bluuebunny/crossref_metadata_2025 huggingface dataset:
A Facile Strategy of Boosting Photothermal Conversion Efficiency through States Transformation for Cancer Therapy
Authors: Li Jie , Wang Jianxing , Zhang Jianyu , Han Ting , Hu Xiyao , Lee Michelle M. S , Wang Dong , Tang Ben Zhong
Published: February 2022

Improving photothermal conversion efficiency (PCE) is critical to facilitate therapeutic performance during photothermal therapy (PTT). However, current strategies of prompting PCE always involve complex synthesis or modification of photothermal agents, thereby significantly inhibiting the practical applications and fundamental understanding of photothermal conversion. We herein present a facile strategy of transforming photothermal agents from aggregated state to dispersed state for boosting PCE. Compared to aggregated state, photothermal agents could rotate freely in dispersed state, allowing for an efficient non-radiative dissipation by formation of highly twisted intramolecular charge transfer (TICT) state. As the molecular motions are completely liberated in this strategy, the PCE enhancement is more remarkable than common methods of supporting molecular motions in aggregates. Noteworthy, this state transformation could be achieved in virtue of a releasing process from nanoparticles in lysosome of cancer cells, demonstrating a distinct photothermal therapeutic performance for cancer ablation. We hope this strategy of transforming state to boost PCE would be a new platform for practical applications of PTT technique.
UV-adVISor: Attention-Based Recurrent Neural Networks to Predict UV-Vis Spectra
Authors: Urbina Fabio , Batra Kushal , Luebke Kevin , White Jason , Matsiev Daniel , Olson Lori , Malerich Jeremiah , Hupcey Maggie , Madrid Peter , Ekins Sean
Published: February 2022

Ultraviolet-visible (UV-Vis) absorption spectra are routinely collected as part of high-performance liquid chromatography (HPLC) analysis systems and can be used to identify chemical reaction products by comparison to reference spectra. Here, we present UV-adVISor as a new computational tool for predicting UV-Vis spectra from a molecule’s structure alone. UV-Vis prediction was approached as a sequence-to-sequence problem. We utilized Long-Short Term Memory and attention-based neural networks with Extended Connectivity Fingerprint diameter 6 or molecule SMILES to generate predictive models for UV-spectra. We have produced two spectrum datasets (Dataset I, N = 949 and Dataset II, N = 2222) using different compound collections and spectrum acquisition methods to train, validate, and test our models. We evaluated the prediction accuracy of the complete spectra by the correspondence of wavelengths of absorbance maxima and with a series of statistical measures (the best test set median model parameters are in parentheses for Model II), including RMSE (0.064), R2 (0.71), and dynamic time warping (DTW, 0.194) of the entire spectrum curve. Scrambling molecule structures with experimental spectra during training resulted in a degraded R2, confirming the utility of the approaches for prediction. UV-adVISor is able to provide fast and accurate predictions for libraries of compounds.
Using Machine Learning to Greatly Accelerate Path Integral Ab Initio Molecular Dynamics
Authors: Li Chenghan , Voth Gregory A.
Published: February 2022

Ab initio molecular dynamics (AIMD) has become one of the most popular and robust approaches for modeling complicated chemical, liquid, and material systems. However, the formidable computational cost often limits its widespread application in simulations of the largest scale systems. The situation becomes even more severe in cases where the hydrogen nuclei may be better described as quantized particles using a path integral representation. Here, we present a computational approach that combines machine learning with recent advances in path integral contraction schemes, and we achieve a two-order-of-magnitude acceleration over direct path integral AIMD simulation while at the same time maintaining its accuracy.
Fatty-acid-derived ester-urethane macromonomers synthesized using bismuth and zinc catalysts
Authors: Niedzwiedz Malwina , Demirci Gokhan , Kantor-Malujdy Nina , Sobolewski Peter , El Fray Miroslawa
Published: February 2022

Minimally invasive surgical approaches require the development of new injectable materials. A particularly attractive strategy involves using photocurable materials that can be delivered as liquids and rapidly cured in situ using UV light. The aim of this work was to synthesize and characterize fatty-acid-derived ester-urethane telechelic (methacrylate) macromonomers, suitable for photopolymerization. The commonly used dibutyltin dilaurate catalyst was replaced with bismuth neodecanoate, bismuth tris(2-ethylhexanoate), and zinc (II) acetyloacetonate as less-toxic alternative catalysts. Additionally, ethyl acetate was used as a “green” solvent. The progress of the two-step synthesis was monitored with infrared spectroscopy. The chemical structure and molecular weight of the obtained viscous materials was characterized with nuclear magnetic resonance spectroscopy and gel permeation chromatography. Photocrosslinking of the macromonomers into elastomeric films was achieved using 150 s per spot of UV light (20 mW/cm2) exposure. Mechanical tensile testing of the films confirmed tensile strength and modulus values in a range of values typical of soft tissue. Finally, in vitro cytotoxicity tests showed high cell viability for the case of materials synthesized using bismuth and zinc catalysts. Overall, our results indicate that bismuth and zinc catalysts are excellent alternatives to organotin compounds in the synthesis of photocurable methacrylate ester-urethanes for biomedical applications, such as minimally invasive surgical protocols.
Elucidating the Role and Interplay of Nickel and Molybdenum Carbide Particles Supported on Zeolite Y in Methane Steam Reforming
Authors: Zhang Xianghui , Wu Di , Ha Su
Published: February 2022

