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41.
Roland A. Obermüller Christoph Etzlstorfer Heinz Falk 《Monatshefte für Chemie / Chemical Monthly》2002,133(1):89-96
Summary. A hypericin derivative was synthesized in which instead of the methyl groups two benzene rings were condensed to the chromophoric
system in order to extend its conjugation. This derivative showed lowered fluorescence and concomitantly enhanced sensitized
production of active oxygen species as compared to hypericin. However, in contrast to intuition its long wavelength band remained
unshifted in comparison to its parent compound hypericin. Geometry and absorption properties were also investigated by means
of semiempirical calculations.
Received July 27, 2001. Accepted August 9, 2001 相似文献
42.
Bernd?Lackner Yulita?Popova Christoph?Etzlstorfer Andrija A.?Smelcerovic Christian W.?Klampfl Heinz?FalkEmail author 《Monatshefte für Chemie / Chemical Monthly》2005,136(5):777-793
Summary. The syntheses of the two heterocyclically substituted title hypericin derivatives were achieved starting either from 6-benzothiazolyl-tri-O-methyl-6-demethylemodin or 6-benzoxazolyl-tri-O-methyl-6-demethylemodin. The use of microwave assisted synthesis for the preparation of these anthraquinone synthons and the chemical as well as photochemical properties of the corresponding unique hypericin derivatives, which might constitute new photodynamic therapy agents, are reported. The tautomeric and stereochemical aspects of these hypericin derivatives were investigated by means of semiempirical calculations (AM1). 相似文献
43.
Christoph Kratky Heinz Falk Ulrich Zrunek 《Monatshefte für Chemie / Chemical Monthly》1985,116(5):607-623
The molecular and crystal structures of the two racemic diastereomeric 3,4-dihydropyrromethenone derivatives1 and2 of configurations (Z) and (E) were determined at 93 K (1, 2) and at room temperature (1). From an analysis of the crystallographically observed temperature coefficients a pseudorotation flexibility of the pyrrolidinone ring in the crystal is deduced. In both compounds a nearly orthogonal arrangement between the two heterocyclic ring systems is observed, which is ascribed to the steric bulk of the substituents in positions 1 and 3 of the pyrrolidinone ring.Herrn Prof.Josef Schurz zum 60. Geburtstag gewidmet. 相似文献
44.
The optically and thermally induced electron transfer pathways of highly symmetrical (D(3)) hexaarylbenzene systems with six triarylamine redox sites have been investigated. Owing to slightly different local redox potentials, the radical trication could be selectively generated by electrochemical methods. This trication shows a strong intervalence charge-transfer band in the near infrared (NIR) that was measured by spectroelectrochemistry and analysed using multi-dimensional Mulliken-Hush theory. Quantum chemical AM1 CI calculations indicate that there is no optically induced concerted three-electron transfer that transforms the ground state into a state in which all three positively charged triarylamine moieties change place with their neutral neighbours. The potential energy surface of the ground state was constructed by using quadratic potentials. From this potential surface it is apparent that there is also no thermally allowed concerted three-electron transfer pathway. Instead, three consecutive one-electron transfer steps are necessary for this process. 相似文献
45.
Gerhard Cordier Christoph Schwidetzky Herbert Schäfer 《Journal of solid state chemistry》1984,54(1):84-88
The new compound BaSb2S4 crystallizes in the monoclinic system (space group: , No. 14) with a = 8.985(2) Å, b = 8.203(3) Å, c = 20.602(5) Å, β = 101.36(3)°. SbS3 ψ tetrahedra and ψ-trigonal SbS4 bipyramids are connected by common corners and edgers to infinite strings. These are arraged cross-wise in sheets perpendicular to the c axis. 相似文献
46.
