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Caitlin Lanssens, Paul W Ayers, Dimitri Van Neck, Stijn De Baerdemacker, Klaas Gunst, Patrick Bultinck
In methods like geminal-based approaches or coupled cluster that are solved using the projected Schrödinger equation, direct computation of the 2-electron reduced density matrix (2-RDM) is impractical and one falls back to a 2-RDM based on response theory. However, the 2-RDMs from response theory are not N-representable. That is, the response 2-RDM does not correspond to an actual physical N-electron wave function. We present a new algorithm for making these non-N-representable 2-RDMs approximately N-representable, i...
February 28, 2018: Journal of Chemical Physics
Hanako Shimura, Chikara Masuta, Yasunori Koda
In nature, mycorrhizal association with soilborne fungi is indispensable for orchid families. Fungal structures from compatible endo-mycorrhizal fungi in orchid cells are digested in cells to be supplied to orchids as nutrition. Because orchid seeds lack the reserves for germination, they keep receiving nutrition through mycorrhizal formation from seed germination until shoots develop (leaves) and become photoautotrophic. Seeds of all orchid species surely geminate with the help of their own fungal partners, and this specific partnership has been acquired for a long evolutional history between orchids and fungi...
2018: Methods in Molecular Biology
Madhuram Krishnamurthy, V Naveen Kumar, Ashok Leburu, Nadeem Jeddy
Fusion and gemination are developmental anomalies which are quite similar to each other but can be distinguished from each other if properly assessed. Fusion and gemination have been described as a result of developmental anomalies of dental tissues. The exact etiology is still unknown, but a genetic predisposition is suggested. This article highlights the importance of clinical and radiographic correlation in arriving at a definitive diagnosis.
January 2018: Journal of Oral and Maxillofacial Pathology: JOMFP
Johannes Wiest, Michael Conner, Michael Kevin Brown
The first synthesis of hebelophyllene E is presented, along with assignment of its previously unknown relative configuration through synthesis of epi-ent-hebelophyllene E. Development of a catalytic enantioselective [2+2] cycloaddition of alkenes and allenoates provides access to the required chiral geminal dimethylcyclobutanes. Key to its success is the identification of a novel oxazaborolidine catalyst, which promotes the cycloaddition in high enantioselectivities with good functional group tolerance (9 examples, up to 97:3 er)...
February 26, 2018: Angewandte Chemie
Dan Zhu, Yuan Yao, Rong Zhao, Yang Liu, Lei Shi
An unprecedented three-component domino oxidative coupling of diazocompounds for the efficient synthesis of α-azido-β-amino esters with non-activated dimethylamino compounds and simple TMSN3 was achieved. The highlighted features of this method are in terms of metal-free catalysis, satisfactory functional group tolerance, general applicability in complex molecule architectures, and excellent diastereoselectivity in the presence of chiral auxiliaries. Besides, several related control experiments have been conducted reasonably to investigate the reaction mechanism...
February 26, 2018: Chemistry: a European Journal
Andreas Zech, Thorsten Bach
The arene ring of the title compounds is cleaved by a reaction cascade which is initiated by an intramolecular ortho photocycloaddition reaction. Tricyclic products were obtained in a highly regio- and diastereoselective fashion via a cyclooctatriene intermediate. The facial diastereoselectivity exerted by a stereogenic center in the tether is moderate to good (d.r. = 65/35 to 82/18). Yields were acceptable (44-87%) except for a single substrate which had a geminal dimethyl substitution in the tether and which gave the respective product in only 14% yield...
February 24, 2018: Journal of Organic Chemistry
Zhuyu Sun, Chaojie Zhang, Lu Xing, Qi Zhou, Wenbo Dong, Michael R Hoffmann
Perfluorooctane sulfonate (PFOS) is a toxic, bioaccumulative and highly persistent anthropogenic chemical. Hydrated electrons (eaq-) are potent nucleophiles that can effectively decompose PFOS. In previous studies, eaq- are mainly produced by photoionization of aqueous anions or aromatic compounds. In this study, we proposed a new photolytic strategy to generate eaq- and in turn decompose PFOS, which utilizes nitrilotriacetic acid (NTA) as a photosensitizer to induce water photodissociation and photoionization, and subsequently as a scavenger of hydroxyl radical (∙OH) to minimize the geminate recombination between ∙OH and eaq-...
