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81.
82.
The spectroscopic, electronic, and DNA-binding characteristics of two novel ruthenium complexes based on the dialkynyl ligands 2,3-bis(phenylethynyl)-1,4,8,9-tetraaza-triphenylene (bptt, 1) and 2,3-bis(4-tert-butyl-phenylethynyl)-1,4,8,9-tetraaza-triphenylene (tbptt, 2) have been investigated. Electronic structure calculations of bptt reveal that the frontier molecular orbitals are localized on the pyrazine-dialkynyl portion of the free ligand, a property that is reflected in a red shift of the lowest energy electronic transition (1: λ(max) = 393 nm) upon substitution at the terminal phenyl groups (2: λ(max) = 398 nm). Upon coordination to ruthenium, the low-energy ligand-centered transitions of 1 and 2 are retained, and metal-to-ligand charge transfer transitions (MLCT) centered at λ(max) = 450 nm are observed for [Ru(phen)(2)bptt](2+)(3) and [Ru(phen)(2)tbptt](2+)(4). The photophysical characteristics of 3 and 4 in ethanol closely parallel those observed for [Ru(bpy)(3)](2+) and [Ru(phen)(3)](2+), indicating that the MLCT excited state is primarily localized within the [Ru(phen)(3)](2+) manifold of 3 and 4, and is only sparingly affected by the extended conjugation of the bptt framework. In an aqueous environment, 3 and 4 possess notably small luminescence quantum yields (3: ?(H(2)O) = 0.005, 4: ?(H(2)O) = 0.011) and biexponential decay kinetics (3: τ(1) = 40 ns, τ(2) = 230 ns; 4: τ(1) ~ 26 ns, τ(2) = 150 ns). Addition of CT-DNA to an aqueous solution of 3 causes a significant increase in the luminescence quantum yield (?(DNA) = 0.045), while the quantum yield of 4 is relatively unaffected (?(DNA) = 0.013). The differential behavior demonstrates that tert-butyl substitution on the terminal phenyl groups inhibits the ability of 4 to intercalate with DNA. Such changes in intrinsic luminescence demonstrate that 3 binds to DNA via intercalation (K(b) = 3.3 × 10(4) M(-1)). The origin of this light switch behavior involves two competing (3)MLCT states similar to that of the extensively studied light switch molecule [Ru(phen)(2)dppz](2+). The solvent- and temperature-dependence of the luminescence of 3 reveal that the extended ligand aromaticity lowers the energy of the (3)ππ* excited state into competition with the emitting (3)MLCT state. Interconversion between these two states plays a significant role in the observed photophysics and is responsible for the dual emission in aqueous environments. 相似文献
83.
N-Acylthioureas 1 can be easily transformed into 2,4-diamino-6-aryl-1,3,5-oxadiazinium salts 12, 2,4-diamino-6-aryl-1,3,5-thiadiazinium salts 13,3-amino-5-aryl-1,2,4-dithiazolium salts 19 and 2-acylimino-benzothiazolines 22, respectively by reaction with different electrophiles. The structure of the compounds prepared is confirmed by analytical data as well as by chemical transformations. 相似文献
84.
Hartmann E Brendebach B Polly R Geckeis H Stumpf T 《Journal of colloid and interface science》2011,353(2):562-568
In order to assess the long-term safety of deep radioactive waste repositories, a precise characterization of the different sorption processes on a molecular basis and the exact definition of geochemical boundary conditions for their relevance are of immense importance. Through sorption on various minerals the migration of radionuclides will be hindered and their retention will be ensured. Using time-resolved laser fluorescence spectroscopy (TRLFS) and extended X-ray absorption fine structure (EXAFS) spectroscopy, it was possible to identify outer-sphere sorbed trivalent lanthanides and actinides onto different montmorillonites and illite. Furthermore, the quantification of Cm(III)/clay outer-sphere sorption in D(2)O at different ionic strengths was shown. The results were confirmed by ion exchange model calculations. Finally, the structural parameters of a Sm(III)/clay outer-sphere complex were obtained by EXAFS measurements. 相似文献
85.
Mono- or 1,1′-bis-acylation of ferrocene, its mono and 1,1′-dimethyl and phenyl derivatives and of [3]ferrocenophane with o-chlorobenzoyl chloride/AlCl3 affords the corresponding (isomeric) chlorobenzoyl ferrocenes in high yields which can be separated by column, layer or high pressure liquid chromatography and in the case of the monomethylferrocene monoketones also by crystallization. The cleavage of the (o-chlorobenzoyl)ferrocenes by potassium-t-butoxide (and traces of water) yields the corresponding ferrocene carboxylic acids except for the α-phenyl derivatives in almost quantitative yields, thus offering a very convenient access to these acids. In all cases the isomer distribution and thereby the relative site reactivities were determined. 相似文献
86.
Brigitte Sarry und Arno Lange 《Fresenius' Journal of Analytical Chemistry》1968,241(3):186-196
Zusammenfassung Die optimalen Bedingungen für die photometrische Bestimmung von Tantal mit Pyrogallol in schwefelsaurer Lösung bei 405 nm wurden ausgearbeitet. Das Verfahren wurde statistisch überprüft.
