Synthesis and characterization of a polycarbon organometallic cluster, [PPN]2[Fe6(CO)18C4

The polycarbon metal cluster [Fe6(CO)18C4]2- is formed by the reaction of CF3SO3SO2CF3 with [Fe3(CO)9(CCO)]2-. Apparently, the SO2CF3 moiety abstracts an oxygen from the ketenylidene (CCO) ligand and C-C coupling occurs to form the C4 ligand. A single-crystal X-ray structure determination reveals that the pattern of C-C bond lengths of the C4 ligand in [Fe6(CO)18C4]2- mimic those in free butadiene.     

Nucleophilic attack on cluster-bound acetylide ligands derived from the iron ketenylidene, [Fe3(CO)9(CCO)]2−

Reaction of the iron ketenylidene (PPN)₂[Fe₃(CO)₉CCO] [PPN =bis (triphenylphosphine)nitrogen(+1)] with trifluoroacetic anhydride forms a highly electrophilic acetylide cluster (PPN)[Fe₃(CO)₉CCOC(O)CF₃] (lc), analogous to the known compounds (PPN)[Fe₃(CO)₉CCOR] [R=Et, (Ia); Ac, (Ib)] prepared from the reaction of ethyl triflate and acetyl chloride on the ketenylidene. Reaction of phosphines and (Ib, c) yield phosphonium acetylides [Fe₃(CO)₉CCPR₃] [(II),R=Ph], with loss of (PPN)[CH₃CO₂] or (PPN)[CF₃CO₂]. Additionally, (Ic) and triphenylarsine react to give an analogous arsonium acetylide [Fe₃(CO)₉CCAsPh₃] (III). No reaction occurs when an excess of arsine is added to (Ib). The reaction of (Ib, c) with anionic nucleophiles is reported, including reaction of Na[CpFe(CO)₂] and (Ib) to afford an unusual metallated acetylide cluster (PPN) [Fe₃(CO)₉CCFe(CO)₂Cp] (IV). Clusters (II), (III), and (IV) are spectroscopically characterized and a single crystal x-ray structure determination of (IV) is reported. (PPN)[Fe₃(CO)₉CCFe(CO)₂Cp] (IV) crystallizes in the monoclinic space group P2₁/n;a=17.793(2) Å;b=16.108(3) Å;c=18.157(3) Å;=107.62(1)⁰;V=4959(3) ų;Z=4. Refinement of 469 variables on 5981 observed [I>3(I)] reflections converged toR=3.5% andRw=4.7%.     

Anion binding studies of fluorinated expanded calixpyrroles

The anion binding properties of fluorinated calix[n]pyrroles (n = 4-6) in aprotic solvents (acetonitrile and DMSO) and modified reaction conditions allowing for the synthesis and isolation of the hitherto missing dodecafluorocalix[6]pyrrole from the condensation of 3,4-difluoro-1H-pyrrole and acetone are described. In acetonitrile solution containing 2% water, the association constants for the 1:1 binding interaction between octafluorocalix[4]pyrrole and chloride anion obtained with isothermal titration calorimetry (ITC) and (1)H NMR titration methods were found to match reasonably well. As compared to its nonfluorinated congener, octafluorocalix[4]pyrrole was found to display enhanced binding affinities for several representative anions in pure acetonitrile as judged from ITC analyses. Similar analyses of the fluorinated calix[n]pyrroles revealed an increase in the relative affinity for bromide over chloride with increasing macrocycle size, as manifest in a decrease in the binding ratio K(a(Cl))/K(a(Br)). Anion binding studies in the solid state, involving single-crystal X-ray diffraction analyses of the chloride and acetate anion complexes of octafluorocalix[4]pyrrole and decafluorocalix[5]pyrrole, respectively, confirmed the expected hydrogen bond interactions between the pyrrolic NH protons and the bound anions.     

Enhanced anion exchange for selective sulfate extraction: overcoming the Hofmeister bias

In this communication, a new approach to enhancing the efficacy of liquid-liquid anion exchange is demonstrated. It involves the concurrent use of appropriately chosen hydrogen-bond-donating (HBD) anion receptors in combination with a traditional quaternary ammonium extractant. The fluorinated calixpyrroles 1 and 2 and the tetraamide macrocycle 4 were found to be particularly effective receptors. Specifically, their use allowed the extraction of sulfate by tricaprylmethylammonium nitrate to be effected in the presence of excess nitrate. As such, the present work provides a rare demonstration of overcoming the Hofmeister bias in a competitive environment and the first to the authors' knowledge wherein this difficult-to-achieve objective is attained using a neutral HBD-based anion binding agent under conditions of solvent extraction.     