Zdzislaw Chilmonczyk Markus Egli Christoph Behringcr AndrS. Dreiding 《Helvetica chimica acta》1989,72(5):1095-1106
In-situ-generated phthalimidonitrene was added to five α, β-unsaturated esters containing a chiral secondary O-function at C(γ). The additions were fully suprafacial, inasmuch as the (E)-isomers 1 afforded only the trans-aziridines 2 and 3 (J(β, γ) = 4.8?5.1 Hz) and the (Z)-isomers 4 only the cis-aziridines 5 and 6 (8.2?8.5 Hz). The products 2 , 3 , 5 , and 6 where shown to possess the arabino-, xylo-, ribo-, and lyxo- configuration, respectively, by X-ray structure analysis of 2b , 2d , and 6a . The diastereoface selectivity of the nitrene additions, induced by the chiral substructure around C(γ), resulted in more 2 than 3 from 1 , but more 6 than 5 from 4 , which means that the preference of attack at the double bond switches from one side to the other depending on the C=C configuration. The preferences were higher at lower temperature. The aziridines 2a , 2d , and 3d exhibit 1H-NMR-visible isomerism at the ring N-atom; the major (78?95 %)invertomer A is always the one with the phthalimido group in trans-position to the (larger) substructure around C(γ). The other aziridines only show 1H-NMR signals of one invertomer, which – by steric reasoning - ought to be A ; this is confirmed by a 1H-NMR argument for 3a , 5a , 6a , 5c , and 6c . 相似文献
47.
The reaction between 1,4-pentadiyne and diethylaminotrimethylstannane leads predominantly to (E)-2-diethylamino-4-trimethylstannyl-2,4-pentaenyne (with either a 1/1 or 1/2 mol ratio of 1,4-pentadiyne and diethylaminotrimethylstannane). With 1/2 stoicheiometry 1,1,5-tris(trimethylstannyl)penta-1,2-dien-4-yne is formed as a minor product. 13C and 119Sn NMR data are reported. 相似文献
48.
A. Golloch Stefan Heidbreder Christoph Lühr 《Analytical and bioanalytical chemistry》1998,361(6-7):545-546
Imitations of amber have been prepared since a long time, but the number of imitations is increasing since modern polymers are available. At present, many imitations are based on a few synthetic polymers and even experts have some problems in distinguishing between real and falsed amber without destruction of the material. IR-Spectroscopy or pyrolysis combined with gas chromatography/mass spectrometry are very efficient methods in identifying amber and imitations but these methods need a sample preparation. By means of near infrared reflection spectroscopy it is possible to identify amber and imitations without any sample preparation in a short time. Optimization of the method and the application are discussed. 相似文献
49.
Baeten V von Holst C Garrido A Vancutsem J Michotte Renier A Dardenne P 《Analytical and bioanalytical chemistry》2005,382(1):149-157
In this paper we present an alternative method for detection of meat and bone meal (MBM) in feedstuffs by near-infrared microscopic (NIRM) analysis of the particles in the sediment fraction (dense fraction (d >1.62) from dichloroethylene) of compound feeds. To apply this method the particles of the sediment fraction are spread on a sample holder and presented to the NIR microscope. By using the pointer of the microscope the infrared beam is focussed on each particle and the NIR spectrum (1112–2500 nm) is collected. This method can be used to detect the presence of MBM at concentrations as low as 0.05% mass fraction. When results from the NIRM method were compared with the classical microscopic method, a coefficient of determination (R2) of 0.87 was obtained. The results of this study demonstrated that this method could be proposed as a complementary tool for the detection of banned MBM in feedstuffs by reinforcement of the monitoring of feeds. 相似文献
50.
Syntheses and Chemical Properties of New Bridged Quinone Derivatives. Coupling Reactions of Aryldiazonium Salts with 2-Methoxy-1,6-methano[10]annulene Coupling of 2-methoxy-1,6-methano[10]annulene (3) with the aryldiazonium salts 4a-4i yields the quinone hydrazones 5a-5i. The spectroscopic properties of these products are described. The reaction of 3 with 4-nitrophenyldiazonium tetrafluoroborate buffered with sodium acetate in dry methanol yielded after chromatographic separation the azo derivative 7 on the one hand and a mixture of the valence tautomers 8a and 8b on the other. 相似文献