February 3, 2018: Environmental Science & Technology
Carmelo E Iacono, Thomas C Stephens, Teena S Rajan, Graham Pattison
Regioselective α,α-difunctionalization adjacent to a ketone is a significant synthetic challenge. Here we present a solution to this problem through the transition-metal-free coupling of esters with geminal bis(boron) compounds. This forms a α,α-bis(enolate) equivalent which can be trapped with electrophiles including alkyl halides and fluorinating agents. This presents an efficient, convergent synthetic strategy for the synthesis of unsymmetrical blocked ketones.
January 30, 2018: Journal of the American Chemical Society
Jiangbin Zhang, Qinying Gu, Thu Trang Do, Kira Rundel, Prashant Sonar, Richard H Friend, Christopher R McNeill, Artem A Bakulin
Herein, we report on the charge dynamics of photovoltaic devices based on two novel small-molecule nonfullerene acceptors featuring a central ketone unit. Using ultrafast near-infrared spectroscopy with optical and photocurrent detection methods, we identify one of the key loss channels in the devices as geminate recombination (GR) of interfacial charge transfer states (CTSs). We find that the magnitude of GR is highly sensitive to the choice of solvent and annealing conditions. Interestingly, regardless of these processing conditions, the same lifetime for GR (∼130 ps) is obtained by both detection methods upon decomposing the complex broadband transient optical spectra, suggesting this time scale is inherent and independent of morphology...
January 29, 2018: Journal of Physical Chemistry. A
Ching-Hong Tan, Jeffrey Gorman, Andrew Wadsworth, Sarah Holliday, Selvam Subramaniyan, Samson A Jenekhe, Derya Baran, Iain McCulloch, James R Durrant
We report the synthesis of two barbiturate end-capped non-fullerene acceptors and demonstrate their efficient function in high voltage output organic solar cells. The acceptor with the lower LUMO level is shown to exhibit suppressed geminate recombination losses, resulting in enhanced photocurrent generation and higher overall device efficiency.
January 26, 2018: Chemical Communications: Chem Comm
Ingo D Meier, Michael P Walker, A Gregory Matera
Gemin4 is a member of the Survival Motor Neuron (SMN) protein complex, which is responsible for the assembly and maturation of Sm-class small nuclear ribonucleoproteins (snRNPs). In metazoa, Sm snRNPs are assembled in the cytoplasm and subsequently imported into the nucleus. We previously showed that the SMN complex is required for snRNP import in vitro, although it remains unclear which specific components direct this process. Here, we report that Gemin4 overexpression drives SMN and the other Gemin proteins from the cytoplasm into the nucleus...
January 25, 2018: Biology Open
Viivi Hirvonen, Nanna Myllys, Theo Kurtén, Jonas Elm
The role of covalently-bound dimer formation is studied using high-level quantum chemical methods. Reaction free energy profiles for dimer formation between common oxygen-containing functional groups are calculated, and based on the Gibbs free energy differences between transition states and reactants, we show that none of the studied two-component gas-phase reactions are kinetically feasible at 298.15 K and 1 atm. Therefore, the catalysing effect of water, base, or acid molecules is calculated, and sulfuric acid is identified to lower the activation free energies significantly...
January 24, 2018: Journal of Physical Chemistry. A
Hung-Cheng Chen, Andrew R Cook, Sadayuki Asaoka, Jeffery S Boschen, Theresa L Windus, John R Miller
Correction for 'Escape of anions from geminate recombination in THF due to charge delocalization' by Hung-Cheng Chen et al., Phys. Chem. Chem. Phys., 2017, 19, 32272-32285.
January 23, 2018: Physical Chemistry Chemical Physics: PCCP
Yu Gao, Jingjing Liu, Zhenjiang Li, Tianfo Guo, Songquan Xu, Hui Zhu, Fulan Wei, Siming Chen, Hailemariam Gebru, Kai Guo
A novel protocol for the activation of Beckmann rearrangement utilizing the readily available and economical geminal dichloroimidazolidinediones (DCIDs) on a substoichiometric scale (10 mol%) has been developed. A unique self-propagating mechanism for substoichiometric dichloroimidazolidinedione-activated transformation was proposed and validated. The substrate scope of the developed protocol has been demonstrated by 23 examples with good to excellent yields (mostly 90-98%) in a short time (mostly 10-30 min), including a substrate for synthesizing monomer of nylon-12 and a complicated steroidal substrate on a preparative scale...
