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Michael Ingleson, Valerio Fasano, Liam Curless, James Radcliffe
N-Me-benzothiazolium salts are introduced as a new family of Lewis acids able to activate Si-H σ bonds. These carbon centered Lewis acids were demonstrated to have comparable Lewis acidity towards hydride as found for the triarylboranes widely used in Si-H σ bond activation. However, they display low Lewis acidity towards hard Lewis bases such as Et3PO and H2O in contrast to triarylboranes. The N-Me-benzothiazolium salts are effective catalysts for a range of hydrosilylation and dehydrosilylation reactions...
October 25, 2016: Chemistry: a European Journal
Laura Hermosilla, Marcos Caroli Rezende, Vanderlei Gageiro Machado, Rafaela I Stock
The cationic halochromism and thermohalochromism of four phenolate dyes conjugated with aryl moieties substituted with one or two nitro groups were investigated in the presence of organic (tetra-n-butylammonium bromide and benzyltriethylammonium chloride) and inorganic (sodium perchlorate) salts, in hydrogen-bond donating (water, 1-propanol, 1-butanol and 2-propanol) and hydrogen-bond accepting (acetonitrile and dimethylsulfoxide) solvents. Although a positive halochromic response was observed in water for tetraalkylammonium salts, their thermohalochromic behavior was negligible...
October 17, 2016: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
Soji Shimizu
Subporphyrinato boron (subporphyrin) was elusive until the syntheses of tribenzosubporphine in 2006 and meso-aryl-substituted subporphyrin in 2007. These novel contracted analogues possess a 14π-electron conjugated system embedded in a bowl-shaped structure. They exhibit absorption and fluorescence in the UV/vis region and nonlinear optical properties due to their octupolar structures. The unique coordination geometry around the central boron atom in the structure of subporphyrin enabled investigation of rare boron species, such as borenium cations, boron hydrides, and boron peroxides...
October 25, 2016: Chemical Reviews
Sudip Das, Tarak Karmakar, Sundaram Balasubramanian
Thermomyces lanuginosus lipase (TLL) is an industrially significant catalyst for the production of biodiesel due to its operability over a wide range of pH and temperature. Molecular dynamics simulations of TLL in aqueous solutions of a biocompatible ionic liquid (IL), cholinium glycinate (ChGly) have been carried out to investigate the microscopic reasons for the experimentally observed enhancement in the activity of TLL, upon addition of room temperature IL, especially at an optimal concentration. Eight different TLL systems in both its open and closed forms at various concentrations of the room temperature IL in water have been studied...
October 25, 2016: Journal of Physical Chemistry. B
Mostafa Fakhraee, Mohammad Reza Gholami
The effects of ester addition on structural and dynamic properties of biodegradable ILs composed of the 1-(alkoxycarbonyl)-3-alkylimidazolium cation ([C1COOCnC1im](+), n = 1, 2, 4) coupled with [Br](-), [NO3](-), [BF4](-), [PF6](-), [TfO](-), and [Tf2N](-) are explored using the molecular dynamics (MD) simulations and quantum theory of atoms in molecules (QTAIM) at 400 K. Formation of the intramolecular H bonds between O atoms of the ester group and H atoms of the imidazolium ring as well as the nearest H atom of the alkyl chain to the ester group are disclosed from reduced density gradient (RDG) results...
October 25, 2016: Journal of Physical Chemistry. B
Anurag Mishra, Yuanyuan Jiang, Sheryl Roberts, Vasilis Ntziachristos, Gil Gregor Westmeyer
Photoacoustic imaging (PAI) is an attractive imaging modality that can volumetrically map the distribution of photoabsorbing molecules with deeper tissue penetration than multiphoton microscopy. To enable dynamic sensing of divalent cations via PAI, we have engineered a new reversible near infrared probe that is more sensitive to calcium as compared to other biologically relevant cations. The metallochromic compound showed a strong reduction of its peak absorbance at 765 nm upon addition of calcium ions that was translated into robust signal changes in photoacoustic images...
October 25, 2016: Analytical Chemistry
Yingying Mi, Wen Liu, Ke R Yang, Jianbing Jiang, Qi Fan, Zhe Weng, Yiren Zhong, Zishan Wu, Gary W Brudvig, Victor S Batista, Henghui Zhou, Hailiang Wang
Confining lithium polysulfide intermediates is one of the most effective ways to alleviate the capacity fade of sulfur-cathode materials in lithium-sulfur (Li-S) batteries. To develop long-cycle Li-S batteries, there is an urgent need for material structures with effective polysulfide binding capability and well-defined surface sites; thereby improving cycling stability and allowing study of molecular-level interactions. This challenge was addressed by introducing an organometallic molecular compound, ferrocene, as a new polysulfide-confining agent...
