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Masahito Murai, Ryuji Taniguchi, Naoki Hosokawa, Yusuke Nishida, Hiroko Mimachi, Toshiyuki Oshiki, Kazuhiko Takai
Stabilization by a silyl group on the methylene carbon and a diamine ligand let to the isolation of gemdichromiomethane species. X-ray crystallography confirmed the identity of the structure of this rare example of reactive gemdimetalloalkane species. The isolated gem-dichromiomethane complex acted as a storable silylmethylidene carbene equivalent, with reactivity that could be changed dramatically upon addition of a Lewis acid (ZnCl2) and a base (TMEDA) to promote both silylalkylidenation of polar aldehydes and silylcyclopropanation of non-polar alkenes...
August 16, 2017: Journal of the American Chemical Society
Ling Liu, Xiuhui Zhang, Zesheng Li, Yunhong Zhang, Maofa Ge
Oxocarboxylic acids are one of the most important organic species found in secondary organic aerosols and can be detected in diverse environments. But the hydration of oxocarboxylic acids in the atmosphere has still not been fully understood. Neglecting the hydration of oxocarboxylic acids in atmospheric models may be one of the most important reasons for the significant discrepancies between field measurements and abundance predictions of atmospheric models for oxocarboxylic acids. In the present paper, glyoxylic acid, as the most abundant oxocarboxylic acids in the atmosphere, has been selected as an example to study whether the hydration process can occur in the atmosphere and what the kinetic process of hydration is...
August 6, 2017: Chemosphere
Anthony Pujol, Mathieu Lafage, Feriel Rekhroukh, Nathalie Saffon-Merceron, Abderrahmane Amgoune, Didier Bourissou, Noel Nebra, Marie Fustier-Boutignon, Nicolas Mézailles
The first gold(III) carbene complex was prepared by reacting a geminal dianion with a (P,C) cyclometallated gold(III) precursor. Its structure and bonding situation have been thoroughly investigated by experimental and computational means. The presence of a high-energy HOMO centered at the carbene center suggests nucleophilic character for the gold(III) carbene complex. This unprecedented feature was confirmed by reactions with two electrophiles (PhNCS and CS2) resulting in two types of C=C coupling.
August 7, 2017: Angewandte Chemie
Elisa Collado-Fregoso, Samantha N Hood, Safa Shoaee, Bob C Schroeder, Iain McCulloch, Ivan Kassal, Dieter Neher, James R Durrant
In this Letter, we study the role of the donor:acceptor interface nanostructure upon charge separation and recombination in organic photovoltaic devices and blend films, using mixtures of PBTTT and two different fullerene derivatives (PC70BM and ICTA) as models for intercalated and nonintercalated morphologies, respectively. Thermodynamic simulations show that while the completely intercalated system exhibits a large free-energy barrier for charge separation, this barrier is significantly lower in the nonintercalated system and almost vanishes when energetic disorder is included in the model...
August 16, 2017: Journal of Physical Chemistry Letters
Kishor S Gavale, Shrawan R Chavan, Navanath Kumbhar, Sonali Kawade, Pooja Doshi, Ayesha Khan, Dilip D Dhavale
A simple strategy for the synthesis of α-geminal disubstituted pyrrolidine iminosugars 3a-c and their C-4 fluorinated derivatives 4a-c has been described from d-glucose. The methodology involves the Corey-Link and Jocic-Reeve reaction with 3-oxo-α-d-glucofuranose and nucleophilic displacement reaction to get the furanose fused pyrrolidine ring skeleton with requisite CH2OH/CO2H functionalities at C-3. The fluorine substituent in target molecules was introduced by nucleophilic displacement of -OTf in 9a/9c with CsF...
July 14, 2017: Bioorganic & Medicinal Chemistry
Rocco Romagnuolo, Corey A Scipione, Santica M Marcovina, Matthew Gemin, Nabil G Seidah, Michael B Boffa, Marlys L Koschinsky
Elevated plasma concentrations of lipoprotein(a) (Lp(a)) are a causal risk factor for cardiovascular disease. The mechanisms underlying Lp(a) clearance from plasma remain unclear, which is an obvious barrier to the development of therapies to specifically lower levels of this lipoprotein. Recently, it has been documented that monoclonal antibody inhibitors of proprotein convertase subtilisin/kexin type 9 (PCSK9) can lower plasma Lp(a) levels by 30%. Since PCSK9 acts primarily through the low density lipoprotein receptor (LDLR), this result is in conflict with the prevailing view that the LDLR does not participate in Lp(a) clearance...
2017: PloS One
Tim Albes, Alessio Gagliardi
In bulk-heterojunction organic solar cells the low permittivity in combination with the spatial and energetic disorder of the organic materials lead to a complex behavior of charge carriers within the active layer. Charges originate from exciton splitting at the heterojunction interface and the successive interplay between mutual Coulomb interactions and transport through the disordered organic can lead to insufficient separation from the interface, increased interface densities with respect to the bulk regions and, hence, affect recombination...
