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Improved hydrophobic subtraction model of reversed-phase liquid chromatography selectivity based on a large dataset with a focus on isomer selectivity
No full textReversed-phase (RP) liquid chromatography is an important tool for the characterization of materials and products in the pharmaceutical industry. Method development is still challenging in this application space, particularly when dealing with closely-related compounds. Models of chromatographic selectivity are useful for predicting which columns out of the hundreds that are available are likely to have very similar, or different, selectivity for the application at hand. The hydrophobic subtraction model (HSM1) has been widely employed for this purpose; the column database for this model currently stands at 750 columns. In previous work we explored a refinement of the original HSM1 (HSM2) and found that increasing the size of the dataset used to train the model dramatically reduced the number of gross errors in predictions of selectivity made using the model. In this paper we describe further work in this direction (HSM3), this time based on a much larger dataset (43,329 total measurements) containing selectivities for compounds covering a broader range of physicochemical properties compared to HSM1. This includes multiple compounds that are actual active pharmaceutical ingredients and related synthetic intermediates and impurities, as well as multiple pairs of closely related structures (e.g., geometric and cis-/trans- isomers). The HSM3 model is based on retention measurements for 75 compounds using 13 RP stationary phases and a mobile phase of 40/60 acetonitrile/25 mM ammonium formate buffer at pH 3.2. This data-driven model produced predictions of ln(alpha) (chromatographic selectivity using ethylbenzene as the reference compound) with average absolute errors of approximately 0.033, which corresponds to errors in alpha of about 3 %. In some cases, the prediction of the trans-/cis- selectivities for positional and geometric isomers was relatively accurate, and the driving forces for the observed selectivity could be inferred by examination of the relative magnitudes of the terms in the HSM3 model. For some geometric isomer pairs the interactions mainly responsible for the observed selectivities could not be rationalized due to large uncertainties for particular terms in the model. This suggests that more work is needed in the future to explore other HSM-type models and continue expanding the training dataset in order to continue improving the predictive accuracy of these models
Electric-field Assisted Spatioselective Deposition of MIL-101(Cr)PEDOT to Enhance Electrical Conductivity and Humidity Sensing Performance
No full textPoly(3,4-ethylenedioxythiophene)-functionalized (PEDOT) MIL-101(Cr) nanoparticles were deposited via drop-casting onto interdigitated electrodes (IDEs). The application of an alternating potential during drop-casting allowed precise spatioselective deposition of the nanoparticles in the interelectrode gaps, generating percolating nanoparticle chains aligned between the finger electrodes. The resulting conductivities of the aligned and chained samples were up to 4 orders of magnitude higher than that of unaligned samples prepared via regular drop-casting. The performance of the unaligned and aligned samples for resistive humidity sensing was investigated, whereby the aligned samples showed a conductivity gain of 230 times at a relative humidity of 90% versus 10%, whereas the unaligned samples showed a lower gain of 40 times at relative humidity 90% versus 10%. Further, the aligned samples could also be utilized as capacitive humidity sensors, showing a change of sensitivity at different frequencies for the aligned sample, whereas unaligned samples show a resistive behavior unsuitable for capacitive sensing. This work demonstrates that simple drop-casting when carried out in conjunction with an applied alternating potential exerts dielectrophoretic control allowing for precise spatioselective deposition, thus leading to higher sample conductivity and enhanced performances for humidity sensing
Lewis acid-catalyzed diastereoselective ene reaction of thioindolinones with bicyclobutanes
No full textBicyclo[1.1.0]butanes (BCBs), featuring two fused cyclopropane rings, have found widespread application in organic synthesis. Their versatile reactivity towards radicals, nucleophiles, cations, and carbenes makes them suitable for various reactions, including ring-opening and annulation strategies. Despite this versatility, their potential as enophiles in an ene reaction remains underexplored. Considering this and given the challenges of achieving diasteroselectivity in ring-opening reactions of BCBs, herein, we present a unique method utilizing BCBs as enophiles in a mild and diastereoselective Sc(OTf)3-catalyzed ene reaction with thioindolinones, delivering 1,3-disubstituted cyclobutane derivatives in high yields and excellent regio- and diastereoselectivity. Notably, structurally different thione derivatives underwent diastereoselective addition to BCBs, affording the corresponding cyclobutanes. The synthesized thioindole-substituted cyclobutanes could serve as a versatile tool for subsequent functional group manipulations
Csp3-Csp2 Coupling of Isonitriles and (Hetero)arenes through a Photoredox-Catalyzed Double Decyanation Process
No full textHerein we demonstrate the ability of isonitriles to be used as alkyl radical precursors in a photoredox-catalyzed transformation involving selective C-N cleavage and Csp3-Csp2 bond formation. This protocol allows for the preparation of functionalized heteroarenes from readily available isonitriles through a decyanation process. The reaction is general for primary, secondary and terciary substrates, including amino acid derivatives and druglike molecules
Computationally predicting the performance of gas sensor arrays for anomaly detection
