排序方式: 共有73条查询结果,搜索用时 0 毫秒
41.
Alexander Schmitt Babette Hinkeldey Mandy Wild Gregor Jung 《Journal of fluorescence》2009,19(4):755-758
We report the synthesis and characterization of the missing reference core compound 4,4-Difluoro-4-bora-(3a,4a)-diaza-s-indacene 1 of the BODIPY fluorescent dye class. The compound exhibits a fluorescence lifetime of 7.2 ns and has a high photostability. 相似文献
42.
An improved protocol for copper-catalyzed triazole formation on the bacterial cell surface is described. Addition of highly pure CuBr to cells treated with azidohomoalanine (2) leads to ca. 10-fold more extensive cell surface labeling than previously observed. This highly active catalyst allows detection of the methionine analogues azidoalanine (1), azidonorvaline (3), and azidonorleucine (4) in cell surface proteins. Azidoalanine was previously believed to be silent with regard to the cellular protein synthesis machinery. 相似文献
43.
The collision induced dissociation of H2 by H atoms was studied by quasiclassical trajectories using the Liu-Siegbahn-Truhlar-Horowitz potential energy surface. Dissociation cross sections were obtained for five highly internally excited initial states of H2 for translational energies up to 100 kcal mol?1. Rate constants for dissociation out of these states were calculated for temperatures of 1000 to 10,000 K. Initial internal energy strongly enhances the probability of collisional dissociation, vibrational energy being more effective than rotational. The results are compared to those from a similar study of the H2?He system, and are discussed in relation tothe respective potential energy surfaces. The implications for the kineticsof thermal dissociation are also considered. 相似文献
44.
The 1,3-diyne and diynophile in hexadehydro-Diels–Alder (HDDA) reaction substrates are typically tethered by linker units that consist of C, O, N, and/or S atoms. We describe here a new class of polyynes based on silicon-containing tethers that can be disposed of and/or functionalized subsequent to the HDDA reaction. The cyclizations are efficient, and the resulting benzoxasiloles are amenable to protodesilylation, halogenation, oxygenation, and arylation reactions. The presence of the silicon atom can also override the innate mode of cyclization in some cases, an outcome attributable to a β-silyl effect on the structure of intermediate diradicals. Overall, this strategy equates formally to an otherwise unknown, bimolecular HDDA reaction and expands the versatility of this body of aryne chemistry.A designer silicon-containing linker enables HDDA chemistry that complements known modes of reactivity. Subsequent removal of the Si liberates a benzenoid product that is formally the result of an intermolecular HDDA reaction. 相似文献
45.
The secondary vinylphosphines Ar(F)P(H)C(R)[double bond]CH(2) [2a, Ar(F) = 2,6-(CF(3))(2)C(6)H(3), R = CH(3); 2b, Ar(F) = 2,6-(CF(3))(2)C(6)H(3), R = C(6)H(5); 2c, Ar(F) = 2,4,6-(CF(3))(3)C(6)H(2), R = CH(3)] were prepared by treating the corresponding dichlorophosphine Ar(F)PCl(2) (1) with H(2)C[double bond]C(R)MgBr. In the presence of catalytic base (DBU or DABCO) the vinylphosphines (2a-c) undergo quantitative 1,3-hydrogen migration over 3 d to give stable and isolable phosphaalkenes Ar(F)P=C(R)CH(3) (3a, Ar(F) = 2,6-(CF(3))(2)C(6)H(3), R = CH(3); 3b, Ar(F) = 2,6-(CF(3))(2)C(6)H(3), R = C(6)H(5); 3c, Ar(F) = 2,4,6-(CF(3))(3)C(6)H(2), R = CH(3)). Under analogous conditions, only 90% conversion is observed in the base-catalyzed rearrangement of MesP(H)C(CH(3))[double bond]CH(2) to MesP[double bond]C(CH(3))(2). Presumably, the increase in acidity of the P-H group when electron-withdrawing groups are employed (i.e. 2a-c) favors quantitative rearrangement to the phosphaalkene tautomer (3a-c). Thus, the double-bond migration reaction is a convenient and practical method of preparing new phosphaalkenes with C-methyl substituents. 相似文献
46.
