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CatTestHub: A Benchmarking Database of Experimental Heterogeneous Catalysis for Evaluating Advanced Materials
No full textThe ability to quantitatively compare newly evolving catalytic materials and technologies is hindered by the widespread availability of catalytic data collected in a consistent manner. While certain catalytic chemistries have been widely studied across decades of scientific research, the ability to quantitatively utilize the available literature information is hindered by variability in reaction conditions, types of reported data, and reporting procedures. Here, we present CatTestHub, a database dedicated to providing benchmarking experimental data for heterogeneous catalysis. Through the selection of probe chemistries, combined with material characterization information and the systematic reporting of kinetic information, the database provides a collection of information that provides a collection of catalytic benchmarks for distinct classes of active sites. We propose that this online and open-access platform could serve as a community wide benchmark, the quality of which is improved through continuous addition of kinetic information on select catalytic systems by members of the heterogeneous catalysis community at large. In this initial iteration, we present benchmarking data relevant to the decomposition of methanol and formic acid over metal surfaces, as well as the Hofmann elimination of alkylamines over aluminosilicate zeolites. Details of the database, the logic of its construction, and the means through which to navigate are presented here, along with examples of catalytic insights readily drawn from the available information
Fingerprints of Chalcogen Bonding Revealed Through 77Se-NMR
No full text77Se-NMR is used to characterise several chalcogen bonded complexes of derivatives of the organoselenium drug ebselen, exploring a range of electron demand. NMR titration experiments support the intuitive understanding that chalcogen bond donors bearing more electron withdrawing substituents give rise stronger chalcogen bonds. The chemical shift of the selenium nucleus is also shown to move upfield as it participates in a chalcogen bond. Solid-state NMR is used to explore chalcogen bonding in co-crystals. Due to the lack of molecular reorientation on the NMR timescale in the solid state, the shape of the chemical shift tensor can be determined using this technique. A range of co-crystals are shown to have extremely large chemical shift anisotropy, which suggests a strongly anisotropic electron density distribution around the selenium atom. A single crystal NMR experiment was conducted using one of the co-crystals, affording the absolute orientation of the chemical shift tensor within the crystal. This showed that the selenium nucleus is strongly shielded in the direction of the chalcogen bond, and strongly deshielded in the perpendicular direction, consistent with the presence of a second sigma-hole which is not participating in a chalcogen bond
De-epimerizing DyKAT of β-Lactones Generated by Isothiourea-Catalysed Enantioselective [2+2] Cycloaddition
No full textModerate diastereoselectivity (typically 70:30 dr) is observed in the isothiourea-catalysed [2+2]-cycloaddition of C(1)-ammonium enolates with pyrazol-4,5-diones to generate spirocyclic β lactones, but subsequent ring-opening with morpholine generatesβ hydroxyamide products with enhanced stereoselectivity (up to >95:5 dr). Stereoconvergence is observed in the ring-opening of diastereoisomeric β-lactones, leading to a single product (>95:5 dr, >99:1 er). Mechanistic studies and DFT analysis indicate a substrate controlled Dynamic Kinetic Asymmetric Transformation (DyKAT) involving epimerisation at C(3) of the β-lactone under the reaction conditions, coupled with a hydrogen bond-assisted nucleophilic addition to the Si face of the β-lactone and stereodetermining ring-opening. The scope and limitations of a one-pot protocol consisting of isothiourea-catalysed enantio-determining [2+2] cycloaddition followed by diastereo-determining ring-opening is subsequently developed. Variation within the anhydride ammonium enolate precursor, as well as N(1)- and C(3)- within the pyrazol-4,5-dione scaffold is demonstrated, giving a range of functionalised β hydroxyamides with high diastereo- and enantiocontrol (>20 examples, up to >95:5 dr and >99:1 er) via this DyKAT
Seamless integration of GEM, a density based-force field, for QM/MM simulations via LICHEM, Psi4 and Tinker-HP
No full textHybrid quantum mechanics/molecular mechanics (QM/MM) simulations have become an essential tool in computational chemistry, particularly for analyzing complex biological and condensed phase systems. Building on this foundation, our work presents a novel implementation of the Gaussian Electrostatic Model (GEM), a polarizable density-based force field, within the QM/MM framework. This advancement provides seamless integration, enabling efficient and optimized QM/GEM calculations in a single step using the LICHEM Code. We have successfully applied our implementation to water dimers and hexamers, demonstrating the ability to handle water systems with varying numbers of water molecules. Moreover, we have extended the application to describe the double proton transfer of the aspartic acid dimer in a box of water, which highlights the method\u27s proficiency in investigating heterogeneous systems. Our implementation offers the flexibility to perform on-the-fly density fitting or to utilize pre-fitted coefficients to estimate exchange and Coulomb contributions. This flexibility enhances efficiency and accuracy in modeling molecular interactions, especially in systems where polarization effects are significant
Complexity from simplicity: intramolecular meta-thermocycloadditions of benzene rings via Wheland intermediates
No full textDearomative cycloadditions are powerful synthetic transformations utilizing aromatic compounds for cycloaddition reactions1-4. Diverse complex three-dimensional architectures could be built upon the flat land of aromatic compounds. In addition, such transformations are atom- and step-economical and, thus, have been widely applied to the preparations of complex biologically relevant compounds5-7. For the ubiquitous and most studied yet challenging benzene ring systems8, ortho- and para-cycloadditions are feasible both photochemically and thermally, while the meta-cycloadditions are still limited to the photochemical processes from the 1960s9,10. Herein, we have realized the meta-thermocycloadditions of benzene rings in an intramolecular fashion. The reaction was proposed to proceed via [4π+2π] cycloadditions of Wheland intermediates from the electrophilic dearomatization of benzene rings. A broad spectrum of readily available C(sp2)-rich aniline-tethered enynes were transformed into C(sp3)-rich 3D complex polycyclic architectures simply by stirring in TFA. Moreover, the reaction could be performed in gram-scales and the products could be diversely elaborated
