bluuebunny/crossref_metadata_2025 huggingface dataset:
In Situ Synthesis of Phenoxazine Dyes in Water: A Cutting-Edge Strategy to "Turn-On" Fluorogenic and Chromogenic Detection of Nitric Oxide
Authors: JENNI Sébastien , RENAULT Kévin , DEJOUY Garance , DEBIEU Sylvain , LALY Myriam , ROMIEU Anthony
Published: February 2022

The synthesis of phenoxazine dyes was revisited in order to access these fluorescent N,O-heterocycles under mild conditions. The combined sequential use of nitrosonium tetrafluoroborate (NOBF4) and triphenylphosphine enables the facile conversion of bis(3-dimethylaminophenyl) ether into the methyl analog of popular laser dye oxazine 1. The ability of nitrosonium cation (NO+) to initiate the domino reaction resulting in pi-conjugated phenoxazine molecules under neutral conditions, then led us to explore the feasibility of expanding it in aqueous media. Thus, we explored the use of reactive signaling molecule nitric oxide (NO) as a biological trigger of phenoxazine synthesis in water. The implementation of a robust analytical methodology based on fluorescence assays and HPLC-fluorescence/-MS analyses, have enabled us to demonstrate the viability of this novel fluorogenic reaction-based process to selectively yield an intense "OFF-ON" response in the near-infrared (NIR-I) spectral region. This study is an important step towards the popularization of the concept of "covalent-assembly" in the fields of optical sensing, bioimaging and molecular theranostics.
Electrochemical Synthesis of Allylic Amines from Alkenes and Amines
Authors: Wang Diana , Targos Karina , Wickens Zachary
Published: February 2022

Allylic amines are valuable synthetic targets en route to diverse biologically active amine products. Current allylic C–H amination strate-gies remain limited with respect to the viable N-substituents. Herein we disclose a new electrochemical process to prepare aliphatic allylic amines by coupling two abundant starting materials: secondary amines and unactivated alkenes. This oxidative transformation proceeds via electrochemical generation of an electrophilic adduct between thianthrene and the alkene substrates. Treatment of these adducts with aliphatic amine nucleophiles and base provides allylic amine products in high yield. This synthetic strategy is also amenable to functionali-zation of feedstock gaseous alkenes at 1 atmosphere. In the case of 1-butene, remarkable Z-selective crotylation is observed. This strategy, however, is not limited to the synthesis of simple building blocks; complex biologically active molecules are suitable as both alkene and amine coupling partners. Preliminary mechanistic studies implicate vinylthianthrenium salts as key reactive intermediates.
Universal promotion of heterogeneous olefin metathesis catalysts by controlling dynamic active site renewal
Authors: Gani Terry Z. H. , Berkson Zachariah J. , Zhu Ran , Kang Jong Hun , Di Iorio John R. , Chan Ka Wing , Consoli Daniel F. , Shaikh Sohel K. , Copéret Christophe , Román-Leshkov Yuriy
Published: February 2022

Olefin metathesis is a versatile strategy for large-scale olefin interconversion, yet mechanistic details over industrial heterogeneous catalysts have remained ambiguous for decades. Here, from rigorous kinetic measurements, spectroscopic studies, and computational modeling of propylene metathesis over model and industrial WOx/SiO2 catalysts, we identify a hitherto unknown site renewal and decay cycle, mediated by proton transfers involving proximal Brønsted acidic OH groups, which operates concurrently with the classical Chauvin cycle. We show how this cycle can be manipulated using small quantities of promoter olefins to drastically increase steady-state propylene metathesis rates by up to 30-fold at 250oC with negligible promoter consumption. The increase in activity and considerable reduction of operating temperature requirements were also observed on MoOx/SiO2 catalysts, showing that this strategy is general and can address major roadblocks associated with industrial metathesis processes.
Structure-based Discovery of a Series of NSD2-PWWP1 Inhibitors
Authors: Li Na , Yang Hong , Liu Ke , Zhou Liwei , Huang Yuting , Cao Danyan , Li Yanlian , Sun Yaoliang , Yu Aisong , Du Zhiyan , Yu Feng , Zhang Ying , Wang Bingyang , Geng Meiyu , Li Jian , Xu Shilin , Xiong Bing , Huang Xun , Liu Tongchao
Published: February 2022

Overexpression, point mutations or translocations of protein lysine methyltransferase NSD2 was occurred in many types of cancer cells. Therefore, it was recognized as onco-protein and considered as a promising anticancer drug target. NSD2 consists of a SET catalytic domain and two PWWP domains binding to methylated histone proteins. Here, we reported our efforts to develop a series of NSD2-PWWP1 inhibitors, and further structure-based optimization resulted a potent inhibitor 38, which has the high selectivity towards NSD2-PWWP1 domain. The detailed biological evaluation revealed that compound 38 can bind to NSD2-PWWP1 and then affect the expression of genes regulated by NSD2. The current discovery will provide a useful chemical probe to the future research in understanding the specific regulation mode of NSD2 by PWWP1 recognition, and pave the way to develop potential drugs targeting NSD2 protein.
Separation of Enantiomers through Local Vorticity: A Screw Model Mechanism
Authors: Duraes Anderson , Gezelter J. Daniel
Published: February 2022

