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Journal of the American Chemical Society Mar 2024Organic-inorganic atomically precise nanoclusters provide indispensable building blocks for establishing structure-property links in hybrid condensed matter. However,...
Organic-inorganic atomically precise nanoclusters provide indispensable building blocks for establishing structure-property links in hybrid condensed matter. However, robust glasses of ligand-protected nanocluster solids have yet to be demonstrated. Herein, we show [CuI(PR)] cubane nanoclusters coordinated by phosphine ligands (PR) form robust melt-quenched glasses in air with reversible crystal-liquid-glass transitions. Protective phosphine ligands critically influence the glass formation mechanism, modulating the glasses' physical properties. A hybrid glass utilizing ethyldiphenylphosphine-based nanoclusters, [CuI(PPhEt)], exhibits superb optical properties, including >90% transmission in both visible and near-infrared wavelengths, negligible self-absorption, near-unity quantum yield, and high light yield. Experimental and theoretical analyses demonstrate the structural integrity of the [CuI(PPhEt)] nanocluster, i.e., iodine-bridged tetranuclear cubane, has been fully preserved in the glass state. The strong internanocluster CH-π interactions found in the [CuI(PPhEt)] glass and subsequently reduced structural vibration account for its enhanced luminescence properties. Moreover, this highly transparent glass enables performant X-ray imaging and low-loss waveguiding in fibers drawn above the glass transition. The discovery of "nanocluster glass" opens avenues for unraveling glass formation mechanisms and designing novel luminescent glasses of well-defined building blocks for advanced photonics.
PubMed: 38433410
DOI: 10.1021/jacs.3c12296 -
Organometallics Feb 2024Nickel carbenes are attracting attention for the development of more sustainable catalysts, among others, for cyclopropanation. Intramolecular trapping of a nickel...
Nickel carbenes are attracting attention for the development of more sustainable catalysts, among others, for cyclopropanation. Intramolecular trapping of a nickel carbene intermediate with an olefin incorporated in a P(C=C)P Ni pincer complex had previously allowed the isolation of a nickelacyclobutane intermediate and a detailed characterization of its reactivity. Herein, we report the reactivity of related nickel pincer complexes bearing a ketone P(C=O)P or an imine P(C=N)P with diazoalkanes as the carbene precursor. The observed reactivity suggests, in both cases, the reaction of the transient nickel carbene with one of the phosphine arms to form phosphorus ylides that subsequently react with the unsaturated backbone. Density functional theory (DFT) calculations are used to shed light on the mechanisms of these reactions.
PubMed: 38425383
DOI: 10.1021/acs.organomet.3c00437 -
Organometallics Feb 2024Ketenyl anions are versatile intermediates in synthetic chemistry and have recently become accessible as isolable reagents from metalated ylides by exchange of the...
Ketenyl anions are versatile intermediates in synthetic chemistry and have recently become accessible as isolable reagents from metalated ylides by exchange of the phosphine with CO. Herein, we report on a systematic study of substituent effects on the structure and bonding situation in ketenyl anions. A series of phosphinoyl-substituted ketenyl anions {[RP(X)CCO] with X = O, NTol, S, Se} were prepared by carbonylation of the corresponding yldiides and isolated as their corresponding potassium salts. NMR and IR spectroscopic analyses together with computational studies demonstrate that the more electron-withdrawing oxo- and iminophosphinoyl substituents increase the s-character in the bond to the ketene moiety and hence the ynolate character of the anion. This trend is particularly seen in solution, whereas the solid-state properties are influenced by packing effects affecting the bonding situation.
PubMed: 38425382
DOI: 10.1021/acs.organomet.3c00530 -
Nanoscale Advances Feb 2024Copper hydrides are highly active catalysts in hydrogenation reactions and reduction processes. Three Stryker-type copper hydride nanoclusters (NCs), [(TPP)CuH],...
