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121.
Switching between three different adsorbed states was achieved using potential control to separately induce electrochemical behaviour associated with changes in binding and orientation of the thiophene and pyridine moieties of 2-(2'-thienyl)pyridine adsorbed to Au(111) in neutral and basic solution. 相似文献
122.
Y. M. Dan Y. R. Zhao Y. Liu S. S. Qu 《Journal of Thermal Analysis and Calorimetry》2006,84(3):531-534
The two complexes, [Ln(Ala)2(Im)(H2O)](ClO4)3 (Ln=Pr,
Gd), were synthesized and characterized. Using a solution-reaction isoperibol
calorimeter, standard enthalpies of reaction of two reactions: LnCl3⋅6H2O(s)+2Ala(s)+Im(s)+3NaClO4(s)=[Ln(Ala)2(Im)(H2O)](ClO4)3(s)+3NaCl(s)+5H2O(l) (Ln=Pr, Gd),
at T=298.15 K, were determined to be (39.26±0.10)
and (5.33±0.12) kJ mol–1 , respectively.
Standard enthalpies of formation of the two complexes at T=298.15
K, ΔfHΘm
{[Ln(Ala)2(Im)(H2O)](ClO4)3(s)} (Ln=Pr, Gd),
were calculated as –(2424.2±3.3) and –(2443.4±3.3)
kJ mol–1 , respectively. 相似文献
123.
Dan Lu Weiyang Zhang Yingnan Jiang Yu Zhang Dabo Pan Dan Zhang 《Natural product research》2019,33(19):2789-2794
A new cycloartane triterpenoid, named gardenolic acid C (1), a new ursane triterpenoid, named 3β,16β,21β,23,24-pentahydroxy urs-12,18,20-trien-28-oic acid γ-lactone (2), together with three know triterpenoids, gardenolic acid A (3), gardenolic acid B (4), and 3α,16β,23,24-tetrahydroxy-28-nor-ursane-12,17,19,21-tetraen (5) were isolated from the fruits of Gardenia jasminoides Ellis. The structures of these compounds were elucidated by analyses of spectroscopic data. All isolates were evaluated for their neuroprotective effects in vitro.
124.
Dirk Steinborn Olaf Gravenhorst Clemens Bruhn Dusan Miklo Michal Dunaj-Jur
o Alfred Kolbe 《无机化学与普通化学杂志》1997,623(12):1954-1958
Synthesis and Characterization of Aquapentachloroplatinates(IV) – Structure of [K(18-crown-6)][PtCl5(H2O)] The crown ether complex of the aquapentachloroplatinic acid of the composition [H13O6][PtCl5(H4O2)] · 2(18-cr-6) ( 2 ) reacts with K2CO3 and [NnBu4]OH in aqueous solution to give [K(18-cr-6)][PtCl5(H2O)] ( 5 a ) and [NnBu4][PtCl5(H2O)] · 1/2 (18-cr-6) · H2O ( 5 b ), respectively. Both compounds were characterized by microanalysis, vibrational (IR, Raman) and NMR (1H, 13C, 195Pt) spectroscopy. The X-ray structure analysis of 5 a (orthorhombic, pnma; a = 16,550(4), b = 18,044(3), c = 7,415(1) Å; Z = 4; R1 = 0,0183; wR2 = 0,0414) reveals that the crystal is threaded by chains built up of [PtCl5(H2O)]? and [K(18-cr-6)]+ units. There are tight K …? Cl contacts (d(K? Cl1)) = 3,0881(9) Å and OW? H? Ocr hydrogen bridges (d(O1 …? O2) = 2,806(3) Å) between these units. The coordination polyhedron [PtCl5O] has approximately C4v symmetry. 相似文献
125.
Tiberiu-M. Gianga Edwige Audibert Anamaria Trandafir Gabriele Kociok-Khn G. Dan Panto 《Chemical science》2020,11(35):9685
We report herein the first all-donor aromatic [2]catenane formed through dynamic combinatorial chemistry, using single component libraries. The building block is a benzo[1,2-b:4,5-b′]dithiophene derivative, a π-donor molecule, with cysteine appendages that allow for disulfide exchange. The hydrophobic effect plays an essential role in the formation of the all-donor [2]catenane. The design of the building block allows the formation of a quasi-fused pentacyclic core, which enhances the stacking interactions between the cores. The [2]catenane has chiro-optical and fluorescent properties, being also the first known DCC-disulphide-based interlocked molecule to be fluorescent.An all-donor [2]catenane has been synthesised via dynamic combinatorial chemistry. It features stacked benzodithiophenes which are quasi-pentacyclic through hydrogen bonding. 相似文献
126.
127.
Bin XIN Dan PU Shao Xiang XIONG* Guang Hui WANG Beijing Mass Spectrometry Center Center for Molecular Science Institute of Chemistry Chinese Academy of Sciences Beijing 《中国化学快报》2003,14(2)
Recently, capillary electrophoresis/electrospray ionization mass spectrometry (CE/ESI- MS) has been rapidly developed as a powerful analytical tool for charged species ranged from small molecules such as carboxylic acids1, phenolic compounds2, metal species3, tetramines4, herbicides5, drugs and drug metabolites6 to peptides and proteins7, 8. The ESI mode has proven to be sensitive, versatile and relatively easy to use in combination with CE. CE confers rapid analysis and efficient separ… 相似文献
128.
