Ether Ligands Research Articles

Low pKa Phosphido-Boranes Capture Carbon Dioxide with Exceptional Strength: DFT Predictions Followed by Experimental Validation.

We have developed a class of phosphido-boranes (BoPh's) with formula X+[R2PBH3-] that bind CO2 with exceptional strength (ΔG = -8.2 to -24.0 kcal/mol) at ambient conditions. We use quantum mechanics (QM) to determine how the choice of electron-donating versus electron-withdrawing ligand impacts the CO2 binding strength, in the presence of a donating borane moiety. We also examine the role of the cation in CO2 binding, finding that the ion position relative to the bound CO2 dramatically alters binding strength. We find that the BoPh with two ethyl ligands Li[Et2PBH3] leads to ΔG = -24.0 kcal/mol upon CO2 binding while Li[Ph2PBH3] leads to ΔG = -12.8 kcal/mol. We synthesized the BoPh with two phenyl ligands Li[Ph2PBH3] to validate the QM-predicted stability and predicted pKa.

Proton-Responsive Ligands Promote CO2 Capture and Accelerate Catalytic CO2/HCO2- Interconversion.

The synthesis and investigation of [Rh(DHMPE)2][BF4] (1) are reported. 1 features proton-responsive 1,2-bis[(dihydroxymethyl)phosphino]ethane (DHMPE) ligands, which readily capture CO2 from atmospheric sources upon deprotonation. The protonation state of the DHMPE ligand was observed to have a significant impact on the catalytic reactivity of 1 with CO2. Deprotonation and CO2 binding to 1 result in a ∼10-fold rate enhancement in catalytic degenerate CO2 reduction with formate, monitored by 12C/13C isotope exchange between H12CO2- and 13CO2. Studies performed using a similar complex lacking the hydroxyl ligand functionality ([Rh(DEPE)2][BF4] where DEPE = 1,2-bis(diethylphosphino)ethane) do not show the same rate enhancements when base is added. Based upon the cation-dependent activity of the catalyst, Eyring analysis, and cation sequestration experiments, CO2 binding to 1 is proposed to facilitate preorganization of formate/CO2 in the transition state via ligand-based encapsulation of Na+ or K+ cations to lower the activation energy and increase the observed catalytic rate. Incorporation of proton-responsive DHMPE ligands provides a unique approach to accelerate the kinetics of catalytic CO2 reduction to formate.

Wide-pore fully porous mixed-mode octyl/pyridyl-bonded silica material with pH-dependent surface charge reversal for high-performance hydrophobic charge-induction chromatography of proteins

In an attempt to overcome silanophilic interactions like observed on popular reversed-phase butyl‑bonded silica stationary phases in protein HPLC, a mixed-mode stationary phase based on wide pore silica (3 µm, 300 Å) was prepared by co-immobilization of octyl and 2-pyridylethyl ligands. The surface modification was performed by a new approach using synthesized functional silatranes of the above ligands and prewetted silica. It allowed to generate a dense polymeric siloxane layer on the silica surface. Butyl-bonded silica and octyl/3-aminopropyl-bonded mixed-mode silica phases were prepared for comparison. The modified silicas were subsequently characterized by elemental analysis regarding ligand densities, by solid-state 29Si and 13C cross polarization/magic angle spinning nuclear magnetic resonance spectroscopy for confirming the surface-bonded structure, and by pH-dependent ζ-potential measurements via electrophoretic light scattering providing net surface charge information at distinct pH values. While the classical butyl‑bonded stationary phase revealed negative ζ-potential over the entire pH range investigated (pH 3.5–9.5) due to residual silanols and the mixed-mode octyl/3-aminopropyl-bonded silica positive ζ-potential over the entire pH range, pH-dependent charge reversal was observed at approximately pH 5.5 for the octyl/pyridyl-bonded stationary phase. Then, a test set of proteins differing in hydrophobicities and isoelectric points was employed to evaluate the retention characteristics of all three synthesized stationary phases over the pH range of 3 to 7.5 by acetonitrile-gradient elution reversed-phase HPLC. Under acidic conditions (pH 3) the mixed-mode phases octyl/pyridyl-silica and octyl/aminopropyl-silica showed reduced retention and improved peak shapes due to repulsive interactions preventing silanophilic interactions, while protein separations by their hydrophobicities were achieved (repulsive charge-assisted protein RPLC). Finally, the prepared novel mixed-mode octyl/pyridyl-bonded stationary phase was evaluated in hydrophobic charge induction chromatography mode for protein separation of the same test set. Instead of an organic modifier gradient, elution was enforced by a pH gradient from almost neutral to acidic pH at constant organic modifier content of 10 %. This chromatographic mode showed orthogonal retention characteristics and reversed elution order compared to above organic gradient RP-HPLC. In addition, significantly less organic solvent was used under these conditions, classifying it as a green protein LC technology.

