bluuebunny/crossref_metadata_2025 huggingface dataset:
Reactant-Induced Photoactivation of a Gold-Catalyzed Csp2-Csp Cross-Coupling Leading to Indoles
Authors: Zhao Fen , Abdellaoui Mehdi , Berthet Jérome , Corcé Vincent , Delbaere Stéphanie , Dossmann Héloïse , Espagne Agathe , Forté Jérémy , Jullein Ludovic , Le Saux Thomas , Mouriès-Mansuy Virginie , Ollivier Cyril , Fensterbank Louis
Published: February 2022

A novel access to 2,3-disubstituted indoles from o-alkynyl aniline and iodoalkyne derivatives via a gold-catalyzed sequence under visible-light irradiation and in the absence of an exogenous photocatalyst was uncovered. A wide scope of the process was observed. Of note, 2-iodo-ynamides that have never been used in any organometallic cross-coupling reaction could be used as electrophiles. The resulting N-alkynyl indoles lend themselves to post-functionalization affording valuable scaffolds, notably benzo[a]carbazoles. Mechanistic studies converged on the fact that a potassium sulfonyl amide generates emissive aggregates in the reaction medium. Static quenching of these aggregates by a vinylgold(I) intermediate yields to an excited state of the latter, which can react with an electrophile via oxidative addition and reductive elimination to forge the key C-C bond. This reactant-induced photoactivation of an organogold intermediate opens rich perspectives in the field of cross-coupling reactions.
Divergent Total Syntheses of Aspidospermidine, N-Methylaspidospermidine, N-Acetylaspidospermidine and Aspido-spermine via a Tandem Cyclization of Tryptamine-Ynamide
Authors: Yang Lu , Huang Siwen , Huang Rongkang , Hou Anbin , Zhang Sen , Su Hongwei , Ding Xiaohong , Lin Bin , Cheng Maosheng , Liu Yongxiang
Published: February 2022

The divergent total syntheses of aspidospermidine, N-methylaspidospermidine, N-acetylaspidospermidine and aspidosperm-ine were achieved from a common pentacyclic indoline intermediate. The common pentacyclic indoline intermediate was synthesized on a gram scale through a Stork-type alkylation of 1H-pyrrolo[2,3-d]carbazole derivatives, which was prepared based on a Brønsted acid-catalyzed tandem cyclization of tryptamine-ynamide. Scalable synthesis of 1H-pyrrolo[2,3-d]carbazole afforded a facile access and practical approach to the Aspidosperma indole alkaloid family.
Uncovering the key role of distortion in tetrazine ligations guides the design of bioorthogonal tools that defy the reactivity/stability tradeoff
Authors: Svatunek Dennis , Wilkovitsch Martin , Hartmann Lea , Houk Kendall , Mikula Hannes
Published: February 2022

The tetrazine/trans-cyclooctene ligation stands out from the bioorthogonal toolbox due to its exceptional reaction kinetics, enabling multiple molecular technologies in vitro and in living systems. Highly reactive 2-pyridyl-substituted tetrazines have become state-of-the-art for time-critical processes and selective reactions at very low concentration. It is widely accepted that the enhanced reactivity of these chemical tools is attributed to the electron-withdrawing effect of the heteroaryl substituent. In contrast, we show that observed reaction rates are way too high to be explained on this basis. Computational investigation of this phenomenon revealed that distortion of the tetrazine caused by intramolecular N-N repulsion plays a key role in accelerating the cycloaddition step. While we show that the limited stability of tetrazines under physiological conditions strongly correlates with the electron-withdrawing effect of the substituent, intramolecular destabilization increases the reactivity without reducing stability. Guided by these fundamental insights we demonstrate application in the design of highly reactive tetrazines with superior stability, finally evading the reactivity/stability trade-off for bioorthogonal tetrazine tools.
A Computational Descriptor Analysis on Excited State Behaviours of a Series of TADF and Non-TADF Compounds
Authors: Ulukan Pelin , Bas Ekin Esme , Ozek Rengin Busra , Dal Kaynak Cansu , Monari Antonio , Aviyente Viktorya , Catak Saron
Published: February 2022

The thermally activated delayed fluorescence (TADF) behaviours of seventeen organic TADF emitters and two non-TADF chromophores bearing various donor and acceptor moieties were investigated, focusing on their torsion angles, singlet-triplet gap (ΔEST), spin orbit couplings (SOC) and topological ΦS index. Electronic structure calculations were performed in the framework of the Tamm-Dancoff approximation (TDA) allowing to characterize reverse intersystem crossing (RISC) probability between the S1 and T1 states. In addition, experimental ΔEST data were taken into account to choose the most appropriate functional and basis set, while absorption spectra were obtained by considering vibrational and dynamical effects through a Wigner sampling of the ground state equilibrium regions. Examining all the parameters obtained in our computational study, we rationalized the influence of electron-donating and electron-accepting groups and the effects of geometrical factors, namely torsion angles, on a wide class of diverse compounds ultimately providing an easy and computationally effective protocol to assess TADF efficiencies.
Tuning the Interfacial Stoichiometry of InP Core and InP/ZnSe Core/Shell Quantum Dots
Authors: Park Nayon , Eagle Forrest , DeLarme Asher , Monahan Madison , LoCurto Talia , Beck Ryan , Li Xiaosong , Cossairt Brandi
Published: February 2022

