Search Results (365)

Lanthanide rare earth elements possess significant promise for material applications owing to their distinctive optical and magnetic characteristics, as well as their versatile coordination capabilities. This study introduced a lanthanide-functionalized magnetic nanocellulose composite (NNC@Fe₃O₄@La(OH)₃) for effective phosphorus/nitrogen (P/N) ligand separation. The hybrid material employs the adaptable coordination geometry and strong affinity for oxygen of La³⁺ ions to show enhanced DNA-binding capacity via multi-site coordination with phosphate backbones and bases. This study utilized cellulose as a carrier, which was modified through carboxylation and amination processes employing deep eutectic solvents (DES) and polyethyleneimine. Magnetic nanoparticles and La(OH)₃ were subsequently incorporated into the cellulose via in situ growth. NNC@Fe₃O₄@La(OH)₃ showed a specific surface area of 36.2 m²·g⁻¹ and a magnetic saturation intensity of 37 emu/g, facilitating the formation of ligands with accessible La³⁺ active sites, hence creating mesoporous interfaces that allow for fast separation. NNC@Fe₃O₄@La(OH)₃ showed a significant affinity for DNA, with adsorption capacities reaching 243 mg/g, mostly due to the multistage coordination binding of La³⁺ to the phosphate groups and bases of DNA. Simultaneously, kinetic experiments indicated that the binding process adhered to a pseudo-secondary kinetic model, predominantly dependent on chemisorption. This study developed a unique rare-earth coordination-driven functional hybrid material, which is highly significant for constructing selective separation platforms for P/N-containing ligands. Full article

A 12-membered pyridinophane scaffold containing two pyridine and two tertiary amine residues is examined as a prototype ligand (^tBuN4) for supporting nitrene transfer to olefins. The known [(^tBuN4)M^II(MeCN)₂]²⁺ (M = Mn, Fe, Co, and Ni) and [(^tBuN4)Cu^I(MeCN)]⁺ cations are synthesized with the hexafluorophosphate counteranion. The aziridination of para-substituted styrenes with PhI=NTs (Ts = tosyl) in various solvents proved to be high yielding for the Cu(I) and Cu(II) reagents, in contrast to the modest efficacy of all other metals. For α-substituted styrenes, aziridination is accompanied by products of aziridine ring opening, especially in chlorinated solvents. Bulkier β-substituted styrenes reduce product yields, largely for the Cu(II) reagent. Aromatic olefins are more reactive than aliphatic congeners by a significant margin. Mechanistic studies (Hammett plots, KIE, and stereochemical scrambling) suggest that both copper reagents operate via sequential formation of two N–C bonds during the aziridination of styrene, but with differential mechanistic parameters, pointing towards two distinct catalytic manifolds. Computational studies indicate that the putative copper nitrenes derived from Cu(I) and Cu(II) are each associated with closely spaced dual spin states, featuring high spin densities on the nitrene N atom. The computed electrophilicity of the Cu(I)-derived nitrene reflects the faster operation of the Cu(I) manifold. Full article

6-Aryl-7H-pyrrolo[2,3-d]pyrimidin-4-amines have promising properties as colony-stimulating factor 1 receptor (CSF1R) inhibitors. Inspired by these antagonists, two series of 1,2,3-triazole analogues (28 compounds) were synthesized and evaluated as CSF1R inhibitors. Enzymatic IC₅₀ profiling showed that 27 of the 28 derivatives had lower IC₅₀ than the reference drug PLX-3397. Three derivatives displayed CSF1R Ba/F3 cellular IC₅₀ well below 1 µM. Profiling of the most promising triazole analogue (compound 27a) toward a panel of kinases reveals a high selectivity for CSF1R with respect to its family kinases, but 27a also inhibits ABL, SRC, and YES kinases. Molecular docking of 27a toward two CSF1R X-ray structures identified two different ligand-inverted binding poses, which triggers interest for further investigations. Full article