We present a model to explain the mechanism behind enantiomeric separation under either shear flow or local rotational motion in a fluid. Local vorticity of the fluid imparts molecular rotation that couples to translational motion, sending enantiomers in opposite directions. Translation-rotation coupling of enantiomers is explored using the molecular hydrodynamic resistance tensor, and a molecular equivalent of the pitch of a screw is introduced to describe the degree of translation-rotation coupling. Molecular pitch is a structural feature of the molecules and can be easily computed, allowing rapid estimation of the pitch of 85 drug-like molecules. Simulations of model enantiomers in a range of fluids such as $\Lambda$- and $\Delta$-Ru(bpy)_3]Cl_2 in water and (R,R)- and (S,S)-atorvastatin in methanol support predictions made using molecular pitch values.A competition model and continuum drift diffusion equations are developed to predict separation of realistic racemic mixtures. We find that enantiomeric separation on a centimeter length scale can be achieved in hours, using experimentally-achievable vorticities. Additionally, we find that certain achiral objects can also exhibit a non-zero molecular pitch.
Preventing bulky cation diffusion in lead halide perovskite solar cells
Authors: Perini Carlo Andrea Riccardo , Rojas-Gatjens Esteban , Rovello Magdalena , Castro Mendez Andres Felipe , Hidalgo Juanita , An Yu , Li Ruipeng , Silva-Acuña Carlos , Correa-Baena Juan-Pablo
Published: February 2022

The impact on device stability of the bulky cation-modified interfaces in halide perovskite solar cells is not well-understood. We demonstrate the thermal instability of the bulky cation interface layers used in some of the highest performing solar cells to date. X-ray photoelectron spectroscopy and synchrotron-based grazing incidence X-ray scattering measurements reveal significant changes under thermal stress in the chemical composition and structure at the surface of these films. The changes impact charge carrier dynamics and device operation, as shown in transient photoluminescence, excitation correlation spectroscopy, and solar cells. The type of cation used for passivation affects the extent of these changes, where long carbon chains provide more stable interfaces and thus longer durability (more than 1000 hrs at 55ºC). Such findings highlight that annealing the treated interfaces before characterization is critical to enable reliable reporting of performances and to drive the selection between different cations.
Freeze-Float System for High-throughput Measurement of Ice Nucleation
Authors: Kamijo Yuki , Derda Ratmir
Published: February 2022

In this publication, we developed the high throughput screening implementation of freeze-float selection platform system we established in the previous publication. The goal of this publication is to expand the system to higher throughput and accuracy. In the following sections, we describe the steps for automated droplets generations, adaptation of freeze-float selection using controlled and uniform temperature cooling system, and semi-automated droplets detection program. We aimed to improve previously published system to add functional advantages, such as; a) increased efficiency of the screening with fewer manipulation steps; b) increased accuracy of measurement due to the increased sample size; c) increased uniformity of temperature distribution by incorporating the controlled-rate freezer. In the following sections, we describe the steps for automated droplets generations, freeze-float system adaptations using controlled and uniform temperature cooling system, and semi-automated droplets detection program.
Learning design rules for selective oxidation catalysts from high-throughput experimentation and artificial intelligence
Authors: Foppa Lucas , Sutton Christopher , Ghiringhelli Luca M. , De Sandip , Löser Patricia , Schunk Stephan , Schaefer Ansgar , Scheffler Matthias
Published: February 2022

The design of heterogeneous catalysts is challenged by the complexity of materials and processes that govern reactivity and by the fact that the number of good catalysts is very small compared to the number of possible materials. Here, we show how the subgroup-discovery (SGD) artificial-intelligence approach can be applied to an experimental plus theoretical data set to identify constraints on key physicochemical parameters, the so-called SG rules, which exclusively describe materials and reaction conditions with outstanding catalytic performance. By using high-hroughput experimentation, 120 SiO 2 -supported catalysts containing ruthenium, tungsten and phosphorus were synthesized and tested in the catalytic oxidation of propylene. As candidate descriptive parameters, the temperature and ten parameters related to the composition and chemical nature of the catalyst materials, derived from calculated free-atom properties, were offered. The temperature, the phosphorus content, and the composition-weighted electronegativity are identified as key parameters describing high yields towards the value-added oxygenate products acrolein and acrylic acid. The SG rules not only reflect the underlying processes particularly associated to high performance but also guide the design of more complex catalysts containing up to five elements in their composition.
Host-Guest Interactions in C2H2/CO2 Discriminative Covalent Organic Framework Probed by Solid-State NMR
Authors: Jiang Weiming , Wang Ping , Otake Ken-ichi , Kitagawa Susumu , Noda Yasuto , Takeda Kazuyuki , Takegoshi Kiyonori
Published: February 2022

Covalent organic frameworks (COF) are promising porous materials for energy-efficient gas separation. However, understanding of the interaction between the host framework and the guest gas molecules, which is crucial for the development of the COF adsorbents, remains insufficient. Here, we look into the host-guest interactions between C2H2/CO2 molecules and a propyl sodium sulfonate group functionalized COF. Gas sorption studies indicate that the synthesized COF, termed Py-Na COF, exhibits C2H2/CO2 discriminative adsorption at ambient temperature. The underlying discriminative mechanism is studied by in situ 23Na solid-state NMR combined with molecular dynamics (MD) and density functional theory (DFT) calculations. The interactions between the C2H2/CO2 molecules and the host sodium ion play an essential role in C2H2/CO2 discrimination in Py-Na COF.
Tuning the Dielectric Response in a Nanocomposite Material through Nanoparticle Morphology
Authors: Adluri Archita , Henderson Brett , Paci Irina
Published: February 2022