We demonstrate fine-tuning of the atomic composition of InP/ZnSe QDs at the core/shell interface. Specifically, we control the stoichiometry of both anions (P, As, S, and Se) and cations (In, Zn) and correlate these changes with the resultant steady-state and time-resolved optical properties of the nanocrystals. Anion deposition on the InP QD surface results in a redshift in the absorption, quenching of the excitonic photoluminescence, and a relative increase in the intensity of the broad trap-based photoluminescence, consistent with delocalization of the exciton wavefunction and relaxation of exciton confinement. Time-resolved photoluminescence data show an overall small change in the decay dynamics on the ns timescale, suggesting the relatively low photoluminescence quantum yields may be attributed to the creation of new thermally activated charge trap states. Cluster-model density functional theory calculations show that the presence of core/shell interface anions give rise to electronic defects contributing to the redshift in the absorption.
A versatile capillaric microfluidics viscometer platform for bar-graph type point-of-care diagnostics
Authors: Meffan Robert Claude , Menges Julian , Dolamore Fabian , Mak Daniel , Fee Conan , Nock Volker , Dobson Renwick
Published: February 2022

A novel capillary action microfluidic viscometer has been designed that can measure the relative viscosity of a sample compared to a control liquid. Using capillary action circuits, the viscosity of a sample is transformed into a microfluidic bar-graph format without the use of external instrumentation. The bars in this case are represented by the distance that a liquid has flown through a microfluidic channel, relative to another liquid in an identical channel. As the device does not require external instrumentation, its use is targeted at point-of-care (PoC) situations. This implementation is made practical through capillaric Field Effect Transistors, and the conditional flow paths they enable. In this paper, we report on the design, operation, and performance of a two-channel version viscometer device exclusively based on capillary action circuits. Using poly-ethylene glycol solutions as viscous samples, we demonstrate that the device can transduce the relative viscosity consistently to within 2%. Enabled by the flexibility of the capillary action circuits, we additionally present a modified device which can measure transparent liquids without the need to add colorants to the sample. The forms of the device presented in this work have applications in both medical care and scientific measurements—particularly for PoC measurements.
Spin statistics for triplet-triplet annihilation upconversion: exchange coupling, intermolecular orientation and reverse intersystem crossing
Authors: Bossanyi David , Sasaki Yoichi , Chekulaev Dimitri , Kimizuka Nobuo , Yanai Nobuhiro , Clark Jenny
Published: February 2022

Triplet-triplet annihilation upconversion (TTA-UC) has great potential for significantly improving the light harvesting capabilities of photovoltaic cells, as well as being sought after for biomedical applications. Many factors combine to influence the overall efficiency of TTA-UC, the most fundamental of which is the spin statistical factor, η, that gives the probability that a bright singlet state is formed from a pair of annihilating triplet states. Using solid rubrene as a model system, we reiterate why experimentally measured magnetic field effects prove that annihilating triplets first form weakly exchange-coupled triplet-pair states. This is contrary to conventional discussions of TTA-UC that implicitly assume strong exchange coupling and we show that it has profound implications for the spin statistical factor η. For example, variations in intermolecular orientation tune η from 2/5 to 2/3 through spin mixing of the triplet-pair wavefunctions. Since the fate of spin-1 triplet-pair states is particularly crucial in determining η, we investigate it in rubrene using pump-push-probe spectroscopy and find additional evidence for the recently reported high-level reverse intersystem crossing channel. We incorporate all of these factors into an updated model framework in which to understand the spin statistics of TTA-UC, and use it to rationalise the differences in reported values of η amongst different common annihilator systems. We suggest that harnessing high-level reverse intersystem crossing channels in new annihilator molecules may be a highly promising strategy to exceed any spin statistical limit.
Cu(II) Catalyzed Unsymmetrical Di-oxidation of gem-Difluoroalkenes to Generate α,α-Difluorinated-α-Phenoxyketones, an Unstudied Substructure
Authors: Koley Suvajit , Cayton Kaylee , Gonzalez-Montiel Gisela , Yadav M. Ramu , Orsi Douglas , Cheong Paul H-Y , Altman Ryan
Published: February 2022

A Cu-based catalyst system convergently couples gem-difluoroalkenes with phenols under aerobic conditions to deliver α,α-difluorinated-α-phenoxy ketones, an unstudied hybrid fluorinated functional group. Composed of α,α-difluorinated ketone and α,α-difluorinated ether moieties, these have only once been previously reported as a synthetic intermediate en route to pharmacologically active compounds. Computational predictions and later experimental corroboration suggest that the sp3-hybridized hydrate adduct of the phenoxy-substituted fluorinated ketone is energetically accessible. The more facile conversion between ketone and hydrate forms suggest that covalent inhibition of proteases and other enzymes may be possible. Further functionalization of the ketone group enables access to other useful fluorinated functional groups.
Setting up the HyDRA blind challenge for the microhydration of organic molecules
Authors: Fischer Taija Lena , Bödecker Margarethe , Zehnacker-Rentien Anne , Mata Ricardo A. , Suhm Martin A.
Published: February 2022

The procedure leading to the first HyDRA blind challenge for the prediction of water donor stretching vibrations in monohydrates of organic molecules is described. A training set of 10 monohydrates with experimentally known and published water donor vibrations is presented and a test set of 10 monohydrates with unknown or unpublished water donor vibrational wavenumbers is described together with relevant background literature. The rules for data submissions from computational chemistry groups are outlined and the planned publication procedure after the end of the blind challenge is discussed.
Activation of H2 with Manganese(I)-Phosphido Complexes
Authors: Abhyankar Preshit , MacMillan Samantha , Lacy David
Published: February 2022