New nano-complexes targeting protein 3S7S in breast cancer and protein 4OO6 in liver cancer investigated in cell line

Cancer, a lethal ailment, possesses a multitude of therapeutic alternatives to combat its presence, metal complexes have emerged as significant classes of medicinal compounds, exhibiting considerable biological efficacy, especially as anticancer agents. The utilization of cis-platin in the treatment of various cancer types, including breast cancer, has served as inspiration to devise novel nanostructured metal complexes for breast cancer therapy. Notably, homo- and hetero-octahedral bimetallic complexes of an innovative multifunctional ether ligand (comprising Mn(II), Ni(II), Cu(II), Zn(II), Hg(II), and Ag(I) ions) have been synthesized. To ascertain their structural characteristics, elemental and spectral analyses, encompassing IR, UV–Vis, 1H-NMR, mass and electron spin resonance (ESR) spectra, magnetic moments, molar conductance, thermal analysis, and electron microscopy, were employed. The molar conductance of these complexes in DMF demonstrated a non-electrolytic nature. Nanostructured forms of the complexes were identified through electron microscopic data. At ambient temperature, the ESR spectra of the solid complexes exhibited anisotropic and isotropic variants, indicative of covalent bonding. The ligand and several of its metal complexes were subjected to cytotoxicity testing against breast cancer protein 3S7S and liver cancer protein 4OO6, with the Ag(I) complex (7) evincing the most potent effect, followed by the Cu(II) with ligand (complex (2)), Cis-platin, the ligand itself, and the Cu(II)/Zn(II) complex (8). Molecular docking data unveiled the inhibitory order of several complexes.

Immobilized lipase based on SBA-15 adsorption and gel embedding for catalytic synthesis of isoamyl acetate

In this study, Candida rugosa lipase (CRL) was immobilized on the silica carrier SBA-15 by physical adsorption, then mixed with hydrophobically modified sodium alginate and dropped into calcium chloride solution. Finally, the adsorption-embedding immobilized lipase (L-SBA-15-Mgel) was successfully prepared. The conformation of the carrier before and after lipase immobilization were analyzed by scanning electron microscopy (SEM), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR) and other characterization techniques. The molecular docking and molecular dynamics simulation of CRL and modifier dodecyl glycidyl ether (DGE) ligand were carried out to analyze the potential influence of modifier on enzyme characteristics. The basic enzymatic properties including the activity, stability and reaction kinetic parameters of the immobilized lipase L-SBA-15-Mgel were studied. L-SBA-15-Mgel showed good storage stability and reusability. After 16 days of storage, the activity retention was 47.85%, and there was still 63.20% of the residual activity after seven cycles of reuse. The immobilized lipase was applied to the efficient synthesis of food flavor ester isoamyl acetate. Under the reaction conditions of 50 °C and 200 rpm, the highest yield of isoamyl acetate catalyzed by L-SBA-15-Mgel was 85.19%.

