Search

The β-diketone scaffold is a commonly used synthetic intermediate, and is a functional group found in natural products such as curcuminoids. This core structure can also act as a chelating ligand for a variety of metals. In order to assess the potential of this scaffold for medicinal inorganic chemistry, seven different κ(2)-O,O’-chelating ligands were used to construct Ru(II) complexes with polypyridyl co-ligands, and their biological activity was evaluated. The complexes demonstrated promising structure-dependent cytotoxicity. Three complexes maintained high activity in a tumor spheroid model, and all complexes demonstrated low in vivo toxicity in a zebrafish model. From this series, the best compound exhibited a ~ 30-fold window between cytotoxicity in a 3-D tumor spheroid model and potential in vivo toxicity. These results suggest that κ(2)-O,O’-ligands can be incorporated into Ru(II)-polypyridyl complexes to create favorable candidates for future drug development.

Rechargeable zinc-ion batteries (RZIBs) are mostly powered by aqueous electrolytes. However, uncontrolled water interactions often confer a small voltage window and poor battery capacity retention. Here, we explore replacing water with ethylene glycol as the primary solvent in zinc electrolyte formulations. The assembled batteries reveal suppressed electrolyte-induced parasitic reactions, leading to (1) expanded voltage stability windows up to 2.2 V, (2) prolonged zinc stripping/plating stability up to 2.4 times longer compared to the water-based counterparts, and (3) doubled cathode capacity retentions as observed in full-cell Zn-FeVO4 RZIBs. Using a combination of synchrotron EXAFS and FTIR, we investigate the molecular level salt-solvent interactions and explain how the chelation ability of EG ligands reduces parasitic reactions to enable the enhanced electrochemical performances. The structural insights should provide guidelines on the selection of salt, concentration, and chelating solvents for robust multivalent-ion battery systems. National Research Foundation (NRF) Accepted version This work was funded by the National Research Foundation of Singapore Investigatorship Award Number NRFI2017-08

Background 64Cu is one of the few radioisotopes that can be used for both imaging and therapy, enabling theranostics with identical chemical composition. Development of stable chelators is essential to harness the potential of this isotope, challenged by the presence of endogenous copper chelators. Pyridyl type chelators show good coordination ability with copper, prompting the present study of a series of chelates DOTA-xPy (x = 1–4) that sequentially substitute carboxyl moieties with pyridyl moieties on a DOTA backbone. Results We found that the presence of pyridyl groups significantly increases 64Cu labeling conversion yield, with DOTA-2Py, −3Py and -4Py quantitatively complexing 64Cu at room temperature within 5 min (1 × 10− 4 M). [64Cu]Cu-DOTA-xPy (x = 2–4) exhibited good stability in human serum up to 24 h. When challenged with 1000 eq. of NOTA, no transmetallation was observed for all three 64Cu complexes. DOTA-xPy (x = 1–3) were conjugated to a cyclized α-melanocyte-stimulating hormone (αMSH) peptide by using one of the pendant carboxyl groups as a bifunctional handle. [64Cu]Cu-DOTA-xPy-αMSH retained good serum stability (> 96% in 24 h) and showed high binding affinity (Ki = 2.1–3.7 nM) towards the melanocortin 1 receptor. Conclusion DOTA-xPy (x = 1–3) are promising chelators for 64Cu. Further in vivo evaluation is necessary to assess the full potential of these chelators as a tool to enable further theranostic radiopharmaceutical development.

Chelating phosphines have long been a mainstay as efficient directing ligands in transition‐metal catalysis. Low‐valent derivatives, namely chelating phosphinidenes, are to date unknown, and could lead to chelating complexes containing more than one metal centre due to the intrisic capacity of phosphinidenes to bind two metal fragments at one P‐centre. Here we describe the synthesis of the first such chelating bis‐phosphinidene ligand, XantP2 (2), generated by the reduction of a diphosphino xanthene derivative, Xant(PH2)2 (1) with iPrNHC (iPrNHC=[:C{N(iPr)C(H)}2]). Initial studies have shown that this novel chelating ligand can act as a bidentate ligand towards element dihalides (i.e. FeCl2, ZnI2, GeCl2, SnBr2), forming cationic complexes with the tetryl elements. In contrast, XantP2 demonstrates an ability to bind multiple metal centres in the reaction with CuCl, leading to a cationic Cu3P3 ring complex, with Cu centres bridged by phosphinidene arms. Density Functional Theory calculations show that 2 indeed holds 4 lone pairs of electrons, shedding further light on the coordination capacity for this novel ligand class through observation of directionality and hybridisation of these electron pairs., It's a P‐P‐Party! A facile synthetic route to a new form of chelating phosphorous ligand, namely the chelating bis‐phosphinidene XantP2, has been developed, allowing for the gram‐scale synthesis of this novel ligand scaffold. Computational investigations corroborate that each P‐centre holds two lone pairs of electrons, allowing for the binding of multiple metal centres. Initial efforts towards the coordination chemistry of XantP2 are reported.