Metal-ligand cooperativity (MLC) predominantly occurs across transition-metal amido moieties. In contrast, there are few reports of activation of H2 or substrate across metal–phosphido linkages, and all of the first-row metal examples use N-heterocyclic phosphido donors. In this report, we highlight a discovery of the first MLC dihydrogen activation with first-row transition metal M-PR2 (R = alkyl or aryl) complexes using dinuclear Mn(I)-bisphosphido complexes. In addition, we demonstrate that oxidative addition of P–Cl bond leads to the same Mn(I)-bisphosphido complexes at elevated temperatures, enabling a simple and versatile strategy for in-situ reduction of phosphine chlorides to phosphine using dihydrogen, a process that appears general having success with both diaryl- and dialkyl-phosphines.
Influence of Glass Composition on the Luminescence Mechanisms of CdSe Quantum Dot-Doped Glasses
Authors: Li Wenke , Zhao Xiujian , Liu Chao , Coudert François-Xavier
Published: February 2022

In this work, we characterized the electronic structure of CdSe quantum dots embedded in a series of x Na2O, (1–x) SiO2 glass matrices (x = 0, 0.25, 0.33 and 0.5). We analyzed the impact of the glass matrix composition on both the atomic structure of the quantum dot (QD) and the QD/glass interface, as well as the luminescence mechanisms, using density functional theory (DFT) calculations. The increase of Na2O content in the glass matrices was found to promote the formation of Cd–O and Se–Na interfacial bonds, and disrupting the Cd–Se bonds network. In particular, we show that the glass composition directly affects the nature of the highest occupied molecular orbitals (HOMO). According to the atomic structure, the band gap distribution and the density of states calculation, we find that there is significant reconstruction of the QD, and that the picture sometimes proposed of a “pristine QD” surrounded by glass is not realistic. The introduction of CdSe QD significantly decreased the bandgap of the glass compared to pristine glasses, and the interfacial bonds greatly contributed to the frontier orbitals without forming midgap states. We propose a new energy diagram, quite different from the traditional model, to explain the luminescence of CdSe quantum dot- doped glasses, originating from the intrinsic emission of this hybrid system {QD + glass}. These results improve our understanding of the luminescence of CdSe quantum dot-doped glasses, explaining the reason for the poor quantum efficiency and broad emission linewidth compared with their colloidal counterparts.
A comprehensive kinetic model for ternary complex catalysis
Authors: Douglass Jr. Eugene F. , Miller Chad J.
Published: February 2022

Ternary-complex directed enzyme catalysis underlies a vast array of biological processes and several clinical therapies including growth hormones, interferon, and heparin. Recently, interest in ternary catalysis drugs has increased significantly with the rapid expansion of research new technologies such as bispecific antibodies and proteolysis targeting chimeras (PROTAC’s). Here, we derive a general model for ternary complex catalysis that defines the timescales of these diverse processes in familiar terms from classical enzyme theory. This was accomplished by solving for the maximum velocity (Vmax) and adapting an under-appreciated strategy within Michaels and Menten’s original publication: integration of the velocity equation. Critically, these equations are simple, conceptually accessible, and enables rapid estimation timescales that are consistent with a wide range of published literature. Finally, we have combined these equations with “big data” from new thermodynamic and kinetic databases to build interactive online tools that enable non-computational investigators to graphically simulate their own systems: • https://douglasslab.com/Btmax_kinetics/ Overall, this work is part of a general trend to reconceptualize pharmacodynamics from classical binding equilibria (e.g. Langmuir-Hill equation) to a kinetic processes with a characteristic timescale.
All-atomistic molecular dynamics study of the glass transition of amorphous polymers
Authors: Tang Zhiye , Okazaki Susumu
Published: February 2022

Glass transition is an important phenomenon of polymer materials and it has been intensively studied over the past a few decades. However, the influencing factors arising from the chemical structures of the polymers are often ignored due to a continuous or coarse-grained description of the polymer. Here, we approached this phenomenon using all-atomistic molecular dynamics (MD) simulations and two conventionally used polymer materials, polycarbonate (PC) and poly-(methyl methacrylate) (PMMA). We reproduced the glass transition temperatures (Tg) of the two materials reasonably well. Then we characterized and investigated the glass transition process by looking at the changes of potential energy, dihedral transition, and thermal fluctuation of the individual degrees of freedom in the systems, over the entire temperature range of glass transition. As previously reported, the dihedral angles stop their conformational changes gradually at the Tg, especially for the main chain dihedrals, and sidechain rotations immediately rooting from the main chain. The volumetric change during the temperature decrease is confirmed to be because of conformational adjustment, probably due to the tendency of chain stretching for the maintenance of the radius of gyration, and the loss of thermal energy. The strength of motions of single degrees of freedom and polymer chains, and overall slow motions obtained by normal mode analysis (NMA) shows that different motions at different spatial scale may gradually stop at distinct temperature in the MD simulation temporal and spatial scales. Presumably, the small spatial scale do not contribute to the glass transition at the experimental scale since the timescale is much longer than their relaxation time.
Radical Fragment Ions in Collision-Induced Dissociation Mass Spectrometry
Authors: Xing Shipei , Huan Tao
Published: February 2022

