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https://www.readbyqxmd.com/read/28731770/transient-magnetophotoinduced-absorption-studies-of-photoexcitations-in-%C3%AF-conjugated-donor-acceptor-copolymers
#1
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
https://www.readbyqxmd.com/read/28731676/enabling-efficient-creation-of-long-lived-charge-separation-on-dye-sensitized-nio-photocathodes
#2
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, i.e. 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%...
July 21, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28722411/pathways-in-the-degradation-of-geminal-diazides
#3
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
https://www.readbyqxmd.com/read/28717802/a-computational-study-on-the-mechanism-of-ynamide-mediated-amide-bond-formation-from-carboxylic-acids-and-amines
#4
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...
July 18, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28715859/influence-of-newly-synthesized-geminal-dicationic-ionic-liquid-on-electrochemical-and-pseudocapacitance-performance-of-conductive-polymer-electroactive-film
#5
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
https://www.readbyqxmd.com/read/28711061/relation-between-cidnp-formed-upon-geminate-and-bulk-recombination-of-radical-pairs
#6
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
https://www.readbyqxmd.com/read/28711054/three-and-four-electron-integrals-involving-gaussian-geminals-fundamental-integrals-upper-bounds-and-recurrence-relations
#7
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
https://www.readbyqxmd.com/read/28702613/four-component-zinc-porphyrin-zinc-salphen-nanorotor
#8
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 12, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/28691817/the-microwave-spectrum-and-molecular-structure-of-z-1-chloro-2-fluoroethylene-acetylene-demonstrating-the-importance-of-the-balance-between-steric-and-electrostatic-interactions-in-heterodimer-formation
#9
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
https://www.readbyqxmd.com/read/28686954/-2-jhh-resolved-hsqc-exclusive-determination-of-geminal-proton-proton-coupling-constants
#10
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
https://www.readbyqxmd.com/read/28686268/smi2-mediated-reductive-cyclization-of-%C3%AE-arylthio-ketones-a-facile-and-diastereoselective-synthesis-of-thiochroman-derivatives
#11
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
https://www.readbyqxmd.com/read/28668019/note-deep-uv-pump-thz-probe-spectroscopy-of-the-excess-electron-in-water
#12
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
https://www.readbyqxmd.com/read/28657152/an-efficient-burn-in-free-organic-solar-cell-employing-a-nonfullerene-electron-acceptor
#13
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
https://www.readbyqxmd.com/read/28655910/magnetic-field-enhancement-of-organic-photovoltaic-cells-performance
#14
S Oviedo-Casado, A Urbina, J Prior
Charge separation is a critical process for achieving high efficiencies in organic photovoltaic cells. The initial tightly bound excitonic electron-hole pair has to dissociate fast enough in order to avoid photocurrent generation and thus power conversion efficiency loss via geminate recombination. Such process takes place assisted by transitional states that lie between the initial exciton and the free charge state. Due to spin conservation rules these intermediate charge transfer states typically have singlet character...
June 27, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28642865/spinal-muscular-atrophy-from-defective-chaperoning-of-snrnp-assembly-to-neuromuscular-dysfunction
#15
REVIEW
Maia Lanfranco, Neville Vassallo, Ruben J Cauchi
Spinal Muscular Atrophy (SMA) is a neuromuscular disorder that results from decreased levels of the survival motor neuron (SMN) protein. SMN is part of a multiprotein complex that also includes Gemins 2-8 and Unrip. The SMN-Gemins complex cooperates with the protein arginine methyltransferase 5 (PRMT5) complex, whose constituents include WD45, PRMT5 and pICln. Both complexes function as molecular chaperones, interacting with and assisting in the assembly of an Sm protein core onto small nuclear RNAs (snRNAs) to generate small nuclear ribonucleoproteins (snRNPs), which are the operating components of the spliceosome...
