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61.
Berhan Teclé Kaniz F. Siddiqui Christopher Ceccarelli John P. Oliver 《Journal of organometallic chemistry》1983,255(1):11-15
The structure of di-trans-β-styrylmercury has been determined by single crystal X-ray methods from counter data. The compound crystallizes in the orthorhombic space group Pbcn with unit cell dimensions a 15.413(6), b 11.161(9), c 7.668(5) Å, V 1319(1) Å3, Dcalc 2.049 g/cm3, and Z = 4. The crystal was solved by conventional heavy atom techniques. The crystal consists of individual molecular units with the mercury atom located on a two fold axis of symmetry. The CHgC fragment is nearly linear with an angle of 178°. The β-styryl groups are oriented so that a dihedral angle of 66.8° is formed between the planes defined by HgC(1)C(2) and HgC(1)′C(2)′ fragments. The HgC bond distance is 2.07(4) Å. 相似文献
62.
The reaction of dimethyldiaryltin reagents Me(2)SnR(2) (R = Ph (1), p-MePh (2), m,m-Me(2)Ph (3), p-(t)BuPh (4), p-MeOPh (5), p-CF(3)Ph (6)) with BCl(3) provided a high-yielding, simple preparative route to the corresponding diarylchloroboranes R(2)BCl (R = Ph (10), p-MePh (11), m,m-Me(2)Ph (12), p-(t)BuPh (13), p-MeOPh (14), p-CF(3)Ph (15)). In some cases, the desired diarylchloroborane was not formed from an appropriate tin reagent Me(2)SnR(2) (R = o-MeOPh (7), o,o-(MeO)(2)Ph (8), o-CF(3)Ph (9)). The reaction of lithiated methyldiaryl- or methyldialkylphosphines with diarylchloroboranes or dialkylchloroboranes is discussed. Specifically, several new monoanionic bis(phosphino)borates are detailed: [Ph(2)B(CH(2)PPh(2))(2)] (25); [(p-MePh)(2)B(CH(2)PPh(2))(2)] (26); [(p-(t)BuPh)(2)B(CH(2)PPh(2))(2)] (27); [(p-MeOPh)(2)B(CH(2)PPh(2))(2)] (28); [(p-CF(3)Ph)(2)B(CH(2)PPh(2))(2)] (29); [Cy(2)B(CH(2)PPh(2))(2)] (30); [Ph(2)B(CH(2)P[p-(t)BuPh](2))(2)] (31); [(p-MeOPh)(2)B(CH(2)P[p-(t)BuPh](2))(2)] (32); [Ph(2)B(CH(2)P[p-CF(3)Ph](2))(2)] (33); [Ph(2)B(CH(2)P(BH(3))(Me)(2))(2)] (34); [Ph(2)B(CH(2)P(S)(Me)(2))(2)] (35); [Ph(2)B(CH(2)P(i)Pr(2))(2)] (36); [Ph(2)B(CH(2)P(t)Bu(2))(2)] (37); [(m,m-Me(2)Ph)(2)B(CH(2)P(t)Bu(2))(2)] (38). The chelation of diarylphosphine derivatives 25-33 and 36 to platinum was examined by generation of a series of platinum dimethyl complexes. The electronic effects of substituted bis(phosphino)borates on the carbonyl stretching frequency of neutral platinum alkyl carbonyl complexes were studied by infrared spectroscopy. Substituents remote from the metal center (i.e. on boron) have minimal effect on the electronic nature of the metal center, whereas substitution close to the metal center (on phosphorus) has a greater effect on the electronic nature of the metal center. 相似文献
63.
Maria A. Curtin Irwin A. Taub Kenneth Kustin Narith Sao Jeremy R. Duvall Katharine I. Davies Christopher J. Doona Edward W. Ross 《Research on Chemical Intermediates》2004,30(6):647-661
The slow reaction between peroxodisulfate and formate is significantly accelerated by ascorbate at room temperature. The products of this induced oxidation, CO2 and oxalate (C2O2–
4), were analyzed by several methods and the kinetics of this reaction were measured. The overall mechanism involves free radical species. Ascorbate reacts with peroxodisulfate to initiate production of the sulfate radical ion (SO–
4), which reacts with formate to produce carbon dioxide radical ion (CO–
2) and sulfate. The carbon dioxide radical reacts with peroxodisulfate to form CO2 or self-combines to form oxalate. Competition occurring between these two processes determines the overall fate of the carbon dioxide radical species. As pH decreases, protonation of the carbon dioxide radical ion tends to favor production of CO2. 相似文献
64.
The structures of halogen atom-benzene complexes were investigated by modern DFT and ab initio computational methods. The spectroscopic properties of the complexes are also predicted and are in good agreement with experiment where such data have been reported. The fluorine atom-benzene complex is predicted to be a sigma complex due to the strength of a C-F bond. The chlorine atom-benzene complex is predicted to have an eta(1) pi complex structure, which is only slightly more favorable (1.1 kcal/mol with the BH&HLYP/6-311++G method including the ZPE correction) than a sigma complex but is significantly more stable (4.4 kcal/mol with the BH&HLYP/6-311++G method including the ZPE correction) than the eta(6) pi complex. The bromine and iodine benzene complexes are also predicted to prefer an eta(1) pi complex structure. 相似文献
65.