The introduction of metal cluster dopants and molecular-scale inclusions in metal oxide matrices provides an opportunity for exploring new high-k solid-state dielectrics with tunable response. The quantum properties of molecular nanoparticles depend strongly on their size and shape, a characteristic that can be exploited in changing the response properties of a material, while the small nanoparticle size can help limit the usual issues of conduction and leakage. Here, we model the polarization of molecular-scale silver inclusions in magnesium oxide, using the Modern Theory of Polarization and Car-Parinello Molecular Dynamics (CPMD). Several trends are considered, including nanoparticle size, shape and orientation relative to the applied field. Dielectric permittivity enhancements of 30-100% were observed with inclusion sizes varying from 8 to 32 atoms, considering both rod-like and disk-like inclusions, with alignment either parallel or perpendicular to the external field. Currents calculated using the modern theory of polarization with periodic boundary conditions can experience box edge jumps due to the distortion of the matrix during the simulations - an approach for addressing these issues in CPMD calculations is outlined within.
Long-lived Excited State in a Solubilized Graphene Nanoribbon
Authors: Drummer Matthew , Glusac Ksenija , Chen Lin , Li Xiaosong , Cordones Amy , Valentine Andrew , Phelan Brian , Gupta Nikita , Weerasooriya Ravindra
Published: February 2022

Graphene nanoribbons exhibit excellent light-absorbing properties, but often exhibit short excited-state lifetimes that prevent their applications in photocatalysis. Here, we report a long-lived charge-transfer triplet excited state in a well solubilized, chlorinated graphene nanoribbon (Cl-GNR) with edges modified by bipyrimidine (bpm) moieties. The photophysical behavior of Cl-GNR was observed and characterized by steady-state UV-vis absorption and emission spectroscopy, transient absorption spectroscopy on the ps-ms timescale, and density functional theory (DFT) calculations. Both the Cl-GNR and its monomeric subunit, chlorinated graphene quantum dot (Cl-GQD), were synthesized using bottom-up techniques to produce the H- analogs of the compounds followed by edge-chlorination to achieve soluble products. The absorption spectra of Cl-GQD and Cl-GNR appear in the UV-vis range with lowest-energy peaks at 375 and 600 nm, respectively. The excitons in Cl-GNR were found to exhibit charge-transfer character with the bpm edges serving as electron acceptors. DFT calculations indicate that the excitons are relatively localized, spreading over at most two monomeric units of the GNR. Transient absorption spectroscopy shows that singlet excited states of Cl-GQD and Cl-GNR undergo intersystem crossing with ~300 ps lifetime to form triplet state that lasts for 15.7 μs (Cl-GQD) and 106 μs (Cl-GNR). These properties, combined with the ability of bpm sites to coordinate transition metals, make Cl-GNRs promising light-harvesting motifs for photocatalytic applications.
Defect Chemistry and Doping of BiCuSeO
Authors: Toriyama Michael , Qu Jiaxing , Snyder G. Jeffrey , Gorai Prashun
Published: February 2022

While p-type BiCuSeO is a well-known mid-temperature oxide thermoelectric (TE) material, computations predict that superior TE performance can be realized through n-type doping. In this study, we use first-principles defect calculations to show that Cu vacancies are responsible for the native p-type self doping; yet, we find that BiCuSeO is n-type dopable under Cu-rich growth conditions, where the formation of Cu vacancies is suppressed. We computationally survey a broad suite of 23 dopants and find that only Cl and Br are effective n-type dopants. Therefore, we recommend that future experimental doping efforts utilize phase boundary mapping to optimize the electron concentration and resolve the anomalous p-n-p transitions observed in halogen-doped BiCuSeO. The prospects of n-type doping, as revealed by our defect calculations, paves the path for rational design of BiCuSeO chemical analogues with similar doping behavior and even better TE performance.
A mechanism of abiogenesis based on complex reaction networks organized by seed-dependent autocatalytic systems
Authors: Peng Zhen , Linderoth Jeff , Baum David
Published: February 2022

Life is the canonical example of a complex system, consisting of diverse chemical components that are organized in a specific way that allows perpetuation of the living state. In contrast, the abiotic environment, which life feeds on and originated from, is much simpler and less organized. The complexity gap between the biotic and abiotic worlds, and the lack of direct observation of abiogenesis, has made explaining the origin of life one of the hardest scientific questions. A promising strategy for addressing this problem is to identify features shared by abiotic and biotic chemical systems that permit the stepwise accretion of complexity. We used such a rationale to compare abiotic and biotic reaction networks in order to evaluate the presence of autocatalysis, the underlying basis of biological self-propagation, to see if it is structured in such a way as to permit stepwise complexification. We develop the concept of, and provide an algorithm to detect, seed-dependent autocatalytic systems (SDASs), namely subnetworks that can use food chemicals to self-propagate but cannot emerge without being first seeded by some non-food chemicals. We show that serial activation of SDASs can result in incremental complexification. Furthermore, we identify life-like features that emerge during the accretion of SDASs that open up new ecological opportunities and improve the efficiency of food utilization. SDAS theory, thus, provides a conceptual roadmap from a simple abiotic environment to primitive forms of life, without the need for linear genetic polymers at the outset (though these may be added later). This framework also suggests new experiments that have the potential to detect the spontaneous emergence of life-like features, such as self-propagation and adaptability.
Mechanochemical synthesis of eco-friendly fertilizer from eggshell (calcite) and KH2PO4
Authors: Borges Roger , Giroto Amanda , Klaic Rodrigo , Wypych Fernando , Ribeiro de Oliveira Caue
Published: February 2022