Methane steam reforming (MSR) reaction is a mature industrial process that has been applied for large-scale hydrogen production. Here, we report the synthesis and characterization, reaction kinetics, and deactivation mechanism of a series of catalysts with metallic nickel (Ni) clusters and molybdenum carbide (Mo2C) particles supported on zeolite Y (Ni-Mo2C/FAU) in MSR reaction at 850 oC. Despite low Ni loading less than 2.4 wt%, MSR on Ni-Mo2C/FAU exhibits high activity and stability, yet deactivation of Ni-FAU (the sample without Mo2C) is significant. Further investigations elucidate that the catalyst deactivation is caused by Ni particle sintering via Ostwald ripening instead of coking, and steam induces hydroxylated Ni surface that accelerates sintering. Moreover, encapsulated Mo2C boosts the activity and stability of Ni on zeolite Y by enhancing CH4 activation rather than activating H2O. The interplays among Mo2C and Ni particles dynamically balance the carbon formation and consumption rates, and inhibit Ni sintering. This study enables insights into an alternative design principle of transition metal carbide – Ni catalysts with high activity and stability for effective MSR by tuning the compositional, structural, and interfacial factors.
A simple setup miniaturisation with multiple benefits for Green Chemistry in nanoparticle synthesis
Authors: Mathiesen Jette , Cooper Susan , Anker Andy , Kinnibrugh Tiffany , Jensen Kirsten , Quinson Jonathan
Published: February 2022

The development of nanomaterials often relies on wet-chemical syntheses performed in reflux setups using round-bottom-flasks. An alternative approach to synthesise nanomaterials is presented that uses glass tubes designed for NMR analysis as reactors. It uses less solvent, generates less waste, provides safer conditions, is less prone to contamination and is compatible with high throughput screening.
One-pot synthesis of benzo[c]chromene-6-ones via domino Suzuki-Miyaura cross-coupling followed by oxidative lactonization catalyzed by in situ generated palladium nanoparticles under aqueous-aerobic condition
Authors: Ray Jayanta Kumar , Nuree Yasin
Published: February 2022

Benzo[c]chromene-6-ones are the very significant class of lactones which constitute core structural subunits of various biologically and pharmaceutically active molecules and some important natural products.Importance of 6H-benzo[c]chromene-6-ones for its potential therapeutic and pharmaceutical properties, has attracted researchers over the decades towards the development of more convenient and straight forward route for the synthesis of these molecules. We have efficiently constructed a novel method for the one-pot synthesis of benzo[c]chromenones and their derivatives by palladium catalyzed domino Suzuki-Miyaura cross coupling and oxidative lactonization under aqueous-aerobic condition. We started our investigation by optimizing the reaction condition.
Dipole Moment and Charge Reorganization in Photoredox Catalysts
Authors: Earley Justin , Zieleniewska Anna , Ripberger Hunter , Lazorski Megan , Mast Zachary , Sayre Hannah , Knowles Robert , McCusker James , Scholes Gregory , Reid Obadiah , Rumbles Garry
Published: February 2022

We report evidence of excited-state ion pair reorganisation in a cationic iridium (III) photoredox catalyst in 1,4-dioxane. Microwave-frequency dielectric-loss measurements allow us to assign both ground and excited-state molecular dipoles and excited-state polarizability volumes. These measurements show significant changes in ground-state dipole moment between [Ir[dF(CF_{3})ppy]_{2}(dtbpy)]PF_{6} (10.74 Debye) and [Ir[dF(CF_{3})ppy]_{2}(dtbpy)]BAr^{F}_{4} (4.86 Debye). Photoexcitation of each complex results in population of highly mixed ligand centered and metal-to-ligand charge transfer states. Relaxation to the lowest lying excited-state leads to a negative change in the dipole for [Ir[dF(CF_{3})ppy]_{2}(dtbpy)]PF_{6}, and a positive change in dipole for [Ir[dF(CF_{3})ppy]_{2}(dtbpy)]BAr^{F}_{4}. These observations are consistent with a sub-nanosecond reorganization with the PF_{6}^{-} counter-ion. Taken together, these observations suggest contact-ion pair formation in [Ir[dF(CF_{3})ppy]_{2}(dtbpy)]PF_{6}. The ion pair reorganisation we observe with the PF_{6}^{-} may modify both the thermodynamic potential available for electron transfer and inhibit oxidative catalysis, providing a possible mechanism for recently observed trends in similar complexes.
Ensemble learning-based quantitative structure-activity relationship platform predicts binding behavior of RNA-targeted small molecules
Authors: Cai Zhengguo , Zafferani Martina , Hargrove Amanda
Published: February 2022

The diversity of RNA structural elements and their documented role in human diseases make RNA an attractive therapeutic target. However, progress in drug discovery and development has been hindered by a limited understanding of the parameters that drive RNA recognition by small molecules, including a lack of experimentally-validated structure-activity relationships (QSAR). We developed an adaptable ensemble learning-based method that quantitatively predicts both affinity and kinetic-based binding parameters of small molecules against the HIV-1 TAR model RNA system. A training set of small molecules was screened against the HIV-1-TAR construct using surface plasmon resonance, which provided the binding kinetics and affinities. Introduction of ensemble learning on these data combined with structure-based molecular descriptors afforded predictive models as well as explicit interpretation of the contributing parameters. The accuracy of the model was tested by external validation where binding properties of additional molecules outside training set were correctly predicted. The ensemble model presented herein is the first application of predictive and experimentally-validated 2D-QSAR against an RNA target, in this case HIV-1-TAR RNA, and provides a platform to guide future synthetic efforts. Furthermore, we expect the workflow described herein to be applicable to other RNA structures, ultimately providing essential insight into the small molecule descriptors that drive selective binding interactions and, consequently, exponentially increasing the efficiency of ligand design and optimization without the need for high-resolution structures.
Functional reconstitution of the insect odorant receptor co-receptor in a tethered lipid bilayer membrane
Authors: Kleinheinz David , D'Onofrio Chiara , Ramach Ulrich , Carraher Colm , Schuster Bernhard , Knoll Wolfgang , Andersson Jakob
Published: February 2022

