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51.
Lobana TS Khanna S Butcher RJ 《Dalton transactions (Cambridge, England : 2003)》2012,41(16):4845-4851
2-Benzoylpyridine thiosemicarbazone {R(1)R(2)C(2)=N(2)·N(3)H-C(1)(=S)-N(4)H(2), R(1) = py-N(1), R(2) = Ph; Hbpytsc} with copper(I) iodide in acetonitrile-dichloromethane mixture has formed stable Cu(II)-I bonds in a dark green Cu(II) iodo-bridged dimer, [Cu(2)(II)(μ-I)(2)(η(3)-N(1),N(2),S-bpytsc)(2)] 1. Copper(I) bromide also formed similar Cu(II)-Br bonds in a dark green Cu(II) bromo-bridged dimer, [Cu(2)(II)(μ-Br)(2)(η(3)-N(1),N(2),S-bpytsc)(2)] 3. The formation of dimers 1 and 3 appears to be due to a proton coupled electron transfer (PCET) process wherein copper(I) loses an electron to form copper(II), and this is accompanied by a loss of -N(3)H proton of Hbpytsc ligand resulting in the formation of anionic bpytsc(-). When copper(I) iodide was reacted with triphenylphosphine (PPh(3)) in acetonitrile followed by the addition of 2-benzoylpyridine thiosemicarbazone in dichloromethane (Cu?:?PPh(3)?:?Hbpytsc in the molar ratio 1:1:1), both Cu(II) dimer 1 and an orange Cu(I) sulfur-bridged dimer, [Cu(2)(I)I(2)(μ-S-Hbpytsc)(2)(PPh(3))(2)] 2 were formed. Copper(I) bromide with PPh(3) and Hbpytsc also formed Cu(II) dimer 3 and an orange Cu(I) sulfur-bridged dimer, [Cu(2)(I)Br(2)(μ-S-Hbpytsc)(2)(PPh(3))(2)] 4. While complexes 2 and 4 exist as sulfur-bridged Cu(I) dimers, 1 and 3 are halogen-bridged. The central Cu(2)S(2) cores of 2 and 4 as well as Cu(2)X(2) of 1 (X = I) and 3 (X = Br) are parallelograms. One set of Cu(II)-I and Cu(II)-Br bonds are short, while the second set is very long {1, Cu-I, 2.565(1), 3.313(1) ?; 3, Cu-Br, 2.391(1), 3.111(1) ?}. The Cu···Cu separations are long in all four complexes {1, 4.126(1); 2, 3.857(1); 3, 3.227(1); 4, 3.285(1) ?}, more than twice the van der Waals radius of a Cu atom, 2.80 ?. The pyridyl group appears to be necessary for stabilizing the Cu(II)-I bond, as this group can accept π-electrons from the metal. 相似文献
52.
Sonia Dopico‐García Ana Ares‐Pernas Jorge Otero‐Canabal Mar Castro‐López José M. López‐Vilariño Victoria González‐Rodríguez María J. Abad‐López 《先进技术聚合物》2013,24(8):723-731
Nowadays, there is a growing availability of biodegradable industrial materials intended to food contact applications whose service life behavior needs to be further investigated. This article is focused on the degradation of two materials based on polylactic acid. The correlation between the rate of degradation and the amount of trapped degradation products was investigated applying three characterization techniques in parallel, namely rheology, high‐performance liquid chromatography (HPLC), and matrix‐assisted laser desorption/ionization (MALDI). The rate of degradation was studied through the evaluation of their rheological properties and calculation of the number of average molecular weights, and weight‐average molecular weights. Water‐soluble oligomers and lactic acid were quantified by HPLC‐ultraviolet. Changes in cyclic and linear oligomers were monitored by MALDI‐time‐of‐flight mass spectrometry. Specimens of 4‐mm thickness of each biopolymer were subjected to hydrolysis in deionized water up to 6 months at two temperatures, simulating service conditions of food packaging. The diminution in viscosity and consequently in molecular weight distribution (20–60%) showed the degradation of the molecular structure of both polylactic acids. The chain scission was followed through the increasing values of lactic acid and hydrolyzed oligomers (twofold to eightfold), and the predominant signal of the linear oligomers over the cyclic ones with aging. Rheology, HPLC, and MALDI showed to be complementary tools to better understand the changes in the molecular structure. The obtained results showed the necessity of adding suitable stabilizers for each particular food packaging application. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
53.