A new synthetic chelating N–hydroxy–N–trioctyl iminophosphorane (HTIP) was prepared through the reaction of trioctylphosphine oxide (TOPO) with N–hydroxylamine hydrochloride in the presence of a Lewis acid (AlCl3 ). Specifications for the HTIP chelating ligand were successfully determined using many analytical techniques,13C–NMR,1H–NMR, FTIR, EDX, and GC–MS analyses, which assured a reasonable synthesis of the HTIP ligand. The ability of HTIP to retain U(VI) ions was investigated. The optimum experimental factors, pH value, experimental time, initial U(VI) ion concentration, HTIP dosage, ambient temperature, and eluents, were attained with solvent extraction techniques. The utmost retention capacity of HTIP/CHCl3 was 247.5 mg/g; it was achieved at pH = 3.0, 25◦C, with 30 min of shaking and 0.99 × 10−3 mol/L. From the stoichiometric calculations, approximately 1.5 hydrogen atoms are released during the extraction at pH 3.0, and 4.0 moles of HTIP ligand were responsible for chelation of one mole of uranyl ions. According to kinetic studies, the pseudo–first order model accurately predicted the kinetics of U(VI) extraction by HTIP ligand with a retention power of 245.47 mg/g. The thermodynamic parameters ∆S◦, ∆H◦, and ∆G◦ were also calculated; the extraction process was predicted as an exothermic, spontaneous, and advantageous extraction at low temperatures. As the temperature increased, the value of ∆G◦ increased. The elution of uranium ions from the loaded HTIP/CHCl3 was achieved using 2.0 mol of H2SO4 with a 99.0% efficiency rate. Finally, the extended variables were used to obtain a uranium concentrate (Na2U2O7, Y.C) with a uranium grade of 69.93% and purity of 93.24%. © 2022 by the authors. Licensee MDPI, Basel, Switzerland. Princess Nourah Bint Abdulrahman University, PNU: PNURSP2022R13 The authors express their gratitude for the support from Princess Nourah bint Abdulrahman University Researchers Supporting Project number (PNURSP2022R13), Princess Nourah bint Abdulrahman University, Riyadh, Saudi Arabia.

Department of Chemistry, Himachal Pradesh University, Summer Hill, Shimla-171 005, India Manuscript received 18 December 1998, revised 22 June 1999, accepted 29 June 1999 The reactivity of di- and triphenyltin(IV) hydroxamate complexes of composition (C6H5)2SnCl2-n(XBHA)n and (C6H5)3Sn(XBHA) (n = 1 and 2; X = p-OMe, o-Cl, p-NO2; BHA = anion of XArCONHOK) with ligands containing labile protons such as acetylacetone (acacll), dibenzoylmethane (dbmH), salicylaldehyde (salH) and o-chlorophenol and thiophenol has been studied to investigate the preferential attack on Sn-C, Sn-CI or Sn-O bond. The title complexes do not react with the chelating ligands. However, the reactions of (C6H5)2SnCI(XBHA) with sodium salt of the chelating ligands NaL (L = acac, dbm and sal) readily proceed to yield the mixed ligand complexes of composition (C6H5)2Sn(XBHA).L, while the treatment of (C6H5)2Sn(XBHA)2 and (C6H5)3Sn(XBHA) with phenols results in the complete displacement of the hydroxamate group with the phenolate ion.