Collision-induced dissociation (CID) is a common fragmentation strategy in mass spectrometry (MS) analysis. A conventional understanding is that fragment ions generated in low-energy CID should follow the even-electron rule. As such, (de)protonated precursor ions should predominately generate (de)protonated fragment ions with very few radical fragment ions (RFIs). However, the extent to which RFIs present in MS2 spectra has not been comprehensively investigated. This work uses the latest NIST 20 tandem mass spectral library to investigate of the occurrence of RFIs in CID MS2 experiments. In particular, RFIs were recognized using their integer double bond equivalent (DBE) values calculated from their annotated molecular formulas. Our study shows unexpected results as 65.4% and 68.8% of MS2 spectra contain at least 10% RFIs by ion-count (total number of ions) in positive and negative electrospray ionization (ESI) modes, respectively. Furthermore, we classified chemicals based on their compound classes and chemical substructures, and calculated the percentages of RFIs in each class. Results show that “Organic 1,3-dipolar compounds” and “Lignans, neolignans and related compounds” are the top 2 compound superclasses which tend to produce RFIs in their CID MS2 spectra. Moreover, aromatic, arylbromide, heteroaromatic, alkylarylether, phenol, and conjugated double bond-containing chemicals are more likely to produce RFIs. We also found four possible patterns of change in RFI percentages as a function of CID collision energy. Finally, we demonstrate that the inadequate consideration of RFIs in most conventional bioinformatic tools might cause problems during in silico fragmentation and de novo annotation of MS2 spectra. This work provides a further understanding of CID MS2 mechanism, and the unexpectedly large percentage of RFIs suggests a need for consideration in the development of bioinformatic software for MS2 interpretation.
Quantitative Analysis of Plasmonic Metal Oxide Nanocrystal Ensembles Reveals the Influence of Dopant Selection on Intrinsic Optoelectronic Properties
Authors: Tandon Bharat , Gibbs Stephen Larken , Zydlewski Z. Benjamin , Milliron Delia J.
Published: February 2022

LSPR arising from free charge carriers in doped metal oxide (MO) nanocrystals (NCs) has been explored abundantly already but there is still much to learn about the effect of dopant identity on the electronic structure of the host and, surface depletion layers. Here, using In2O3 as the host lattice, we discuss the contribution of a dopant to the electronic structure and rationalize an empirical understanding of how a particular dopant can impact surface depletion, carrier concentration, and carrier damping in doped MO NCs. To do this, we leverage a slow injection synthesis to incorporate four different dopants (Sn, Zr, Ti, and Ce) in In2O3 NCs of different radius. By fitting their plasmonic response, we extracted intrinsic electronic properties of the NCs such as surface depletion layer thickness, carrier concentration, and carrier damping, and rationalized the influence of dopant selection on each parameter.
Electrochemical Regeneration of Anthraquinones for Lifetime Extension in Flow Batteries
Authors: Jing Yan , Zhao Evan Wenbo , Goulet Marc-Antoni , Bahari Meisam , Fell Eric , Jin Shijian , Davoodi Ali , Jónsson Erlendur , Wu Min , Grey Clare , Gordon Roy , Aziz Michael
Published: February 2022

Aqueous organic redox flow batteries (AORFBs) offer a safe and potentially inexpensive solution to the problem of storing massive amounts of electricity produced from intermittent renewables. However, molecular decomposition is the major barrier preventing AORFBs from being commercialized. Structural modifications can improve molecular stability at the expense of increased synthetic cost and molecular weight. Utilizing 2,6-dihydroxy-anthraquinone (DHAQ), without further structural modification, we demonstrate that electrochemical regeneration could be a viable route to achieve low-cost, long-lifetime AORFBs. In situ (online) NMR and EPR and complementary electrochemical analyses reveal that decomposition compounds i.e., 2,6-dihydroxy-anthrone (DHA) and its tautomer, 2,6-dihydroxy-anthranol (DHAL), can be converted back to DHAQ in two steps: first DHA(L)2− are oxidized to the dimer (DHA)24− at − 0.32 V vs. SHE by one-electron transfer; subsequently, the (DHA)24− is oxidized to DHAQ2− at +0.57 V vs. SHE by three-electron transfer. Electrochemical regeneration rejuvenates not only DHAQ2−, but also the positive electrolyte – rebalancing the states of charge of both electrolytes without introducing extra ions. We demonstrate the repeated capacity recovery with DHAQ | potassium ferro-/ferricyanide flow battery in basic conditions, and show the approach is also effective for anthraquinone-2,7-disulfonate in acid. Electrochemical regeneration strategies may extend the useful lifetime of many water-soluble organic molecules with anthraquinone core structures in electrochemical cells.
Interfacially-Adsorbed Particles Enhance the Self-Propulsion of Oil Droplets in Aqueous Surfactant
Authors: Cheon Seong Ik , Batista Capaverde Silva Leonardo , Khair Aditya , Zarzar Lauren
Published: February 2022