As membrane proteins are among the most important drug targets, it is critical to study membrane proteins to improve drug design. However, due to the myriad roles fulfilled by the cellular membrane, it is a highly complex environment and challenging to study. Tethered membranes reproduce the basic physicochemical properties of the cellular membrane without their inherent complexity, and their high electrical resistance and stability makes them ideal to study membrane proteins, particularly ion channels. However, due to the close proximity of the membrane to the support and the reduced fluidity and high packing density, they are unsuitable to study larger membrane proteins. We present here a tethered membrane system into which the functional the odorant receptor coreceptor from Drosophila melanogaster, a tetrameric ionotropic receptor was incorporated and its sensitivity to various ligands was examined via electrochemical impedance spectroscopy and atomic force microscopy.
Molecular Chirality and Cloud Activation Potentials of Dimeric α-Pinene Oxidation Products
Authors: Thomson Regan , Geiger Franz , Bellcross Aleia , Bé Ariana
Published: February 2022

The surface activity of ten atmospherically relevant α-pinene-derived dimers having varying terminal functional groups and backbone stereochemistry is reported. We find ~10 percent differences in surface activity between diastereomers of the same dimer, demonstrating that surface activity depends upon backbone stereochemistry. Octanol¬–water (KOW) and octanol–ammonium sulfate partitioning coefficient (KOAS) measurements of our standards align well with the surface activity measurements, with the more surface-active dimers exhibiting increased hydrophobicity. Our findings establish a link between molecular chirality and cloud activation potential of secondary organic aerosol particles. Given the diurnal variations in enantiomeric excess of biogenic emissions, possible contributions of such a link to biosphere:atmosphere feedbacks as well as aerosol particle viscosity and phase separation are discussed.
Evidence for Charge Delocalization in Diazafluorene Ligands Supporting Low-Valent [Cp*Rh] Complexes
Authors: Henke Wade , Stiel Jonah , Day Victor , Blakemore James
Published: February 2022

Ligands based upon the 4,5-diazafluorene core are an important class of emerging ligands in organometallic chemistry, but the structure and electronic properties of these ligands have received less attention than they deserve. Here, we show that 9,9′-dimethyl-4,5-diazafluorene (Me2daf) can stabilize low-valent complexes through charge delocalization into its conjugated π-system. Using a new platform of [Cp*Rh] complexes with three accessible formal oxidation states (+III, +II, and +I), we show that the methylation in Me2daf is protective, blocking Brønsted acid-base chemistry commonly encountered with other daf-based ligands. Electronic absorption spectroscopy and single-crystal X-ray diffraction analysis of a family of eleven new compounds, including the unusual Cp*Rh(Me2daf), reveal features consistent with charge delocalization driven by π-backbonding into the LUMO of Me2daf, reminiscent of behavior displayed by the workhorse 2,2′-bipyridyl ligand. Taken together with spectrochemical data demonstrating clean conversion between oxidation states, our findings show that 9,9′-dialkylated daf-type ligands are promising building blocks for applications in reductive chemistry and catalysis.
Building Machine Learning Force Fields of Proteins with Fragment-Based Approach and Data Transfer
Authors: Cheng Zheng , Du Jiahui , Zhang Lei , Ma Jing , Li Wei , Li Shuhua
Published: February 2022

We combined our generalized energy-based fragmentation (GEBF) approach and transfer learning technique to construct machine learning force fields (MLFFs) for proteins only from quantum mechanics (QM) calculations of small subsystems. Using a kernel-based model called Gaussian Approximation Potential (GAP), our protocol can automatically generate training sets with high efficiency. To facilitate the construction of training sets for various proteins, a protein’s data library is created to store all data of subsystems generated from trained proteins. With this data library, for a new protein only its subsystems with new topological types are required for the construction of the corresponding training set. With two polypeptides, 4ZNN and 1XQ8 segment, as examples, we demonstrate that GEBF-MLFFs can be constructed by either kernel methods or neural network methods with full QM quality. Therefore, the present work provides an effi-cient and systematic way to build force fields for biological systems like proteins with QM accuracy.
Hydrophobic association and solvation of neopentane in Urea, TMAO and Urea-TMAO solution
Authors: Hajari Timir , Dixit Mayank , Yadav Hari O. S.
Published: February 2022

