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31.
Treatment of several divalent transition-metal trifluoromethanesulfonates [M(II)(OTf)2; M(II) = Mn, Co, Ni] with [NEt4][Tp*Fe(III)(CN)3] [Tp* = hydridotris(3,5-dimethylpyrazol-1-yl)borate] in DMF affords three isostructural rectangular clusters of {[Tp*Fe(III)(CN)3M(II)(DMF)4]2[OTf]2} x 2DMF (M(II) = Mn, 3; Co, 4; Ni, 5) stoichiometry. Magnetic studies of 3-5 indicate that the Tp*Fe(CN)3(-) centers are highly anisotropic and exhibit antiferromagnetic (3 and 4) and ferromagnetic (5) exchange to afford S = 4, 2, and 3 spin ground states, respectively. ac susceptibility measurements suggest that 4 and 5 exhibit incipient single-molecule magnetic behavior below 2 K. 相似文献
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Abstract The purification by column chromatography of a phenol-oxidizing enzyme, mushroom tyrosinase, was investigated using solid phase adsorbents designed to have specific affinity for the enzyme. Sepharose 4B, aminophenyl-bearing porous glass, and p-aminobenzylcellulose were chemically modified to introduce phenolic, catecholic, or benzoic groups on the polymer surface. The resulting preparations were tested for their effectiveness in separating tyrosinase from an impure protein mixture. The phenolic and benzoic polymers displayed no specific affinity for tyrosinase. Aminophenyl glass, with or without an attached phenolic group, adsorbed appreciable quantities of protein nonspecif-ically, thus complicating studies of its tyrosinase affinity properties. Dopamine, a dihydroxyphenyl derivative, was bound to Sepharose and was found to be effective in retaining tyrosinase at pH 5.5; elution of the enzyme by washing at pH 8.8 resulted in its purification by a factor of 10 to 14. Enzymatic oxidation of the adsorbent limited the number of purification cycles which could be carried out on a single column. 相似文献
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The catalytic activity of ruthenium(II) bis(diimine) complexes cis‐[Ru(6,6′‐Cl2bpy)2(OH2)2](Z)2 ( 1 , Z = CF3SO3; 2 , Z = (3,5‐(CF3)2C6H3)4B, i.e. BArF) and cis‐[Ru(4,4′‐Cl2bpy)2(OH2)2](Z)2 ( 3 , Z = CF3SO3; 4 , Z = BArF) for the hydrogenation and/or the hydrogenolysis of furfural (FFR) and furfuryl alcohol (FFA) was investigated. The molecular structures of cis‐[Ru(4,4′‐Cl2bpy)2(CH3CN)2](CF3SO3)2 ( 3 ′) and dimeric cis‐[(Ru(4,4′‐Cl2bpy)2Cl)2](BArF)2 ( 5 ) were characterized by X‐ray crystallography. The structures are consistent with the anticipated reduction in steric hindrance about the ruthenium centers in comparison with corresponding complexes containing 6,6′‐Cl2bpy ligands. While compounds 1 , 2 , 3 , 4 are all active and highly selective catalysts for the hydrogenation of FFR to FFA under modest reaction conditions, 3 and 4 showed decreased activity. This is best explained in terms of reduced Lewis acidity of the Ru2+ centers and reduced steric hindrance about the metal centers of catalysts 3 and 4 . cis‐[Ru(6,6′‐Cl2bpy)2(OH2)2](BArF)2 ( 2 ) also displayed high catalytic efficiency for the hydrogenation of FFA to tetrahydrofurfuryl alcohol. Presumably, this is because coordination of C═C bonds of FFA to the ruthenium center is poorly inhibited by non‐coordinating BArF counterions. Interestingly, cis‐[Ru(6,6′‐Cl2bpy)2(OH2)2](CF3SO3)2 ( 1 ) showed some catalytic activity in ethanol for the hydrogenolysis of FFA to 2‐methylfuran, albeit with fairly modest selectivity. Nonetheless, these results indicate that ruthenium(II) bis(diimine) complexes need to be further explored as catalysts for the hydrogenolysis of C―O bonds of FFR, FFA, and related compounds. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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Inside Cover: Stapled Peptides with γ‐Methylated Hydrocarbon Chains for the Estrogen Receptor/Coactivator Interaction (Angew. Chem. Int. Ed. 13/2016)
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Shijing Cheng Mingqiang Zhang Tianyu Wu Sean T. Hemp Brian D. Mather Robert B. Moore Timothy E. Long 《Journal of polymer science. Part A, Polymer chemistry》2012,50(1):166-173
Copolymers of n‐butyl acrylate and phosphonium ionic liquid monomers possessing various alkyl substituents and counterions were synthesized through a combination of conventional free radical copolymerization and anion exchange. Differential scanning calorimetry and dynamic mechanical analysis provided the thermal and mechanical properties of these phosphonium cation‐containing random copolymers. Factors including alkyl chain length of phosphonium substituents, counterion type, as well as ionic concentration significantly influenced the association of phosphonium cations. Phosphonium ionomers with trialkyl substituents on phosphonium cations did not display the characteristic small‐angle X‐ray scattering peak, suggesting the absence of ionic clusters. However, low q peaks in wide‐angle X‐ray diffraction was indicative of significant concentration fluctuations wherein the ionic monomeric units associated. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
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Andrew J. Guenthner Vandana Vij Timothy S. Haddad Josiah T. Reams Kevin R. Lamison Christopher M. Sahagun Sean M. Ramirez Gregory R. Yandek Suresh C. Suri Joseph M. Mabry 《Journal of polymer science. Part A, Polymer chemistry》2014,52(6):767-779
The synthesis and physical properties of new silicon‐containing polyfunctional cyanate ester monomers methyl[tris(4‐cyanatophenyl)]silane and tetrakis(4‐cyanatophenyl)silane, as well as polycyanurate networks formed from these monomers are reported. The higher crosslinking functionality compared to di(cyanate ester) monomers enables much higher ultimate glass transition temperatures to be obtained as a result of thermal cyclotrimerization. The ability to reach complete conversion is greatly enhanced by cocure of the new monomers with di(cyanate ester) monomers such as 1,1‐bis(4‐cyanatophenyl)ethane. The presence of silicon in these polycyanurate networks imparts improved resistance to rapid oxidation at elevated temperatures, resulting in char yields as high as 70% under nitrogen and 56% in air in the best‐performing networks. The water uptake in the silicon‐containing networks examined is 4–6 wt % after 96 h of immersion at 85 °C, considerably higher than both carbon‐containing and/or di(cyanate ester) analogs. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 767–779 相似文献