Understanding the chemo-mechanical mechanisms that direct the motion of self-propulsive colloids is important for the development of active materials and exploration of dynamic, collective phenomena. Here, we demonstrate that the adsorption of solid particles on the surface of solubilizing oil droplets can significantly enhance the droplets’ self-propulsion speeds. We investigate the relationship between the self-propulsion of bromodecane oil droplets containing silica particles of varying concentration in Triton X-100 surfactant, noting up to order of magnitude increases in propulsion speeds. Using fluorescently labeled silica, we observe packing of the particles at the oil-water interfaces of the rear pole of the moving droplets. For bromodecane oil droplets in Triton X-100, the highest droplet speeds were achieved at approximately 40% particle surface coverage of the droplet interface. We find particle-assisted propulsion enhancement in ionic surfactants and different oil droplet compositions as well, demonstrating the breadth of this effect. While a precise mechanism for the propulsion enhancement remains unclear, the simple addition of silica particles to droplet oil-water interfaces provides a straightforward route to tune active droplet dynamics.
Spin crossover of thiophosgene via multidimensional heavy-atom quantum tunneling
Authors: Heller Eric R. , Richardson Jeremy O.
Published: February 2022

The spin-crossover reaction of thiophosgene has drawn broad attention from both experimenters and theoreticians as a prime example of radiationless intramolecular decay via intersystem crossing. Despite multiple attempts over 20 years, theoretical predictions have typically been orders of magnitude in error relative to the experimentally measured triplet lifetime. We address the T1 → S0 transition by the first application of semiclassical golden-rule instanton theory in conjunction with on-the-fly electronic-structure calculations based on multireference perturbation theory. Our first-principles approach provides excellent agreement with the experimental rates. This was only possible due to the fact that instanton theory goes beyond previous methods by locating the optimal tunneling pathway in full dimensionality and thus captures "corner cutting" effects. Since the reaction is situated in the Marcus inverted regime, the tunneling mechanism can be interpreted in terms of two classical trajectories, one traveling forwards and one backwards in imaginary time, which are connected by particle--antiparticle creation and annihilation events. The calculated mechanism indicates that the spin crossover is sped up by many orders of magnitude due to multidimensional quantum tunneling of the carbon atom even at room temperature.
Metal-Free Photoredox Phosphonation of C–N and C–X Bonds in Aqueous Solvent Mixtures
Authors: Pan Lei , Kelley Alexandra , Cooke Maria Victoria , Deckert Macy , Laulhé Sébastien
Published: February 2022

Aryl phosphonate esters are valuable moieties for the pharmaceutical and agrochemical industries. Accessing such compounds from affordable and abundant phosphite reagents and a wide range of aromatic building blocks under metal-free, visible light-induced reaction conditions would represent a desirable technology. Herein, we present an efficient and mild methodology for the synthesis of aromatic phosphonate esters in good to excellent yields using DBU and phenothiazine as a photoredox catalyst. The reaction exhibits wide functional group compatibility enabling the transformation in presence of ketone, amide, ester, amine, and alcohol moieties. Importantly, the reaction proceeds using a green solvent mixture primarily composed of water, thus lowering the environmental footprint of this transformation compared to current methods.
Ag(I)/PPh3-Catalyzed Diastereoselective Syntheses of the Spiro[indole-3,4'-piperidine] Scaffold and Its Derivatives via Chelation-Controlled Cycloisomerizations of Tryptamine-Ynamides
Authors: Chen Yanyu , Wang Zhaobo , Sun Shitao , Yang Lu , Xie Fukai , Zhang Junpeng , Zhang Di , Cheng Maosheng , Lin Bin , Liu Yongxiang
Published: February 2022

A Ag(I)/PPh3-catalyzed chelation-controlled cycloisomerization of tryptamine-ynamide was developed to access the spiro[indole-3,4'-piperidine] scaffold. The asymmetric products with this scaffold were obtained through a diastereoselective synthesis via a chiral pool approach. Such a synthesis could be realized on a gram scale and derivatization of this scaffold afforded various derivatives. DFT calculations indicated that strong non-covalent effects between the substrate and catalyst/ligand complex stabilized the spiroindoleninium intermediate via cation-π-π interactions, leading to the diastereoselective syntheses of spiro[indole-3,4'-piperidine derivatives.
Dipole Moment Calculations Using Multiconfiguration Pair-Density Functional Theory and Hybrid Multiconfiguration Pair-Density Functional Theory
Authors: Lykhin Aleksandr , Truhlar Donald , Gagliardi Laura
Published: February 2022

The dipole moment is the molecular property that most directly indicates molecular polarity. The accuracy of computed dipole moments depends strongly on the quality of the calculated electron density, and the breakdown of single-reference methods for strongly correlated systems can lead to poor predictions of the dipole moments in those cases. Here, we derive the analytical expression for obtaining the electric dipole moment by multiconfiguration pair density functional theory (MC-PDFT), and we assess the accuracy of MC-PDFT for predicting dipole moments at equilibrium and nonequilibrium geometries. We show that MC-PDFT dipole moment curves have reasonable behavior even for stretched geometries, and they significantly improve upon the CASSCF results by capturing more electron correlation. The analysis of a dataset consisting of 18 first-row transition metal diatomics and 6 main-group polyatomic molecules with multireference character suggests that MC-PDFT and its hybrid extension (HMC-PDFT) perform comparably to CASPT2 and MRCISD+Q methods and have a mean unsigned deviation of 0.2–0.3 D with respect to the best available dipole moment reference values. We explored the dependence of the predicted dipole moments upon the choice of the on-top density functional and active space, and we recommend the tPBE and hybrid tPBE0 on-top choices for the functionals combined with the moderate correlated participating orbital scheme for selecting the active space. With these choices, the mean unsigned deviations (in debyes) of the calculated equilibrium dipole moments from the best estimates are 0.77 for CASSCF, 0.29 for MC-PDFT, 0.24 for HMC-PDFT, 0.28 for CASPT2, and 0.25 for MRCISD+Q. These results are encouraging because the computational cost of MC-PDFT or HMC-PDFT is largely reduced compared to the CASPT2 and MRCISD+Q methods.
Operando surface chemistry of micro- and nanocubic copper catalysts for electrochemical CO2 reduction
Authors: Banjac Karla , Phan Thanh Hai , Cometto Fernando P. , Alexa Patrick , Liang Yunchang , Gutzler Rico , Lingenfelder Magalí
Published: February 2022

