modulation patterns, highlighting their synergistic roles. This work provides a unified platform for disentangling metal- and ligand-driven effects and offers feasible strategies for the rational tuning of redox properties in heterometallic Fe–S clusters. Full article

The design and manufacture of bifunctional electrocatalysts are of great significance in the electrolysis of water. Herein, porous organic polymers (POPs) of metal–N-heterocyclic carbene were synthesized from imidazolium borate ionic POPs and supported on a nickel foam surface (Pd–NHC/NF, Ag–NHC/NF, and Cu–NHC/NF). Among them, Pd–NHC/NF exhibited high activity for both hydrogen evolution reaction and oxygen evolution reaction. The oxygen evolution overpotential of Pd–NHC/NF was 245 mV with a Tafel slope of 83 mV dec⁻¹; the hydrogen evolution overpotential was 139 mV with a Tafel slope of 94 mV dec⁻¹ at 10 mA cm⁻² in alkaline media. Additionally, the assembled Pd–NHC/NF||Pd–NHC/NF electrolyzer demonstrated excellent performance in electrocatalytic water-splitting, achieving a voltage of 1.55 V at 10 mA cm⁻² and showing outstanding stability for over 90 h in the long-term test. The results highlighted the substantial capability of Pd–NHC as a bifunctional catalyst for electrocatalytic water-splitting. Full article

Azolium-derived metallates are well-established intermediates in metal–N-heterocyclic carbene chemistry; however, their potential as standalone therapeutic agents remains largely unexplored. Herein, we report the first systematic biological investigation of a diverse family of Au(I), Cu(I), Pt(II), Pd(II), and Ru(II) metallates paired with functionalized azolium cations. The complexes were synthesized quantitatively through a simple, atom-economical, and purification-free protocol under aerobic conditions in technical-grade green solvents. Structural characterization by multinuclear NMR spectroscopy and single-crystal X-ray diffraction confirmed metallate formation and enabled the first isolation and crystallographic characterization of unprecedented azolium-derived ruthenates. The antiproliferative activity of the complexes was evaluated against cisplatin-sensitive (A2780) and cisplatin-resistant (A2780cis) ovarian cancer cell lines, alongside non-cancerous MRC-5 fibroblasts. Backbone-functionalized derivatives emerged as the most potent compounds, displaying activities comparable or superior to cisplatin in A2780 cells and up to 1000-fold higher potency in the resistant A2780cis model. Notably, unlike cisplatin, the metallates retained nearly unchanged IC₅₀ values across both ovarian cancer lines, strongly suggesting resistance-evasive mechanisms of action. While benzylazido- and methyl guanosine-derived complexes generally exhibited lower overall potency, several members retained significant activity in resistant cells while showing markedly reduced toxicity toward normal fibroblasts, highlighting promising selectivity profiles. Ethoxide-functionalized derivatives and platinum-based metallates combined pronounced anticancer activity with favourable therapeutic windows. Overall, this work establishes azolium-derived metallates as a previously overlooked class of metal-based anticancer agents combining exceptional synthetic accessibility, broad structural tunability, and remarkable activity against platinum-resistant ovarian cancer. Full article

Gold(I) complexes are particularly useful as catalysts in a variety of reactions including, in particular, the electrophilic activation of alkyne substrates, yet they generally require the addition of a silver salt to activate the gold complex by removing an anionic ligand. This results into higher costs and possible problems related to the non-innocence of the silver additive. In this contribution, we highlight the possibility to proficiently use a dinuclear monocationic gold(I) complex developed in our laboratory as a silver-free catalyst. The complex, featuring a bridging N-phosphanyl-N-heterocyclic carbene (NHCP) ligand, indeed exhibits notable activity and selectivity in standard alkyne hydroamination and hydroalkoxylation reactions, particularly in the case of internal alkynes and secondary aromatic amines as substrates. Full article

N-Heterocyclic carbene (NHC) catalysis has emerged as a powerful and versatile strategy for constructing silicon derivatives, offering a metal-free alternative to traditional transition-metal methods. This review comprehensively summarizes recent advances in the NHC-catalyzed synthesis of organosilicon derivatives. Key transformations discussed include both asymmetric and non-asymmetric silylation reactions, as well as the construction of silicon-stereogenic centers. The content is systematically organized according to the types of silicon products and their underlying catalytic mechanisms. Our own perspectives on future development within this rapidly evolving field are also outlined. Full article