The present article, based on reverse logistic, provides an environmentally beneficial and cost-effective method of producing calcium phosphate bioceramics (potassium calcium phosphates) aimed for soil conditioning, by a free-solvent mechanochemical process between eggshell waste and KH2PO4. The K3CaH(PO4)2 and possibly CaKPO4 phases formed provide better nutrient management of P, K and Ca, when applied in soil system the material first release K and form hydroxyapatite and important P and Ca bioavailable source at pH ~ 5, which comprises a large part of many countries soils.
A Chiral Interlocking Auxiliary Strategy for the Synthesis of Mechanically Planar Chiral Rotaxanes
Authors: de Juan Alberto , Lozano David , Heard Andrew , Jinks Michael , Meijide Suarez Jorge , Tizzard Graham , Goldup Stephen
Published: February 2022

We have serendipitously discovered a combination of reaction partners that function as a “chiral interlocking auxiliary” to both orientate a macrocycle and, effectively, load it onto a new axle to generate mechanically planar chiral rotaxanes in high stereopurity (93-99% ee). We demonstrate the potential of the chiral interlocking auxiliary strategy through the synthesis of a number of targets in high enantiopurity, including so called “impossible” rotaxanes whose axles lack any functional groups that would allow their direct synthesis by other means. Intriguingly, by varying the order of bond forming steps, we can effectively choose which end of an axle the macrocycle is loaded onto, allowing the synthesis of both hands of a single target using the same reactions and building blocks.
Linker Redox Mediated Control of Morphology and Properties in Semiconducting Iron-Semiquinoid Coordination Polymers
Authors: Wang Lei , Papoular Robert , Horwitz Noah , Xie Jiaze , Zhao Norman , Cheng Baorui , Ma Tengzhou , Filatov Alexander , Anderson John
Published: February 2022

The emergence of conductive 2D, and less commonly 3D, coordination polymers (CPs) and metal–organic frameworks (MOFs) promises novel applications in chemical sensing, energy storage, optoelectronics, thermoelectrics, and spintronics. While classic CPs and MOFs now have relatively sophisticated synthetic parameters to control morphology, crystallinity, and phase purity, similar parameters are not thoroughly understood for electronically more complex materials. In particular, many linkers used in conducting CPs have multiple accessible redox states and the relationship between starting linker oxidation state and final material structure and properties is not well understood. Here we report a new 3D semiconducting coordination polymer, Fe5(C6O6)3, which is composed of hexagonal Fe2(C6O6)3 layers which are bridged by additional Fe ions. This material, which is a fusion of 2D Fe-semiquinoid materials and recently reported 3D cubic Fex(C6O6)y materials, is obtained by using a different initial redox-state of the C6O6 linker. The material displays high electrical conductivity (0.02 S cm–1), broad electronic transitions in the visible to middle-infrared region, promising thermoelectric behavior (S2σ = 4.2×10–9 W m–1 K–2), and strong antiferromagnetic interactions even at room temperature. The unique structure and properties of this material illustrates that controlling the oxidation states of redox-active components in conducting CPs can be a “presynthetic” strategy to carefully tune material topologies, properties, and functionalities in contrast to more commonly encountered post-synthetic modifications.
Sustainable Polymers Square Table Final Report
Authors: de Pablo Juan , Hillmyer Marc , Buenaflor Jeffrey , Chan Daphne , Mysona Josh , Rauscher Phil , Sample Caitlin , Schneider Ludwig
Published: February 2022

This is the final report from a NSF-sponsored Square Table on Sustainable Polymers that brought together a diverse cohort of stakeholders to develop broad-ranging, integrated, and futuristic ideas and strategies in the area of sustainable polymers. The Square Table included emerging and established leaders from a wide range of backgrounds and institutional types such that a clear picture of the key challenges and needs were developed. Over the course of two half-day sessions, a group of more than 50 participants (see Appendix 1) discussed strategies for advancing the science, technology, and more overarching systems associated with sustainable polymers. The Square Table concept provides structure and self-facilitated interactions among stakeholders who do not typically interact with one another to bridge gaps that exist between industry, federal agencies, and academia in an open and unbiased manner. This was accomplished by mixing participants in breakout discussion with guiding questions, followed by reporting back to the group and repeating with a new mix of participants, questions, and discussion points. Select participants that not only contributed to the discussion but also acted as scribes for sub-sessions were essential to help capture the sum of the views, suggestions, and inputs from the participants. In this way, the discussions cut to the root cause of successes and opportunities in a rapid and less biased manner than traditional roundtables or workshops. The Square Table objectives included developing proposed answers to key questions such as (1) What are the critical basic and applied questions that, when addressed together, could improve the possibility for impact in terms of moving fundamental research thrusts and translational efforts? (2) What prevents large-scale, coordinated efforts between industry, academia, and federal agencies? (3) What is needed to help reduce these barriers in terms of data resources, physical infrastructure, and/or workforce training? (4) How can data and advanced modeling approaches be shared in a collaborative way that would allow data-driven science and engineering to be accelerated in a translational sense? (5) What partnerships are needed to foster an environment/culture to realize more sustainable polymer solutions in the future?
Control of Cu morphology on Ru-passivated and Ru-doped TaN Surfaces – promoting growth of 2D conducting copper for CMOS interconnects
Authors: Nies Cara-Lena , Kondati Natarajan Suresh , Nolan Michael
Published: February 2022