A detailed knowledge on hydrophobic association and solvation is crucial in understanding the con-formational stability of proteins and polymers in osmolyte solutions. Using Molecular Dynamics simulations, we found the hydrophobic association using neopentane molecules is greater in mixed urea-TMAO-water solution in comparison to that in 8 M urea solution, in 4 M TMAO solution and in neat water. The neopentane association in urea solution is greater than that in TMAO solution or neat water. We find the association is even less in TMAO solution than pure water. From free ener-gy calculations, it is revealed that the neopentane sized cavity creation in mixed urea-TMAO-water is most unfavorable and that causes the highest hydrophobic association. The cavity formation in urea solution is either more unfavorable or comparable to that in TMAO solution. Importantly, it is found that the population of neopentane-neopentane contact pair and the free energy contribution for cavity formation step in TMAO solution are very sensitive towards the choice of TMAO force-fields. A careful construction of TMAO force-fields is important for studying hydrophobic associa-tion. Interestingly it is observed that the total solute-solvent dispersion interaction energy contribu-tion is always most favorable in mixed urea-TMAO-water. The magnitude of this interaction energy is greater in urea solution relative to TMAO solution for two different force-fields of TMAO, whereas the lowest value is obtained in pure water. It is revealed that the extent of the overall hy-drophobic association in osmolyte solutions is mainly governed by the cavity creation step and it nullifies the contribution comes from the solute-solvent interaction contribution.
Stabilizing Highly Dispersed Halo Sites in Thermally Restructured Palladium Core@shell Nanoparticles for Improved Catalyst Activity and Durability
Authors: Hill Alexander , Bhat Adarsh , Berquist Zachary , Fisher Galen , Lenert Andrej , Schwank Johannes
Published: February 2022

Stabilizing high dispersions of catalytically active metals is integral to improving the lifetime, activity, and material utilization of catalysts that are periodically exposed to high temperatures during operation or maintenance. We have found that annealing palladium-based core@shell catalysts in air at elevated temperature (800°C) promotes the redispersion of active metal into highly dispersed sites, which we refer to as halo sites. Here, we examine the restructuring of Pd@SiO2 and Pd@CeO2 core@shell catalysts over successive 800°C aging cycles to understand the formation, activity, nanoscale structure and stability of these palladium halo sites. While encapsulation generally improves metal utilization by providing a physical barrier that promotes redispersion over agglomeration, our cycled aging experiments demonstrate that halo sites are not stable in all catalysts. Halo sites continue to migrate in Pd@SiO2 due to poor metal-support bonding, which leads to palladium agglomeration. In contrast, halo sites formed in Pd@CeO2 remain stable. The dispersed palladium also synergistically stabilizes the ceria from agglomerating. We attribute this stability, in addition to an observed improvement in catalytic activity, to the coordination between palladium and reducible ceria that arises during the formation of halo sites. We probe the importance of ceria oxidation state on the stability of halo sites by aging Pd@CeO2 after it has been reduced. While some halo sites agglomerate, we find that returning to air aging mitigates the loss of these sites and catalytic activity. Our findings illustrate how nanoscale catalyst structures can be designed to promote the formation of highly stable and dispersed metal sites.
Facile surface modification with hexamethyldisilazane to generate atomically flat and hydrophobic substrates for filament gliding assays with molecular motors
Authors: Tengganu Isadonna , Karerakattil Neil , Dey Swarup , Kishnan Devika , Hariadi Rizal
Published: February 2022

In vitro gliding assay is a well-established assay for determining the activity of protein motors, such as actin-associated myosins and microtubule-associated kinesins and dyneins. In one of the conventional methods, protein motors are immobilized onto a nitrocellulose-coated coverslip and it propels actin filaments in the presence of ATP. Gliding assays also serve as the foundation for protein-motor-based nanotechnological devices such as biosensing and sorting. However, the preparation of nitrocellulose-coated coverslips is time-consuming and produces rough surfaces. Furthermore, the nitrocellulose film exhibits high background autofluorescence, which can be a problem in single-molecule measurements. Here, we investigated the use of hexamethyldisilazane (HMDS) to study actomyosin function and characterized its physical properties on glass coverslips and glass capillary tubes. We showed that the total preparation time to coat a coverslip with HMDS is <30 minutes, which is 1 order of magnitude faster than the >12-hour protocol for coating glass surfaces with nitrocellulose. In contrast to nitrocellulose film, HMDS vapor deposition is effortless and provides an atomically flat surface with low autofluorescence. In addition, HMDS does not interfere with myosin function, which is indicated by the similar actin gliding speed when compared with nitrocellulose. Our results show that HMDS vapor deposition is a more favorable surface treatment to nitrocellulose for in vitro gliding assay.
A simple surface modification to generate atomically-flat and hydrophobic substrates for gliding assays with protein motors
Authors: Tengganu Isadonna , Karerakattil Neil , Dey Swarup , Kishnan Devika , Hariadi Rizal
Published: February 2022

In vitro gliding assay is a well-established assay for determining the activity of protein motors, such as actin-associated myosins and microtubule-associated kinesins and dyneins. In one of the conventional methods, protein motors are immobilized onto a nitrocellulose-coated coverslip and it propels actin filaments in the presence of ATP. Gliding assays also serve as the foundation for protein-motor-based nanotechnological devices such as biosensing and sorting. However, the preparation of nitrocellulose-coated coverslips is time-consuming and produces rough surfaces. Furthermore, the nitrocellulose film exhibits high background autofluorescence, which can be a problem in single-molecule measurements. Here, we investigated the use of hexamethyldisilazane (HMDS) to study actomyosin function and characterized its physical properties on glass coverslips and glass capillary tubes. We showed that the total preparation time to coat a coverslip with HMDS is <30 minutes, which is 1 order of magnitude faster than the >12-hour protocol for coating glass surfaces with nitrocellulose. In contrast to nitrocellulose film, HMDS vapor deposition is effortless and provides an atomically flat surface with low autofluorescence. In addition, HMDS does not interfere with myosin function, which is indicated by the similar actin gliding speed when compared with nitrocellulose. Our results show that HMDS vapor deposition is a more favorable surface treatment to nitrocellulose for in vitro gliding assay.
Red-Emissive Nanocrystals of Cs4MnxCd1-xSb2Cl12 Layered Perovskite
Authors: Sartori Emanuela , Campolucci Marta , Baranov Dmitry , Zeng Min , Toso Stefano , Ferretti Maurizio , Hens Zeger , Manna Liberato , Locardi Federico
Published: February 2022