Nitronyl nitroxides (NNs) are widely employed in chemistry, physics, and materials science due to their inherently high stability and magnetic properties. However, the synthesis of C(2)-organoelement derivatives remains a challenging task. This paper reports on the efficient synthesis and characterization of an unusual organosilver complex consisting of the [Ag–(IPr)₂]⁺ cation and the [Ag–(NN)₂]⁻ anion. The salt [Ag–(IPr)₂][Ag–(NN)₂] was prepared in high yields (88–96%) by two synthetic routes: by reacting the carbene ligand precursor IPr·HCl with Ag₂O and nitronyl nitroxide NN–H, or by addition of NN–H/^tBuONa to a THF solution of IPrAgCl (generated in situ from IPr·HCl and Ag₂O) under microwave irradiation. Electrochemical analysis of [Ag–(IPr)₂][Ag–(NN)₂] revealed a reversible one-electron oxidation peak at E_1/2 = −0.258 V and an irreversible reduction peak at E_p = −2.169 V, which is likely related to the electrochemical transformation of the nitronyl nitroxide moieties. Crystallization from an acetone/benzene solution yielded crystals of [Ag–(IPr)₂][Ag–(NN)₂]·2H₂O solvate, in which the diradical anion [Ag–(NN)₂]⁻ is bound to two water molecules by hydrogen bonds. These hydrogen bonds stabilize a planar conformation of the [Ag–(NN)₂]⁻ anion, in which both NN fragments lie in the same plane and, according to DFT calculations, are linked by fairly strong antiferromagnetic interaction. DFT calculations also predict the dissociation of the complex with water in toluene solution and a conformational change leading to the appearance of about 90° between NN fragments and a significant decrease in exchange interaction. Full article

A novel multidentate ligand with an O,N,O-tridentate ligand moiety and an N-heterocyclic carbene (NHC) was synthesized. Its palladium complex, in which the NHC part coordinates to the palladium atom, was synthesized and structurally characterized. The O,N,O-part coordinated to an early transition metal such as titanium. The Ti-Pd heterobimetallic complex was observed in solution. Full article

The rapid growth of polyethylene terephthalate (PET) waste and the limitations of conventional recycling methods for mixed waste streams emphasize the need for chemical recycling routes that deliver high-value monomers in a sustainable, resource-efficient manner. This work explores N-heterocyclic carbenes (NHCs) as organocatalysts for the glycolysis of PET with ethylene glycol to bis(hydroxyethyl)terephthalate (BHET), aiming for milder conditions and higher activity. A systematic catalyst screening links steric and electronic properties (percent buried volume, Tolman electronic parameter) of the NHCs to performance in the glycolysis process, resulting in a catalyst system with high PET conversion (up to 97%) and BHET yield (up to 65%). Mechanistic investigations (experimental and computational) support an anionic activation pathway for glycolysis. To lower the reaction temperature, selective cosolvent systems were explored, albeit with some loss of catalytic activity. Cooperative catalysis combining NHCs with Lewis acids enhances activity, leading to a high conversion (up to 90%) while maintaining lower temperatures than state-of-the-art glycolysis methods. The process was successfully transferred to post-consumer waste streams to validate the practicality. Full article

Background/Objectives: Cutaneous leishmaniasis (CL) is a prevalent vector-borne disease characterized by a broad spectrum of clinical manifestations resulting from protozoan parasites belonging to the genus Leishmania. The challenges associated with the treatment of CL are attributable to various factors, including but not limited to: drug resistance, the adverse effects of conventional therapeutic interventions and the imperative for novel therapeutic alternatives to address the global health burden posed by this neglected tropical disease. Methods: In this study, The therapeutic efficacy of two silver(I)-N-heterocyclic carbene (NHC) complexes, namely chloro[1-methallyl-3-(2,4,6-trimethylbenzyl)-5,6-dimethylbenzimidazole-2-ylidene]silver(I) (2a) and chloro[1-methallyl-3-(4-chlorobenzyl)-5,6-dimethylbenzimidazole-2-ylidene]silver(I) (2b), was evaluated against promastigotes in vitro and in vivo in an experimentally induced CL model in Balb/c mice. Results: The findings of this study indicated that these compounds possess the potential to function as effective therapeutic agents, particularly in the treatment of CL. Subsequently, the silver(I) complexes were analyzed by means of molecular docking against LaGP63, LaARG, N-myristoyltransferase and farnesyl pyrophosphate synthase. Conclusions: According to the docking evaluations, complex 2a emerged as the most notable molecule in terms of its potential antileishmanial activity. Full article

Encouraged by the promising anticancer activity of a iodidogold(I)-N-heterocyclic carbene (NHC) complex with a 1,3-diethyl-4-anisyl-5-(4-chlorophenyl)imidazol-2-ylidene ligand system, a series of new gold(I), gold(III) and platinum(II) complexes coordinated to this ligand system were designed, prepared, and characterized using NMR spectroscopy and mass spectrometry methods. A preliminary anticancer screening of the complexes using four esophageal adenocarcinoma (EAC) cell lines showed promising activities for the cationic triphenylphosphino-NHC-gold(I) and bis-NHC-gold(I) complexes, accompanied by strong antiproliferative, colony-, and spheroid-forming inhibitory effects. The compounds were relatively less toxic to the normal esophageal cell line Het-1A and the monocyte cell line THP-1. Moreover, these compounds induced caspase 3/7 activity and downregulated anti-apoptotic proteins (Bcl-XL, Bcl-2, and Mcl-1) in EAC cells. Further, the cell cycle promoter cyclin D1 was suppressed by these NHC-gold(I) complexes. Finally, we observed strong reactive oxygen species (ROS) induction in EAC cells with NHC-gold(I) complexes 8 and 11. Full article