2017: Frontiers in Molecular Biosciences
https://www.readbyqxmd.com/read/28632940/characterization-of-the-i4399m-variant-of-apolipoprotein-a-implications-for-altered-prothrombotic-properties-of-lipoprotein-a
#16
Corey A Scipione, Jackson T McAiney, Daniel J Simard, Zainab A Bazzi, Matthew Gemin, Rocco Romagnuolo, Fraser L Macrae, Robert A Ariëns, Robert A Hegele, Janeen Auld, James W Gauld, Michael B Boffa, Marlys L Koschinsky
BACKGROUND: Lipoprotein(a) (Lp(a)) is a causal risk factor for a variety of cardiovascular diseases. Apolipoprotein(a) (apo(a)), the distinguishing component of Lp(a), is homologous to plasminogen, suggesting that Lp(a) can interfere with the normal fibrinolytic functions of plasminogen. This has implications for the persistence of fibrin clots in the vasculature and hence to atherothrombotic diseases. A single nucleotide polymorphism (rs3798220) in the gene encoding apo(a) has been reported that results in an Ile to Met substitution in the protease-like domain (I4399M variant)...
June 20, 2017: Journal of Thrombosis and Haemostasis: JTH
https://www.readbyqxmd.com/read/28628737/analysis-of-structure-activity-relationships-based-on-the-hcv-sliib-ires-rna-targeting-gghyrfk-cu-complex
#17
Martin J Ross, Insiya Fidai, James Allan Cowan
New therapeutics for the targeting of the hepatitis C virus have been released in recent years. Although these therapies are less prone to resistance, they are still administered in cocktails as a combination of drugs targeting various aspects of the viral life cycle. Herein, we aim to contribute to an arsenal of new HCV therapeutics by targeting HCV internal ribosomal entry sequence (IRES) RNA via development of catalytic metallodrugs that function to degrade rather than inhibit the target molecule. Based on a previously characterized HCV IRES stem-loop IIb RNA-targeting metallopeptide Cu-GGHYrFK (1-Cu), an all L-analogue (3-Cu) and a series of additional complexes with single alanine substitutions in the targeting domain were prepared and screened to determine the influence each amino acid side-chain on RNA localization and recognition, and catalytic reactivity toward the RNA...
June 19, 2017: Chembiochem: a European Journal of Chemical Biology
https://www.readbyqxmd.com/read/28605914/transition-metal-free-homologative-cross-coupling-of-aldehydes-and-ketones-with-geminal-bis-boron-compounds
#18
Thomas C Stephens, Graham Pattison
We report a transition-metal-free coupling of aldehydes and ketones with geminal bis(boron) building blocks which provides the coupled, homologated carbonyl compound upon oxidation. This reaction not only extends an alkyl chain containing a carbonyl group, it also simultaneously introduces a new carbonyl substituent. We demonstrate that enantiopure aldehydes with an enolizable stereogenic center undergo this reaction with complete retention of stereochemistry.
June 13, 2017: Organic Letters
https://www.readbyqxmd.com/read/28598178/multidisciplinary-approach-to-the-treatment-of-double-bilateral-upper-permanent-incisors-in-a-young-boy
#19
G F Ferrazzano, P Festa, T Cantile, V D'Antò, A Ingenito, R Martina
BACKGROUND: A double tooth is a rare developmental anomaly referring to the fusion of two adjacent tooth buds or the gemination of a single bud. CASE REPORT: This case report describes the multidisciplinary approach to an 11-year-old patient with two double upper permanent incisors. The clinical intraoral examination showed a mixed dentition with bilateral double maxillary central incisors, molar Class I malocclusion and palatal ectopy of two lateral upper incisors...
June 2017: European Journal of Paediatric Dentistry: Official Journal of European Academy of Paediatric Dentistry
https://www.readbyqxmd.com/read/28585086/a-mechanistic-study-of-geminal-dicationic-ionic-liquids-as-mobile-phase-additives-for-improving-the-separation-performance-of-high-performance-liquid-chromatography
#20
Guanglong Ding, Wenbing Zhang, Zhaopeng Zhang, Dong Guo, Gang Tang, Yanran Li, Jianqiang Li, Yongsong Cao
Due to the acidity and strong polarity of auxinic herbicides, separation of these compounds in food and environmental samples is a great challenge. In this study, 12 geminal dicationic ionic liquids (GDILs) were synthesized and used as mobile phase additives to separate six auxinic herbicides. The effects of the kind of dication, the length of linkage chain, the kind of anion, the concentration of GDILs, and the pH of mobile phase for the separation were investigated in detail. Compared with [C4MIm][BF4], GDILs ([C8(MIm)2][BF4]2) showed higher resolution, better peak shape, and lower retention factor...
June 6, 2017: Analytical and Bioanalytical Chemistry
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