January 19, 2018: Journal of Organic Chemistry
Andrey Yu Sosorev, Dmitry Yu Godovsky, Dmitry Yu Paraschuk
The modeling of organic solar cells (OSCs) can provide a roadmap for their further improvement. Many OSC models have been proposed in recent years; however, the impact of the key intermediates from photons to electricity-hot charge-transfer (CT) states-on the OSC efficiency is highly ambiguous. In this study, we suggest an analytical kinetic model for OSC that considers a two-step charge generation via hot CT states. This hot kinetic model allowed us to evaluate the impact of different material parameters on the OSC performance: the driving force for charge separation, optical bandgap, charge mobility, geminate recombination rate, thermalization rate, average electron-hole separation distance in the CT state, dielectric permittivity, reorganization energy and charge delocalization...
January 18, 2018: Physical Chemistry Chemical Physics: PCCP
Liu Ye, Qiang-Shuai Gu, Yu Tian, Xiang Meng, Guo-Cong Chen, Xin-Yuan Liu
The development of a general catalytic method for the direct and stereoselective construction of cyclopropanes bearing highly congested vicinal all-carbon quaternary stereocenters remains a formidable challenge in chemical synthesis. Here, we report an intramolecular radical cyclopropanation of unactivated alkenes with simple α-methylene group of aldehydes as C1 source via a Cu(I)/secondary amine cooperative catalyst, which enables the single-step construction of bicyclo[3.1.0]hexane skeletons with excellent efficiency, broad substrate scope covering various terminal, internal alkenes as well as diverse (hetero)aromatic, alkenyl, alkyl-substituted geminal alkenes...
January 15, 2018: Nature Communications
Thomas Sandberg, Christian Weinberger, Didem Şen Karaman, Jessica M Rosenholm
The interaction between disulfiram (Antabus®) and silica was studied experimentally by adsorption from apolar solvent onto highly porous silica material (Santa Barbara Amorphous material-3, SBA-3) with large surface area. The adsorption isotherm was fitted to the Langmuir model by accounting two different affinities contributing to the overall behavior, which were attributed to two different types of silanol groups (i.e. geminal and vicinal) present on amorphous silica surfaces. This assumption was supported by theoretical calculations...
December 28, 2017: Journal of Pharmaceutical Sciences
Sara V Tadayon, Elizabeth S Foreman, Craig Murray
Reactions of the simplest Criegee intermediate (CH2OO) with a series of alcohols have been studied in a flash photolysis flow reactor. Laser photolysis of diiodomethane at 355 nm in the presence of molecular oxygen was used to produce CH2OO, and the absolute number densities were determined as a function of delay time from analysis of broadband transient absorption spectra obtained using a pulsed LED. The kinetics for the reactions of CH2OO with methanol, ethanol, and 2-propanol were measured under pseudo-first-order conditions at 295 K, yielding rate constants of (1...
December 29, 2017: Journal of Physical Chemistry. A
Olga Dmitrieva
The present study seeks to answer the question of whether consonant duration is perceived differently across consonants of different manners of articulation and in different contextual environments and whether such differences may be related to the typology of geminates. The results of the cross-linguistic identification experiment suggest higher perceptual acuity in labeling short and long consonants in sonorants than in obstruents. Duration categories were also more consistently and clearly labeled in the intervocalic than in the preconsonantal environment, in the word-initial than in the word-final position, and after stressed vowels than between unstressed vowels...
March 1, 2017: Language and Speech
Ayelén Florencia Crespi, Agustin Jesus Byrne, Daniel Vega, Ana Karina Chattah, Gustavo Alberto Monti, Juan Manuel Lázaro-Martínez
The stability of gem-diol forms in imidazolecarboxaldehyde isomers was studied by solid-state nuclear magnetic resonance (ss-NMR) combined with single-crystal X-ray diffraction studies. These methodologies also allowed determining the factors governing the occurrence of such rare functionalization in carbonyl moieties. Results indicated that the position of the carbonyl group is the main factor that governs the generation of geminal diols, having a clear and direct effect on hydration, since, under the same experimental conditions, only 36% of 5-imidazolecarboxaldehydes and 5% of 4-imidazolecarboxaldehydes were hydrated, as compared to 2-imidazolecarboxaldehydes, with which a 100% hydration was achieved...
December 20, 2017: Journal of Physical Chemistry. A
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