The electrochemical reduction of CO2 (CO2RR) into multicarbon compounds is a promising pathway towards renewable chemicals. Structure-product selectivity studies highlight that copper (100) facets favour C2+ product formation. However, the atomic processes leading to the formation of (100)-rich Cu cubes remains elusive. Herein, we use Cu and graphene-protected Cu surfaces to reveal the differences in structure and composition of common Cu-based electrocatalysts, from nano to micrometer scales. We show that stripping/electrodeposition cycles lead to thermodynamically controlled growth of Cu2O micro/nanocubes, while multi-layered Cu nanocuboids form universally during CO2RR upon polarization-driven re-organization of Cu0 atoms. A synergy of electrochemical characterization by scanning tunnelling microscopy (EC-STM), operando EC-Raman and quasi-operando X-Ray Photoemission spectroscopy (XPS) allows us to shed light on the role of oxygen on the dynamic interfacial processes of Cu, and to demonstrate that chloride is not needed for the stabilization of cubic Cu nanostructures.
A Systematic Study to Unravel the Potential of using Polysaccharides based Organic Nanoparticles Versus Hybrid Nanoparticles for Pesticide Delivery
Authors: Mahajan Ritu , Selim Abdul , K M Neethu , Sharma Sandeep , Shanmugam Vijayakumar , Jayamurugan Govindasamy
Published: February 2022

To daze conventional pesticide release limitations, nanotechnology-mediated pesticide delivery using natural polymers has been actively investigated. However, the lack of information on what are the beneficial/non-beneficial aspects of using hybrid- and organic- nanoparticles (NP) and among the polysaccharides which are better suited concerning pesticide loading efficiency (PLE wt%), entrapment efficiency (E.E %), and sustained-pesticide-release (SPR %) has prompted us to investigate this study. In this report, we systematically investigated a series of polysaccharides such as starch (S), cellulose (C), aminocellulose (AC), and sodium carboxymethylcellulose (NaCMC) coated on magnetite NP (MNP, Fe3O4) and complete organic nanocarrier systems (starch and cellulose) that have no MNP part were compared for the PLE wt% and SPR % efficiencies for chlorpyrifos (ChP) insecticide. Overall, all nanocarriers (NCs) have shown good to excellent PLE wt% due to the smaller-sized NP obtained through optimal conditions. However, among the hybrid polysaccharides studied, starch MNP (S-MNP) has shown a maximum PLE of 111 wt% in comparison with other polysaccharides (80 – 94 wt%) coated hybrid-NCs as well as with organic-NCs (81 – 87 wt%). The use of inorganic support does improve the PLE wt% markedly for starch but not for cellulose derivatives. Similarly, the SPR results of S-NP showed a remarkably better sustained-release profile for ChP of 88 % in 14 days. In contrast, other unfunctionalized and functionalized celluloses exhibited poor release profiles of 60 – 20 % for the same period. This study may help the researchers choose the right system for designing and achieving enhanced pesticide efficiency.
A Validation Study on the Simultaneous Quantification of Multiple Wine Aroma Compounds with Static Headspace-Gas Chromatography-Ion Mobility Spectrometry (SHS-GC-IMS)
Authors: Zhu Wenyao , Benkwitz Frank , Sarmadi Bahareh , Kilmartin Paul
Published: February 2022

A new quantitative method based on static headspace−gas chromatography−ion mobility spectrometry (SHS−GC−IMS) is proposed, which enables the simultaneous quantification of multiple aroma compounds in wine. The method was first evaluated for its stability and the necessity of using internal standards as a quality control measure. The two major hurdles in applying GC-IMS in quantification studies, namely, non-linearity and multiple ion species, were also investigated using the Boltzmann function and generalized additive model (GAM) as potential solutions. Metrics characterizing the model performance, including root mean squared error, bias, limit of detection, limit of quantification, repeatability, reproducibility, and recovery were investigated. Both non-linear fitting methods, Boltzmann function and GAM, were able to return desirable analytical outcomes with an acceptable range of error. Potential pitfalls that would cause inaccurate quantification i.e., effects of ethanol content and competitive ionization, were also discussed. The performance of the SHS-GC-IMS method was subsequently compared against a currently established method, namely, GC-MS, using actual wine samples. These findings provide an initial validation of a GC-IMS-based quantification method, as well as a starting point for further enhancing the analytical scope of GC-IMS.
Guided Inquiry in Sophomore Organic Lecture: Deducing Mechanisms by Reaction Mapping
Authors: Taber Douglass
Published: February 2022

Arrow-pushing mechanisms can be understood more readily if the changes from starting material to product are systematically charted. This can be done by labeling the relevant atoms in the starting material and in the product, then making lists of the bonds to be broken and the bonds to be formed.
Modulating Electric Field Distribution by Alkali Cations for CO2 Electroreduction in Strongly Acidic Medium
Authors: Gu Jun , Liu Shuo , Ni Weiyan , Ren Wenhao , Haussener Sophia , Hu Xile
Published: February 2022