Synthesis of cationic lanthanoid tetraphenylborate crown ether complexes

The efficacy of Me3NHBPh4 as a protolytic agent in the generation of reactive lanthanoid cations has been further explored. Reaction of [Nd(BH4)3(thf)4] with Me3NHBPh4 in a 1:3 mole ratio, and dibenzo-18-crown-6 (DB18C6) in thf did not yield [Nd(thf)n][BPh4]3, but [Nd(BH4)2(DB18C6)][BPh4]⋅2THF (1), a complex primed for further functionalisation, was isolated. The structure has an eight coordinate Nd atom with two trans tridentate BH4− ligands. Redox transmetallation/protolysis (RTP) reactions between Yb metal, PhHgC6F5, and Me3NHBPh4 in the presence of 18-crown-6 (18C6) or DB18C6 in MeCN or in thf followed by work up with MeCN yields [Yb(CE)(MeCN)3][BPh4]2⋅nMeCN (CE = 18C6, n = 0 (2), and DB18C6 n = 3 (3)), the structures of which have nine coordinate Yb atoms. Two pairs of MeCN ligands are transoid, whereas the third pair have a small cis NYbN angle. In the absence of a crown ether ligand, the RTP reaction in MeCN yields the known [Yb(MeCN)8] [BPh4]2.

Synthesis, crystal structure and anti-cancer activity of the complex chlorido-(η2-ethyl-ene)(quinolin-8-olato-κ2N,O)platinum(II) by experimental and theoretical methods.

The complex [Pt(C9H6NO)Cl(C2H4)], (I), was synthesized and structurally characterized by ESI mass spectrometry, IR, NMR spectroscopy, DFT calculations and X-ray diffraction. The results showed that the deprotonated 8-hy-droxy-quinoline (C9H6NO) coordinates with the PtII atom via the N and O atoms while the ethyl-ene coordinates in the η2 manner and in the trans position compared to the coordinating N atom. The crystal packing is characterized by C-H⋯O, C-H⋯π, Cl⋯π and Pt⋯π inter-actions. Complex (I) showed high selective activity against Lu-1 and Hep-G2 cell lines with IC50 values of 0.8 and 0.4 µM, respectively, 54 and 33-fold more active than cisplatin. In particular, complex (I) is about 10 times less toxic to normal cells (HEK-293) than cancer cells Lu-1 and Hep-G2. Furthermore, the reaction of complex (I) with guanine at the N7 position was proposed and investigated using the DFT method. The results indicated that replacement of the ethyl-ene ligand with guanine is thermodynamically more favorable than the Cl ligand and that the reaction occurs via two consecutive steps, namely the replacement of ethyl-ene with H2O and the water with the guanine mol-ecule.

Paraptotic Cell Death as an Unprecedented Mode of Action Observed for New Bipyridine-Silver(I) Compounds Bearing Phosphane Coligands.

In this work, we investigated the anticancer activity of several novel silver(I) 2,2'-bipyridine complexes containing either triphenylphosphane (PPh3) 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. MES-OV 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.

Cyanometallic charge engineering in spin crossover metal-organic frameworks.

In this study, we successfully synthesize cationic/neutral/anionic inverse-Hofmann-type spin crossover (SCO) frameworks with 1,1,2,2-tetrakis(4-(pyridine-4-yl)phenyl)-ethene ligand by means of cyanometallic charge engineering strategy. The cationic and neutral frameworks exhibit single-step thermally induced spin transition behaviors, while the SCO capability of anionic framework can be aroused by partial desolvation. This strategy provides a new idea to construct ionic SCO frameworks and extends the toolkit for SCO materials.

Two-dimensional spin-crossover coordination polymers based on the 1,1,2,2-tetra(pyridin-4-yl)ethene ligand.

A series of two-dimensional (2D) spin-crossover coordination polymers (SCO-CPs) [FeII(TPE)(NCX)2]·solv (1: X = BH3, solv = H2O·2CH3OH·DMF; 2: X = Se, solv = H2O·2CH3OH·0.5DMF; 3: X = S, solv = H2O·2CH3OH·0.5DMF) were synthesized by employing 1,1,2,2-tetra(pyridin-4-yl)ethene (TPE) and pseudohalide (NCX-) coligands. Magnetic measurements indicated that complexes 1-3 exhibited SCO behaviors with diminishing thermal hysteresis (7/4/0 K) upon decreasing the ligand-field strength. The critical temperatures (Tc) during spin transition were found to be inversely proportional to the coordination ability parameters (a™) with a linear correlation. The guest effect was also investigated in the solvent-exchanged phases 1-SE/2-SE/3-SE wherein the DMF molecules were replaced by methanol molecules. Compared with 1-3, 1-SE/2-SE/3-SE displayed more abrupt and complete single-step SCO behaviors but narrower thermal hysteretic loops. The results reported here demonstrate that the Tc values of these two families were dominated by the ligand-field strength of the NCX- anions (NCBH3 > NCSe > NCS), whereas the guest effect only modulated the kinetic factor of the SCO nature in this system.