Prolonging the lifetime of Cu as level 1 and level 2 interconnect metal in future nanoelectronic devices is a significant challenge as device dimensions continue to shrink and device structures become more complex. At nanoscale dimensions Cu has high resistivity which prevents it functioning as a conducting wire and prefers to form non-conducting 3D islands. Given that changing from Cu to an alternative metal is challenging, we are investigating new materials that combine properties of diffusion barriers and seed liners to reduce the thickness of this layer and to promote successful electroplating of Cu to facilitate the coating of high-aspect ratio interconnect vias and to allow for optimal electrical conductance. In this study we propose a new combined barrier/liner materials based on modifying the surface layer of TaN barrier through Ru incorporation. Simulating a model Cu29 structure at 0 K and through finite temperature ab initio molecular dynamics on these surfaces allows us to demonstrate how the Ru content can control copper wetting, adhesion and thermal stability properties. Activation energies for single atom migrations onto a nucleating island of Cu allow insight into the growth mechanism of a Cu thin-film. Using this understanding allows us to tailor the Ru content on TaN to control the final morphology of the Cu film.
Photoluminescence and Electrochemiluminescence of Thermally Activated Delayed Fluorescence (TADF) Emitters Containing Diphenylphosphine Chalcogenide-Substituted Carbazole Donors
Authors: Kumar Shiv , Tourneur Pauline , Adsetts Jonathan , Wong Michael , Rajamalli Pachaiyappan , Chen Dongyang , Lazzaroni Roberto , Viville Pascal , Cordes David , Slawin Alexandra , Olivier Yoann , Cornil Jerome , Ding Zhifeng , Zysman-Colman Eli
Published: February 2022

Aiming to develop efficient blue-emitting thermally activated delayed fluorescence (TADF) compounds, we have designed and synthesized derivatives of the well-known sky-blue emitter 2CzPN that contain electron-accepting phosphine chalcogenide groups to stabilize the HOMO level relative to the pristine compound, thus increasing the HOMO-LUMO gap and blue-shifting the emission wavelength. By cyclic voltammetry, photophysical data and quantum-chemical calculations, it was found that polar solvents and matrices validated the proposed concept, but these trends were not recovered in non-polar media. The suitability of these 2CzPN derivatives in polar matrices for optoelectronic applications was explored with electrochemiluminescence (ECL) by measuring emission delays, radical stability, emission stabilities, emission efficiencies and emission spectra. Some of the 2CzPN derivatives showed an unprecedented delayed onset of the ECL, and delayed rising time to the ECL maximum, as well as long ECL emission decay. All of these mentioned delay times suggest that these luminophores primarily emit via organic long-persistent electrochemiluminescence (OLECL) mechanisms. The derivatization of the donor groups of the emitters affected both the radical stability and the predominant emission mechanism, providing important insight into their potential as emitters in solid-state electroluminescent devices.
Enantioselective Tertiary Electrophile (Hetero)Benzylation: Pd-Catalyzed Substitution of Isoprene Monoxide with Arylacetates
Authors: Doyle Michael , Gabbey Alexis , McNutt Wesley , Lundgren Rylan
Published: February 2022

The enantioselective generation of quaternary carbon centers remains challenging but is of growing importance for the preparation of functional molecules. Transition metal catalyzed allylic alkylations of tertiary electrophiles have provided access to these substructures but remain generally incompatible with organometallic benzyl nucleophiles. In this study we demonstrate that electron-deficient arylacetates can serve as benzyl nucleophile surrogates to generate enantioenriched acyclic molecules containing a quaternary carbon center via a two-step substitution-decarboxylation process using isoprene monoxide. The reaction gives products typically in >90% ee using a commercially available catalyst system and tolerates an array of electron-withdrawing functional groups on the arylacetate moiety. The lactone intermediate generated by the initial substitution reaction can be used in further stereoselective transformations to prepare molecules with acyclic vicinal quaternary stereocenters.
Photodeposited polyamorphous CuOx hole-transport layers in organic photovoltaics
Authors: Randell Nicholas , Miclette Lamarche Renaud , Tintori Francesco , Chernikov Roman , Welch Gregory , Trudel Simon
Published: February 2022