The reaction of carbon dioxide with hydroxide to form carbonate in near neutral or alkaline medium severely limits the energy and carbon efficiency of CO2 electroreduction. Here we show that by suppressing the otherwise predominant hydrogen evolution using alkali cations, efficient CO2 electroreduction can be conducted in acidic medium, overcoming the carbonate problem. The cation effects are general for three typical catalysts including carbon supported tin oxide, gold, and copper, leading to Faradaic efficiency of as high as 90% for formic acid and CO formation. Our analysis suggests hydrated alkali cations physisorbed on the cathode modify the distribution of electric field in the double layer, which impedes hydrogen evolution by suppress the migration of hydronium ions while at the same time promotes CO2 reduction by stabilizing key intermediates.
Measuring solute concentration with terahertz time-domain spectroscopy in single and multiphase systems
Authors: Kölbel Johanna , Li Qi , Threlfall Terry , Zeitler J. Axel
Published: February 2022

A versatile setup based on a microfluidics platform allows investigation of liquid samples at various temperatures with terahertz time-domain spectroscopy. The set up is applied to develop a novel method that performs temperature and concentration calibrations of liquid samples at terahertz frequencies. Other than measuring the concentration of pure liquid phase solutions, it enables the studies of local concentration of semi-crystalline systems. An equivalent solute concentration during crystallisation can be calculated from the extracted absorption at low frequencies. The MgSO4-water system is discussed as an example to illustrate the idea of this method.
Estimating the cooperativity of PROTAC-induced ternary complexes using 19F NMR displacement assay
Authors: Castro Guilherme , Ciulli Alessio
Published: February 2022

Cooperativity is an important parameter to understand the ternary complexes formed by protein degraders. We developed fluorine NMR competition binding experiments to determine cooperativity of PROTACs. We show applicability to estimate both positive and negative cooperativity, also with homo-dimerizers, and highlight key features and considerations for optimal assay development.
Inherent Promotion of Ionic Conductivity via Coherent Vibrational Strong Coupling of Water
Authors: Fukushima Tomohiro , Yoshimitsu Soushi , Murakoshi Kei
Published: February 2022

The vibrational strong coupling, where vibrational energy states of molecules and an optical cavity mode are hybridized, is an emerging method for the modification of ground-state thermochemical reactivity of molecules. Here, we report that vibrational strong coupling promotes ionic conductivity of aqueous electrolyte. A Fabry-Pérot cavity were fabricated for the spectroscopic analysis and electrochemical impedance measurements of electrolyte solution. We observed the splitting of vibrational state of water in optical cavity with the Rabi splitting energy of 760 cm−1 by matching cavity mode frequency to OH stretching mode frequency of water molecules. From the electrochemical impedance measurements, we discovered the modulation of relative dielectric constants and one-fold promotion of proton conductivity of the aqueous electrolyte. This study demonstrates that the use of vibrational strong coupling system for the promotion of ionic conductivity utilized for the electrochemical energy conversion system without light pumping.
Tetra(hetero)arylated Cyclopentadienone Iron Tricarbonyl Complexes for Noble Metal-free Photocatalytic Hydrogen Generation
Authors: Baeuerle Peter , Riediger Saskia , Weigand Wolfgang , Buday Philipp
Published: February 2022

A versatile method for the straightforward synthesis of rarely known tetra(hetero)arylated cyclopentadienone iron tricarbonyl complexes 3a-3j is presented. In a [2+2+1]-cycloaddition reaction, a series of di(hetero)arylated ethynylenes 1a-1j are reacted with iron pentacarbonyl to yield the corresponding “Knölker-type” complexes, which bear substituents of different electronic nature. This type of iron complexes is active in photocatalytic hydrogen evolution reaction and the influence of the substituents on the catalytic activity was investigated.
Enantiomer stability of atropisomeric 1,5-disubstituted 1,2,3-triazoles
Authors: Meloni Fernanda , Brittain William , Male Louise , Le Duff Cécile , Buckley Benjamin , Leach Andrew , Fossey John
Published: February 2022

The synthesis and characterisation of axially chiral atropisomeric 1,5-disubstituted 1,2,3-triazoles is reported. Molecules designed to display restricted rotation about 1,2,3-triazole N-1-aryl or 1,2,3-triazole C-5-aryl bonds were investigated by physical and computational techniques. The barrier to 1,2,3-triazole N-1-aryl rotation was found to be higher than that for 1,2,3-triazole C-5-aryl rotation, confirming axial chirality stemming from restricted rotation about an N-1-aryl bond in a 1,5-disubstituted 1,2,3-triazole to be the most suitable for the development of an axial chirality triazole-based platform.
Delivering anion transporters to lipid bilayers in water
Authors: McNaughton Daniel A. , To Tsz Ying (Teresa) , Hawkins Bryson A. , Hibbs David E. , Gale Philip Alan
Published: February 2022

CYCLODEXTRINS HAVE BEEN EMPLOYED AS DELIVERY AGENTS FOR LIPOPHILIC ANION TRANSPORTERS, WHICH ALLOW THEIR INCORPORATION INTO LIPID BILAYERS WITHOUT USING AN ORGANIC SOLVENT OR PRE-INCORPORATION.
Development of an N-Terminal BRD4 Bromodomain-Targeted Degrader
Authors: Divakaran Anand , Zahid Huda , Lin Wenwei , Chen Taosheng , Harki Dan , pomerantz william
Published: February 2022