Modelling the growth reaction pathways of zincone ALD/MLD hybrid thin films: a DFT study.

ALD/MLD hybrid thin films can be fabricated by combining atomic layer deposition (ALD) and molecular layer deposition (MLD). Even though this deposition method has been extensively used experimentally, the computational work required to acquire the reaction paths during the thin film deposition process is still in dire demand. We investigated hybrid thin films consisting of diethyl zinc and either 4-aminophenol or hydroquinone using both gas-phase and surface reactions to gain extensive knowledge of the complex phenomena occurring during the process of hybrid thin film deposition. We used density functional theory (DFT) to obtain the activation energies of these kinetic-dependent deposition processes. Different processes of ethyl ligand removal as ethane were discovered, and we found that the hydroxyl group of 4-aminophenol was more reactive than the amino group in the migration of hydrogen to an ethyl ligand within a complicated branching reaction chain.

Ligand Modulation of Active Sites to Promote Cobalt-Doped 1T-MoS2 Electrocatalytic Hydrogen Evolution in Alkaline Media.

Highly efficient hydrogen evolution reaction (HER) electrocatalyst will determine the mass distributions of hydrogen-powered clean technologies, while still faces grand challenges. In this work, a synergistic ligand modulation plus Co doping strategy is applied to 1T-MoS2 catalyst via CoMo-metal-organic frameworks precursors, boosting the HER catalytic activity and durability of 1T-MoS2 . Confirmed by Cs corrected transmission electron microscope and X-ray absorption spectroscopy, the polydentate 1,2-bis(4-pyridyl)ethane ligand can stably link with two-dimensional 1T-MoS2 layers through cobalt sites to expand interlayer spacing of MoS2 (Co-1T-MoS2 -bpe), which promotes active site exposure, accelerates water dissociation, and optimizes the adsorption and desorption of H in alkaline HER processes. Theoretical calculations indicate the promotions in the electronic structure of 1T-MoS2 originate in the formation of three-dimensional metal-organic constructs by linking π-conjugated ligand, which weakens the hybridization between Mo-3d and S-2p orbitals, and in turn makes S-2p orbital more suitable for hybridization with H-1s orbital. Therefore, Co-1T-MoS2 -bpe exhibits excellent stability and exceedingly low overpotential for alkaline HER (118 mV at 10 mA cm-2 ). In addition, integrated into an anion-exchange membrane water electrolyzer, Co-1T-MoS2 -bpe is much superior to the Pt/C catalyst at the large current densities. This study provides a feasible ligand modulation strategy for designs of two-dimensional catalysts.

Ligand Modulation of Active Sites to Promote Cobalt‐Doped 1T‐MoS2 Electrocatalytic Hydrogen Evolution in Alkaline Media

AbstractHighly efficient hydrogen evolution reaction (HER) electrocatalyst will determine the mass distributions of hydrogen‐powered clean technologies, while still faces grand challenges. In this work, a synergistic ligand modulation plus Co doping strategy is applied to 1T−MoS2 catalyst via CoMo‐metal‐organic frameworks precursors, boosting the HER catalytic activity and durability of 1T−MoS2. Confirmed by Cs corrected transmission electron microscope and X‐ray absorption spectroscopy, the polydentate 1,2‐bis(4‐pyridyl)ethane ligand can stably link with two‐dimensional 1T−MoS2 layers through cobalt sites to expand interlayer spacing of MoS2 (Co−1T−MoS2‐bpe), which promotes active site exposure, accelerates water dissociation, and optimizes the adsorption and desorption of H in alkaline HER processes. Theoretical calculations indicate the promotions in the electronic structure of 1T−MoS2 originate in the formation of three‐dimensional metal‐organic constructs by linking π‐conjugated ligand, which weakens the hybridization between Mo‐3d and S‐2p orbitals, and in turn makes S‐2p orbital more suitable for hybridization with H‐1s orbital. Therefore, Co−1T−MoS2‐bpe exhibits excellent stability and exceedingly low overpotential for alkaline HER (118 mV at 10 mA cm−2). In addition, integrated into an anion‐exchange membrane water electrolyzer, Co−1T−MoS2‐bpe is much superior to the Pt/C catalyst at the large current densities. This study provides a feasible ligand modulation strategy for designs of two‐dimensional catalysts.