Indirect detection of paracetamol was accomplished using a capillary electrophoresis-chemiluminescence (CE-CL) detection system, which was based on its inhibitory effect on a luminol-potassium hexacyanoferrate(III) (K3[Fe(CN)6]) CL reaction. Paracetamol migrated in the separation capillary, where it mixed with luminol included in the running buffer. The separation capillary outlet was inserted into the reaction capillary to reach the detection window. A four-way plexiglass joint held the separation capillary and the reaction capillary in place. K3[Fe(CN)6] solution was siphoned into a tee and flowed down to the detection window. CL was observed at the tip of the separation capillary outlet. The CL reaction of K3[Fe(CN)6] oxidized luminol was employed to provide the high and constant background. Since paracetamol inhibits the CL reaction, an inverted paracetamol peak can be detected, and the degree of CL suppression is proportional to the paracetamol concentration. Maximum CL signal was observed with an electrophoretic buffer of 30 mM sodium borate (pH 9.4) containing 0.5 mM luminol and an oxidizer solution of 0.8 mM K3[Fe(CN)6] in 100 mM NaOH solution. Under the optimal conditions, a linear range from 6.6 × 10−10 to 6.6 × 10−8 M (r = 0.9999), and a detection limit of 5.6 × 10−10 M (signal-to-noise ratio = 3) for paracetamol were achieved. The relative standard deviation (R.S.D.) of the peak area for 5.0 × 10−9 M of paracetamol (n = 11) was 2.9%. The applicability of the method for the analysis of pharmaceutical and biological samples was examined. 相似文献
129.
G. Lehmann und T. Bruhn 《Fresenius' Journal of Analytical Chemistry》1968,243(1):300-314
Zusammenfassung Ein Verfahren zur quantitativen Bestimmung der Ascorbinsäure und Dehydroascorbinsäure nach der Hydroxamatmethode wird beschrieben. Das Verfahren gestattet die Erfassung von Ascorbinsäure und Dehydroascorbinsäure in einer Reaktion, wobei in saurer Lösung beständige Eisen(III)-hydroxamatkomplexe bei 500 nm photometrisch ausgewertet werden können. Die Methode ist leicht durchführbar und nicht so störanfällig wie andere Nachweise; sie kann auch zur qualitativen Probe z. B. auf der Dünnschichtplatte herangezogen werden, wenn Ascorbinsäure neben anderen Carbonsäuren nachzuweisen ist.Es wird ferner die dünnschicht-chromatographische Trennung auf Celluloseschichten der Hydroxamsäuren, die aus der Ascorbinsäure und Dehydroascorbinsäure entstehen, beschrieben.
Unserem verehrten Lehrer, Herrn Prof. Dr. O. Neunhoeffer, danken wir für sein stetiges Interesse an der Arbeit und seine anregenden Diskussionen, Herrn Prof. Dr. B. Eistert für wertvolle Hinweise und Unterstützung durch Institutsmittel.
Herrn Prof. Dr. B. Eistert zum 65. Geburtstag gewidmet.
Auszug aus der Diplomarbeit von T. Bruhn: Bestimmung der Ascorbinsäure mit Hilfe ihrer Hydroxylaminoderivate, Saarbrücken 1968. 相似文献
On the behaviour of Ascorbic acid towards hydroxylamine, a contribution to the analysis of vitamin C
A spectrometric method is presented for the quantitative determination of 0.5–5 mg/100 ml of ascorbic and dehydroascorbic acids. It is based on the formation of hydroxamates by reaction with hydroxylamine. The conditions and the application of this method are discussed. Colouring matter and phenolic compounds, which can present difficulty in the photometric measurement, are eliminated by treatment with polyamide powder. Furthermore, the separation of the hydroxamic acid derivatives of ascorbic and dehydroascorbic acids by thinlayer chromatography on cellulose is described.
Unserem verehrten Lehrer, Herrn Prof. Dr. O. Neunhoeffer, danken wir für sein stetiges Interesse an der Arbeit und seine anregenden Diskussionen, Herrn Prof. Dr. B. Eistert für wertvolle Hinweise und Unterstützung durch Institutsmittel.
Herrn Prof. Dr. B. Eistert zum 65. Geburtstag gewidmet.
Auszug aus der Diplomarbeit von T. Bruhn: Bestimmung der Ascorbinsäure mit Hilfe ihrer Hydroxylaminoderivate, Saarbrücken 1968. 相似文献
130.
Karlberg M Stjerndahl M Lundberg D Piculell L 《Langmuir : the ACS journal of surfaces and colloids》2005,21(21):9756-9763
Mixtures of hydrophobically modified hydroxyethyl cellulose (HMHEC) and alkali-sensitive cleavable betaine ester surfactants have been studied by viscometry, 1H NMR, absorbance measurements, and birefringence determinations. Before the hydrolysis, the surfactants behaved as conventional nondegradable surfactants in terms of the effect on the viscosity of increasing surfactant concentration. As the surfactants were hydrolyzed, systems with time-dependent viscosity were obtained. The viscosity either decreased monotonically or went through a maximum as a function of time, depending on the initial surfactant concentration. Different surfactant chain lengths gave rise to different viscosity profiles. The rate of hydrolysis, and thus the time-dependency of the surfactant concentration, could be controlled by changing the pH of the solution. 相似文献