Layered double perovskite are currently investigated as emerging halide-based materials for optoelectronic applications. Herein, we present the synthesis of Cs4MnxCd1-xSb2Cl12 (0 ≤ x ≤ 1) nanocrystals (NCs). X-ray powder diffraction evidences the retaining of the same crystal structure for all the inspected composition; transmission electron microscopy revealed monodisperse particles with a mean size of 10.6 nm. The absorption spectra seem to be mostly determined by transitions related to Sb3+, whereas Mn2+ induced a red emission in the 625 – 650 nm range. The emission intensity and position varies with the Mn2+ content and reaches the maximum for the composition with x = 0.12. Finally, we demonstrated that the photoluminescence quantum yield (PLQY) of the latter NCs was boosted from 0.3% to 3.9% through a post-synthesis treatment. The present work enlarges the knowledge of colloidal layered double perovskite nanocrystals, stimulating future investigations of this emerging class of material.
Identifying gas composition changes to which non-injective gas sensor arrays are unresponsive
Authors: Gantzler Nickolas , Henle Adrian , Thallapally Praveen , Fern Xiaoli , Simon Cory
Published: February 2022

A gravimetric, MOF-based (MOF = metal-organic framework) sensor array functions by measuring the mass of gas adsorbed in an array of MOFs. Changes in the gas composition are expected to produce detectable changes in the mass of gas adsorbed in the MOFs. In practical settings, multiple components of the gas adsorb into the MOFs. As a result, the map from gas compositions to sensor response vectors will be non-injective (many-to-one). Here, we outline a mathematical method to determine undetectable changes in gas composition to which non-injective gas sensor arrays are unresponsive. This is important for understanding their limitations and vulnerabilities. Our method relies on a mixed-gas adsorption model in the MOFs comprising the sensor array. We illustrate the identification of unresponsive subspaces and ranked responsive directions for gas sensor arrays based on Co-MOF-74 and HKUST-1 aimed at quantitative sensing of CH4/N2/CO2/C2H6 mixtures (relevant to the natural gas industry).
Machine learning for functional group identification in vibrational spectroscopy: A pedagogical lab for undergraduate chemistry students
Authors: Thrall Elizabeth , Lee Seung Eun , Schrier Joshua , Zhao Yijun
Published: February 2022

Here we report a computational activity that introduces undergraduate physical chemistry students to machine learning (ML) in the context of vibrational spectroscopy. In the first part of the activity, students use ML binary classification algorithms to distinguish between carbonyl-containing and non-carbonyl-containing molecules on the basis of their infrared absorption spectra and test modifications to this basic analysis. In a further extension of the activity, students implement a multiclass classification to predict whether carbonyl-containing molecules contain a ketone, a carboxylic acid, or another carbonyl group. This activity is designed to introduce students both to the basic workflow of a ML classification analysis and to some of the ways in which machine learning analyses can fail. We provide a comprehensive handout for the activity, including theoretical background and a detailed protocol, as well as datasets and code to implement the exercise in Python or Mathematica.
Harnessing Colossal Magnetic Anisotropy in Sandwiched 3d^2-Metallocenes
Authors: Nain Sakshi , Khurana Rishu , Ali Md. Ehesan
Published: February 2022

Single-molecule magnet (SMM) based quantum technology is gaining attentions in recent years with growing focus on achieving higher barrier of magnetization reversal. Metallocenes owing unique sandwiched-structure, assure themselves as plausible molecular systems for development of novel SMMs. Here in this work, we have explicitly investigated metallocenes of first row transition metal elements, along with their one electron oxidized (cationic) and reduced (anionic) analogues, for their magnetic anisotropies (D) adopting multi-reference ab initio calculations. Herein, we report the unprecedented high D values for 3d^2 systems among all the 3d-metallocenes.
In silico investigation of ligand-regulated palladium-catalysed formic acid dehydrative decomposition under acidic conditions
Authors: Shen Chaoren , Dong Kaiwu , Wei Zhihong , Tian Xinxin
Published: February 2022

In silico investigation of ligand-regulated palladium-catalysed formic acid dehydrative decomposition to carbon monoxide under acidic conditions was conducted. The contribution from the pyridyl group implanted in pytbpx ligand on enhancing the activity of palladium catalyst and the specific role of para-toluenesulfonic acid as the promoter of dehydration were uncovered.
In silico investigation of ligand-regulated palladium-catalysed formic acid dehydrative decomposition under acidic conditions
Authors: Shen Chaoren , Dong Kaiwu , Wei Zhihong , Tian Xinxin
Published: February 2022