IR spectroscopic characterization of products of methane and cyclopropane activation by Ru cations

Methane and cyclopropane (c-C3H6) were reacted with Ru+ ions in a room temperature ion trap and the resulting products were identified using a combination of mass spectrometry, IR action spectroscopy, and density functional theory calculations. In the reaction with methane, no products with odd numbers of carbon atoms were located, whereas significant amounts of products with even numbers of carbon atoms were observed. We identified [Ru,2C,4H]+ as the Ru+ ion with an ethene ligand attached, and [Ru,4C,6H]+ as a Ru(η4-cis-1,3-butadiene)+ complex. The barrier toward formation of Ru(C2H4)+ + 2H2 was calculated at the B3LYP/def2-TZVPPD level to be 0.80 eV above the energy of the ground state Ru+ (4F) + 2 CH4 reactants. In the reaction of c-C3H6 with Ru+, we identified the dehydrogenation product [Ru,3C,4H]+ as Ru(η2-propyne)+, [Ru,2C,2H]+ as Ru+ with an ethyne ligand, and [Ru,5C,5H]+ as Ru(η5-c-C5H5)+ having a cyclopentadienyl ligand.

Evaluating an electric field modulated plasma enhanced atomic layer deposition of platinum layers on different substrates

Atomic layer deposition is a key technique for preparing large area uniformity, three-dimensional conformal, and ultrathin films due to its sequential self-limiting saturated chemisorption properties. Electric fields of varying magnitudes and directions were applied on Si, Al2O3, Au, and Ni substrates in Pt plasma enhanced atomic layer deposition processes. Studying the influences of electric fields on the initial nucleation and growth of Pt films on different substrates helps to understand the dynamic knowledge and underlying physical mechanisms so as to obtain ultrathin, continuous films and full control over the morphology and distribution of deposited materials. The XPS results reveal that the Pt coverage rate increases on all substrates with applied voltages. The induced dipole moment causes the (MeCp)PtMe3 molecule to rotate in a certain direction resulting in a more compact arrangement, and the energy generated by electric fields also helps the dissociation of methyl, ethyl, Cp, and MeCp ligands, which greatly mitigate the spatial site resistance effect, thus improving initial monolayer chemisorption efficiency and the Pt coverage. We also find that Pt prefers to grow in the (111) direction due to the increase in adsorption of (MeCp)PtMe3 molecules caused by the gradient forces under electric fields. However, applied electric fields can also influence the morphology by inducing surface diffusion and acting on plasma species.

New Insights into the Catalytic Activity of Second Generation Hoveyda–Grubbs Complexes Having Phenyl Substituents on the Backbone

One of the most effective synthetic pathways to produce unsaturated compounds and polymers, meant for both industrial and pharmaceutical applications, is olefin metathesis. These useful reactions are commonly promoted by ruthenium-based precatalysts, namely the second-generation Grubbs’ catalyst (GII) and complexes bearing a styrenyl ether ligand, referred to as the second-generation Hoveyda–Grubbs’ catalyst (HGII). By altering the steric and electronic characteristics of substituents on the backbone and/or on the nitrogen atoms of the NHC ligand, it is possible to increase the reactivity and stability of second-generation ruthenium catalysts. The synthesis of an HG type II complex bearing two anti-phenyl backbone substituents (anti-HGIIPh-Mes) with mesityl N-substituents is reported. The catalytic performances of the new complex were investigated in standard ring-closing metathesis (RCM) and ring-opening metathesis polymerization (ROMP) and compared to those of the analogue complex syn-HGIIPh-Mes and to the classic HGII complex. A thorough analysis of the temperature dependence of the performances, along with a detailed comparison with the commercially available HGII, is conducted. The HGIIPh-Mes complexes are more thermally stable than their parent HGII, as shown by the fact that their activity in the ROMP of 5-ethylidene-2-norbornene does not alter when the polymerization is carried out at room temperature after the complexes have been held at 180 °C for two hours, making them particularly interesting for materials applications.