Für die Durchführung der Untersuchungen standen Mittel aus dem ERP-Sondervermögen und dem Fonds der Chemischen Industrie zur Verfügung, für die wir auch an dieser Stelle bestens danken.
Herrn Professor Dr. E. Asmus zum 60. Geburtstag gewidmet. 相似文献
Investigations on the photometric determination of tantalum with pyrogallol
The optimum conditions for the photometric determination of tantalum with pyrogallol in sulphuric acid solution at 405 nm have been elaborated. The method has been checked statistically.
Für die Durchführung der Untersuchungen standen Mittel aus dem ERP-Sondervermögen und dem Fonds der Chemischen Industrie zur Verfügung, für die wir auch an dieser Stelle bestens danken.
Herrn Professor Dr. E. Asmus zum 60. Geburtstag gewidmet. 相似文献
87.
Zusammenfassung Mit Hilfe eines einfachen quantenmechanischen Näherungsansatzes wird versucht, Bindungsabstände und Normalfrequenzen des Hydrogendifluoridions sowie des entsprechenden deuterierten Ions zu berechnen. Hierbei wird die Elektronenwechselwirkung der beiden Fluoridionen untereinander durch einen der Statistik entlehnten Ausdruck berücksichtigt. Die Methode liefert für die Abstände gute, für die Normalfrequenzen durchaus befriedigende Ergebnisse.
Der Deutschen Forschungsgemeinschaft danken wir für die Gewährung eines Stipendiums an Karl Hensen. 相似文献
On the basis of a quantum mechanical treatment the bond distances and the normal frequences of the hydrogen difluoride ion and its deuterated analogue are calculated. The electronic interaction of the two fluoride ions is approximated by a statistical calculation. The results are in fairly good agreement with the experimental values.
Résumé Sur la base d'un traitement quantique simple, le calcul des distances de liaison et des fréquences normales est tenté pour l'ion de bifluorure d'hydrogène et son analogue deutéré. L'intéraction électronique des deux ions fluorures est approximée au moyen d'un calcul statistique. Les résultats sont en très bon accord avec les valeurs expérimentales.
Der Deutschen Forschungsgemeinschaft danken wir für die Gewährung eines Stipendiums an Karl Hensen. 相似文献
88.
Gottfried WAGNER Bernhard Traulich KarlM. Hartmann Dieter Oesterhelt 《Photochemistry and photobiology》1987,46(3):393-402
Quantitative action spectroscopy was performed in Halobacterium halobium. using four suited pigment mutants, namely the bacteriorhodopsin and halorhodopsin positive mutant strain M-l (BR+, HR+), the bacteriorhodopsin positive but halorhodopsin negative strain M-18 (BR+, HR-), the bacteriorhodopsin negative but halorhodopsin positive strain L-33 (BR-, HR+), and the bacteriorhodopsin and halorhodopsin negative strain L-07 (BR-, HR+). The approached questions were: First, photoenergetic synergism of halorhodopsin and bacteriorhodopsin in intact cells; second, photochromism and cellular function of the blue light-absorbing intermediates, i.e. M-412 and HR-410 in bacteriorhodopsin and in halorhodopsin, respectively. Dark-adapted cells of mutant strain M-l show wavelength-dependency of quantum yield of photo-phosphorylation, φATP. An 1.4-fold enhancement was found at 575 nm wavelength where the long wavelength absorbance bands of bacteriorhodopsin and halorhodopsin intersect. The enhancement vanished after a 30 min pulse of orange light (600 Wm-2 bandpass from 495 to 750 nm), but was restored after a 30 min pulse of blue light (100 Wm-2 bandpass from 325 to 480 nm). Photoreversibility of this enhancement probably reflects phototransformation of halorhodopsin from its ground state into its inactive intermediate, HR-410, and vice versa. The halorhodopsin-mediated enhancement with maximum quantum yield of photophosphorylation, φATP= 0.06, i.e. a quantum requirement of = 17 photons/ATP, is partly substituted by a rise in phosphate potential and explained in terms of a voltage-regulated gating effect on the H+-driven ATP-synthase, superimposed on the chemiosmotic mechanism of energy coupling. The blue-absorbing photochromic intermediate, M-412 of bacteriorhodopsin, dissipates light energy upon photoexcitation that is reflected by a spectral decline in quantum yield of photophosphorylation to a minimum value of = 0.01 at 415 nm, i.e. a quantum requirement of = 100 photons/ATP. 相似文献
89.
90.
R. G?tz P. Enge P. Friesel K. Roch B. Schilling B. Hartmann H. Wunsch 《Fresenius' Journal of Analytical Chemistry》1994,348(10):694-695
Sampling and determination of dissolved and particlebound PCBs and HCB in the river Elbe are described. A new filtration/adsorption unit for sampling of dissolved lipophilic contaminants was developed. The detection limit for dissolved PCBs and HCB was 5 pg/l. The data show that more than 98% of the PCBs and of HCB in the water of the river Elbe are particle-bound. 相似文献