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91.
Johansson A Abrahamsson M Magnuson A Huang P Mårtensson J Styring S Hammarström L Sun L Akermark B 《Inorganic chemistry》2003,42(23):7502-7511
The preparation of donor (D)-photosensitizer (S) arrays, consisting of a manganese complex as D and a ruthenium tris(bipyridyl) complex as S has been pursued. Two new ruthenium complexes containing coordinating sites for one (2a) and two manganese ions (3a) were prepared in order to provide models for the donor side of photosystem II in green plants. The manganese coordinating site consists of bridging and terminal phenolate as well as terminal pyridyl ligands. The corresponding ruthenium-manganese complexes, a manganese monomer 2b and dimer 3b, were obtained. For the dimer 3b, our data suggest that intramolecular electron transfer from manganese to photogenerated ruthenium(III) is fast, k(ET) > 5 x 10(7) s(-)(1). 相似文献
92.
The new 10 μg l−1 arsenic standard in drinking water has been a spur to the search for reliable routine analytical methods with a limit of detection at the μg l−1 level. These methods also need to be easy to handle due to the routine analyses that are required in drinking water monitoring. Graphite furnace atomic absorption spectrometry (GFAAS) meets these requirements, but the limit of detection is generally too high except for methods using a pre-concentration or separation step. The use of a high-intensity boosted discharge hollow-cathode lamp decreases the baseline noise level and therefore allows a lower limit of detection. The temperature program, chemical matrix modifier and thermal stabilizer additives were optimized for total inorganic arsenic determination with GFAAS, without preliminary treatment. The optimal furnace program was validated with a proprietary software. The limit of detection was 0.26 μg As l−1 for a sample volume of 16 μl corresponding to 4.2 pg As. This attractive technique is rapid as 20 samples can be analysed per hour. This method was validated with arsenic reference solutions. Its applicability was verified with artificial and natural groundwaters. Recoveries from 91 to 105% with relative standard deviation <5% can be easily achieved. The effect of interfering anions and cations commonly found in groundwater was studied. Only phosphates and silicates (respectively at 4 and 20 mg l−1) lead to significant interferences in the determination of total inorganic arsenic at 4 μg l−1. 相似文献
93.
Reaction of benzotriazol‐1‐yl acetone 1 with phenyl isothiocyanate followed with α‐chloroacetone or ethyl‐α‐chloroacetate afforded 2‐anilinothiophenes 3 or 4 , respectively. Treatment of 3 with malononitrile at different reaction conditions afforded 6 or 7 . Reaction of 1 with CS2 in DMF and phenacylbromide afforded S‐alkylated thiophene 10 . Reactions of the latter compound with different active methylene nitriles afforded thienylthiopyridine derivatives 14 and 15 . Condensation of 10 with hydrazine hydrate afforded hydrazon derivative 16 . Reaction of thiophene 17 with formamide in DMF afforded 19 which converted to N‐thienylpyrimidine 20 when treated with malononitrile. The structure of the newly synthesized compounds has been established on the basis of their analytical and spectral data. The compounds were also investigated for antibacterial and antifungal activities. 相似文献
94.
H. -H. Perkampus und K. Kortüm 《Fresenius' Journal of Analytical Chemistry》1962,190(1):111-126
Zusammenfassung Durch Vergleich der Absorptionsspektren der Metall-8-hydroxychinolinate mit denen der Metall-4-hydroxy-acridinate und -phenazinate ließ sich die Frage, ob in diesen Komplexen das Kation oder das Anion des organischen Liganden vorliegt, zugunsten des Anions beantworten. Die geringe Auftrennung der beiden langwelligen 1
L
a- und 1
L
b-Banden im Absorptionsspektrum des 8-Hydroxy-chinolins erlaubtekeine zweifelsfreie Beantwortung dieser Frage.Unter der Annahme des elektrostatischen Modells lassen sich bei den Oxinaten der Übergangsmetalle die Absorptionsspektren qualitativ verstehen, was sowohl für die Beeinflussung der 1
L
a-Banden der Liganden durch das Zentralion als auch für die Zentralionenbanden gilt. Die nach diesem Modell diskutierten Komplexe mit zweifach positiven Zentralionen zeigen ferner eine starke Lösungsmittelabhängigkeit ihrer Absorptionsspektren, die in der 1
L
a-Bande und der Zentralionenbande entgegengesetzte Effekte bewirkt. Auch diese Effekte lassen sich mit dem elektrostatischen Modell deuten.Interessant ist noch, daß die absolute Rotverschiebung der 1
L
a-Bande für den gleichen Komplex unter vergleichbaren Bedingungen, bezogen auf die Lage der 1
L
a-Bande im Anion, vom 8-Hydroxy-chinolin zum 4-Hydroxy-phenazin abnimmt. Ihr Betrag ist für das CuII-Oxinat mit 4200 cm–1 am größten und für das CuII-4-hydroxy-phenazinat mit 1600 cm–1 am kleinsten und liegt damit in der Größenordnung der Verschiebung beim Mg- und Zn-Oxinat, die wohl als kovalente Komplexe zu formulieren sind. Gerade die letzteren Komplexe zeichnen sich außerdem durch ihr Fluorescenzvermögen gegenüber den Komplexen der Übergangsmetalle aus, wie von verschiedenen Autoren festgestellt wurde20. Nach Umland u. Haar
22 liegt das Fluorescenzmaximum des Zinkoxinats z.B. um 10000 cm–1 rotverschoben zum Absorptionsmaximum. In dieser Richtung ergeben sich daher außerordentlich interessante Effekte, über die bisher keine näheren Untersuchungen vorliegen, die jedoch sicherlich weitere Aussagen über die Natur dieser Komplexe vermitteln würden.Für das Interesse an diesen Untersuchungen danken wir dem Institutsdirektor Herrn Prof. Dr. Dr. h. c. R. Suhrmann herzlich.Dem Verband der Chemischen Industrie und der Deutschen Forschungsgemeinschaft danken wir für die Unterstützung dieser Arbeiten. Der Max-Buchner-Forschungsstiftung dankt der eine von uns (K. K.) für ein Stipendium.Herrn Prof. Dr. W. Fischer zum 60. Geburtstag gewidmet. 相似文献
95.