Observations of Ethylene-for-CO Ligand Exchanges on a Zeolite-Supported Single-Site Rh Catalyst by X-ray Absorption Spectroscopy

Quick-scanning X-ray absorption fine structure (QXAFS) measurements were used to characterize the exchanges of ethylene and CO ligands in a zeolite HY-supported single-site Rh complex at a sampling rate of 1.0 Hz. The two ligands were reversibly exchanged on the rhodium, with quantitative results determined for the C2H4-for-CO exchange that are consistent with a first-order process. The apparent rate constant for the exchange decreased with increasing temperature. Fourier-transform infrared spectra characterizing the C2H4 sorbed in the zeolite showed that the amount decreased with increasing temperature, consistent with the decrease in the exchange rate with increasing temperature. The results, illustrating the dynamics of ligand exchanges on a single-site supported metal catalyst, demonstrate the broad emerging applicability of the QXAFS technique for characterizing the dynamics of reactive intermediates on catalysts.

Abstract 4905: Anticancer activity and paraptosis induction of novel bipyridine-silver(I) compounds against resistant colorectal and ovarian cancer cell lines

Abstract Background: Platinum-based anticancer drugs (e.g. Carboplatin and Oxaliplatin) are frequently applied in chemotherapy regimens against several types of cancer including ovarian carcinoma (OC) and colorectal carcinoma (CRC). However, intrinsic or acquired tumor resistance severely limit their clinical application. Here, we investigated the anticancer activity of several novel silver(I) 2,2’-bipyridine derivatives, containing either triphenylphosphane (PPh3) or 1,2-bis(diphenylphosphino)ethane (dppe) ligands and tested their potential to overcome platinum resistance. Methods: Cytotoxicity and cross resistance profiles of the newly synthesized compounds were tested against two OC models (SKOV-3 and MES-OV), a CRC model (HCT-116) and their corresponding sublines resistant to carboplatin or oxaliplatin, as well as non-malignant fibroblasts (F331) via an MTT-based cell viability assay after 72 h continuous drug exposure. Moreover, the intracellular levels of silver were measured via ICP-MS. In addition, thioredoxin reductase (TrxR) inhibition properties, impact on cell cycle distribution and apoptosis induction potential were investigated via multiple molecular biological methods. Morphological changes induced by the silver compounds were characterized via spinning disk confocal microscopy. Results: All tested compounds displayed pronounced anticancer activity and cancer cell selectivity. Moreover, cell intrinsic resistance to carboplatin or oxaliplatin was not impacting on the cytotoxic activity of the compounds. Noteworthy, MES-OV and HCT-116 cells showed exceptional sensitivity to several silver(I) 2,2’-bipyridine derivatives with a 1,2-bis(diphenylphosphino)ethane (dppe) (AP-compounds). This sensitivity was not based on enhanced drug uptake, pronounced TrxR inhibition nor apoptosis induction or cell cycle arrest. In contrast, hypersensitive cells displayed pronounced endoplasmic reticulum (ER)-derived vesicles together with multiple others hallmarks of paraptotic cell death. Conclusion: Our findings did not only demonstrate that the new silver compounds were unaffected by cancer cell intrinsic resistance mechanisms to platinum-based chemotherapy, but also indicated a high vulnerability of tumor (sub)types towards these bipyridine silver complexes. This hypersensitivity is based on the induction of paraptosis, a novel form of programmed cell death. To summarize, these silver compounds represent a new class of promising anticancer drugs, which demand further preclinical development. Citation Format: Alessia Stefanelli, Ricardo G. Teixeira, Adhan Pilon, Rebecca Warmers, Ingo Ott, Christian R. Kowol, Anamaria Brozovic, Ana Isabel Tomaz, Andreia Valente, Petra Heffeter. Anticancer activity and paraptosis induction of novel bipyridine-silver(I) compounds against resistant colorectal and ovarian cancer cell lines. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4905.