Improved Rate Capability for Dry Thick Electrodes Through Finite Elements Method and Machine-Learning Coupling
No full textA coupled Finite Elements Method (FEM) and Machine-Learning (ML) workflow is presented to optimize the rate capability of thick positive electrodes (ca. 150 µm and 8 mAh/cm²). An ML model is trained based on the geometrical observables of individual LiNi0.8Mn0.1Co0.1O2 particles and their average state of discharge (SOD) predicted from FEM modeling. This model not only bypasses lengthy FEM simulations, but also provides deeper insights on the importance of pore tortuosity and the active particles size, identified as the limiting phenomenon during the discharge. Based on these findings, a bi-layer configuration is proposed to tackle the identified limiting factors for the rate capability. The benefits of this structured electrode are validated through FEM by comparing its performance to a pristine mono-layer electrode. Finally, experimental validation using dry processing demonstrates a 40% higher volumetric capacity of the bi-layer electrode when compared to the previously reported thick NMC electrodes
Electronic coherences built by an attopulse control the forces on the nuclei
No full textAttopulses have an energy bandwidth broad enough to coherently excite several electronic states of molecules. Towards the control of chemical reactivity by attopulses we derive the quantum mechanical expression for the force exerted on the nuclei in such a vibronic wave packet both during and after the exciting pulse. Tuning the pulse parameters allows accessing specific electronic coherences that determine the force strength and direction during and after the pulse. Following the pulse, the force due to the non adiabatic interactions accelerates or slows down the motion of the vibronic wave packet on the excited electronic states and its sign controls the direction of population transfer. Computational results for the LiH and LiT molecules and the probing by the emission dipole are discussed
Non-adiabatic couplings and conversion dynamics between localized and charge transfer excitations from Many-Body Green\u27s Functions Theory
No full textWe investigate the determination of non-adiabatic couplings between localized excitations (LEs) and charge-transfer (CT) excitations based on many-body Green\u27s functions theory in the GW approximation with the Bethe--Salpeter equation (GW-BSE). Using a small molecule dimer system, we first study the influence of different diabatization methods, as well as different model choices within GW-BSE, such as the self-energy models or different levels of self-consistency, and find that these choices affect the LE-CT couplings only minimally. We then consider a large-scale low-donor morphology formed from rubrene and fullerene and evaluate the LE-CT couplings based on coupled GW-BSE-molecular mechanics calculations. For these disordered systems of bulky molecules, we observe differences in the couplings based on the Edmiston--Ruedenberg compared to the more approximate Generalize Mulliken--Hush and Fragment Charge Difference diabatization formalisms. In a kinetic model for the conversion between LE and CT states, these differences affect the details of state populations in an intermediate timescale but not the final populations
A Novel Carbazolophane: A Comparison of the Performance of Two Planar Chiral CP-TADF Emitters
No full textThe prototypical example of a (cyclo)phane, [2.2]paracyclophane (PCP), has proven to be a versatile stereogenic moiety within the design of circularly polarized thermally activated delayed fluorescence (CP-TADF) emitters; however, the exploration of other cyclophanes within CP-TADF emitter design has been largely neglected. Here, a comparative study of the photophysical and optoelectronic properties of two cyclophane emitters, (1,7)tBuCzpPhTrz and its isomer (1,4)tBuCzpPhTrz, is presented. The carbazolophane-triazine compound (1,7)tBuCzpPhTrz, obtained via an unprecedented intramolecular rearrangement, is the first example of a planar chiral TADF emitter deviating from the PCP scaffold. Significant geometrical change of the enclosed carbazole in (1,7)tBuCzp results in an attenuation of the donor strength, while the merits of rigidity and steric bulk remain. In particular, the full width at half maximum (FWHM) of the photoluminescence spectrum in toluene of (1,7)tBuCzpPhTrz is reduced by 34% and blue-shifted by 20 nm compared to that of (1,4)tBuCzpPhTrz. In doped films, the compounds reach high photoluminescence quantum yields (ΦPL) of 91 and 81%, respectively. The chiroptical properties reveal dissymmetry factors |gPL| of up to 5 × 10-4. These results demonstrate the impact of the cyclophane for the development of CPL-active TADF materials and add to the currently limited scope of available planar chiral donor building blocks
NFC Smartphone-based electrochemical microfluidic device integrated with nanobody recognition for C-reactive protein
No full textPoint-of-care testing (POCT) devices play a crucial role as tools for disease diagnostics. The integration of biorecognition elements with electronic components into these devices widens their functionalities and facilitates the development of complex quantitative assays. Unfortunately, biosensors that exploit large conventional IgG antibodies to capture relevant biomarkers are often limited in terms of sensitivity, selectivity, and storage stability, considerably restricting the use of POCT in real-world applications. Therefore, we used nanobodies, as they are more suitable for fabricating electrochemical biosensors with near-field communication (NFC) technology. Moreover, a flow-through microfluidic device was implemented in this system for the detection of C-reactive protein (CRP), an inflammation biomarker and a model analyte. The resulting sensors not only have high sensitivity and portability but also retain automated sequential flow properties through capillary transport without the need for an external pump. We also compared the accuracy of CRP quantitative analyses between the commercial PalmSens4 and the NFC-based potentiostats. Furthermore, the sensor reliability was evaluated using three biological samples (artificial serum, plasma, and whole blood without any pretreatment). This platform will streamline the development of POCT devices by combining operational simplicity, low cost, fast analysis, and portability