No full textIn many gas sensing tasks, we simply wish to become aware of gas compositions that deviate from normal, "business-as-usual" conditions. We provide a methodology, illustrated by example, to computationally predict the performance of a gas sensor array design for detecting anomalous gas compositions. Specifically, we consider a sensor array of two zeolitic imidazolate frameworks (ZIFs) as gravimetric sensing elements for detecting anomalous gas compositions in a fruit ripening room. First, we define the probability distribution of the concentrations of the key gas species (CO₂, C₂H₄, H₂O) we expect to encounter under normal conditions. Next, we construct a thermodynamic model to predict gas adsorption in the ZIF sensing elements in response to these gas compositions. Then, we generate a synthetic training data set of sensor array responses to "normal" gas compositions. Finally, we train a support vector data description to flag anomalous sensor array responses and test its false alarm and missed-anomaly rates under conceived anomalies. We find the performance of the anomaly detector diminishes with (i) greater variance in humidity, which can mask CO₂ and C₂H₄ anomalies or cause false alarms, (ii) higher levels of noise emanating from the transducers, and (iii) smaller training data sets. Our exploratory study is a step towards computational design of gas sensor arrays for anomaly detection
Triptycene-based diiron(II) mesocate: spin-crossover in solution
No full textTriptycene-based diiron(II) and dizinc(II) mesocates were obtained using a novel rigid ligand with two pyridylbenzimidazole chelating units fused into the triptycene scaffold. Studies on the diiron(II) assembly in solution showed that the complex undergoes thermal-induced one-step spin-crossover with T1/2 at 243 K (Evans method)
Addition, Elimination, and Rearrangement Reactions of Cyclopropyl-Substituted Nitrenium Ions: A Computational and Experimental Investigation
No full textTwo cyclopropyl substituted nitrenium ions were generated through photolysis of their corresponding N-aminopyridinium ion photoprecursors. In the case of N-biphenyl-N-cyclopropyl nitrenium ion (5). Stable products are derived from a combination of cyclopropyl ring expansion, forming N-biphenylazetium ion, and ethylene elimination, forming biphenylisonitrilium ion. When present in high concentrations, methanol can add to the cyclopropyl ring forming N-3-methoxypropyl-N-biphenyl iminium ion. In contrast, the only detectable product from N-benzyl-N-cyclopropyl nitrenium ion (6) is benzylisonitrile, resulting from elimination of ethylene. DFT calculations predict the product distributions from the more stable biphenyl system 5 with reasonable accuracy. However product distributions from the less stable benzyl system 6 are forecast with less accuracy
Modern Electrospray Ionization Mass Spectrometry Techniques for the Characterisation of Supramolecules and Coordination Compounds
No full textMass spectrometry is routinely used for myriad applications in clinical, industrial, and research laboratories worldwide. Developments in the areas of ionisation sources, high-resolution mass analysers, tandem mass spectrometry, and ion mobility have significantly extended the repertoire of mass spectrometrists, however for coordination compounds and supramolecules, mass spectrometry remains underexplored and arguably underappreciated. Here, the reader is guided through different tools of modern electrospray ionization mass spectrometry that are suitable for larger inorganic complexes. All steps, from sample preparation and technical details to data analysis and interpretation are discussed. The main target audience of this tutorial are synthetic chemists as well as technicians/mass spectrometrists with little experience in characterising labile inorganic compounds
Capturing Carbon Dioxide from Air with Charged-Sorbents
No full textEmissions reduction and greenhouse gas removal from the atmosphere are both necessary to achieve net-zero emissions and limit climate change.1 There is thus a need for improved sorbents for the capture of carbon dioxide from the atmosphere, a process known as direct air capture. In particular, low-cost materials that can be regenerated at low temperatures would overcome the limitations of current technologies. In this work, we introduce a new class of designer sorbent materials known as “charged-sorbents”. These materials are prepared through a battery-like charging process which accumulates ions in the pores of low-cost activated carbons, with the inserted ions then serving as adsorption sites for carbon dioxide adsorption. We use our charging process to accumulate reactive hydroxide ions in the pores of a carbon electrode, and find that the resulting sorbent material can rapidly capture carbon dioxide from ambient air via (bi)carbonate formation. Unlike traditional bulk carbonates, charged-sorbent regeneration can be achieved at low temperatures (90-100 ºC), and the sorbent\u27s conductive nature permits direct Joule heating regeneration2,3 using renewable electricity. Given their highly tailorable pore environments and low cost, we anticipate that charged-sorbents will find numerous potential applications in chemical separations, catalysis, and beyond
Optimizing Oil Recovery: A Comprehensive Review of Foam Applications in Enhanced Oil Recovery.
No full textAs global oil demand continues to rise and operators scale back on exploration investments, the adoption of enhanced oil recovery (EOR) technology is becoming increasingly essential. This approach strategically aims to optimize reserves in existing fields, maximizing production through efficient processes. In recent years, there has been a notable surge in the adoption of foam applications in EOR. These foam applications are particularly effective in managing gas mobility in injector wells and preventing gas blockages in production wells. The use of foam has proven to be an effective method for addressing reservoir heterogeneity concerns, including viscosity fingering, gravity segregation, and channeling. These solutions maintain operational stability while improving the efficiency of oil recovery. However, persistent challenges remain ongoing, such as foam solution quality, foamability, stability under high pressures and temperatures, and interactions with the oil phase. Thus, ongoing research and development are crucial to overcome these challenges and optimize the use of foam in enhanced oil recovery. This paper aims to comprehensively review and synthesize the most pertinent studies on foam-based enhanced oil recovery (EOR). The study thoroughly investigates the factors that affect foam stability and efficiency, offering a comprehensive understanding of foam generation in porous media. The paper review identifies knowledge gaps and proposes methods to incorporate physical understandings of experiments into assessments of foam project performance. The paper explores the applications of foam in laboratory and field settings, highlighting recent advancements in improving foam stability