In silico investigation of ligand-regulated palladium-catalysed formic acid dehydrative decomposition to carbon monoxide under acidic conditions was conducted. Two types of bidentate tertiary phosphine ligands were selected on the basis of previous experimental study. And the promoting effect of para-toluenesulfonic acid (PTSA) was specifically investigated. The pyridyl group implanted in pytbpx ligand is found to mainly contribute on enhancing the activity of palladium catalyst. The PTSA promoter displays specific role for regenerating active species and supressing dehydrogenation during Pd-pytbpx/Pd-dtbpx catalysed dehydration process. CO releasing process catalysed by Pd-dtbpx also facilitated by adding PTSA. According to the mechanism hereby supposed, introducing electron-withdrawing substitution at para-position of pyridyl rings may further improve the dehydrative decomposition activity of Pd-pytbpx.
Profiling single-molecule reaction kinetics under nanopore confinement
Authors: Liu Wei , Yang Zhonglin , Yang Chaonan , Ying Yi-Lun , Long Yi-Tao
Published: February 2022

The development of single-molecule reaction inside nanoconfinement is benefit to study the intrinsic molecular mechanism of a complex chemical reaction. However, the reaction kinetics model of single-molecule reaction inside confinement remains elusive. Herein we engineered the Aerolysin nanopore reactor to elaborate the single-molecule reaction kinetics inside nanoconfinement. By identifying bond forming and non-forming events directly, a four-state kinetics model is proposed for the first time. Our results demonstrated that the single-molecule reaction kinetics inside a nanopore depends on the voltage-dependent frequency of captured individual reactant and the fraction of effective collision inside nanopore confined space. This new insight will guide the design of nanoconfinement for resolving the single-molecule chemistry, and shed light on the mechanistic understanding of dynamic covalent chemistry in-side a nanopore
Color-tunable and high quantum-yield luminescence from a biomolecule-inspired single species emitter of white light
Authors: Ebrahim Fatmah Mish , Fumanal Maria , Gladysiak Andrzej , Kadioglu Ozge , Jablonka Kevin , Ongari Daniele , Mace Amber , Shyshkanov Serhii , Saris Seryio , Ireland Christopher , Dyson Paul , Stylianou Kyriakos , Smit Berend
Published: February 2022

Single-species light emitters with high photoluminescence quantum yields (PLQYs) and broad- spectrum color tunability are sought-after for applications ranging from bio-imaging to artificial lighting. We explore a new strategy to design such emitters, inspired by bioluminescent fireflies and click-beetles. These organisms use a single molecular substrate, D-Luciferin (LH2), to emit light ranging in color from green to red. By combining LH2 with metals, we synthesize new bio-analogous, color-tunable, luminescent metal complexes. The copper complex forms an organic molecule of intrinsic microporosity (OMIM), which crystallizes into a stable structure with intermolecular voids. By changing the composition of guest molecules in the voids, we can tune the emitted color. The optimum composition gives nearly perfect white light, with the highest PLQY reported for a single-species white- light emitter. Similarities between our OMIM and the luciferase active site provide a new approach to investigating the heavily-debated mechanisms underlying in-vivo bioluminescence color variations. Moreover, as a proof of principle, we show that these materials can be used in a new type of light- emitting device (LED). The current generation of LEDs requires at least two active layers to achieve color tunability. The tunability is intrinsic in our materials, and therefore may lead to simpler device fabrication.
Highly Active Platinum Single-Atom Catalyst grafted onto 3D Carbon Cloth Support for the Electrocatalytic Hydrogen Evolution Reaction
Authors: Yu Po-Wei , Elmas Sait , Pan Xun , Yin Yanting , Gibson Christopher T. , Andersson Gunther G. , Andersson Mats R.
Published: February 2022

Platinum single-atom catalysts (PtSACs) on 3D support are emerging as new frontier in catalysis due to their atom-economy, outstanding performance and the advantage to bridge the gap between homogeneous and heterogeneous catalysis. Here we report on a simple, single-step electrochemical grafting attachment of a metal-selective ligand, 2,6:2’,2”-terpyridine, and the synthesis of platinum single-atom electrocatalyst via metal uptake from aqueous salt solution. At an ultra-low loading of 0.26 ±0.02 μgcm-2 of platinum, the single atom catalysts supported on porous 3D carbon cloth electrode via chemical bonding revealed the highest reported mass activity of 77.1 AgPt-1 at η = 50 mV/RHE compared to the commercial catalyst 20 % Pt/C. The electro-grafted terpyridine ligand can also act as an effective scavenger for leached platinum from the counter electrode during extended operational hours. The method to make the PtSAC is facile, non-hazardous and versatile without involving any elaborative pre- and/or post-treatment steps and, the value of the added platinum to the ligand is only 0.1 US$m-2.
Sensitivity of Molecular Dynamics Simulations to Equilibration Scheme: A Case Study of Bromodomain Protein BRD4-Ligand Complex System
Authors: Ge Yunhui , Calabro Gaetano , Bayly Christophe , Mobley David
Published: February 2022

In molecular dynamics (MD) simulations, an equilibration phase is used to bring the system to the desired conditions (e.g. temperature and pressure) before collecting data in more extensive production phases. Ideally, the equilibration phase would bring the system to the correct equilibrium ensemble appropriate for the target thermodynamic conditions. Many studies give relatively little attention to details of the equilibration protocol as long as the system eventually reaches stabilization at the correct temperature, pressure, volume, etc. However, in a previous study we found a surprising instability of two ligands in a binding site. That led us to study the origin of this instability more, and in the present work we have traced it to details of the equilibration protocol. We found for the studied system, different equilibration schemes caused dramatic differences in sampled configurations of the system in production runs, highlighting the importance of careful consideration of equilibration schemes in MD simulations.
Water Boosts the Performances of Glass Anodes for Lithium-Ion Batteries
Authors: Jiang Zhenjing , Qi Shibin , Gao Chengwei , Li Xiangyu , Zhang Yanfei , Yue Yuanzheng
Published: February 2022