October 25, 2016: Angewandte Chemie
Tao-Tao Liu, Jun Liang, Yuan-Biao Huang, Rong Cao
A bifunctional cationic porous organic polymer based on a Salen-(Al) metalloligand (Al-CPOP) containing imidazolium functionality exhibited enhanced activity and good recyclability in the cycloaddition of carbon dioxide to produce cyclic carbonates without the addition of co-catalysts at atmospheric pressure.
October 25, 2016: Chemical Communications: Chem Comm
Peifang Wang, Chuangfei Wu, Yong Guo, Chao Wang
Wheat straw-derived biochar (BC-4-700) with a large surface area (2263.10 m(2) g(-1)) has been synthesized using potassium hydroxide as an activating agent, and its sorption performance is evaluated by sorbing methylene blue (MB) and methyl orange (MO). The sorption behaviours of both MO and MB by BC-4-700 all follow pseudo-second-order and Langmuir models, and the driving forces for the two sorptions are attributed to the pi-pi interaction. The largest sorption quantity for MO by BC-4-700 is 3.24 mmol g(-1), being 1...
October 25, 2016: Physical Chemistry Chemical Physics: PCCP
Nagamalai Vasimalai, Maria T Fernandez-Arguelles
Highly fluorescent gold nanodots have been synthesized through a novel rapid, facile and one-pot room temperature route using trithiocyanuric acid as mild reducing agent and surface ligand. The proposed synthesis overcomes limitations of other synthetic routes in terms of cost, time, complexity and environmental risks, and gives rise to highly fluorescent gold nanodots within 10 min at room temperature, with a maximum emission wavelength at 623 nm and a large Stokes shift (213 nm). Moreover, the synthesized gold nanodots showed a large emission QY (9...
November 25, 2016: Nanotechnology
Kai Ma, Ruirui Xing, Ti-Feng Jiao, Guizhi Shen, Chengjun Chen, Junbai Li, Xuehai Yan
Self-assembling peptide-based materials are playing an important role in fabricating drug delivery carriers, however, they are often limited by several challenges, such as precise structure modulation, desirable nanoscale size and sufficient circulation lifetime in the body. To address this issue, herein one type of injectable dipeptide-based nanocarriers with well-modulated size and structure has been developed by adjusting glutaraldehyde (GA) assisted cationic dipeptide (CDP) assembly. After loading a model photosensitive drug (Ce6) and further decorating CDP nanoparticles (NPs) with heparin polymers (Hep), the desired dipeptide-based NPs are achieved with average diameter of 100 nm and surface charge of -25 mV, which are favorable for the enhanced permeability and retention effects...
October 25, 2016: ACS Applied Materials & Interfaces
Simin Zhang, Yanmei Zheng, Shengyan Yin, Jingzhi Sun, Bao Li, Lixin Wu
In this study, a uniform complex dual micelle bearing gadolinium substituted polyoxometalate core, hydrophobic middle, and biocompatible organic shell, which exhibited a uniform size and definite molecular weight and chemical composition, was constructed for fluorescent and magnetic resonance imaging contrast agent, via a simple two-step preparation. A paramagnetic polyoxometalate cluster K13[Gd(β2-SiW11O39)2] was firstly encapsulated with a cationic dendron in 3-generation (D-3) bearing triethylene glycol monomethyl ether terminal groups through ionic substitution...
October 24, 2016: Chemistry: a European Journal
Nico Schwarze, Boris Kurscheid, Simon Steinhauer, Beate Neumann, Hans-Georg Stammler, Nikolai Ignat'ev, Berthold Hoge
As recently shown, the introduction of pentafluoroethyl functionalities into silicon compounds is of general interest due to an enhanced Lewis acidity of the resulting species. By this means, the synthesis of previously inaccessible hypervalent silicon derivatives is enabled. While an easy access to tris(pentafluoroethyl)silanes has already been published, synthetic strategies for the selective preparation of bis derivatives are yet unknown. In this contribution, a convenient protocol for the synthesis of functional bis(pentafluoroethyl)silicon compounds is presented...
October 25, 2016: Chemistry: a European Journal
Márcia Pessêgo, Sandra Gago, Nuno Basílio, César A T Laia, A Jorge Parola, João C Lima, Fernando Pina
A structurally constrained derivative of 4',7-dihydroxyflavylium was studied in aqueous solution and in CTAB micelles by pH jumps, flash photolysis and continuous irradiation with spectroscopic details assessed as well by theoretical calculations. In water, up to pH = 8, the compound shows only acid base chemistry with deprotonation of the flavylium cation to form a quinoidal base that further deprotonates with pKas of 4.8 and 7.4. In the basic region, unprotonated trans-chalcones are formed. No neutral trans-chalcone (Ct) is formed in water preventing the establishment of the well-known photochromism involving photoisomerization of this species with subsequent formation of the flavylium cation...