Hydrodesulfurization (HDS) is a widely used process currently employed in petroleum refineries to eliminate organosulfur compounds in fuels. The current hydrotreating process struggles to remove organosulfur compounds with a steric hindrance due to the electronic nature of the current catalysts employed. In this work, the effects of adding chelating ligands such as ethylenediaminetetraacetic acid (EDTA), citric acid (CA) and acetic acid (AA) to rhodium (Rh) and active molybdenum (Mo) species for dibenzothiophene (DBT) HDS catalytic activity was evaluated. HDS activities followed the order of RhMo/ɣ-Al2O3 (88%) &gt, RhMo-AA/ɣ-Al2O3 (73%) &gt, RhMo-CA/ɣ-Al2O3 (72%) &gt, RhMo-EDTA/ɣ-Al2O3 (68%). The observed trend was attributed to the different chelating ligands with varying electronic properties, thus influencing the metal–support interaction and the favorable reduction of the Mo species. RhMo/ɣ-Al2O3 offered the highest HDS activity due to its (i) lower metal–support interaction energy, as observed from the RhMo/ɣ-Al2O3 band gap of 3.779 eV and the slight shift toward the lower BE of Mo 3d, (ii) increased Mo-O-Mo species (NMo-O-Mo ~1.975) and (iii) better sulfidation of Rh and MoO in RhMo/ɣ-Al2O3 compared to the chelated catalysts. The obtained data provides that HDS catalytic activity was mainly driven by the structural nature of the RhMo-based catalyst, which influences the formation of more active sites that can enhance the HDS activity.

Signal Amplification By Reversible Exchange (SABRE) is a particularly simple hyperpolarisation approach. However, compared to other hyperpolarisation methods, SABRE is more limited in substrate scope. Therefore, it is critical to understand and overcome the factors limiting generalization. Past developments in SABRE catalyst optimization have emphasized large enhancements in the canonical SABRE substrate: pyridine and structurally closely related motifs. However, the pyridine-optimized catalysts are not efficient at hyperpolarising more sterically demanding substrates, including 2-substituted pyridine derivatives. Here we report that modifications of the catalyst ligand sphere, using a chelating ligand in particular, can increase the volume fraction available for substrate coordination to the iridium catalyst, thus permitting significant signal enhancements on otherwise sterically hindered substrates. The system yields (1)H enhancements on the order of 100-fold over 8.5 T thermal measurements for 2-substituted pyridine derivatives, and smaller, yet significant (1)H enhancement for provitamin B(6) and caffeine. For the 2-substituted pyridine derivatives we further show (15)N enhancements on the order of 1000-fold and (19)F enhancements of 30-fold over 8.5 T thermal polarisations.

Since the remarkable work by Werner, the design and use of chelating ligands have played an essential part in coordination chemistry. While ligands such as 2,4-pentanedione (acac) and 1,5-diazapentadienyl (NacNac) have been established in the literature for over a century and their rich coordination chemistry is well known, 1,3,5-triazapentadiene ligands remain the significantly less explored members of this family. Also known as imidoyl amidine (ImAm), the coordination chemistry of this ligand framework has recently attracted a great deal of attention due to its multiple binding sites, ability to be incorporated into organic and inorganic materials, and diverse applicability (catalysis, biomolecular probes, materials science, etc.) making them a class of chelates like no other. The scope of this review is to provide a critical overview of the research progress on the chemistry of ImAm as well as complexation with different metal ions. General synthetic routes and new insights for the preparation of ImAm are discussed along with their use as starting materials or intermediates in organic and coordination chemistry in the development of materials that have found use in fields ranging from magnetic, conducting and luminescent materials to catalysis and biomedical applications. Concluding remarks including the limitations and perspectives of ImAm are discussed.

Mn(II) has several favorable physicochemical characteristics and a good toxicity profile, which makes it a viable alternative to the Gd(III)-based MRI contrast agents currently used in clinics. Although many studies have been undertaken in the last 10 years, this is a field of investigation still in rapid and continuous development. This review aims to critically discuss the chemical and magnetic properties of Mn(II) compounds relevant as MRI probes, both small complexes and nanosystems containing a large number of metal centers, the possible approaches for optimizing their efficiency by understanding the role of various molecular parameters that control the relaxation processes, and the most important issues related to stability and kinetic inertness.