Owing to their disordered open network structure, oxide glasses are a promising class of anode materials for Lithium-Ion Batteries (LIBs). However, the relatively low capacities of glass anodes severely limit their practical application for large energy storage devices. Here we show an unconventional novel approach, which significantly enhances the electrochemical performances of glass anodes for LIBs. Specifically, we incorporated water into an electrochemically active glass system, i.e., TeO2-V2O5-P2O5 (TVP) glass powder via humidity treatment, and then mix the hydrated powder with additives to fabricate anode. The optimized humidity treatment led to the structural modification of the TVP glass powder, which boosted the capacity of the TVP anode by more than 200%, and maintained the reversible capacity for extra-long cycles. The boosted performances are associated both with the depolymerized structural network for Li+ diffusion and with the hydration-induced nanocrystals. These findings help develop superior glass electrodes in an economically effective way.
Emissive Organogel Mediated Construction of Flexible Covalent Organic Polymer for the Separation of Aniline for Water Purification
Authors: Das Apurba K. , Maiti Sayan , Ghosh Tapas , Samal Arati
Published: February 2022

A flexible covalent organic polymer (COP) has been successfully synthesized via dynamic covalent gel (DCG) formation through imine condensation reaction between 6-hydrazinonicotinic hydrazide hydrate and benzene-1,3,5-tricarboxaldehyde within 7 min under ambient condition. An emissive organogel mediated protocol has been developed for the construction of amorphous polymer (COP), selectively in N,N-dimethyl acetamide (DMA). Interestingly, two non-emissive building block units without large π-conjugated structures have been engaged for the construction of green emissive COP-gel. The green emission of COP-gel is generated by the intermolecular H-bonding assisted aggregation induced emission phenomenon. The dried COP efficiently adsorbs aniline molecules into its cavities and separate them from binary mixtures of aniline/nitrobenzene and aniline/water, respectively.
Group Contribution and Machine Learning Approaches to Predict Abraham Solute Parameters, Solvation Free Energy, and Solvation Enthalpy
Authors: Chung Yunsie , Vermeire Florence H. , Wu Haoyang , Walker Pierre J. , Abraham Michael H. , Green William H.
Published: February 2022

We present a group contribution method (SoluteGC) and a machine learning model (SoluteML) to predict the Abraham solute parameters, as well as a machine learning model (DirectML) to predict solvation free energy and enthalpy at 298 K. The proposed group contribution method uses atom-centered functional groups with corrections for ring and polycyclic strain whilst the machine learning models adopt a directed message passing neural network. The solute parameters predicted from SoluteGC and SoluteML are used to calculate solvation energy and enthalpy via linear free energy relationships. Extensive data sets containing 8366 solute parameters, 20253 solvation free energies, and 6322 solvation enthalpies are compiled in this work to train the models. The three models are each evaluated on the same test sets using both random and substructure-based solute splits for solvation energy and enthalpy predictions. The results show that the DirectML model is superior to the SoluteML and SoluteGC models for both predictions and can provide accuracy comparable to that of advanced quantum chemistry methods. Yet, even though the DirectML model performs better in general, all three models are useful for various purposes. Uncertain predicted values can be identified by comparing the 3 models, and when the 3 models are combined together, they can provide even more accurate predictions than any one of them individually. Finally, we present our compiled solute parameter, solvation energy, and solvation enthalpy databases (SoluteDB, dGsolvDBx, dHsolvDB) and provide public access to our final prediction models through a simple web-based tool, software package, and source code.
Potassium fluoride and carbonate lead to immediate cell failure in potassium-ion batteries
Authors: Marbella Lauren , Ells Andrew , May Richard
Published: February 2022

While Li-ion is the prevailing commercial battery chemistry, development of batteries using earth abundant alkali metals (e.g., Na and K) alleviates reliance on Li with potentially cheaper technologies. While electrolyte engineering has been a major thrust of Li-ion battery (LIB) research, it is unclear if the same electrolyte design principles apply to K-ion batteries (KIBs). Fluoroethylene carbonate (FEC) is a well-known additive used in Li-ion electrolytes, because the products of its sacrificial decomposition aid in forming a stable solid electrolyte interphase (SEI) on the anode surface. Here, we show that FEC addition to KIBs containing hard carbon anodes results in a dramatic decrease in capacity and cell failure in only two cycles, whereas capacity retention remains high (> 90% over 80 cycles at C/10 for both KPF6 and KFSI) for electrolytes that do not contain FEC. Using a combination of 19F solid-state nuclear magnetic resonance (SSNMR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and electrochemical impedance spectroscopy (EIS), we show that FEC decomposes during galvanostatic cycling to form insoluble KF and K2CO3 on the anode surface, which correlate with increased interfacial resistance. Our results strongly suggest KIB performance is sensitive to accumulation of an inorganic SEI, likely due to sluggish K diffusion in these compounds. This mechanism of FEC decomposition was confirmed in two separate electrolyte formulations using KPF6 or KFSI. Interestingly, the salt anions do not decompose themselves, unlike their Li analogues. Insight from these results indicates that electrolyte decomposition pathways and favorable SEI components are significantly different in KIBs and LIBs, suggesting that entirely new approaches to KIB electrolyte engineering are needed.
Highly ordered N-heterocyclic carbene monolayers on Cu(111)
Authors: Angove Eloise , Grillo Federico , Früchtl Herbert , Veinot Alex , Singh Ishwar , Horton Hugh , Crudden Cathleen , Baddeley Christopher
Published: February 2022