Boström J Böhm M Gundertofte K Klebe G 《Journal of chemical information and computer sciences》2003,43(3):1020-1027
The molecular alignments obtained from a previously reported pharmacophore model have been employed in a three-dimensional quantitative structure-activity relationship (3D QSAR) study, to obtain a more detailed insight into the structure-activity relationships for D(2) and D(4) receptor antagonists. The frequently applied CoMFA method and the related CoMSIA method were used. Statistically significant models have been derived with these two methods, based on a set of 32 structurally diverse D(2) and D(4) receptor antagonists. The CoMSIA and the CoMFA methods produced equally good models expressed in terms of q(2) values. The predictive power of the derived models were demonstrated to be high. Graphical interpretation of the results, provided by the CoMSIA method, brings to light important structural features of the compounds related to either low- or high-affinity D(2) or D(4) antagonism. The results of the 3D QSAR studies indicate that bulky N-substituents decrease D(2) binding, whereas D(4) binding is enhanced. Electrostatically favorable and unfavorable regions exclusive to D(2) receptor binding were identified. Likewise, certain hydrogen-bond acceptors can be used to lower D(2) affinity. These observations may be exploited for the design of novel dopamine D(4) selective antagonists. 相似文献
96.
3-(2S-Heptylcycloprop-1S-yl)propanoic acid 2-phenylethanamide was synthesised from cis-cyclopropan-1,2-dimethanol via enzymatic desymmetrisation of the dibutyrate; it gave identical NMR spectroscopic data to those reported for grenadamide but had an equal and opposite absolute rotation, indicating that the latter is the 2R,1R-enantiomer. 相似文献
97.
Daniela Walterová Zdeně;K Stránský Vladimír Preininger Prof. Dr. Vilím Šimánek 《Electrophoresis》1985,6(3):128-132
The isotachophoretic behavior of quaternary benzo/c/phenanthridine, protoberberine and aporphine alkaloids in different electrolyte systems is described. The concentration of the leading ion and the pH value of the leading electrolyte affect the relative effective mobilities of the alkaloids. The system of pH 4.7, containing the leading ion K+ (0.005 M) counter ion acetate, and the terminating ion β-alanine (0.02 M), has been selected for the quantitative determination of the studied alkaloids in model mixtures and plant extracts. 相似文献
98.
The flaws in the Reply [1] to our paper [2] have been pointed out. Elber and Karplus (EK) have not disproved our irrefutable global statement that the energy average cannot be minimized which rebuts the theoretical background of EK-type calculations. Another statement of ours has shown that even a curve for which the average energy is locally minimal for all directional perturbations in the sense of classical variational calculus cannot be identical with the reaction path (RP) defined as a steepest descent path (SDP). EK found an error in the early preprint of our theoretical paper [3] and because of this error they qualified our correct variational statement as false for all the SDPs consisting of a straight line each. Mixing global and variational arguments, EK refuted our criticism in a logically incorrect manner. In this Comment we prove that both of our earlier statements invariably remain in force and the criticism included in those has been as well-established and solid as was before. 相似文献
99.
The [Et4N][M(CO)5SCOPh] complexes (1a, M = Mo; 2a, M = W) have been prepared at ambient temperatures by reacting the photogenerated M(CO)5 THF intermediate with [Et4N][SCOPh] in THF. Kinetic studies of the reactions of the anions [M(CO)5SCOPh]– with the tri(iso-propyl)phosphite (L) ligand under pseudo-first-order conditions indicate that these reactions are first-order in substrate and are independent of the P(OPr-i)3 concentration. It is thus envisaged that these CO substitutions proceed via a mechanism which involves initial cis-M—CO bond-breaking, followed by fast attack of the incoming nucleophile on the resulting intermediate to give [cis-M(CO)4{P(O-Pri)3}SCOPh]–. This facile displacement of cis-CO indicates the labilizing nature of the thiobenzoate ligand, most probably by virtue of distal oxygen atom participation. Activation parameters for the reactions are: [M(CO)5SCOPh]– + L cis-[M(CO)4(L)SCOPh]– + CO M = Mo, H
= 24.6(2) kcal mol–1, S
= 8.2(6) eu; M = W, H
= 28.4(2) kcal mol–1, S
= 11.3(5) eu. Kinetic data and the mechanism of these ligand-substitutions are discussed. 相似文献
100.
An on-line method developed for separating plutonium and americium was developed. The method is based on the use of HPLC pump
with three analytical chromatographic columns. Plutonium is reduced throughout the procedure to trivalent oxidation state,
and is recovered in the various separation steps together with americium. Light lanthanides and trivalent actinides are separated
with TEVA resin in thiocyanate/formic acid media. Trivalent plutonium and americium are pre-concentrated in a TCC-II cation-exchange
column, after which the separation is performed in CS5A ion chromatography column by using two different eluents. Pu(III)
is eluted with a dipicolinic acid eluent, and Am(III) with oxalic acid eluent. Radiochemical and chemical purity of the eluted
plutonium and americium fractions were ensured with alpha-spectrometry. 相似文献