Selahattin Ede Mandy Schenk Donald Bierer Hilmar Weinmann Keith Graham 《Molecules (Basel, Switzerland)》2021,26(6)
DNA-encoded libraries (DEL) are increasingly being used to identify new starting points for medicinal chemistry in drug discovery. Herein, we discuss the development of methods that allow the conversion of both primary amines and anilines, attached to DNA, to their corresponding azides in excellent yields. The scope of these diazo-transfer reactions was investigated, and a proof-of-concept has been devised to allow for the synthesis of macrocycles on DNA. 相似文献
47.
Mandy Hecht Tobias Fischer Dr. Paul Dietrich Werner Kraus Dr. Ana B Descalzo Dr. Wolfgang E S Unger Dr. Knut Rurack 《ChemistryOpen》2013,2(1):25-38
A family of bright boron-dipyrromethene-type fluorophores with a high number of fluorine atoms (F-BODIPYs) has been developed and characterized by X-ray crystallography and optical spectroscopy. The introduction of 3,5-bis(trifluoromethyl)phenyl and pentafluorophenyl moieties significantly enhances the photostability of such dyes, yielding for instance photostable near-infrared (NIR) fluorophores that show emission maxima>750 nm, when the BODIPY’s π system is extended with two (dimethylamino)styryl and (dimethylamino)naphthastyryl moieties, or green-emitting BODIPYs with fluorescence quantum yields of unity. When equipped with a suitable group that selectively reacts for instance with amines, F-BODIPYs can be used as potent dual labels for the quantification of primary amino groups on surfaces by X-ray photoelectron spectroscopy (XPS) and fluorescence, two powerful yet complementary tools for the analysis of organic surface functional groups. The advantage of reactive F-BODIPYs is that they allow a fast and non-destructive mapping of the labelled supports with conventional fluorescence scanners and a subsequent quantification of selected areas of the same sample by the potentially traceable XPS technique. The performance is exemplarily shown here for the assessment of the amino group density on SiO2 supports, one of the most common reactive silica supports, in particular, for standard microarray applications. 相似文献
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49.
Two organogelators, CO-01 and CO-03 , featuring benzimidazole and long-chain pyridine carboxyamide groups were prepared and their physical properties were fully explored. CO-01 and CO-03 are capable of transforming various organic solvents to organogels. The morphologic investigations of these organogels have shown that the supramolecular assemblies, in the forms of fibers and spheres, are readily generated from the aggregates of CO-01 and CO-03 . The sol–gel interconversion can be readily achieved by tuning the gelator concentration and temperature. By manipulating the redox state of anthraquinone group in CO-03 , the gel–sol transition for the organogels of CO-03 can be reversibly tuned by either chemical or electrochemical oxidation/reduction reactions. The presence of polarized imidazole and amide N–H groups allows anion-induced gel collapse. The accompanying colorimetric and ratiometric fluorescent responses of gels CO-01 and CO-03 to F− and CN− render these organogelators being sensitive and selective anion probes. 相似文献
50.
Richard J. C. Brown Mandy C. Shaw Matthew R. Roberts† 《International journal of environmental analytical chemistry》2013,93(6):453-460
A robust and accurate method for the quantitative determination of the water-soluble and water-insoluble, Ni, Cd, Pb and Zn contents of deposited ambient dust is presented. The extraction of the soluble metal phase from deposited ambient dust has been validated using commercially available ambient dust certified reference material. Results from a 6 month measurement campaign, from July to December 2004, are presented. Quantitative analysis of the two fractions, of different aqueous solubility (referred to here as ‘solubility speciation analysis’), within deposited ambient dust is reported for the first time. Additionally, the two Bergerhoff dust deposit gauges used in parallel to acquire the dust deposit samples have shown good inter-sampler comparability. The measured total deposition fluxes compare well with those previously reported in urban and semi-rural locations around the UK. 相似文献