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141.
Sharma HK Cervantes-Lee F Pannell KH 《Journal of the American Chemical Society》2004,126(5):1326-1327
Treatment of FpCH2SiR2Cl [Fp = (eta5-C5H5)Fe(CO)2] with lithium diisopropylamide leads to the formation of new metallacycle complexes. When R2 = Me2 and MenBu, these ring-open to form a new class of organometallic polymer. When R2 = nBu2, the metallacycle resists ring-opening and may be structurally characterized as the Ph3P-substituted species. 相似文献
142.
Laura Marcu Javier A. Jo Pramod V. Butte William H. Yong Brian K. Pikul Keith L. Black Reid C. Thompson 《Photochemistry and photobiology》2004,80(1):98-103
Fluorescence spectroscopy of the endogenous emission of brain tumors has been researched as a potentially important method for the intraoperative localization of brain tumor margins. We investigated the use of time‐resolved, laser‐induced fluorescence spectroscopy for demarcation of primary brain tumors by studying the time‐resolved spectra of gliomas. The fluorescence of human brain samples (glioblastoma multiforme, cortex and white matter: six patients, 23 sites) was induced ex vivo with a pulsed nitrogen laser (337 nm, 3 ns). The time‐resolved spectra were detected in a 360–550 nm wavelength range using a fast digitizer and gated detection. Parameters derived from both the spectral‐ (intensities from narrow spectral bands) and the time domain (average lifetime) measured at 390 and 460 nm were used for tissue characterization. We determined that high‐grade gliomas are characterized by fluorescence lifetimes that varied with the emission wavelength (>3 ns at 390 nm, <1 ns at 460 nm) and their emission is overall longer than that of normal brain tissue. Our study demonstrates that the use of fluorescence lifetime not only improves the specificity of fluorescence measurements but also allows a more robust evaluation of data collected from brain tissue. Combined information from both the spectraland the time domain can enhance the ability of fluorescencebased techniques to diagnose and detect brain tumor margins intraoperatively. 相似文献
143.
Leita BA Moubaraki B Murray KS Smith JP Cashion JD 《Chemical communications (Cambridge, England)》2004,(2):156-157
The dinuclear iron(II) complex [(pypzH)(NCSe)Fe([micro sign]-pypz)(2)Fe(NCSe)(pypzH)].2H(2)O displays a single, sharp spin crossover transition between the [HS-HS] and [LS-LS] states and is structurally characterised above and below the T(1/2)= 225 K value 相似文献
144.
A standard HPLC was adapted to polymer supported oligosaccharide synthesis. Solution-based reagents are delivered using a software-controlled solvent delivery system. The reaction progress and completion can be monitored in real time using a standard UV detector. All steps of oligosaccharide assembly including loading, glycosylation, deprotection, and cleavage can be performed using this setup. 相似文献
145.
We examine the morphological structures of asymmetric poly(ethylene oxide)-b-poly(1,1'-dihydroperflurooctyl methacrylate) (PEO-b-PFOMA) thin films upon annealing in a compressible fluid, supercritical CO2 (Sc-CO2). The strong affinity between PFOMA and CO2 is found to induce phase segregation when annealing PEO-b-PFOMA films at the same temperature as compared with vacuum. In vacuum, PEO-b-PFOMA films remain disordered from 80 to 180 degrees C, whereas, in Sc-CO2 at 13.9 MPa, an upper order-disorder transition (UODT) between 116 and 145 degrees C is found. In Sc-CO2, the observed ordered structure is layers of PEO spheres embedded in the matrix of PFOMA, followed by a brush layer, in which PEO wets the substrate. The swelling isotherms of PFOMA and PEO in CO2 are correlated with the Sanchez-Lacombe equation of state (SLEOS) to estimate the interaction parameters, XPFOMA-CO2 and XPEO-CO2. The phase segregation (order) induced by CO2 relative to vacuum at a given temperature is explained in terms of two factors: (1) copolymer volume fraction upon dilution with CO2, phi, and (2) the relative interaction parameter, DeltaX= XPEO-CO2 - XPFOMA-CO2. The latter factor favors order and is dominant at low temperatures over the phi factor, which always favors disorder. At high temperatures (above the T(ODT)), the preferential swelling of PFOMA by CO2 is less pronounced ( DeltaX decreases), and the copolymer is disordered. 相似文献
146.