Hole-selective charge transport layers are an important part of modern thin-film electronics, serving to direct electron flow and prevent leakage current. Crystalline metal-oxide hole-transport layers (HTLs) such as NiO and CuOx exhibit high performance and stability. However they are traditionally not amenable to scalable and sustainable solution-processing techniques. Conversely, amorphous metal oxides are much more readily prepared by lowtemperature solution processing methods but often lack the charge transport properties of crystalline semiconductors. Herein we report the fabrication of amorphous a-CuOx thin films from commercially available starting material using a simple UV-based thin-film deposition method. Subsequent thermal annealing of the a-CuOx induces an amorphous-to-amorphous phase transition resulting in p-type semiconducting behavior. The resulting thin films were used as HTLs in organic photovoltaic devices with power conversion efficiencies comparable to those fabricated with PEDOT:PSS.
Design, Synthesis and Biological Activity of 16,17-Dihydroheronamide C and ent-Heronamide C
Authors: Kanoh Naoki , Terashima Ryusei , Nishiyama Hiromichi , Terajima Yuta , Nagasawa Shota , Sasano Yusuke , Iwabuchi Yoshiharu , Saito Hiroaki , Egoshi Syusuke , Dodo Kosuke , Sodeoka Mikiko , Pan Chengqian , Ikeuchi Yoshinobu , Nishimura Shinichi , Kakeya Hideaki
Published: February 2022

16,17-Dihydroheronamide C (8) and ent-heronamide C (ent-1) were designed as probes for the mode-of-action analysis of heronamide C (1). These molecules were synthesized by utilizing a highly modular strategy developed in the preceding paper. Evaluation of the antifungal activity of these compounds revealed the exceptional importance of the C16-C17 double bond for the biological activity of heronamide C, and the existence of chiral recognition between heronamide C (1) and cell membrane components.
Self-assembled Structures Formed by Fmoc modified aliphatic amino acids
Authors: Gour Nidhi , Koshti Bharti , Naskar Soumick , Kshtriya Vivekshinh , Narode Hanuman
Published: February 2022

We report the self-assembled structures formed by Fmoc modified aliphatic uncharged single amino acids. The self-assembling properties of (((9H-fluoren-9-yl)methoxy)carbonyl)-L-alanine (Fmoc-Ala-OH), (((9H-fluoren-9-yl)methoxy)carbonyl)-L-leucine (Fmoc-Leu-OH), (((9H-fluoren-9-yl)methoxy)carbonyl)-L-isoleucine (Fmoc-Ile-OH), and (((9H-fluoren-9-yl)methoxy)carbonyl)-L-valine (Fmoc-Val-OH) were studied under varying conditions such as concentration and temperature. Fmoc-Ala-OH shows flower-like self-assembled structure at both low and high concentration under room temperature as well as on heating at 70ºC. We also studied self-assembly of the modified branched chain amino acids (BCAA) i.e. Fmoc-Leu-OH, Fmoc-Ile-OH, and Fmoc-Val-OH. Fmoc-Leu-OH forms flower-like morphology at both low and high concentration under room temperature which changes to small tube-like structure on heating. Fmoc-Ile-OH on the other hand shows fibres-like self-assembly at lower and higher concentration at room temperature. While, on heating at lower concentration they formed a tube like self-assembled structure and at higher concentration they formed a fibres-like morphology. In the case of Fmoc-Val-OH they form a flower-like morphology at lower concentration at room temperature and at higher concentration they formed fibres-like assembly at room temperature. On the other hand, on heating Fmoc-Val-OH shows a fibres-like assembly at lower and higher concentration. Once the self-assembled structure of all Fmoc single amino acid characterized through the optical microscopy then our future aims to characterized those self-assembled structure through sophisticated microscopy and spectroscopy techniques and understand the mechanisms of self-assembled structure. Hence, the modified amino acids may pave the way for the design of novel self-assembled architectures which can be controllable manipulated to impart desired function..
Effect of Mono-Vacant Defects on the Adsorption Properties of Deep Eutectic Solvents onto Hexagonal Boron-Nitride Nanoflakes
Authors: Shakourian-Fard Mehdi , Taimoory S. Maryamdokht , Ghenaatian Hamid Reza , Kamath Ganesh , Trant John
Published: February 2022

Hexagonal boron nitride is a promising material for a variety of electronic, optical, and material science applications. Both the synthesis of the material through exfoliation, and its various applications almost inevitably require its solvation. Deep eutectic solvents (DES) are extremely useful solvents for these types of applications due to their non-volatility, inflammability, biocompatibility, and reasonable cost. There are many different deep eutectic solvents available, and their suitability for any given application is particularly dependent on the specific of their structure. DES have been examined computationally for use with boron nitride, but these calculations use idealized, perfect boron nitride sheets instead of the more realistic, defect-containing systems. In this report, we investigated four DESs with two experimentally observed defective boron nitride, one with a single boron vacancy, the other with a single nitrogen vacancy. All DESs bound with higher affinity to the defective boron nitride than to the pristine surface. Charge transfer was minimal in all cases although the surfaces tended to donate electron density to the solvents. The interactions between the solvents and the surfaces are primarily non-covalent although in several cases natural bond order analysis indicates a partial covalent interaction that helps explain the higher-than-expected affinity for particular DES. The DESs have little effect on the predicted optical behaviour of the pristine boron nitride but do significantly change the adsorption spectrum of the defective boron nitride nanoflakes; the effect on bulk material might be limited. Together these results suggest that the choice of DES can either be made to limit any effect on the properties of the material (urea-choline chloride) or to affect the optical and electronic nature of the material (benzoic acid-choline chloride).
Investigating oxidative stability of lithium-ion battery electrolytes using synthetic charge-discharge profile voltammetry
Authors: Mathew Alma , Lacey Matthew , Brandell Daniel
Published: February 2022