Various functional secondary and tertiary phosphines, or their derivatives, containing stationary chiral phosphorus and flexible chiral axis were prepared, which could be further modified to afford diversely chelating ligands. The flexible axial chirality was fixed by stereogenic phosphorus via a cyclic linkage of chemical bonds or coordination with a metallic ion.

Incorporating nanoparticles into devices for a wide range of applications often requires the formation of thick films, which is particularly necessary for improving magnetic power storage, microwave properties, and sensor performance. One approach to assembling nanoparticles into films is the use of electrophoretic deposition (EPD). This work seeks to develop methods to increase film thickness and stability in EPD by increasing film-substrate interactions via functionalizing conductive substrates with various chelating agents. Here, we deposited iron oxide nanoparticles onto conductive substrates functionalized with three chelating agents with different functional moieties and differing chelating strengths. We show that increasing chelating strength can increase film-substrate interactions, resulting in thicker films when compared to traditional EPD. Results will also be presented on how the chelating strength relates to film formation as a function of deposition conditions. Yield for EPD is influenced by deposition conditions including applied electric field, particle concentration, and deposition time. This work shows that the functionalization of substrates with chelating agents that coordinate strongly with nanoparticles (phosphonic acid and dopamine) overcome parameters that traditionally hinder the deposition of thicker and more stable films, such as applied electric field and high particle concentration. We show that functionalizing substrates with chelating agents is a promising method to fabricate thick, stable films of nanoparticles deposited via EPD over a larger processing space by increasing film-substrate interactions.

Schrock alkylidenes are highly versatile, very active olefin metathesis catalysts, but their pronounced sensitivity to air still hinders their applications. Converting them into more robust but inactive 18-electron adducts was suggested previously to facilitate their handling. Generating the active species from the inactive adducts, however, required a high-temperature Lewis acid treatment and resulted in an insoluble by-product, limiting the practicality of the methodology. Herein, we introduce an approach to circumvent the inconvenient, costly, and environmentally taxing activation process. We show that 18-electron adducts of W- and Mo-based Schrock catalysts with finite stability constants (typically K = 200–15,000 M−1) can readily be prepared and isolated in excellent yields. The adducts display enhanced air-stability in the solid state, and in solution they dissociate spontaneously, hence liberating the active alkylidenes without chemical assistance. Air-sensitive molybdenum olefin metathesis catalysts are known to form stable but inactive adducts with appropriate chelating ligands, but regenerating the active catalyst requires the use of Lewis acids and vigorous conditions. Here, tuning the electron donor capacity of the ligands leads to air-stable solid adducts of tungsten and molybdenum alkylidenes that spontaneously release the active catalysts in solution.

The reaction of [(arene)MCl2]2 with ligands 4-hydroxy-benzhydrazide (L1) and 3-methoxy-benzhydrazide (L2) leads to formation of cationic complexes 1-6 having the general formula [(arene)M(L)Cl]+ {arene = p-cymene, M = Ru; arene = Cp*; M = Rh/Ir; L = L1 and L2}. The reaction of [CpRu(PPh3)2Cl] with L1 and L2 yielded cationic complexes that have been formulated as [CpRu(L)PPh3]Y {Y = Cl (7), Y = PF6 (8)}. The molecular structures of 1, 2 and 4 revealed that these complexes adopt typical three-legged “piano stool” geometry. The arene ring occupies the apex of the stool, terminal chloride and N,O-bidentate ligands are coordinated to the metal center at the base of the stool. The antibacterial activity of the ligands and complexes was evaluated on Gram-positive S. aureus, B. thuringiensis and Gram-negative E. coli, P. aeruginosa strains; some complexes exhibit moderate antibacterial activity towards gram-positive bacteria. The antioxidant studies of these complexes have been carried out, and the results showed that these complexes have strong DPPH-scavenging properties.

International audience; Long overlooked, chelating ligands have garnered recently increasing interest in gold chemistry. They enforce bending at gold(I) and thereby, noticeably modify its electronic properties. This review focuses on -complexes with alkenes and alkynes side-on coordinated to gold(I), as well as gold(I) carbene complexes. The influence of the chelating ligand on the structure, bonding and reactivity of these species is thoroughly discussed.