Dr. Daniel Brodbeck Dr. Sonia Álvarez-Barcia Dr. Jan Meisner Dr. Florian Broghammer Julian Klepp Dr. Delphine Garnier Dr. Wolfgang Frey Prof. Dr. Johannes Kästner Prof. Dr. René Peters 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(6):1515-1524
Asymmetric 1,2-additions of cyanide yield enantioenriched cyanohydrins as versatile chiral building blocks. Next to HCN, volatile organic cyanide sources are usually used. Among them, cyanoformates are more attractive on technical scale than TMSCN for cost reasons, but catalytic productivity is usually lower. Here, the development of a new strategy for cyanations is described, in which this activity disadvantage is overcome. A Lewis acidic Al center cooperates with an aprotic onium moiety within a remarkably robust bifunctional Al–F–salen complex. This allowed for unprecedented turnover numbers of up to 104. DFT studies suggest an unexpected unique trimolecular pathway in which the ammonium bound cyanide attacks the aldehyde, which itself is activated by the carbonyl group of the cyanoformate binding to the Al center. In addition, a novel practical carboxycyanation method was developed that makes use of KCN as the sole cyanide source. The use of a pyrocarbonate as carboxylating reagent provided the best results. 相似文献
54.
Otero A Fernández-Baeza J Tejeda J Lara-Sánchez A Franco S Martínez-Ferrer J Carrión MP López-Solera I Rodríguez AM Sánchez-Barba LF 《Inorganic chemistry》2011,50(5):1826-1839
New enantiopure imines (1-9) with a chiral substrate to control the stereochemistry of a newly created stereogenic center have been synthesized by reaction of the commercially available (1R)-(-)-myrtenal and different primary amines. The diastereomerically enriched lithium-scorpionate compounds [Li(κ(3)-mobpza)(THF)] (10) (mobpza = N-p-methylphenyl-(1R and 1S)-1-[(1R)-6,6-dimethylbicyclo[3.1.1]-2-hepten-2-yl]-2,2-bis(3,5-dimethylpyrazol-1-yl)ethylamide), [Li(κ(3)-mobpza)(THF)] (11) (mobpza = N-p-methoxyphenyl-(1R and 1S)-1-[(1R)-6,6-dimethylbicyclo[3.1.1]-2-hepten-2-yl]-2,2-bis(3,5-dimethylpyrazol-1-yl)ethylamide), [Li(κ(3)-fbpza)(THF)] (12) (fbpza = N-p-fluorophenyl-(1R and 1S)-1-[(1R)-6,6-dimethylbicyclo[3.1.1]-2-hepten-2-yl]-2,2-bis(3,5-dimethylpyrazol-1-yl)ethylamide), and [Li(κ(3)-clbpza)(THF)] (13) (clbpza = N-p-chlorophenyl-(1R and 1S)-1-[(1R)-6,6-dimethylbicyclo[3.1.1]-2-hepten-2-yl]-2,2-bis(3,5-dimethylpyrazol-1-yl)ethylamide) were obtained by a diastereoselective 1,2-addition of an organolithium reagent to imines in good yield and with good diastereomeric excess (ca. 80%). The complexes [LiCl(κ(2)-R,R-fbpzaH)(THF)] (14) and [LiCl(κ(2)-R,R-clbpzaH)(THF)] (15) were obtained in enantiomerically pure form by the treatment of THF solutions of 12 or 13 with NH(4)Cl. The enantiomerically pure amines (R,R-mbpzaH) (16), (R,R-mobpzaH) (17), (R,R-fbpzaH) (18), and (R,R-clbpzaH) (19) were obtained by hydrolysis of the lithium-scorpionate compounds 10-13 with H(2)O. The lithium compound 12 was reacted with [TiCl(4)(THF)(2)] or [ZrCl(4)] to give the enantiopure complexes [MCl(3)(κ(3)-R,R-fbpza)] [M = Ti (20), Zr (21)]. The amine compound 18 reacted with [MX(4)] (M = Ti, X = O(i)Pr, OEt; M = Zr; X = NMe(2)) to give the complexes [MX(3)(κ(3)-R,R-fbpza)] (22-24). The reaction of Me(3)SiCl with [Zr(NMe(2))(3)(κ(3)-R,R-fbpza)] (24) in different molar ratios led to the halide-amide-containing complexes [ZrCl(NMe(2))(2)(κ(3)-R,R-fbpza)] (25) and [ZrCl(2)(NMe(2))(κ(3)-R,R-fbpza)] (26) and the halide complex 21. The isolation of only one of the three possible diastereoisomers of complexes 25 and 26 revealed that chiral induction from the ligand to the zirconium center took place. The structures of these compounds were elucidated by (1)H and (13)C{(1)H} NMR spectroscopy, and the X-ray crystal structures of 5, 12, 14, 15, and 24 were also established. 相似文献
55.