Among the many properties which determine the applicability of a Li-ion battery electrolyte, electrochemical stability is a key parameter to consider. The conventional linear sweep voltammetry (LSV) technique often leads to an over-estimation of oxidative stability. In this study, an alternative approach termed Synthetic Charge-discharge Profile Voltammetry (SCPV) is explored to investigate oxidative electrolyte stability. We have found this to be a convenient method of quantifying the anodic stability of the electrolyte in a more practically representative manner, in which passivation kinetics and electrode potential changes at the electrode-electrolyte interface are more appropriately reproduced. The viability of this technique is explored with liquid electrolytes based on ether, carbonate, sulfone, and carbonate-sulfone mixtures, all with LiPF6 salt, tested for a potential profile equivalent to LiNi0.5Mn1.5O4 electrodes. The credibility of this technique is validated by correlations to the coulombic efficiencies of corresponding half-cells.
Comprehensive chemical description of pyrolysis chars from low-density polyethylene (LDPE) by thermal analysis hyphenated to different mass spectrometric approaches
Authors: Friederici Lukas , Schneider Eric , Burnens Gaëtan , Streibel Thorsten , Giusti Pierre , Rüger Christopher Paul , Zimmermann Ralf
Published: February 2022

The production and demand of plastics has drastically increased, with severe environmental impact. Waste incineration is not favored, and efficient recycling strategies are needed. Pyrolysis is a promising approaches but the nature of the residual coke is not fully understood. To explore the value of this feedstock, thermal analysis with mass spectrometric detection is deployed. With soft photoionization, we were able to identify alkenes, dienes, and polycyclic aromatic hydrocarbons, which were emitted at four distinct mass loss events. Resonance-enhanced multiphoton ionization allows selectively addressing the aromatic constituents. Interestingly, we found an enrichment of UV-stabilizers, such as benzophenone, within the macromolecular nature. High-resolution mass spectrometry addressing the isobaric complexity and pyrolysis gas chromatography was used for structural elucidation. We hypothesize island- and archipelago-type structural motives comparable to asphaltenes but with almost no heteroatoms. The in-depth chemical description of plastic pyrolysis coke will be valuable knowledge in reactor design and material science.
Metal-Free Z-Selective Allylic C-H Nitrogenation, Oxygenation, and Carbonation of Alkenes by Thianthrenation
Authors: Shu Wei , Liu Ming-Shang , Du Hai-Wu
Published: February 2022

Selective functionalization of allylic C-H bonds into other chemical bonds with Z-selectivity are among the most straightforward and attractive, yet challenging transformations. Herein, a transition-metal-free protocol for direct allylic C-H nitrogenation, oxygenation, and carbonation of alkenes by thianthrenation was developed. This operationally simple protocol allows for the unified allylic C-H amination, esterification, etherification, and arylation of vinyl thiathrenium salts. Notably, the reaction preferably provides multialkyl substituted allylic amines, esters, and ethers with Z-selectivity. The reaction proceeds under mild conditions with excellent functional group tolerance and could be applied to late-stage allylation of natural products, drug molecules and peptides with excellent chemoselectivity.
Impact of deamidation on the structure and function of anti-apoptotic Bcl-xL.
Authors: Tanriver Gamze , Monard Gerald , Catak Saron
Published: February 2022

Bcl-xL is an anti-apoptotic mitochondrial trans-membrane protein, known to play a crucial role in the survival of tumor cells. The deamidation of Bcl-xL is a pivotal switch that regulates its biological function. The potential impact of deamidation on the structure and dynamics of Bcl-xL is directly linked to the intrinsically disordered region (IDR), which is the main site for post-translational modifications (PTMs). In this study, we explored deamidation-induced conformational changes in Bcl- xL to gain insight into its loss of function by performing microsecond-long molecular dynamics (MD) simulations. MD simulation outcomes showed that the IDR motion and interaction patterns have changed notably upon deamidation. Principal component analysis (PCA) demonstrates significant differences between wild type and deamidated Bcl-xL and suggests that deamidation affects the structure and dynamics of Bcl-xL. Differences in contact patterns and essential dynamics in the binding groove (BG) are clear indications of deamidation-induced allosteric affects.
Don’t help them to bury the light. The interplay between intersystem crossing and hydrogen transfer in photoexcited curcumin revealed by state-hopping dynamics.
Authors: Losantos Raul , Pasc Andreea , Monari Antonio
Published: February 2022

Curcumin is a natural compound extracted from turmeric (curcuma longa), which has shown remarkable antiinflammatory, antibacterial, and possibly anticancert properties. The intense absorption in the visible domain, and the possibility of intersystem crossing make curcumin attractive also for photodynamic therapy purposes. In the present contribution we unravel, thanks to non-adiabatic state hopping dynamics, the competition between intersystem crossing and hydrogen transfer within enol, the most stable tautomer of curcumin. Most notably, we show that while hydrogen-transfer is ultrafast and happens in the sub-ps regime, intersystem crossing is still present, as shown by the non-negligible population of the triplet state manifold after 2 ps. Hence, while the hydrogen transfer channel can act as an unfavorable deactivating channel, curcumin, also in the red-shifted absorption enol form, can still be regarded as potentially favorable for photodynamic therapy applications.
Selective solvent conditions influence sequence development and supramolecular assembly in step-growth copolymerization
Authors: Hamblin Ryan , Nguyen Nhu , DuBay Kateri
Published: February 2022