August 9, 2017: Physical Chemistry Chemical Physics: PCCP
Uyen N V Huynh, Tek P Basel, Eitan Ehrenfreund, Gang Li, Yang Yang, S Mazumdar, Z Valy Vardeny
We have utilized a plethora of transient and steady state optical and magneto-optical spectroscopies in a broad spectral range (0.25-2.5 eV) for elucidating the primary and long-lived photoexcitations in a low band-gap π-conjugated donor-acceptor (DA) copolymer used for efficient photovoltaic solar cells. We show that both singlet excitons (SE) and intrachain triplet-triplet (TT) pairs are photogenerated in the DA-copolymer chains. From the picosecond transient magnetic field response of these species we conclude that the SE and TT spin states are coupled...
July 7, 2017: Physical Review Letters
Robert J Dillon, Leila Alibabaei, Thomas J Meyer, John M Papanikolas
The hole-injection and recombination photophysics for NiO sensitized with RuP ([Ru(II)(bpy)2(4,4'-(PO3H2)2-bpy)](2+)) are explored. Ultrafast transient absorption (TA) measurements performed with an external electrochemical bias reveal the efficiency for productive hole-injection, that is, quenching of the dye excited state that results in a detectable charge-separated electron-hole pair, is linearly dependent on the electronic occupation of intragap states in the NiO film. Population of these states via a negative applied potential increases the efficiency from 0% to 100%...
August 16, 2017: ACS Applied Materials & Interfaces
Kristina Holzschneider, Andreas P Häring, Alexander Haack, Daniel J Corey, Thorsten Benter, Stefan F Kirsch
The degradation of geminal diazides is described. We show that diazido acetates are converted into tetrazoles through the treatment with bases. The reaction of dichloro ketones with azide anions provides acyl azides, through in situ formation of diazido ketones. We present experimental and theoretical evidence that both fragmentations may involve the generation of acyl cyanide intermediates. The controlled degradation of terminal alkynes into amides (by loss of one carbon) or ureas (by loss of two carbons) is also shown...
July 19, 2017: Journal of Organic Chemistry
Song-Lin Zhang, Hai-Xing Wan, Zhu-Qin Deng
This paper reports a computational study elucidating the reaction mechanism for ynamide-mediated amide bond formation from carboxylic acids and amines. The mechanisms have been studied in detail for ynamide hydrocarboxylation and the subsequent aminolysis of the resulting adduct by an amine. Ynamide hydrocarboxylation is kinetically favorable and thermodynamically irreversible, resulting in the formation of a key low-lying intermediate CP1 featuring geminal vinylic acyloxy and sulfonamide groups. The aminolysis of CP1 by the amine is proposed to be catalyzed by the carboxylic acid itself that imparts favourable bifunctional effects...
August 2, 2017: Organic & Biomolecular Chemistry
A Ehsani, E Kowsari, F Boorboor Ajdari, R Safari, H Mohammad Shiri
In present work, for improving the electrochemical performance of conductive polymer, POAP/3-methyl-1-[2-(2-{2-[2-[(3-methyl-1-H-imidazol-3-ium-1-yl)ethoxy]ethoxy}-ethoxy)ethyl]-1-H-imidazol-3-ium dichloride (MIEID) composite films have been fabricated by poly ortho aminophenol (POAP) electropolymerization in the presence of MIEID as active electrodes for electrochemical supercapacitors. Different electrochemical methods including galvanostatic charge discharge experiments, cyclic voltammetry and electrochemical impedance spectroscopy have been applied to study the system performance...
July 3, 2017: Journal of Colloid and Interface Science
Denis V Sosnovsky, Olga B Morozova, Alexandra V Yurkovskaya, Konstantin L Ivanov
A theoretical approach to time-resolved Chemically Induced Dynamic Nuclear Polarization (CIDNP) is proposed, which allows one to obtain the general relation between polarization formed upon recombination of geminate spin-correlated radical pairs, the so-called G-pairs, and upon recombination of radical pairs formed by encounters of free radicals in solution, the so-called F-pairs. This relation is described by a universal parameter denoted as γ. In this work, the γ value is computed for the arbitrary spin multiplicity, singlet or triplet, of the precursor of the G-pairs as well as for arbitrary recombination rate constants of radical pairs in singlet and triplet states, kS and kT, respectively...
July 14, 2017: Journal of Chemical Physics
Giuseppe M J Barca, Pierre-François Loos
We report the three main ingredients to calculate three- and four-electron integrals over Gaussian basis functions involving Gaussian geminal operators: fundamental integrals, upper bounds, and recurrence relations. In particular, we consider the three- and four-electron integrals that may arise in explicitly correlated F12 methods. A straightforward method to obtain the fundamental integrals is given. We derive vertical, transfer, and horizontal recurrence relations to build up angular momentum over the centers...