Copper hydrides are highly active catalysts in hydrogenation reactions and reduction processes. Three Stryker-type copper hydride nanoclusters (NCs), [(TPP)CuH], [(TCP)CuH] and [(TOP)CuH] (TPP = triphenylphosphine, TCP = tricyclohexylphosphine and TOP = tri--octylphosphine), were synthesized in this study. Due to variations in the electron-donating properties of the phosphine ligands, the UV-visible absorption spectra of the three NCs exhibited notable distinctions. The influence of the phosphine ligands on the effectiveness of the NCs as hydride sources in hydrogenation processes, as well as on the applicability as homogeneous catalysts for reduction reactions, was systematically studied. Due to the highest electron-donating properties of the TOP ligand, [(TOP)CuH] was found to exhibit superior performance in both hydrogenation reactions and catalytic reduction reactions. Moreover, these hydrophobic NCs worked well as heterogeneous catalysts in the reduction of 4-nitrophenol.
PubMed: 38419875
DOI: 10.1039/d3na01145c -
Ecotoxicology and Environmental Safety Mar 2024Organophosphorus flame retardants (OPFRs) have been frequently detected with relatively high concentrations in various environmental media and are considered emerging...
Organophosphorus flame retardants (OPFRs) have been frequently detected with relatively high concentrations in various environmental media and are considered emerging environmental pollutants. However, their biological effect and underlying mechanism is still unclear, and whether chlorinated OPFRs (Cl-OPFRs) cause adverse outcomes with the same molecular initial events or share the same key events (KEs) remains unknown. In this study, in vitro bioassays were conducted to analyze the cytotoxicity, mitochondrial impairment, DNA damage and molecular mechanisms of two Cl-OPFRs. The results showed that these two Cl-OPFRs, which have similar structures, induced severe cellular and molecular damages via different underlying mechanisms. Both tris(2-chloroethyl) phosphate (TCEP) and tris(1-chloro-2-propyl) (TCPP) induced oxidative stress-mediated mitochondrial impairment and DNA damage, as shown by the overproduction of intracellular reactive oxygen species (ROS) and mitochondrial superoxide. Furthermore, the DNA damage caused by TCPP resulted in p53/p21-mediated cell cycle arrest, as evidenced by flow cytometry and real-time PCR. At the cellular and molecular levels, TCPP increased the sub-G1 apoptotic peak and upregulated the p53/Bax apoptosis pathway, possibly resulted in apoptosis associated with its stronger cytotoxicity. Although structurally similar to TCPP, TCEP did not induce mitochondrial impairment and DNA damage by the same KEs. These results provide insight into the toxicity of Cl-OPFRs with similar structures but different mechanisms, which is of great significance for constructing adverse outcome pathways or determining intermediate KEs.
Topics: Organophosphorus Compounds; Flame Retardants; Tumor Suppressor Protein p53; Organophosphates; DNA Damage; Phosphines
PubMed: 38417316
DOI: 10.1016/j.ecoenv.2024.116158 -
Chemical Science Feb 2024Metalloproteins with dinuclear cores are known to bind and activate dioxygen, with a subclass of these proteins having active sites containing FeMn cofactors and...
Metalloproteins with dinuclear cores are known to bind and activate dioxygen, with a subclass of these proteins having active sites containing FeMn cofactors and activities ranging from long-range proton-coupled electron transfer (PCET) to post-translational peptide modification. While mechanistic studies propose that these metallocofactors access FeMn intermediates, there is a dearth of related synthetic analogs. Herein, the first well-characterized synthetic Fe-(μ-O)-Mn complex is reported; this complex shows similar spectroscopic features as the catalytically competent FeMn intermediate X found in Class Ic ribonucleotide reductase and demonstrates PCET function towards phenolic substrates. This complex is prepared from the oxidation of the isolable Fe-(μ-O)-Mn species, whose stepwise assembly is facilitated by a tripodal ligand containing phosphinic amido groups. Structural and spectroscopic studies found proton movement involving the FeMn core, whereby the initial bridging hydroxido ligand is converted to an oxido ligand with concomitant protonation of one phosphinic amido group. This series of FeMn complexes allowed us to address factors that may dictate the preference of an active site for a heterobimetallic cofactor over one that is homobimetallic: comparisons of the redox properties of our FeMn complexes with those of the di-Fe analogs suggested that the relative thermodynamic ease of accessing an FeMn core can play an important role in determining the metal ion composition when the key catalytic steps do not require an overly potent oxidant. Moreover, these complexes allowed us to demonstrate the effect of the hyperfine interaction from non-Fe nuclei on Fe Mössbauer spectra which is relevant to MnFe intermediates in proteins.