Exploring human plasma proteome strategies: high efficiency in-solution digestion protocol for multi-dimensional protein identification technology

Multi-dimensional protein identification technology (MudPIT) is becoming a prevalent proteomic approach due to its high-throughput separations and accurate mass detection. Prior to MudPIT analysis, complicated samples required in-solution digestion. Unlike in-gel digestion, in which enzymes work on just a few proteins, in-solution digestion involves simultaneous digestion of hundreds or thousands of proteins. In-solution digestion protocols must therefore be very efficient. Few investigations have evaluated the efficiency of in-solution digestion protocols. The present research compared three such protocols. Results suggest that a protocol utilizing trifluoroethanol (TFE) as denaturant is most efficient.     

DTO体系分子反应动力学

基于DTO分子( 1A1)的氢同位素效应,得到修正的Born-Oppenheimer(B-O)理论下多体展式分析势能函数.用准经典的Monte-Carlo轨迹法研究了D+ TO(0 ,0)和T+ DO(0 ,0)的分子反应动力学过程.结果表明:在碰撞能量较低时( < 209.2 kJ. mol - 1 ),D+ TO(0 ,0)和T+DO(0,0)反应主要生成O+ DT,并且该反应是无阈能的;有少量的交换反应产物DO (TO)生成,并伴有极少量的络合物产生.碰撞能大于209.2kJ . mol - 1后,逐渐出现分子被完全碰散成D,T ,O 原子的情形.反应 D+TO(0 ,0) →OD + T和 T +DO(0 ,0) →OT + D是无热反应但是有阈能存在.由于D和T原子的同位素效应,置换产物轨线存在非一致性.     

Conductivity and dielectric constant of the polymeric solid electrolyte, (PEO)8NH4SO3CF3, in the 100 Hz to 1010 Hz range

Frequency dependent conductivity and dielectric constant of crystalline and amorphous phases of the polymeric solid electrolyte-(PEO)₈NH₄SO₃CF₃ were studied in the frequency range from dc to 37 GHz. The complex permittivity variation with frequency conforms to the dynamic percolation model.     

Lithiation of meso-octamethylcalix[4]pyrrole: a general route to C-Rim monosubstituted calix[4]pyrroles

Lithiation and subsequent addition of an electrophile to meso-octamethylcalix[4]pyrrole provides a straightforward synthetic route to new, C-rim monosubstituted calix[4]pyrroles. A variety of electrophiles were used, resulting in calix[4]pyrroles with appended functional groups including carboxyl, ester, iodo, and formyl. This method was optimized to give maximum yields of the monosubstituted derivatives with lowest possible contamination by di- and trisubstituted congeners. Solid-state studies, performed for a number of these derivatives, showed unexpected supramolecular interactions involving both solvents and the monosubstituted calix[4]pyrrole derivatives themselves.     

Study on particle removal efficiency of an impinging jet by an image-processing method

 An image-processing method is proposed to obtain the distribution of the removal efficiency of particles on a plate by an air jet. This method can be used to measure particle removal from a flat surface by processing the image of the reflected light from the surface. Factors affecting the particle removal efficiency such as air pressure, distance between the nozzle and the impinging surface and the impinging angle are discussed. Optimal conditions are determined to obtain the most effective particle removal by the air jet. Received: 10 April 2001 / Accepted: 2 August 2001     

Single crystal polarized Raman spectra of the solid electrolyte Cu2HgI4; attempt frequencies for ion motion in Ag2HgI4

The polarized Raman scattering from small single crystals of Cu₂HgI₄ provided assignments for the more prominent Raman features to specific irreducible representations. The E symmetry assignment, mass dependence, and pressure dependence of the 36 cm^?1 band in Cu₂HgI₄ and 24 cm^?1 band in Ag₂HgI₄ indicate that these features approximate the attempt frequency for ion hopping. The unusually high pre-exponential factor in the Arrhenius expression for ion hopping is discussed in light of the observed attempt frequency; we conclude that despite the high activation energy the conduction mechanism is similar to other heavy-metal solid electrolytes.