Co(II) complexes have shown promising applications as single-molecule magnets (SMMs) in quantum computing and structural biology. Deciphering the Co(II) complexes may facilitate the development of SMM materials. Structural optimizations and calculations of chemical and magnetic properties were performed for Co(II) complexes with a tripodal tetradentate phenolate-amine ligand using MP2/aug-cc-pvdz, MP2/Def2svp, and CASSCF/Def2svp methods. The Second Order Perturbation Theory Analysis of Fock Matrix in NBO Basis unravels that Co(II) ions form unusual coordinate quasi-double bonds with ligand oxygen donor atoms, and the bond strengths range from 142.01 kcal/mol to 167.36 kcal/mol but lack further spectrometric evidence. The average 151.70 kcal/mol of the Co(II-O coordinates quasi-double bonds are formed mainly by two lone pairs of electrons from the ligand phenolate donor oxygen atoms. Dispersion forces contribute 24%, 28%, 27%, and 31% to the Co(II)-ligand interaction. Theoretical results of ZFS D, transversal ZFS E, and g-factor agree well with the experimental values. Magnetic susceptibility parameters calculated based on 5 doublet roots account for 85% of results computed 40 doublet roots are specified. These insights may aid in the rational design of SMM materials and Co(II) porphyrin fullerene conjugate for CO₂ electroreduction with superior magnetic properties. Full article

Ordered mesoporous carbon materials (OMCMs) are widely used as high-performance electrode materials due to their uniform pore structure, excellent electrical conductivity, and good stability. In this paper, three OMCMs with controllable N content were prepared by a nanocasting method using Fe₃O₄ nanocrystals as the template and organic ligands as the carbon source. By adopting a ligand exchange strategy, oleic acid, oleic amine, and octyl amine were successfully capped onto the Fe₃O₄ nanocrystals, respectively, which allowed the rational control of the elemental composition of OMCMs at the molecular level. Further characterizations revealed that the nitrogen content of the resulting OMCMs increased as the proportion of nitrogen atoms in the ligand increased, while the order of the porous structure decreased as the hydrocarbon chain length decreased. This study demonstrates that both the N-doping content and the order of the OMCMs are influenced by the N-containing ligand. This finding will provide a fundamental aspect for their further applications as high-performance electrode and catalytic materials in the field of electrochemistry. Full article

Bis-(o-dipheylphosphinophenyl)amine, a tridentate (PNP) chelating ligand, and several of their Rare Earth (RE) metal complexes, [bis-(o-dipheylphosphinophenyl)amido]-RER₂, {[(C₆H₅)₂P-o-(C₆H₄)]₂NMR₂ (R = -CH₂-o-(C₆H₄)NMe₂: M = Y, 1; Nd, 2; Gd, 3;), are prepared in high yields. When activated with the strong Lewis acid MMAO-7, all these complexes exhibit catalytic activity toward the polymerization of isoprene (IP) in non-protic hydrocarbons. While the Nd complex (2) showed moderate activity and stereoselectivity, the Y and Gd complexes (1 and 3) exhibited extremely high catalytic efficiency in IP homo-polymerization, and produced polyisoprene rubber (PI) with 95% to over 99% cis-1,4 stereoselectivity and narrow polydispersity indices (<2.0). Moreover, under industrially relevant conditions, complex 3 can catalyze IP to produce ultrahigh molecular weight PI (UHMW-PI, MW up to 1200–2600 kg/mol) rubber with a very narrow polydispersity index (PDI ca. 1.1–1.6), a high-performance elastomeric material mimic of natural rubber (NR). Full article