The benzannulated N-heterocyclic carbene, 1,3-dibenzylbenzimidazolylidene (NHCDBZ) forms large, highly ordered domains when adsorbed on a Cu(111) surface under ultrahigh vacuum conditions. A combination of scanning tunneling microscopy (STM), high resolution electron energy loss spectroscopy (HREELS) and density functional theory (DFT) calculations reveals that the overlayer consists of vertical benzannulated NHC moieties coordinating to Cu adatoms. Long range order results from the placement of the two benzyl units from a single NHC on opposite sides of the benzimidazole moiety, with the planes of their aromatic rings approximately parallel to the surface. The organization of three surface-bound benzyl substituents from three different NHCs into a triangular array controls the formation of a highly ordered Kagome-like lattice on the surface. This study illustrates the importance of dispersive interactions to control the binding geometry and self-assembly of the NHC.
Synthesis of (–)-Kopsifoline A and (+)-Kopsifoline E
Authors: Myeong In-Soo , Avci Nadide Hazal , Movassaghi Mohammad
Published: February 2022

We report the first total synthesis of (–)-kopsifoline A and (+)-kopsifoline E. Our synthetic strategy features a biogenetically inspired regioselective C17-functionalization of a versatile intermediate containing the pentacyclic core of aspidosperma alkaloids. While this advance intermediate provides (–)-kopsifoline D via C3–C21 bond formation, regioselective C17-boronation of its indoline substructure prior to introduction of the F-ring enables access to (–)-kopsifoline A and (+)-kopsifoline E. The vinylogous urethane substructure of the key intermediate was critical in C17-boronation over a competing C7-boronation in related indole derived substrates. After oxidation of the C17–B bond to introduce the C17-ether, the C3–C21 bond of the targets is secured under the Mitsunobu reaction conditions with the vinylogous urethane as the nucleophilic component.
Medium and Large N-Heterocycle Formation via Allene Hydroamination with a Bimetallic Rh(I) Catalyst
Authors: Forson Kelton , Bohman Benjamin , Wayment Coriantumr , Owens Rachel , McKnight Caitlyn , Davis Rhen , Stillwell Lillian , Smith Stacey , Michaelis David
Published: February 2022

We report the synthesis of a bimetallic Rh(I) complex containing a bridging CO ligand that facilitates Rh–Rh bond formation. This bimetallic complex enables intramolecular allene hydroamination to form seven to ten-member rings in high yield. Monometallic Rh complexes, in contrast, fail to achieve any product formation. We demonstrate a broad substrate scope for formation of a variety of N-heterocycles in good to excellent yields. Macrocyclization reactions that form eleven to fifteen-membered heterocycles are also demonstrated. Mechanistic studies show that the reaction likely proceeds via catalyst protonation by trifluoroacetic acid, followed by reversible allene insertion and C–N bond-forming reductive elimination. The difference in product selectivity observed with our bimetallic catalyst vs monometallic Rh complexes may result from cooperativity between the two metals.
α-Diimine Synthesis via Titanium-Mediated Multicomponent Diimination of Alkynes with C-Nitrosos
Authors: Frye Connor , Egger Dominic , Kounalis Errikos , Pearce Adam , Cheng Yukun , Tonks Ian
Published: February 2022

α-Diimines are commonly used as supporting ligands for a variety of transition metal-catalyzed processes, most notably in α-olefin polymerization. They are also precursors to valuable synthetic targets, such as chiral 1,2-diamines. Their synthesis is usually performed through acid-catalyzed condensation of amines with α-diketones. Despite the simplicity of this approach, accessing unsymmetrical α-diimines is challenging. Herein, we report the Ti-mediated intermolecular diimination of alkynes to afford a variety of symmetrical and unsymmetrical α-diimines through the reaction of diazatitanacyclohexadiene intermediates with C-nitrosos. These diazatitanacycles can be readily accessed in situ via the multicomponent coupling of Ti≡NR imidos with alkynes and nitriles. The formation of α-diimines is achieved through formal [4+2]-cycloaddition of the C-nitroso to the Ti and γ- carbon of the diazatitanacyclohexadiene followed by two subsequent cycloreversion steps to eliminate nitrile and afford the α- diimine and a Ti oxo.
Targeted Exploration of Bio-inspired Cascade Reactions: A One-Step Total Synthesis of Nesteretal A
Authors: Leblond Axel , Houari Inès , Leblanc Karine , Poupon Erwan , Beniddir Mehdi
Published: February 2022

Nesteretal A was recently isolated from a marine actinomycete. An appealing and challenging cage-structure along with an unusual biosynthetic pathway prompted us to explore an expeditious bio-inspired total synthesis of nesteretal A. An unconventional strategy was chosen and a cascade reaction starting from diacetyl was studied. Under organocatalytic conditions mimicking an aldolase-type sequence with a cyclic secondary amine, nesteretal A was detected and targeted through LC-MS/MS and NMR analyses. Starting from a double aldolization of three units, an intramolecular succession of aldolizations and acetalizations probably drives the highly reproducible formation of nesteretal A. An easy isolation protocol has been devised to overcome a non-surprising low yield but largely counterbalanced by the straightforwardness and cost-effectiveness of this first total synthesis of nesteretal A.