October 25, 2016: Organic & Biomolecular Chemistry
Yusif Abdullayev, Vagif Abbasov, Lucas C Ducati, Avtandil Talybov, Jochen Autschbach
The mechanisms of a tetrasubstituted imidazole [2-(2,4,5-triphenyl-1 H-imidazol-1-yl)ethan-1-ol] synthesis from benzil, benzaldehyde, ammonium acetate, and ethanolamine in [Et2NH2][HSO4] ionic liquid (IL) are studied computationally. The effects of the presence of the cationic and anionic components of the IL on transition states and intermediate structures, acting as a solvent versus as a catalyst, are determined. In IL-free medium, carbonyl hydroxylation when using a nucleophile (ammonia) proceeds with a Gibbs free energy (ΔG(≠)) barrier of 49...
October 2016: ChemistryOpen
Takahiro Ichikawa, Akiyoshi Okafuji, Takashi Kato, Hiroyuki Ohno
We have designed an amphiphilic zwitterion with an iodine-substituted imidazolium cation. Although it forms a layered assembly with flat interfaces, the addition of an equimolar amount of bis(trifluoromethane)sulfonimide results in the formation of a bicontinuous cubic liquid-crystalline assembly with a primitive-type infinite periodic minimal surface, where its zwitterionic headgroup sits regularly. IR measurements revealed that halogen bond between the iodine atoms on the imidazolium cation and the anions is involved in its molecular-assembly behavior...
October 2016: ChemistryOpen
Sandeep Sen, Kadukothanahally Nagaraju Shivaprakash, Neelavara A Aravind, Gudasalamani Ravikanth, Selvadurai Dayanandan
Conservation managers and policy makers are often confronted with a challenging dilemma of devising suitable strategies to maintain agricultural productivity while conserving endemic species that at the early stages of becoming pests of agricultural crops. Identification of environmental factors conducive to species range expansion for forecasting species distribution patterns will play a central role in devising management strategies to minimize the conflict between the agricultural productivity and biodiversity conservation...
September 2016: Ecology and Evolution
Wei Wang, Hongxian Zhou, Hong Yang, Min Cui
The objective of this study was to evaluate the effects of different salts (NaF, NaCl, NaBr, NaI, K2SO4, KCl, KNO3, KSCN, LiCl) on freeze-thaw stability, gel strength and rheological properties of potato starch. Addition of the structure-making (salting-out) ions, such as F(-) and SO4(2-), decreased freeze-thaw stability and increased gel strength, maximal storage modulus (G') and maximal loss modulus (G″) of potato starch, due to a stronger three-dimensional network by promoting the starch retrogradation and inhibiting starch gelatinization...
September 2016: Journal of Food Science and Technology
Hong-Xin Liu, Kai Chen, Yuan Liu, Can Li, Jie-Wei Wu, Zhi-Fang Xu, Hai-Bo Tan, Sheng-Xiang Qiu
Callviminols A-E (1-5), five rare phloroglucinols bearing a framework embodying a hexahydrodibenzo[b,d]furan or 2-phenylcyclohexanol nucleus derived from a phloroglucinol-monoterpene adduct, were isolated from the leaves of Callistemon viminalis. Their structures were established via extensive spectroscopic measurements, with the absolute configuration of 5 determined by electronic circular dichroism (ECD) calculations. The plausible biogenetic pathway suggested that a unique oxidative radical addition and classic cationic cyclization were key biosynthetic steps...
October 21, 2016: Fitoterapia
Daull Philippe, Feraille Laurence, Barabino Stefano, Cimbolini Nicolas, Antonelli Sophie, Mauro Virgine, Garrigue Jean-Sébastien
Dry eye disease (DED) is a complex, multifactorial pathology characterized by corneal epithelium lesions and inflammation. The aim of the present study was to evaluate the efficacy of a cationic emulsion of cyclosporine A (CsA) in a mouse model that mimics severe dry eye. Eight to 12-week-old female C57BL/6N mice with tail patches of scopolamine were housed in controlled environment chambers to induce dry eye. At day three, following dry eye confirmation by corneal fluorescein staining (CFS, score 0-15) and phenol red thread (PRT) lacrimation test, the mice (n = 10/gp) were either treated 3 times a day in both eyes with drug-free cationic emulsion, a 0...
October 21, 2016: Experimental Eye Research
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