Targeted protein degradation is a powerful induced-proximity tool to control cellular concentrations of native proteins using small molecules. However, the design of selectivity in protein degradation remains challenging. In the case of Bromodomain and Extra-Terminal (BET) family proteins, BRD4 has emerged as the primary therapeutic target over other family members BRD2, 3 and T, but strategies to selectively degrade BRD4 rely on the use of pan-BET inhibitors optimized for BRD4:E3 protein-ubiquitin ligase (E3) ternary complex formation. Here, we report a potent and selective inhibitor for the first bromodomain of BRD4, iBRD4-BD1 (IC50 = 12 nM, 23-6200-fold intra-BET selectivity). We further use this novel inhibitor to develop dBRD4-BD1 that induces selective degradation of BRD4 at a DC50 of 280 nM. The design of BRD4 selectivity up-front enables the study of BRD4 biology in the absence of wider BET-inhibition, simplifies design of future BRD4-selective degraders as new E3 recruiting ligands are discovered, and provides a tool to design additional heterobifunctional BRD4-selective probes.
Enhanced Hydrophobicity of CeO2 Thin Films by Surface Engineering
Authors: Mamedov Damir , Åsland Anna Cecilie , Cooil Simon , Røst Håkon Ivarssønn , Bakkelund Johannes , Wells Justin William , Karazhanov Smagul
Published: February 2022

Due to its advanced surface properties and many technologically important applications, cerium dioxide (CeO2, ceria) has become the focus of extensive research. This work presents a study of factors influencing the wetting properties of ceria. For this, CeO2 thin films were deposited on substrates with different morphologies and characterized by means of XRD, SEM, XPS and water contact angle (WCA) measurements. The obtained results on wetting behavior were expanded using different organic materials on top of the CeO2 thin films to enhance their hydrophobicity. The achieved WCAs were compared with those from samples without ceria to find the effect of the material on the water repelling properties. The results revealed that all factors – the surface material, adsorbed organic molecules and surface texturization – modify the wetting properties of CeO2 thin films independently. This indicates that to achieve a superhydrophobic condition it is necessary to assess all the parameters which may control water behavior on the surface.
Icolos: A workflow manager for structure based post-processing of de novo generated small molecules
Authors: Moore J. Harry , Bauer Matthias R. , Guo Jeff , Patronov Atanas , Engkvist Ola , Margreitter Christian
Published: February 2022

We present Icolos, a workflow manager written in Python as a tool for automating complex structure-based workflows. Icolos can be used as a standalone tool, for example in virtual screening campaigns, or can be used in conjunction with deep learning-based molecular generation facilitated for example by REINVENT, a previously published de novo design package. In this publication, we focus on the internal structure and general capabilities of Icolos, using docking experiments as an illustration. The source code is freely available at https://github.com/MolecularAI/Icolos under the Apache 2.0 licence. Tutorial notebooks containing minimal working examples can be found at https://github.com/MolecularAI/IcolosCommunity.
PEMANFAATAN MEDIA LIFT THE FLAP BOOK UNTUK MENINGKATKAN KEMAMPUAN MEMBACA
Authors: Triyanto Yuli , Zubaidah Enny
Published: February 2022

This research is about the reading skills of the grade I students and the method is classroom action research by doing classroom study using lift the flap book media. The purpose of the research is to improve the reading skills of the grade I students of SD Negeri Puren Depok Sleman using the lift the flap book media.  Learning to read in grade I SD Negeri Puren is still not in accordance with the expected results.  Evidenced by the results of reading skills, there are still many who have not reached the complete score. The results showed that the use of lift the flap book media can improve student’s reading skills.  This can be seen from the increase in the learning process on each indicator of reading ability.  Students are increasingly interested in learning, and teachers have used other media besides books from school.  The process of learning to read has increased, namely that the average score increase from cycle 1 the score is 76 and in cycle 2 the score is 83. Students whose average scores are above the average increase from cycle 1 by 46.4% and cycle 2 as much as 85%.Penelitian yang dilakukan ini tentang kemampuan membaca siswa kelas 1, dan metode yang digunakan adalah penelitian tindakan kelas (classroom action research) dengan melakukan pembelajaran didalam kelas menggunakan media lift the flap book. Tujuan penelitian adalah kemampuan membaca siswa kelas 1 SD Negeri Puren Depok meningkat dengan menggunakan bantuan media lift the flap book. Kegiatan belajar mengajar membaca di SD Negeri Puren kelas I hasilnya masih belum sesuai dengan yang diharapkan. Terbukti dengan kemampuan membaca masih banyak yang yang nilainya belum sesuai yang diharapkan. Hasil penelitian kemampuan membaca meningkat setelah menggunakan media lift the flap book hal ini dapat diketahui meningkatnya pada proses pembelajaran pada setiap indikator kemampuan membaca. Siswa semakin tertarik mengikuti pembelajaran, dan guru sudah menggunakan media lain selain buku dari sekolah. Proses pembelajaran membaca mengalami peningkatan yaitu nilai rata-rata meningkat dari siklus 1 nilainya 76 dan siklus 2 nilainya 83. Siswa yang nilainya diatas rata-rata meningkat dari siklus 1 sebanyak 46,4% dan siklus 2 sebanyak 85%.