Search Results (215)

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

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

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

Iron(II) complexes bearing N-heterocyclic carbene (NHC) ligands have emerged as promising earth-abundant dye sensitizers for applications in dye-sensitized solar cells (DSSCs). In this work, we present a computational study of a set of 42 Fe–NHC dyes derived from seven ligand frameworks, systematically functionalized with donor, acceptor, and donor–acceptor groups to tune or enhance their photophysical properties. The calculated geometries reveal that substitution modulates Fe–N bond lengths and ligand dihedral angles only slightly, preserving the structural integrity of the complexes. TD-DFT calculations show clear and predictable electronic trends: donor groups raise the HOMO, acceptor groups lower the LUMO, and the combined push–pull configuration produces the most pronounced HOMO–LUMO gap narrowing and largest redshifts in MLCT transitions. Key DSSC performance descriptors, including electron-injection and dye-regeneration free energies, light-harvesting efficiency, excited-state lifetimes, and hole-transport reorganization energies, collectively identify the double-acceptor and push–pull derivatives as the most promising candidates across multiple frameworks. Full article

Nature-inspired ligands, including natural product scaffolds and bio-inspired motifs, have emerged as an important source for the development of gold(I) complexes with promising preclinical anticancer activity. This review focuses on structurally characterised gold(I) complexes derived from these ligands, emphasising how ligand structure and gold coordination influence the biological activity. This paper covers the synthesis of nature-inspired gold(I) complexes, alkynyl, N-heterocyclic carbene (NHC), heteroatom-donor, and heterobimetallic complexes, which collectively contribute to enhanced cytotoxicity, stability, and mechanistic diversity. By focusing on these nature-inspired gold(I) complexes, this review provides a concise structure–activity perspective and outlines future opportunities for rational design in anticancer research. Full article

For those who did not follow the invention and development of enantioselective catalysis, this review introduces pertinent historical aspects of the field and presents the scientific concepts of asymmetric bio- and organocatalysis. They are powerful technologies applied in organic laboratories and industry. They realize chiral amplification by converting inexpensive achiral substrates and reagents into enantiomerically enriched products using readily recoverable solvents, if any are used. Racemic substrates can also be deracemized catalytically. More sustainable fabrications are now available that require neither toxic metallic species nor costly reaction conditions in terms of energy, atmosphere control, product purification, and safety. Nature has been the source of the first asymmetric catalysts (microorganisms, enzymes, alkaloids, amino acids, peptides, terpenoids, sugars, and their derivatives). They act as temporary chiral auxiliaries and lower the activation free energy of the reaction by altering the reaction mechanism. Reductions, oxidations, carbon-carbon and carbon-heteroatom bond-forming reactions are part of the process panoply. Asymmetric catalyzed multicomponent and domino reactions are becoming common. Typical modes of activation are proton transfers, hydrogen bonded complex formation, charged or uncharged acid/base pairing (e.g., σ-hole catalysts), formation of equilibria between achiral aldehydes and ketones with their chiral iminium salt or/and enamine intermediates, umpolung of aldehydes and ketones by reaction with N-heterocyclic carbenes (NHCs), phase transfer catalysis (PTC), etc. Often, the best enantioselectivities are observed with polyfunctional catalysts derived from natural compounds, but not always. They may combine to form chiral structures containing nitrogen, phosphorus, sulfur, selenium, and iodine functional moieties. Today, man-made enantiomerically enriched catalysts, if not enantiomerically pure, are available in both enantiomeric forms. Being robust, they are recovered and reused readily. Full article

Apart from in hydrosilylation, platinum has traditionally played a limited role in homogeneous catalysis due to its high thermodynamic stability and lower intrinsic reactivity compared to other group 10 metals. However, the emergence of N-heterocyclic carbene (NHC) ligands has substantially broadened the catalytic profile of transition metals by enabling access to new mechanistic pathways and enhancing robustness under demanding conditions. This review summarizes advances in Pt–NHC catalysis reported between 2010 and 2025. These transformations encompass hydrosilylation of amides and CO₂, hydroboration and diboration, hydroamination, alkyne hydration, hydrogenation, selective alkyne dimerization, Suzuki–Miyaura coupling, arene C–H borylation, and cycloisomerization reactions, in which NHC ligands enhance bond activation, control regio- and stereoselectivity, and stabilize reactive Pt intermediates, including chiral architectures, enabling high enantioselectivity. Full article