Langley SK Chilton NF Gass IA Moubaraki B Murray KS 《Dalton transactions (Cambridge, England : 2003)》2011,40(47):12656-12659
Two isostructural tetranuclear lanthanide clusters of general formula [Ln(III)(4)(μ(3)-OH)(2)(o-van)(4)(O(2)CC(CH(3))(3))(4)(NO(3))(2)]·CH(2)Cl(2)·1.5H(2)O (Ln = Gd (1) and Dy (2)) (o-van = 3-methoxysalicylaldehydato anion) are reported. The metallic cores of both complexes display a planar 'butterfly' arrangement. Magnetic studies show that both are weakly coupled, with 2 displaying probable SMM behaviour. 相似文献
147.
Turner DR Chesman AS Murray KS Deacon GB Batten SR 《Chemical communications (Cambridge, England)》2011,47(37):10189-10210
The chemistry of the anions dicyanamide and tricyanomethanide (dca and tcm, respectively) has produced a plethora of discoveries over the past few decades, particularly in relation to transition-metal coordination polymers with magnetic coupling. Over recent years there have been an increasing number of reports of heterofunctionalised cyano-containing anions, typically derivatives of dicyanomethanide. Our own group has been particularly concerned with the amide- and nitroso-functionalised anions carbamoyldicyanomethanide (cdm) and dicyanonitrosomethanide (dcnm), respectively. This feature article examines the fascinating diversity of materials and complexes that can be obtained using small cyano anions, ranging from coordination polymers to heterometallic clusters and hydrogen bonding networks. In particular, we focus on results from our own laboratories in the past few years. The magnetic properties of these materials are briefly discussed. 相似文献
148.
Chan CK Tao CH Li KF Wong KM Zhu N Cheah KW Yam VW 《Dalton transactions (Cambridge, England : 2003)》2011,40(40):10670-10685
A series of luminescent multinuclear platinum(II) alkynyl complexes containing triethynylbenzene or 1,4-bis(3,5-diethynylphenyl)buta-1,3-diyne as cores has been successfully synthesized and characterized. The electronic absorption, emission, nanosecond transient absorption and electrochemical properties of these complexes have been reported. These complexes show long-lived emissions in degassed benzene solution and in alcoholic glass at 77 K. Moreover, they are found to exhibit two-photon absorption (2PA) and two-photon induced luminescence (TPIL) properties, and their two-photon absorption cross-sections have been determined to be 6-191 GM upon excitation at 720 nm. Through a systematic comparison, it has been found that tetra- and hexanuclear platinum(II) complexes show better 2PA and TPIL properties than their di- and trinuclear counterparts. 相似文献
149.
Ayako Yano Nobuyuki Akai Hiroshi Ishii Chikahiro Satoh Takayuki Hironiwa Keith R. Millington Munetaka Nakata 《Polymer Degradation and Stability》2013
Thermal oxidative degradation of additive-free polypropylene pellets heated isothermally in dry air at 150 and 180 °C (below and above the melting point of 163 °C) was investigated by multichannel Fourier-transform chemiluminescence spectroscopy. The initial peak wavelength of chemiluminescence emission at 490 nm remained constant during the early stages of thermal degradation, but new emissions developed with time in the red spectral region over an extended oxidation period. The time-dependent luminescence spectra were deconvoluted into three emission bands by least-squares fitting using Gaussian curves. We concluded that at least three groups of luminescent species (luminophores), having different conjugation lengths, were generated by thermal oxidation over extended periods and show luminescence around 490, 660, and 740 nm. 相似文献
150.
Variation in the position of CF3 groups in several aromatic Group‐14 compounds was studied by 19F‐NMR spectroscopy. In these compounds RnECl4?n (n=1 or 2; E=Si, Ge, or Sn; R=2,4,6‐(CF3)3C6H2 (=Ar), 2,6‐(CF3)2C6H3 (=Ar′), or 2,4‐(CF3)2C6H3 (=Ar″)), Ar, Ar′, and Ar″ are all bulky, strongly electron‐withdrawing ligands. The 19F‐NMR studies of the variation in position of the CF3 substituents in these compounds as revealed by chemical shifts could be correlated with the electronegativities of the central elements E, and with intramolecular E–F interactions derived from single‐crystal X‐ray diffraction data. These interactions are considered to play an important role in the stabilization of these compounds. 相似文献