In our research aimed at replacing precious transition metals like platinum with abundant base metals such as nickel for efficient triplet emitters, we synthesized and studied Ni(II) complexes [Ni(L^NHR)Cl]. These complexes containing the N^C^N cyclometalating dipyridyl-phenide ligand, equipped with pending H-bonding amine groups (NH(C₆H₅) (L^NHPh) and NH(C₆H₅CH₂), ClL^NHBn). Molecular structures determined from experimental X-ray diffractometry and density functional theory (DFT) calculations in the ground state showed marked deviation of the Cl⁻ coligand (ancillary ligand) from the ideal planar coordination, with τ₄ values of 0.35 and 0.33, respectively, along with hydrogen bonding interactions of the ligand NH function with the Cl⁻ coligand. The complexes exhibit long-wavelength absorption bands at approximately 425 nm in solution, with the experimental spectra being accurately reproduced through time-dependent density functional theory (TD-DFT) calculations. Vibrationally structured emission profiles and steady-state photoluminescence quantum yields of 30% for [Ni(L^NHPh)Cl] and 40% for [Ni(L^NHBn)Cl] (along with dual excited state lifetimes in the ns and in the ms range) were found in frozen 2-methyl-tetrahydrofuran (2MeTHF) glassy matrices at 77 K. Furthermore, within a poly(methyl methacrylate) matrix, the complexes showed emission bands centered at around 550 nm within a temperature range from 6 K to 300 K with lifetimes similar to 77 K. Based on TD-DFT potential scans along the metal–ligand (Ni–N) coordinate, we found that in a rigid environment that restricts the geometry to the Franck-Condon region, either the triplet T₅ or the singlet S₄ state could contribute to the photoluminescence. Full article

Heterocyclic aromatic amines (HAAs), known for their mutagenic and carcinogenic potential, are formed during the heating of protein-rich food items. Detecting HAAs swiftly and accurately poses challenges due to complex food matrices and low HAA concentrations. In this study, a simple and efficient magnetic solid-phase extraction (MSPE) strategy was developed for the simultaneous isolation and enrichment of three HAAs such as 2-amino-3,4,8-trimethylimidazo [4,5-f]quinoxaline (4,8-DiMeIQx), 2-amino-3,8-dimethylimidazo [4,5-f]quinoxaline (MeIQx), and 2-amino-3-methylimidazo [4,5-f]quinoline (IQ) in processed meats, employing the magnetic covalent organic framework Fe₃O₄@MOF-545-AMSA as an adsorbent. It was synthesized via a solvothermal method, with Fe₃O₄ as the magnetic core. Its building blocks are as follows: zirconium (Zr) as the coordination metal ion, tetrakis(4-carboxyphenyl)porphyrin and benzoic acid as organic ligands, and aminomethanesulfonic acid (AMSA). This composite captures targeted HAAs efficiently by exploiting the unique porous MOF-545-AMSA structure, specific metal–ligand coordination, and AMSA’s amino and sulfonic acid groups. The quantification of HAAs was achieved through the combination of Ultra-Performance Liquid Chromatography–Tandem Mass Spectrometry (UPLC-MS/MS) and MSPE, demonstrating satisfactory linearity (R² ≥ 0.9917), high recovery rates (83.7–111.0%), and low detection limits (0.1–1.0 μg/kg). Moreover, an automated high-throughput detection system was developed using MSPE to assess the presence of HAAs in meat products. Full article

Metal complexes have potential applications in drug discovery due to their unique properties. For example, zinc(II) ions (Zn^II) exhibit a high affinity for DNA and have been used as active centers in artificial protein/small-molecule metallonucleases. In this study, we designed a series of ligands containing a biaryl moiety as a photosensitizer to synthesize Zn^II complexes with enhanced DNA affinity for use as DNA photocleavage reagents. The DNA photocleavage activity of these complexes was evaluated using the pUC19 plasmid, revealing that the Zn^II complex bearing the 4′-biphenyl-bpa (bpa = bis(2-picolyl)amine) ligand L1 exhibited the strongest DNA photocleavage activity. Further analysis of the biological activity of the Zn^II complex of L1 in the human pancreatic cancer cell line MIA PaCa-II demonstrated that its cytotoxic activity increased in a UV irradiation time-dependent manner, with an IC₅₀ value of 14.2 μM. Fluorescence staining revealed that the Zn^II complex of L1 generates reactive oxygen species in cells, leading to DNA double-strand breaks upon UV irradiation and ultimately resulting in necrotic cell death. These findings highlight the potential of the Zn^II complex of L1 as a photochemotherapeutic agent for pancreatic cancer. Full article