PubMed: 38404374
DOI: 10.1039/d3sc04900k -
Chemical Science Feb 2024Pd clusters offer unique selectivity and exploitable reactivity in catalysis. Understanding the behavior of Pd clusters is thus critical for catalysis, applied synthetic...
Pd clusters offer unique selectivity and exploitable reactivity in catalysis. Understanding the behavior of Pd clusters is thus critical for catalysis, applied synthetic organic chemistry and greener outcomes for precious Pd. The Pd cluster, [Pd(μ-Cl)(μ-PPh)(PPh)][Cl] (denoted as PdCl), which exhibits distinctive reactivity, was synthesized and immobilized on a phosphine-functionalized polystyrene resin (denoted as immob-PdCl). The resultant material served as a tool to study closely the role of Pd clusters in a prototypical Suzuki-Miyaura cross-coupling of 4-fluoro-1-bromobenzene and 4-methoxyphenyl boronic acid at varying low Pd ppm concentrations (24, 45, and 68 ppm). Advanced heterogeneity tests such as Hg poisoning and the three-phase test showed that leached mononuclear or nanoparticulate Pd are unlikely to be the major active catalyst species under the reaction conditions tested. EXAFS/XANES analysis from (pre)catalyst and filtered catalysts during and after catalysis has shown the intactness of the triangular structure of the PdX cluster, with exchange of chloride (X) by bromide during catalytic turnover of bromoarene substrate. This finding is further corroborated by treatment of immob-PdCl after catalyzing the Suzuki-Miyaura reaction with excess PPh, which releases the cluster from the polymer support and so permits direct observation of [Pd(μ-Br)(μ-PPh)(PPh)] ions by ESI-MS. No evidence is seen for a proposed intermediate in which the bridging halogen on the Pd motif is replaced by an aryl group from the organoboronic acid, formed by a transmetallation-first process. Our findings taken together indicate that the 'PdX' motif is an active catalyst species, which is stabilized by being immobilized, providing a more robust Pd cluster catalyst system. Non-immobilized PdCl is less stable, as is followed by stepwise XAFS of the non-immobilized PdCl, which gradually changes to a species consistent with 'Pd(PPh)' type material. Our findings have far-reaching future implications for Pd cluster involvement in catalysis, showing that immobilization of Pd cluster species offers advantages for rigorous mechanistic examination and applied chemistries.
PubMed: 38404373
DOI: 10.1039/d3sc06447f -
Journal of Medicinal Chemistry Apr 2024In this work, we investigated the anticancer activity of several novel silver(I) 2,2'-bipyridine complexes containing either triphenylphosphane (PPh) or...
In this work, we investigated the anticancer activity of several novel silver(I) 2,2'-bipyridine complexes containing either triphenylphosphane (PPh) or 1,2-bis(diphenylphosphino)ethane (dppe) ligands. All compounds were characterized by diverse analytical methods including ESI-MS spectrometry; NMR, UV-vis, and FTIR spectroscopies; and elemental analysis. Moreover, several compounds were also studied by X-ray single-crystal diffraction. Subsequently, the compounds were investigated for their anticancer activity against drug-resistant and -sensitive cancer cells. Noteworthily, neither carboplatin and oxaliplatin resistance nor p53 deletion impacted on their anticancer efficacy. MESOV cells displayed exceptional hypersensitivity to the dppe-containing drugs. This effect was not based on thioredoxin reductase inhibition, enhanced drug uptake, or apoptosis induction. In contrast, dppe silver drugs induced paraptosis, a novel recently described form of programmed cell death. Together with the good tumor specificity of this compound's class, this work suggests that dppe-containing silver complexes could be interesting drug candidates for the treatment of resistant ovarian cancer.