Reactions of C10H7-1-N(PPh2)2 (1) and C10H7-1-N(P(Se)Ph2)2 (2) ligands with mercury(II)iodide in equimolar ratio gave cis-[HgI2{1-��2P,P}] (3) and cis-[HgI2{2-��2Se,Se}] (4). Also, refluxing of monooxidized thioyl and selenoyl bis(phosphino)amine ligands C10H7-1-N(P(E)Ph2)(PPh2) (E = S (5), Se (6)) with [Ru(CO)3Cl2]2 dimer afforded cis-[Ru(CO)2Cl2{5-��2P,S}] (7) and cis-[Ru(CO)2Cl2{6-��2P,Se}] (8). Complexes 3, 4, 7 and 8 were identified and characterized by multinuclear NMR (1H, 13C, 31P and 77Se NMR) and IR spectroscopy. The molecular structure of 5 was determined by single X-ray crystallography. 5 is the first structurally characterized example of this kind of ��2P,S -bidentate ligand. The novel ruthenium(II) complexes 7 and 8 show high catalytic activity in the transfer hydrogenation of acetophenone derivatives to 1-phenylethanol derivatives in the presence of 2-propanol as the hydrogen source.

Reactions of BeEt2 with S(NSiMe3)2 and carbodiimides RNCNR yielded homoleptic bisdiimidosulfinate [EtS(NSiMe3)2]2Be (1) and amidinate complexes [EtC(NAr)2]2Be (Ar = 2,6-i-Pr2-C6H3 2, SiMe3 3). In addition, the heteroleptic amidinate [t-BuC(NAr)2]BeEt (4) and β-diketiminate [HC(CMeNAr′)2]Be(i-Bu) (6) (Ar′ = 2,4,6-Me3C6H2) complexes were obtained by alkane elimination reactions of BeEt2 with t-BuC(NSiMe3)N(H)SiMe3 and Be(i-Bu)2 with β-diketimine [Ar′N(H)C(Me)CHC(Me)NAr′], respectively. In addition, 4 was found to react with dry oxygen with formation of the corresponding alkoxide [t-BuC(NAr)2]BeOEt (5). 1–6 were characterized by multinuclear NMR (1H, 9Be, 13C) and IR spectroscopy as well as by single-crystal X-ray diffraction (1, 2, 4, 5, 6).

Background 64Cu is one of the few radioisotopes that can be used for both imaging and therapy, enabling theranostics with identical chemical composition. Development of stable chelators is essential to harness the potential of this isotope, challenged by the presence of endogenous copper chelators. Pyridyl type chelators show good coordination ability with copper, prompting the present study of a series of chelates DOTA-xPy (x = 1–4) that sequentially substitute carboxyl moieties with pyridyl moieties on a DOTA backbone. Results We found that the presence of pyridyl groups significantly increases 64Cu labeling conversion yield, with DOTA-2Py, −3Py and -4Py quantitatively complexing 64Cu at room temperature within 5 min (1 × 10− 4 M). [64Cu]Cu-DOTA-xPy (x = 2–4) exhibited good stability in human serum up to 24 h. When challenged with 1000 eq. of NOTA, no transmetallation was observed for all three 64Cu complexes. DOTA-xPy (x = 1–3) were conjugated to a cyclized α-melanocyte-stimulating hormone (αMSH) peptide by using one of the pendant carboxyl groups as a bifunctional handle. [64Cu]Cu-DOTA-xPy-αMSH retained good serum stability (> 96% in 24 h) and showed high binding affinity (Ki = 2.1–3.7 nM) towards the melanocortin 1 receptor. Conclusion DOTA-xPy (x = 1–3) are promising chelators for 64Cu. Further in vivo evaluation is necessary to assess the full potential of these chelators as a tool to enable further theranostic radiopharmaceutical development. Supplementary Information The online version contains supplementary material available at 10.1186/s41181-020-00119-4.

Fossilization yields stable polymers diagnostic of tissue type, biomineralization, and the place of animals in the tree of life., Proteins, lipids, and sugars establish animal form and function. However, the preservation of biological signals in fossil organic matter is poorly understood. Here, we used high-resolution in situ Raman microspectroscopy to analyze the molecular compositions of 113 Phanerozoic metazoan fossils and sediments. Proteins, lipids, and sugars converge in composition during fossilization through lipoxidation and glycoxidation to form endogenous N-, O-, and S-heterocyclic polymers. Nonetheless, multivariate spectral analysis reveals molecular heterogeneities: The relative abundance of glycoxidation and lipoxidation products distinguishes different tissue types. Preserved chelating ligands are diagnostic of different modes of biomineralization. Amino acid–specific fossilization products retain phylogenetic information and capture higher-rank metazoan relationships. Molecular signals survive in deep time and provide a powerful tool for reconstructing the evolutionary history of animals.