Background: Gold (Au) complexes have emerged as promising anticancer candidates due to their distinct coordination chemistry and ability to modulate thiol-dependent and redox-regulated cellular pathways, particularly thioredoxin reductase (TrxR). In recent years, structurally diverse Au(I) and Au(III) complexes have been reported with potent in vitro anticancer activity; however, cross-study comparability and design principles remain unclear. Aim: This systematic review critically evaluates anticancer Au(I/III) complexes reported since 2016, with the specific aim of identifying how oxidation state, coordination geometry, and ligand class influence in vitro potency, selectivity, and translational potential. Methods: A PRISMA-guided literature search was performed in Scopus, Web of Science, PubMed, and ScienceDirect for studies published between January 2016 and March 2025. Two independent reviewers screened titles/abstracts and full texts according to predefined inclusion criteria. Only original studies reporting anticancer activity of structurally characterized Au(I/III) complexes in human cancer models were included. After the removal of duplicates, 1100 records were screened at the title and abstract level. Of these, 240 articles were assessed in full text for eligibility. Ultimately, 128 studies reporting anticancer activity of structurally characterized Au(I/III) complexes met the inclusion criteria and were included in the qualitative synthesis. Biological potency data were harmonized to μM units where applicable, and results were synthesized qualitatively due to heterogeneity in experimental design. Results: A total of 128 studies met the inclusion criteria. Au(I) complexes—particularly phosphine- and N-heterocyclic carbene (NHC)-based compounds—consistently showed sub-micromolar cytotoxicity in TrxR-dependent cancer cell lines, whereas Au(III) complexes displayed greater structural diversity but variable stability and redox behavior. In vivo efficacy was reported for a limited subset of compounds and was frequently constrained by solubility, systemic toxicity, or metabolic instability. Conclusions: The available evidence indicates that anticancer activity of gold complexes is strongly dependent on oxidation state, ligand environment, and redox stability. While Au(I) scaffolds show more reproducible in vitro potency, successful translation to in vivo models remains limited. This review defines structure–activity and structure–liability relationships that can guide the rational design of next-generation gold-based anticancer agents. Full article

1-Butyl-3-methylimidazolium (bmim) ionic liquids (ILs) are widely used for lignocellulose fractionation, yet their role extends beyond mere solvents. This study revealed that bmim-based ILs act as active chemical reagents, modifying the lignin structure in an anion-dependent manner. Thermal treatment (80–150 °C) of spruce dioxane lignin with [bmim]OAc, [bmim]Cl, and [bmim]MeSO₄ resulted in two distinct transformation pathways. In [bmim]MeSO₄, acidic catalysis dominates, leading to lignin condensation (increase in weight-average molecular weight, M_w, to 15.2 kDa at 150 °C) and intense sulfur incorporation (up to 9.9%) via anion-derived methylation/sulfation. Conversely, [bmim]OAc promotes depolymerization (decrease in M_w to 3.6 kDa) and efficient covalent bonding of the bmim cation to lignin (up to 10.8 cations per 100 aromatic units and a 6.5% nitrogen content at 150 °C), preventing condensation. Two-dimensional NMR and HPLC-HRMS analyses revealed the formation of a C–C bond between the C₂ atom of the imidazole ring and the α-carbon of the phenylpropane lignin fragments and allowed for the identification of a number of individual nitrogen-containing lignin oligomers in the [bmim]OAc-treated samples. Their formation likely proceeds via nucleophilic addition of the N-heterocyclic carbene (NHC), derived from the bmim cation by deprotonation with the highly basic acetate anion, to aldehyde groups. The action of [bmim]Cl primarily induces acid-catalyzed transformations of lignin with minimal covalent modification. These findings redefine imidazolium ILs as reactive media in biorefining, where their covalent interactions can influence the properties of lignin but complicate its native structure and the recyclability of the IL. Full article