Ayesha Kausar Sonia Zulfiqar Liaquat Ali Muhammad Ilyas Sarwar 《Monatshefte für Chemie / Chemical Monthly》2011,17(3):201-209
Abstract
New diacid dichlorides bearing phenyl thiourea groups were prepared by a facile synthetic approach and characterized using spectroscopic and elemental analyses. A series of novel aromatic and semiaromatic polyamides were prepared via a condensation route from the synthesized diacid dichlorides with 4,4′-oxydianiline. The polymers were characterized by FT-IR, 1H NMR, 13C NMR, and their physical properties, including their solution viscosities, solubilities and thermal properties, were studied too. Polyamides with phenyl thiourea moieties in the backbone showed good solubilities in amide solvents such as DMAc, DMF, DMSO, and NMP. All of the synthesized polymers had η inh values of 0.042–0.053 dm3/g, and were obtained in quantitative yield. GPC measurements of the synthesized polyamides indicated M w values of 64,759–86,172. The crystallinity of the polymers was evaluated via their X-ray diffraction patterns. Their glass transition temperatures were found to be 218–229 °C. Furthermore, thermogravimetric analysis indicated that the polymers were thermally stable in the range 300–398 °C in a N2 atmosphere. 相似文献56.
Parthasarathy Saravanan Suparna Gupta Arpita DattaGupta Sonia Gupta Vinod K. Singh 《合成通讯》2013,43(15):2695-2699
The cleavage of α-hydroxy tert-butyldimethylsilyl ether to diol takes place efficiently with LAH. It has been proposed that the reaction proceeds via intramolecular hydride transfer from the alkoxy aluminium hydride. In order to substantiate this, reduction of TBDMS ether with LAH in a variety of substrates was studied. 相似文献
57.
Shariff?E.?KabirEmail author M.?Arzu?Miah M.?Abdur?Rahim Sonia?Sultana G.?M.?Golzar?Hossain Ebbe?Nordlander Edward?Rosenberg 《Journal of Cluster Science》2005,16(1):93-110
Treatment of Ru3(CO)12 with dpphSe2 (dpph = 1,6-bis(diphenylphosphino)hexane) in refluxing toluene in the presence of Me3NO afforded two new compounds, Ru3(CO)7(-CO)(3-Se)(-dpph) (1) and Ru3(CO)7(3-Se)2(-dpph) (2). A similar reaction of Ru3(CO)12 with dpppeSe2 (dpppe = 1,5-bis(diphenylphosphino)pentane) gave exclusively Ru3(CO)7(3-Se)2(-dpppe) (3). Treatment of Ru3(CO)12 with dpphS2 and dpppeS2 at 110°C in the presence of Me3NO afforded Ru3(CO)7(3-S)2(-dpph) (4) and Ru3(CO)7(3-S)2(-dpppe) (5), respectively. Reactions of Fe3(CO)12 with dpphSe2 and dpppeSe2, under identical conditions, afforded Fe3(CO)7(3-Se)2(-dpph) (6) and Fe3(CO)7(3-Se)2(-dpppe) (7), respectively. Compounds 1–7 were characterized spectroscopically and the molecular structures of compounds 1–4 were determined by single crystal X-ray crystallography. The core of 1 contains an equilateral triangle of ruthenium atoms with one capping selenium, one bridging dpph, one doubly bridging carbonyl and seven terminal carbonyl ligands. Complexes 2–4 have a square-pyramidal structure with two metal and two chalcogenide atoms alternating in the basal plane and the third metal atom at the apex of the pyramid, and belong to the family of well-known nido clusters with seven skeletal electron pairs. 相似文献
58.
Herrebout WA Melikova SM Delanoye SN Rutkowski KS Shchepkin DN van der Veken BJ 《The journal of physical chemistry. A》2005,109(13):3038-3044
Mid-infrared spectra of mixed solutions in liquid xenon containing fluoroform and either ammonia or pyridine have been investigated at temperatures between 173 and 213 K. For both Lewis bases, a new band is found in the CH stretching region at a frequency approximately 5 cm(-1) higher than that of monomer fluoroform, which is assigned to a complex between fluoroform and the Lewis base. A detailed analysis of the nu1/2nu(4) Fermi resonance in the proton donor shows that the blue shifts observed for the complexes are not caused by a strengthening of the CH bond during the complexation, but are due to the changes in the Fermi resonance interactions. Information on the nu1/2nu(4) Fermi resonance was also obtained for the complexes of fluoroform with dimethyl ether and trimethyl amine. 相似文献
59.
Meallet-Renault R Pansu R Amigoni-Gerbier S Larpent C 《Chemical communications (Cambridge, England)》2004,(20):2344-2345
A fluorescent sensor for Cu(2+) at the nanomolar level in water has been designed by associating a BODIPY fluorophore and a selective ligand (cyclam) in ultrafine polymer nanoparticles. 相似文献
60.
López C Caubet A Pérez S Solans X Font-Bardía M 《Chemical communications (Cambridge, England)》2004,(5):540-541
The synthesis of the first examples of diastereomerically pure platinacycles having simultaneously a chiral carbon and a sigma[Pt-C(sp(2), ferrocene)] bond is described. 相似文献