Carbon dioxide methanation was carried out over Ni-based catalysts on different supports and chelating ligands in microreactors. To investigate the influence of chelating ligands and supports, the Ni catalysts were prepared using different support such as CeO2, Al2O3, SiO2, and SBA-15 by a citric acid (CA)-assisted impregnation method. The properties of the developed catalysts were studied by X-ray diffraction (XRD), Transmission electron microscope (TEM), and X-ray photoelectron spectroscopy (XPS) measurement, and the results show that the addition of CA in the impregnation solution improved the dispersion, refines the particle size, and enhanced the interaction of nickel species. The catalytic performance of the developed Ni catalysts were evaluated by CO2 methanation in microreactors in the temperature range of 275 °C–375 °C under 12.5 bar pressure. All the catalysts exhibit high CO2 conversion and extremely high selectivity to methane. However, the catalysts prepared via CA-assisted method exhibited excellent activity and stability, compared with Ni catalysts prepared by a conventional impregnation method, which could be attributed to highly dispersed nickel particles with strong metal–support interaction. The activity of CO2 methanation followed the order of Ni/CeO2-CA > Ni/SBA-15-CA > Ni/Al2O3-CA > Ni/SiO2-CA > Ni/CeO2. The Ni/CeO2 catalysts have also been prepared using different chelating ligands such as ethylene glycol (EG), sucrose (S), oxalic acid (OA) and ethylene diamine tetra acidic acid (EDTA). Among the tested catalysts prepared with different support and chelating ligands, the Ni/CeO2 catalyst prepared via CA-assisted method gave superior catalytic performance and it could attain 98.6% of CO2 conversion and 99.7% methane selectivity at 325 °C. The partial reduction of the CeO2 support generates more surface oxygen vacancies and results in a high CO2 conversion and methane selectivity compared with other catalysts. The addition of CA as promoter favored the synergistic effect of Ni and support, which led to high dispersion, controls the size, and stabilizes the Ni nanoparticles. Furthermore, the Ni/CeO2-CA catalyst yields high CO2 conversion in a time-on-stream study due to the ability of preventing the carbon deposition and sintering of Ni particles under the applied reaction conditions. However, the Ni/Al2O3-CA and Ni/SBA-15-CA catalysts showed stable performance for 100 h of time on stream.

A series of gold(I) N-heterocyclic carbene complexes containing monoanionic acylchalcogenourea (chalcogen = S, Se) ligands was prepared and characterised by various spectroscopic methods and X-ray diffraction. The compounds were conveniently accessible in good yields through a one-pot reaction involving [AuCl(tht)] (tht = tetrahydrothiophene), the imidazolium salt and the acylchalcogenourea in the presence of excess base. The X-ray diffraction experiments showed that in these complexes, the normally chelating ligands adopt the rare κS/Se-coordination mode in which only the chalcogen is bound to gold.

Over the past decades, the need for rare earth elements (REEs) has increased substantially, mostly because these elements are used as valuable additives in advanced technologies. However, the difference in ionic radius between neighboring REEs is small, which renders an efficient sized-based separation extremely challenging. Among different types of extraction methods, solid-phase extraction (SPE) is a promising candidate, featuring high enrichment factor, rapid adsorption kinetics, reduced solvent consumption and minimized waste generation. The great challenge remains yet to develop highly efficient and selective adsorbents for this process. In this regard, ordered mesoporous materials (OMMs) possess high specific surface area, tunable pore size, large pore volume, as well as stable and interconnected frameworks with active pore surfaces for functionalization. Such features meet the requirements for enhanced adsorbents, not only providing huge reactional interface and large surface capable of accommodating guest species, but also enabling the possibility of ion-specific binding for enrichment and separation purposes. This short personal account summarizes some of the recent advances in the use of porous hybrid materials as selective sorbents for REE separation and purification, with particular attention devoted to ordered mesoporous silica and carbon-based sorbents.