July 14, 2017: Journal of Chemical Physics
Merve S Özer, Anup Rana, Pronay K Biswas, Michael Schmittel
An off-axis supramolecular rotor was composed of four components: a zinc-porphyrin based stator with four phenanthroline stations and a zinc-salphen based rotator were self-assembled with DABCO and four copper(i) ions to furnish the rotor ROT-2 in quantitative yield. The DABCO serves as a connecting axle between the rotator and the stator, while the rotator is additionally connected to two copper(i)-loaded phenanthroline stations of the stator via its two pyridine terminals (Npy → [Cu(phen)](+)). For the thermally activated rotation both Npy → [Cu(phen)](+) interactions have to be cleaved...
July 25, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
Helen O Leung, Mark D Marshall, Nazir D Khan
The structure of the gas-phase heterodimer formed between (Z)-1-chloro-2-fluoroethylene and acetylene is determined via Fourier transform microwave spectroscopy from 5.5 to 20.8 GHz. In the first instance where in the presence of both a fluorine atom and a chlorine atom on the haloethylene the protic acid binds to the chlorine atom, the acetylene adopts a configuration similar to that in the analogous complex with vinyl chloride. Positioned in a manner to interact favorably with both the chlorine atom and the hydrogen atom geminal to it, the acetylene molecule is able to maximize the overall electrostatic stabilization even though other regions of the haloethylene offer individual sites of greater positive or negative electrostatic potential...
July 21, 2017: Journal of Physical Chemistry. A
Núria Marcó, Pau Nolis, Roberto R Gil, Teodor Parella
The measurement of two-bond proton-proton coupling constants ((2)JHH) in prochiral CH2 groups from the F2 dimension of 2D spectra is not easy due to the usual presence of complex multiplet J patterns, line broadening effects and strong coupling artifacts. These drawbacks are particularly pronounced and frequent in AB spin systems, as those normally exhibited by the pair of diastereotopic CH2 protons. Here, a novel (2)JHH-resolved HSQC experiment for the exclusive and accurate determination of the magnitude of (2)JHH from the doublet displayed along the highly-resolved indirect F1 dimension is described...
June 23, 2017: Journal of Magnetic Resonance
Hui Mao, Bing-Xin You, Lie-Jin Zhou, Ting-Ting Xie, Yi-Hang Wen, Xin Lv, Xiao-Xia Wang
SmI2-mediated reductive cyclization of β-arylthio ketones to generate thiochroman derivatives is not a generally observed process and the reported examples are limited to geminal disubstitution in the substrates. The results of the current study show that the cyclization also occurs when other substitution patterns are present, affording a general approach to dihydrothiochroman-ols in good yields and high degrees of diastereoselectivity. Besides, the halogen substitution on β-aryl is tolerated in most cases here although reductive dehalogenation has been reported to predominate in the reductive cyclization process...
July 7, 2017: Organic & Biomolecular Chemistry
Arian Berger, Janne Savolainen, Andrey Shalit, Peter Hamm
In the work of Savolainen et al. [Nat. Chem. 6, 697 (2014)], we studied the excess (hydrated) electron in water with the help of transient THz spectroscopy, which is a sensitive probe of its delocalization length. In that work, we used laser pulses at 800 nm, 400 nm, and 267 nm for photoionization. While the detachment mechanism for 400 nm and 267 nm is complicated and requires a concerted nuclear rearrangement, we provided evidence that 800 nm pumping excites the excess electron directly and vertically into the conduction band, despite a highly nonlinear field-ionization process...
June 28, 2017: Journal of Chemical Physics
Hyojung Cha, Jiaying Wu, Andrew Wadsworth, Jade Nagitta, Saurav Limbu, Sebastian Pont, Zhe Li, Justin Searle, Mark F Wyatt, Derya Baran, Ji-Seon Kim, Iain McCulloch, James R Durrant
A comparison of the efficiency, stability, and photophysics of organic solar cells employing poly[(5,6-difluoro-2,1,3-benzothiadiazol-4,7-diyl)-alt-(3,3'″-di(2-octyldodecyl)-2,2';5',2″;5″,2'″-quaterthiophen-5,5'″-diyl)] (PffBT4T-2OD) as a donor polymer blended with either the nonfullerene acceptor EH-IDTBR or the fullerene derivative, [6,6]-phenyl C71 butyric acid methyl ester (PC71 BM) as electron acceptors is reported. Inverted PffBT4T-2OD:EH-IDTBR blend solar cell fabricated without any processing additive achieves power conversion efficiencies (PCEs) of 9...
June 28, 2017: Advanced Materials
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