Mark Strobel Stewart Corn Christopher S. Lyons Gary A. Korba 《Journal of polymer science. Part A, Polymer chemistry》1987,25(5):1295-1307
ESCA and contact angle measurements were used to characterize the surfaces of Polyethylene and polypropylene films exposed to SF6, CF4, and C2F6 plasmas. None of these gases polymerized in the plasma. However, all plasma treatments grafted fluorinated functionalities directly to the polymer surfaces. SF6 plasmas graft fluorine atoms to a polyolefin surface. CF4 plasmas also react by a mechanism dominated by fluorine atoms, but with some contribution from CFx-radical reactions. Although C2F6 does not polymerize, the mechanism of grafting is still dominated by the reactions of CFx radicals. For all gases studied, the lack of polymerization is attributed to competitive ablation and polymerization reactions occurring under conditions of ion bombardment. 相似文献
66.
Two protocols for functionalization of glass supports with hexaethylene glycol (HEG)-linked oligonucleotides were developed.
The first method (standard amidite protocol) made use of the 2-cyanoethyl-phosphoramidite derivative of 4,4′-dimethoxytrityl-protected
HEG. This was first coupled to the support by standard solid-phase phosphoramidite chemistry followed by extension with a
thymidylic acid icosanucleotide. Stepwise addition of the linker phosphoramidite graduated at 1% (relative to the total sites
available) perstep at 50°C resulted in an optimal yield of immobilized oligonucleotides at a density of 2.24 × 1010 strands/mm2. This observed loading maximum lies well below the theoretical maximum loading owing to nonspecific adsorption of HEG on
the glass and subsequent blocking of reactive sites. Surface loadings as high as 3.73 × 1010/mm2 and of excellent sequence quality were achieved with a reverse amidite protocol. The support was first modified into a 2-cyanoethyl-N,N-diisopropylphosphoramidite analog followed by coupling with 4,4′-dimethoxytrityl-protected HEG. This protocol is conveniently
available when using a conventional DNA synthesizer. The reverse amidite protocol allowed for control of the surface loading
at values suitable for subsequent analytical applications that make use of immobilized oligonucleotides as probes for selective
hybridization of sample nucleic acids of unknown sequence and concentration. 相似文献
67.
Alexander Aster Christopher Rumble Anna-Bea Bornhof Hsin-Hua Huang Naomi Sakai Tom olomek Stefan Matile Eric Vauthey 《Chemical science》2021,12(13):4908
1,4,5,8-Naphthalenediimides (NDIs) are widely used motifs to design multichromophoric architectures due to their ease of functionalisation, their high oxidative power and the stability of their radical anion. The NDI building block can be incorporated in supramolecular systems by either core or imide functionalization. We report on the charge-transfer dynamics of a series of electron donor–acceptor dyads consisting of a NDI chromophore with one or two donors linked at the axial, imide position. Photo-population of the core-centred π–π* state is followed by ultrafast electron transfer from the electron donor to the NDI. Due to a solvent dependent singlet–triplet equilibrium inherent to the NDI core, both singlet and triplet charge-separated states are populated. We demonstrate that long-lived charge separation in the triplet state can be achieved by controlling the mutual orientation of the donor–acceptor sub-units. By extending this study to a supramolecular NDI-based cage, we also show that the triplet charge-separation yield can be increased by tuning the environment.Ultrafast electron transfer from singlet and triplet excited states in equilibrium results in the population of both singlet and triplet charge-separated states. 相似文献
68.
Diaper CM Sutherland A Pillai B James MN Semchuk P Blanchard JS Vederas JC 《Organic & biomolecular chemistry》2005,3(24):4402-4411
Aziridine analogues of diaminopimelic acid (DAP) have been prepared stereoselectively for the first time and evaluated as inhibitors of DAP epimerase. (2R,3S,3'S)-3-(3'-Aminopropane)aziridine-2,3'-dicarboxylate was synthesised and shown to be a reversible inhibitor of DAP epimerase with an IC(50) value of 2.88 mM. (2S,4S)- and (2S,4R)-2-(4-Amino-4-carboxybutyl)aziridine-2-carboxylic acid (ll-azi-DAP and dl-azi-DAP ) were made as pure diastereomers, and both were shown to be irreversible inhibitors of DAP epimerase. ll-Azi-DAP selectively binds to Cys-73 of the enzyme active site whereas dl-azi-DAP binds to Cys-217 via attack of sulfhydryl on the methylene of the inhibitor aziridine ring. These observations are consistent with the two base mechanism proposed for the epimerization of ll-DAP and meso-DAP by DAP epimerase. 相似文献
69.
Haes AJ Zhao J Zou S Own CS Marks LD Schatz GC Van Duyne RP 《The journal of physical chemistry. B》2005,109(22):11158-11162
A novel method to produce solution-phase triangular silver nanoparticles is presented. Ag nanoparticles are prepared by nanosphere lithography and are subsequently released into solution. The resulting nanoparticles are asymmetrically functionalized to produce either single isolated nanoparticles or dimer pairs. The structural and optical properties of Ag nanoparticles have been characterized. Mie theory and the Discrete Dipole Approximation method (DDA) have been used to model and interpret the optical properties of the released Ag nanoparticles. 相似文献
70.
The synthesis of the alkaloid jamtine and the antidepressant paroxetine have been addressed by a strategy involving asymmetric desymmetrisation of prochiral imides by a chiral lithium amide base. A short reaction sequence, starting with a cyclohexane fused succinimide, led to the structures originally reported for the alkaloid jamtine and its derived N-oxide. The structures synthesised are shown not to correspond with those originally reported. A second sequence involves desymmetrisation of a 4-arylglutarimide, and provides a short enantioselective synthesis of the drug substance paroxetine. 相似文献