A series of mononuclear complexes, [Fe(L5)(bylim)](BPh₄), where L5 represents a pentadentate Schiff base ligand, bylim is 1-benzyl-1-imidazole, and BPh₄⁻ is the tetraphenylborate anion, was synthesized. The determined crystal structures indicate the absence of significant cooperative interactions, which influence the properties of the eventual spin transition. Changes in magnetic behavior induced by substitution of the pentadentate ligand were investigated through magnetic susceptibility measurements. It was found that only complexes containing a non-substituted secondary amino group exhibit some form of spin crossover, whereas the majority of those with a methyl substituent remain in the high-spin state across the entire measured temperature range (2–300 K). The changes induced by the substitution of the secondary amine group were further explored through theoretical calculations at DFT and CASSCF/NEVPT2 levels of theory. The topology and energetics of electron density and atomic charges were investigated through QT-AIM calculations. Full article

The reaction of the short-bite bis(diphosphino)amine ligand Ph₂PN(Me)PPh₂ (Medppa) with an equimolar amount of [Co₂(CO)₈] in toluene solution yielded the diphosphane-bridged complex bis(µ₂-carbonyl)(µ-bis(diphenylphosphino)methylamine)-tetracarbonyl-dicobalt(0) (Co—Co) · 0.5 toluene, [Co₂(CO)₆(µ-Medppa)] 1. Using a 3:1 ratio, the ion-pair complex [Co(CO)(η²-Medppa)₂][Co(CO)₄] 2 was formed. The ionic intermediate [Co(CO)₂(η²-Medppa)(η¹-Medppa)][Co(CO)₄] 3 was spectroscopically observed during the stoichiometric reaction involving [Co₂(CO)₈] and 2 eq. Medppa. Complexes 1 and 2 were characterized using IR and NMR spectroscopy and by single-crystal X-ray analysis performed at 100 K. Full article

The synergistic solvent extraction of La(III), Eu(III) and Lu(III) with a chelating extractant, 4-benzoyl-3-methyl-1-phenyl-2-pyrazolin-5-one (HL), and neutral bidentate heterocyclic amines, such as 1,10-phenanthroline (S1 (phen)) or 2,2′-bipyridine (S2 (bipy)) in an ionic liquid of the imidazolium family [C₁C₄im⁺][Tf₂N⁻] was investigated. Synergistic effects have been observed to result from the formation of a ternary complex in the organic phase, particularly in cases where the ligand S is a neutral synergistic agent. Examples include La(L)₂(S2)₂, Eu(L)₃(S2) and Lu(L)_x(S2)₂, as well as La(L)₃(S1)₂, Eu(L)₂(S1) and Lu(L)₃(S1)_x). The parameters of the solvent extraction process were determined and the influence of the synergistic agent on the extraction process was discussed. Additionally, the synergistic increase and separation factors were determined. The equilibrated organic phases were analyzed using ¹H NMR spectroscopy to elucidate the synergism in an extraction mechanism. The role of the ionic diluent in complexation processes and selectivity was investigated with the employment of the two synergistic agents for various metal s-, p-, d- and f-cations in the periodic table, with almost 22 metal ions. Full article

