Search Results (143)

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

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

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

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

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

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

Lanthanide coordination polymers have been developed at a fast rate during the past two decades due to their appealing applications in the modern field of materials science and emerging technologies like luminescence, magnetism, sensing, gas adsorption, and catalysis. The role of lanthanides in imparting specific properties to the coordination polymers has been fully documented in extensive studies carried out by numerous research groups. It has been shown that because lanthanide(III) ions possess a variable coordination number, they readily build two-dimensional and three-dimensional architectures with definite channels, permanent pores, and distinct surface areas. Due to their strong oxophilic propensity and hard Lewis acid character, lanthanides favor the construction of stable coordination polymers and MOF configurations by strongly binding the coordinating groups of the organic linkers. Associated with palladium complexes, the lanthanide ions provide synergistic effects with Lewis acid sites, beneficial to the catalytic activity. These attractive characteristics of lanthanides enabled them to be fruitfully applied in Pd-Ln coordination polymers with catalytic properties. This review covers an array of Pd-Ln coordination polymers applied as heterogeneous catalysts in Suzuki–Miyaura C(sp²)-C(sp²) cross-coupling reactions. The activity and chemoselectivity of Pd(II) ions and Pd nanoparticles associated in coordination polymers with different lanthanides from a selected array of rare earth elements (Eu, Sm, Eu, Gd, Pr, Nd, Ce, La, or Tb) is discussed. High yields (>99%) are attained under optimized reaction conditions. The specific role of lanthanides and organic ligands in creating sustainable and recyclable heterogeneous Pd catalysts is evidenced. Mechanistic aspects of the C(sp²)-C(sp²) cross-coupling reactions are considered. The synergistic interaction between lanthanides and palladium as well as with the organic ligands is highlighted. Full article

The purpose of this work was to study water-soluble platinum complexes as potential therapeutic agents. We used water-soluble platinum(II) complexes containing sulfonated N-heterocyclic carbene ligands (NHC), applied on two human cell models: human NB4 acute promyelocytic leukemia and PC3 prostatic cancer cells. We studied the toxic effects on these two types of human tumor cells. We analyzed metabolic activity, membrane damage, cell cycle, DNA fragmentation and programmed cell death. In human NB4 leukemia cells, the water-soluble dimethyl NHC complex 5Me proved highly toxic. It extinguished cell metabolism at 1 mM for 24 h. This treatment gave rise to the presence of fragmented DNA (subdiploid DNA). This compound promoted programed cell death in 60% of the cells. At longer times, the treatments produced neither higher fragmentation of DNA nor augmented apoptosis. 5Me complex, at 100 µM, showed slight toxicity on NB4 cells. In PC3 cells, dimethyl complex 5Me (1 mM for 24 h) is less toxic (reduced DNA fragmentation and programmed cell death) than in NB4 cells. Mono-NHC complexes 4 and 5 treatments at a high concentration for 24 h on PC3 cells produced apoptosis (30% of the cells) but their damage on cell permeability and DNA fragmentation was weak. Thus, PC3 cells are more resistant to NHC platinum(II) complexes than NB4 cells. Full article

We report the synthesis and biological characterization of N-heterocyclic carbene (NHC) complexes with gold(I), silver(I), copper(I), and palladium(II) metal centers, and 3-(2,6-diisopropyl-phenyl) imidazolinium- and imidazolium-based ligands, including their biscarbene complexes, along with metal complexes of 4-(S)-tert-butyl-imidazolinium-derived carbenes carrying various substituents in position 1. Compared to the imidazolium complexes, the corresponding imidazolinium complexes displayed superior cytotoxicity against the Mes-Sa uterine sarcoma cell line, while the biscarbene complexes exhibited greatly enhanced cytotoxicity with nanomolar activity. The ABCB1-overexpressing multidrug-resistant sublines of Mes-Sa demonstrated only marginal resistance to monocarbene imidazolinium complexes lacking a 4-(S)-tert-butyl group, whereas significant resistance was observed for all other complexes, with its extent further influenced by the nature of the metal center. Probing a subset of the complexes confirmed their strong cytotoxicity against the CST murine breast cancer cell line and its cisplatin-resistant variant, with little or no cross-resistance observed. Within a defined subset, compounds triggered apoptosis, and intracellular ROS production was consistently induced by the copper complexes. Collectively, these results indicate that imidazolinium-based metal NHCs are promising anticancer drug candidates, with copper and silver centers standing out for their potent cytotoxicity and evasion of both ABCB1-mediated and cisplatin resistance. Full article

A new zirconium trichloride complex, supported by a monoanionic, pyrrole-based bisphosphinimine NNN-pincer ligand, [LZrCl₃] (L = 2,5-[ⁱPr₂P=N(4-ⁱPrC₆H₄)]₂NH(C₆H₂) (1), is reported. Comparison with a related iminopincer complex reveals significant differences in bond lengths and angles between the atoms around the metal centre, largely due to the more electron donating phosphinimine (R₃P=NR (R = alkyl, aryl)) functionality. The P=N bonds in complex (1•benzene) are longer than in the proteo ligand HL (L = 2,5-[Ph₂P=N(4-ⁱPrC₆H₄)]₂NH(C₆H₂)), which is consistent with phosphinimine coordination to a metal. This is the only reported zirconium complex with this specific ligand scaffold; no analogous complexes have been reported for other group 4 metals. This structure expands the library of Zr pincer complexes that bear tridentate ligand frameworks and sets the stage for the preparation of related complexes. Full article

Transition metal complexes bearing protic N-heterocyclic carbene (pNHC) ligands are promising precatalysts for organic reactions due to their capacity for unique hydrogen-bonding interactions. Herein, we report the synthesis and structural characterization of the first Pd(II) complex featuring a pNHC derived from 1,2,4-triazole—a heterocyclic system previously unexplored for the preparation of metal/pNHC complexes. The complex was synthesized via oxidative addition of 3-bromo-5-cyclohexyl-1-methyl-1H-1,2,4-triazole to Pd(PPh₃)₄ in the presence of NH₄BF₄. Its molecular structure was characterized by NMR spectroscopy and X-ray diffraction analysis. Full article

The compound dichloro[bis(diisopropylphosphorimidoyl-κN-(4,6-dimethylpyrimidine-κN))pyrrole-κN]yttrium(III) was synthesized from one equivalent of NaL [L = 2,5-[ⁱPr₂P=N(Pym^Me)]₂NH(C₄H₂); Pym^Me = 4,6-dimethylpyrimidine] and YCl₃(THF)_3.5 and crystallized from toluene. X-ray quality crystals of LYCl₂ were obtained with one toluene solvent molecule in the asymmetric unit. The geometry, bond lengths and angles were analyzed and found to contain similar parameters to comparable structures in the literature, and the product was further characterized by NMR spectroscopy. To the best of our knowledge, this is the first reported seven-coordinate Y(III) complex supported by a pentadentate ligand wherein all five donor atoms are nitrogen. Full article