Sequence control in synthetic copolymers remains a tantalizing objective in polymer science due to the influence of sequence on material properties and self-organization. A greater understanding of sequence development throughout the polymerization process will aid the design of simple, generalizable methods to control sequence and tune supramolecular assembly. In previous simulations of solution-based step-growth copolymerizations, we have shown that weak, non-bonding attractions between monomers of the same type can produce a microphase separation among the lengthening nascent oligomers and thereby alter sequence. This work explores the phenomenon further, examining how effective attractive interactions, mediated by a solvent selective for one of the reacting species, impact the development of sequence and the supramolecular assembly in a simple A-B copolymerization. We find that as the effective attractions between monomers increase, an emergent self-organization of the reactants causes a shift in reaction kinetics and sequence development. When the solvent-mediated interactions are selective enough, the simple mixture of A and B monomers oligomerize and self-assemble into structures characteristic of amphiphilic copolymers. The composition and morphology of these structures and the sequences of their chains are sensitive to the relative balance of affinities between the comonomer species. Our results demonstrate the impact of differing A-B monomer-solvent affinities on sequence development in solution-based copolymerizations and are of consequence to the informed design of synthetic methods for sequence controlled amphiphilic copolymers and their aggregates.
A new twist in eutectic composition: deracemization of a racemic compound amino acid by Viedma ripening and temperature fluctuation.
Authors: VIEDMA CRISTOBAL , Ortíz José Eugenio
Published: February 2022

Viedma ripening and Temperature fluctuation are process based on solution phase racemization and dissolution-growth of racemic or scalemic conglomerates resulting in solid-phase deracemization. The dissolution-growth process is performed by abrasive grinding in the first case and by the temperature fluctuation in the second. But both methods have the intrinsic drawback of being only applicable to conglomerates, accounting for only 10% of all chiral molecules and are not suitable for the 90% of chiral compounds that crystallize as racemic compound. Herein we show that the enantiomeric excess in the eutectic point formed by a racemic compound and one of its enantiomers in suspension changes dramatically by continuous nucleation-growth-dissolution of the crystals, converting the racemic compound into the desire enantiomer. With this new finding the scope of Viedma ripening and temperature fluctuation could be significantly expanded and can shed new ideas about the origin of biological homochirality on earth.
A thermalized electrokinetics model including stochastic reactions suitable for multiscale simulations of reaction-advection-diffusion systems
Authors: Tischler Ingo , Weik Florian , Kaufmann Robert , Kuron Michael , Weeber Rudolf , Holm Christian
Published: February 2022

We introduce a scheme to simulate the spatial and temporal evolution of the densities of charged species, taking into account diffusion, thermal fluctuations, coupling to a carrier fluid, and chemical reactions. To this end, the diffusive fluxes in the electrokinetic model by Capuani et al. [1] are supplemented with thermal fluctuations. Chemical reactions are included via an additional source term in the mass balance equation. The diffusion-reaction model is then coupled to a solver for fluctuating hydrodynamics based on the lattice Boltzmann method. We describe our implementations, one based on the automatic code generation tools using pystencils and lbmpy, and another one contained as in the molecular dynamics package ESPResSo which allows the coupling of particles to the density fields. We validate our implementations by demonstrating that the expected influence of density fluctuations on the reaction rate for chemical reactions of order > 1 is reproduced. Our novel algorithm will be applicable to coarse-grained catalysis problems as well as to many other multi-scale problems that require the coupling of explicit-particle simulations with flow fields, diffusion, and reaction problems in arbitrary geometries.
A thermalized electrokinetics model including stochastic reactions suitable for multiscale simulations of reaction-advection-diffusion systems
Authors: Tischler Ingo , Weik Florian , Kaufmann Robert , Kuron Michael , Weeber Rudolf , Holm Christian
Published: February 2022

We introduce a scheme to simulate the spatial and temporal evolution of the densities of charged species, taking into account diffusion, thermal fluctuations, coupling to a carrier fluid, and chemical reactions. To this end, the diffusive fluxes in the electrokinetic model by Capuani et al. [1] are supplemented with thermal fluctuations. Chemical reactions are included via an additional source term in the mass balance equation. The diffusion-reaction model is then coupled to a solver for fluctuating hydrodynamics based on the lattice Boltzmann method. This combination is particularly useful for soft matter simulations, due to the ability to couple particles to the lattice-Boltzmann fluid. These could, e.g., be charged colloids or polymers, which then interact with an ion distribution. We describe one implementations based on the automatic code generation tools pystencils and lbmpy, and another one that is contained in the molecular dynamics package ESPResSo and that allows for an easy coupling of particles to the density fields. We validate our implementations by comparing to several known analytic results. Our method can be applied to coarse-grained catalysis problems as well as to many other multi-scale problems that require the coupling of explicit-particle simulations to flow fields, diffusion, and reaction problems in arbitrary geometries.