Engineering Pore Environments of Sulfate-Pillared Metal-Organic Framework for Efficient C2 H2 /CO2 Separation with Record Selectivity.

Engineering pore environments exhibit great potential in improving gas adsorption and separation performances but require specific means for acetylene/carbon dioxide (C2 H2 /CO2 ) separation due to their identical dynamic diameters and similar properties. Herein, a novel sulfate-pillared MOF adsorbent (SOFOUR-TEPE-Zn) using 1,1,2,2-tetra(pyridin-4-yl) ethene (TEPE) ligand with dense electronegative pore surfaces is reported. Compared to the prototype SOFOUR-1-Zn, SOFOUR-TEPE-Zn exhibits a higher C2 H2 uptake (89.1 cm3 g-1 ), meanwhile the CO2 uptake reduces to 14.1 cm3 g-1 , only 17.4% of that on SOFOUR-1-Zn (81.0 cm3 g-1 ). The high affinity toward C2 H2 than CO2 is demonstrated by the benchmark C2 H2 /CO2 selectivity (16 833). Furthermore, dynamic breakthrough experiments confirm its application feasibility and good cyclability at various flow rates. During the desorption cycle, 60.1 cm3 g-1 C2 H2 of 99.5% purity or 33.2 cm3 g-1 C2 H2 of 99.99% purity can be recovered by stepped purging and mild heating. The simulated pressure swing adsorption processes reveal that 75.5 cm3 g-1 C2 H2 of 99.5+% purity with a high gas recovery of 99.82% can be produced in a counter-current blowdown process. Modeling studies disclose four favorable adsorption sites and dense packing for C2 H2 .

Tunable and Switchable Catalysis Enabled by Cation-Controlled Gating with Crown Ether Ligands

ConspectusCatalysis has become an essential tool in science and technology, impacting the discovery of pharmaceuticals, the manufacture of commodity chemicals and plastics, the production of fuels, and much more. In most cases, a particular catalyst is optimized to mediate a particular reaction, continually producing a desired product at a given rate. There is enormous opportunity in developing catalysts that are dynamic, capable of responding to a change in the environment to alter structure and function. Controlled catalysis, in which the activity or selectivity of a catalytic reaction can be adjusted through an external stimulus, offers opportunities for innovation in catalysis. Catalyst discovery could be simplified if a single thoughtfully designed complex could work synergistically with additives to optimize performance rather than trying a multitude of different metal/ligand combinations. Temporal control could be gained to facilitate the execution of multiple reactions in the same flask, for example, by activating one catalyst and deactivating another to avoid incompatibilities. Selectivity switching could enable copolymer synthesis with well-defined chemical and material properties. These applications might sound futuristic for synthetic catalysts, but in nature, such a degree of controlled catalysis is commonplace. For example, allosteric interactions and/or feedback loops modulate enzymatic activity to enable complex small-molecule synthesis and sequence-defined polymerization reactions in complex mixtures containing many catalytic sites. In many cases, regulation is achieved by "gating" substrate access to the active site. Fundamental advances in catalyst design are needed to better understand the factors that enable controlled catalysis in the arena of synthetic chemistry, particularly in achieving substrate gating outside of macromolecular environments. In this Account, the development of design principles for achieving cation-controlled catalysis is described. The guiding hypothesis was that gating substrate access to a catalyst site could be achieved by controlling the dynamics of a hemilabile ligand through secondary Lewis acid/base and/or cation-dipole interactions. To enforce such interactions, catalysts sitting at the interface of organometallic catalysis and supramolecular chemistry were designed. A macrocyclic crown ether was incorporated into a robust organometallic pincer ligand, and these "pincer-crown ether" ligands have been explored in catalysis. Complementary studies of controlled catalysis and detailed mechanistic analysis guided the development of iridium, nickel, and palladium pincer-crown ether catalysts capable of substrate gating. Toggling the gate between open and closed states leads to switchable catalysis, where cation addition/removal changes the turnover frequency or the product selectivity. Varying the degree of gating leads to tunable catalysis, where the activity can be tuned based on the identity and amount of salt added. Research has focused on reactions of alkenes, particularly isomerization reactions, which has in turn led to design principles for cation-controlled catalysts.