CD44, a pivotal cell surface molecule, plays a crucial role in many cellular functions, including cell-cell interactions, adhesion, and migration. It serves as a receptor for hyaluronic acid and is involved in lymphocyte activation, recirculation, homing, and hematopoiesis. Moreover, CD44 is a commonly used cancer stem cell marker associated with tumor progression and metastasis. The development of CD44 aptamers that specifically target CD44 can be utilized to target CD44-positive cells, including cancer stem cells, and for drug delivery. Building on the primary sequences of our previously selected thioaptamers (TAs) and observed variations, we developed a bead-based X-aptamer (XA) library by conjugating drug-like ligands (X) to the 5-positions of certain uridines on a complete monothioate backbone. From this, we selected an XA with high affinity to the CD44 hyaluronic acid binding domain (HABD) from a large combinatorial X-aptamer library modified with N-acetyl-2,3-dehydro-2-deoxyneuraminic acid (ADDA). This XA demonstrated an enhanced binding affinity for the CD44 protein up to 23-fold. The selected CD44 X-aptamers (both amine form and ADDA form) also showed enhanced binding affinity to CD44-overexpressing human ovarian cancer IGROV cells. Secondary structure predictions of CD44 using MFold identified several binding motifs and smaller constructs of various stem-loop regions. Among our identified binding motifs, X-aptamer motif 3 and motif 5 showed enhanced binding affinity to CD44-overexpressing human ovarian cancer IGROV cells with ADDA form, compared to the binding affinities with amine form and scrambled sequence. The effect of ADDA as a binding affinity enhancer was not uniform within the aptamer, highlighting the importance of optimal ligand positioning. The incorporation of ADDA not only broadened the XA’s chemical diversity but also increased the binding surface area, offering enhanced specificity. Therefore, the strategic use of site-directed modifications allows for fine-tuning aptamer properties and offers a flexible, generalizable framework for developing high-performance aptamers that target a wide range of molecules. Full article

An efficient method has been developed for the rapid production of diverse arrays of 3,5-bis-aminated pyrazolo[1,5-a]pyrimidines. The method utilizes CuI (5 mol%) and carbazole-based ligand L-1 (N-(9H-carbazol-9-yl)-1H-pyrrole-2-carboxamide) (10 mol%) for efficient Ullmann-type coupling of various amines to 5-amino-3-bromopyrazolo[1,5-a]pyrimidine precursors after heating in diethylene glycol (DEG) for only 1 h at 80 °C (microwave heating). 3,5-Bis-aminated products were obtained in good to excellent yields (60–93%, 83% average for 29 examples). 1° and 2° alkylamines, as well as a variety of aryl- or heteroarylamines coupled efficiently, and 1° and 2° alkyl (or aryl) amines at C-5 were well tolerated. The optimized conditions worked well on both the 50 mg and 1.0 g scales and gave products in only two steps from commercially available 3-bromo-5-chloropyrazolo[1,5-a]pyrimidine. Advantages provided by this method include short reaction time, excellent yields, broad substrate scope, and avoidance of toxic reagents commonly utilized for reductive aminations of C-3 NH₂ substituted precursors. Full article

In this study, the palladium-catalyzed aminocarbonylation of 1-iodoisoquinoline was accomplished in the presence of various amines. While the reactions with simple primary and secondary amines were carried out by using the well-known Pd(OAc)₂/PPh₃ catalyst, the application of amines with lower basicity (e.g., aromatic amines) or more difficult structures (e.g., amino acid methyl esters, nortropine, diethyl (α-aminobenzyl)phosphonate) required the use of bidentate XantPhos ligand to achieve complete conversion in short reaction time (2–8 h). In this way, several valuable isoquinoline-1-carboxamides were synthesized in chemoselective carbonylation and isolated in good to high yields (55–89%). Furthermore, the aminocarbonylation of the model compound in the presence of several amines was also investigated in three biomass-derived solvents (GVL, ethyl levulinate, and 2-MeTHF). After comparing the outcome of the reactions in DMF and the above green solvents, similar reactivity was observed, justifying that they could be considered a feasible alternative reaction medium. Full article