Topics: Humans; Phosphines; Antineoplastic Agents; Silver; 2,2'-Dipyridyl; Cell Line, Tumor; Coordination Complexes; Apoptosis; Crystallography, X-Ray; Ligands; Cell Death; Drug Screening Assays, Antitumor; Structure-Activity Relationship; Drug Resistance, Neoplasm
PubMed: 38401050
DOI: 10.1021/acs.jmedchem.3c01036 -
Polymers Feb 2024Aluminum butylmethylphosphinate AiBMP as a flame retardant and phenolphthalein as a synergistic agent were applied in a thermoplastic polyester elastomer (TPEE)) in the...
Aluminum butylmethylphosphinate AiBMP as a flame retardant and phenolphthalein as a synergistic agent were applied in a thermoplastic polyester elastomer (TPEE)) in the current study. The thermal properties, flame retardancy, crystallization and mechanical properties of TPEE/AiMBP with or without phenolphthalein were investigated using various characterizations, including the limiting oxygen index (LOI), vertical burning test (UL 94), thermogravimetric analysis TG, differential scanning calorimetry, microcombustion calorimeter (MCC), scanning electron microscopy (SEM), and mechanical tests. The results revealed that AiBMP alone is an efficient flame retardant of TPEE. Adding 15 wt.% AiBMP increases the LOI value of TPEE from 20% to 36%. The formula TPEE-15 AiBMP passed the UL 94 V-0 rating with no dripping occurring. The MCC test shows that AiBMP depresses the heat release of TPEE. In comparison with pure TPEE, the heat release rate at peak temperature and the heat release capacity of TPEE-15AiBMP are reduced by 46.1% and 55.5%, respectively. With the phenolphthalein added, the formula TPEE/13AiBMP/2Ph shows a higher char yield at high temperatures (>600 °C), and the char layer is stronger and more condensed than TPEE-15AiBMP.The tensile strength and elongation at break values of TPEE-13AiBMP-2Ph are increased by 29.63% and 4.8% in comparison with TPEE-15AiBMP. The SEM morphology of the fracture surface of the sample shows that phenolphthalein acts as a plasticizer to improve the dispersion of AiBMP within the matrix. The good char charming ability of phenolphthalein itself and improved dispersion of AiBMP make the TPEE composites achieve both satisfying flame retardancy and high mechanical properties.
PubMed: 38399930
DOI: 10.3390/polym16040552 -
PloS One 2024People with muco-obstructive pulmonary diseases such as cystic fibrosis (CF) and chronic obstructive pulmonary disease (COPD) often have acute or chronic respiratory...
People with muco-obstructive pulmonary diseases such as cystic fibrosis (CF) and chronic obstructive pulmonary disease (COPD) often have acute or chronic respiratory infections that are difficult to treat due in part to the accumulation of hyperconcentrated mucus within the airway. Mucus accumulation and obstruction promote chronic inflammation and infection and reduce therapeutic efficacy. Bacterial aggregates in the form of biofilms exhibit increased resistance to mechanical stressors from the immune response (e.g., phagocytosis) and chemical treatments including antibiotics. Herein, combination treatments designed to disrupt the mechanical properties of biofilms and potentiate antibiotic efficacy are investigated against mucus-grown Pseudomonas aeruginosa biofilms and optimized to 1) alter biofilm viscoelastic properties, 2) increase mucociliary transport rates, and 3) reduce bacterial viability. A disulfide bond reducing agent (tris(2-carboxyethyl)phosphine, TCEP), a surfactant (NP40), a biopolymer (hyaluronic acid, HA), a DNA degradation enzyme (DNase), and an antibiotic (tobramycin) are tested in various combinations to maximize biofilm disruption. The viscoelastic properties of biofilms are quantified with particle tracking microrheology and transport rates are quantified in a mucociliary transport device comprised of fully differentiated primary human bronchial epithelial cells. The combination of the NP40 with hyaluronic acid and tobramycin was the most effective at increasing mucociliary transport rates, decreasing the viscoelastic properties of mucus, and reducing bacterial viability. Multimechanistic targeting of biofilm infections may ultimately result in improved clinical outcomes, and the results of this study may be translated into future in vivo infection models.
Topics: Humans; Mucociliary Clearance; Pseudomonas aeruginosa; Hyaluronic Acid; Anti-Bacterial Agents; Tobramycin; Pseudomonas Infections; Biofilms
PubMed: 38394229
DOI: 10.1371/journal.pone.0294120