scholarly journals Fluorescent Orthopalladated Complexes of 4-Aryliden-5(4H)-Oxazolones from the Kaede Protein: Synthesis and Characterization

Molecules ◽  
2021 ◽  
Vol 26 (5) ◽  
pp. 1238
Author(s):  
Eduardo Laga ◽  
David Dalmau ◽  
Sofía Arregui ◽  
Olga Crespo ◽  
Ana I. Jimenez ◽  
...  
Keyword(s):  
Intramolecular Interactions ◽  
Ortho Position ◽  
Fluorescent Properties ◽  
Ancillary Ligands ◽  
X Ray ◽  
Mononuclear Complexes ◽  
Fluorescence Measurements ◽  
Anionic Ligands ◽  
Order Of Magnitude

The goal of the work reported here was to amplify the fluorescent properties of 4-aryliden-5(4H)-oxazolones by suppression of the hula-twist non-radiative deactivation pathway. This aim was achieved by simultaneous bonding of a Pd center to the N atom of the heterocycle and the ortho carbon of the arylidene ring. Two different 4-((Z)-arylidene)-2-((E)-styryl)-5(4H)-oxazolones, the structures of which are closely related to the chromophore of the Kaede protein and substituted at the 2- and 4-positions of the arylidene ring (1a OMe; 1b F), were used as starting materials. Oxazolones 1a and 1b were reacted with Pd(OAc)2 to give the corresponding dinuclear orthometalated palladium derivates 2a and 2b by regioselective C–H activation of the ortho-position of the arylidene ring. Reaction of 2a (2b) with LiCl promoted the metathesis of the bridging carboxylate by chloride ligands to afford dinuclear 3a (3b). Mononuclear complexes containing the orthopalladated oxazolone and a variety of ancillary ligands (acetylacetonate (4a, 4b), hydroxyquinolinate (5a), aminoquinoline (6a), bipyridine (7a), phenanthroline (8a)) were prepared from 3a or 3b through metathesis of anionic ligands or substitution of neutral weakly bonded ligands. All species were fully characterized and the X-ray determination of the molecular structure of 7a was carried out. This structure has strongly distorted ligands due to intramolecular interactions. Fluorescence measurements showed an increase in the quantum yield (QY) by up to one order of magnitude on comparing the free oxazolone (QY < 1%) with the palladated oxazolone (QY = 12% for 6a). This fact shows that the coordination of the oxazolone to the palladium efficiently suppresses the hula-twist deactivation pathway.

Development of a method for multielemental determination in water by EDXRF with radioisotopic source of 238Pu.

2019 ◽  
Vol 7 (2A) ◽  
Author(s):  
Camilo Fuentes Serrano ◽  
Juan Reinaldo Estevez Alvares ◽  
Alfredo Montero Alvarez ◽  
Ivan Pupo Gonzales ◽  
Zahily Herrero Fernandez ◽  
...  
Keyword(s):  
Thin Layer ◽  
Expanded Uncertainty ◽  
Considerable Decrease ◽  
X Ray ◽  
Precipitation Efficiency ◽  
Method Of Determination ◽  
Sensitivity Curves ◽  
Order Of Magnitude ◽  
Metrological Parameters

A method for determination of Cr, Fe, Co, Ni, Cu, Zn, Hg and Pb in waters by Energy Dispersive X Ray Fluorescence (EDXRF) was implemented, using a radioisotopic source of 238Pu. For previous concentration was employed a procedure including a coprecipitation step with ammonium pyrrolidinedithiocarbamate (APDC) as quelant agent, the separation of the phases by filtration, the measurement of filter by EDXRF and quantification by a thin layer absolute method. Sensitivity curves for K and L lines were obtained respectively. The sensitivity for most elements was greater by an order of magnitude in the case of measurement with a source of 238Pu instead of 109Cd, which means a considerable decrease in measurement times. The influence of the concentration in the precipitation efficiency was evaluated for each element. In all cases the recoveries are close to 100%, for this reason it can be affirmed that the method of determination of the studied elements is quantitative. Metrological parameters of the method such as trueness, precision, detection limit and uncertainty were calculated. A procedure to calculate the uncertainty of the method was elaborated; the most significant source of uncertainty for the thin layer EDXRF method is associated with the determination of instrumental sensitivities. The error associated with the determination, expressed as expanded uncertainty (in %), varied from 15.4% for low element concentrations (2.5-5 μg/L) to 5.4% for the higher concentration range (20-25 μg/L).

Compositional Determination of Sputtered Tantalum—Aluminum Thin Films

1971 ◽  
Vol 25 (4) ◽  
pp. 489-493
Author(s):  
James D. Nohe ◽  
David A. Green
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Atomic Absorption ◽  
Unit Area ◽  
X Ray ◽  
Glass Substrates ◽  
Fluorescence Measurements ◽  
Before And After ◽  
Film Weight

Tantalum–aluminum thin film composition has been determined destructively by atomic absorption and nondestructively by x-ray fluorescence spectroscopy. Samples representing several compositions (20–80 at.% aluminum) and thicknesses (500–6000 Å) were sputtered on glass, graphite, and platinum substrates. The films were dissolved from the platinum substrates for the determination of aluminum by atomic absorption. The weights of tantalum per unit area obtained by difference using this destructive technique were applied to the same samples on glass substrates for correlation with nondestructive x-ray fluorescence measurements. A linear curve, which is free from enhancement and absorption effects, is obtained for tantalum. This curve relates the nondestructive fluorescence intensities to film weights (µg/cm2) of tantalum. The composition of the film is determined nondestructively by utilizing this curve and the total film weight which is obtained by weighing the substrate before and after sputtering. Alternately, composition may be determined destructively by atomic absorption utilizing films dissolved from platinum substrates

Polytypism in GaAs nanowires: determination of the interplanar spacing of wurtzite GaAs by X-ray diffraction

2015 ◽  
Vol 22 (1) ◽  
pp. 67-75 ◽  
Author(s):  
Martin Köhl ◽  
Philipp Schroth ◽  
Andrey A. Minkevich ◽  
Jean-Wolfgang Hornung ◽  
Emmanouil Dimakis ◽  
...  
Keyword(s):  
Interplanar Spacing ◽  
Stacking Sequence ◽  
X Ray Diffraction ◽  
X Ray ◽  
Zinc Blende ◽  
Gaas Nanowires ◽  
Mean Diameter ◽  
Order Of Magnitude ◽  
Focused Beam

In GaAs nanowires grown along the cubic [111]cdirection, zinc blende and wurtzite arrangements have been observed in their stacking sequence, since the energetic barriers for nucleation are typically of similar order of magnitude. It is known that the interplanar spacing of the (111)cGa (or As) planes in the zinc blende polytype varies slightly from the wurtzite polytype. However, different values have been reported in the literature. Here, the ratio of the interplanar spacing of these polytypes is extracted based on X-ray diffraction measurements for thin GaAs nanowires with a mean diameter of 18–25 nm. The measurements are performed with a nano-focused beam which facilitates the separation of the scattering of nanowires and of parasitic growth. The interplanar spacing of the (111)cGa (or As) planes in the wurtzite arrangement in GaAs nanowires is observed to be 0.66% ± 0.02% larger than in the zinc blende arrangement.

Determination of Heavy Metals in Environmental Water by Total Reflection X-Ray Fluorescence Method using Optimized Roentgen Optics Cut-Off Filter

1991 ◽  
Vol 35 (B) ◽  
pp. 959-963 ◽  
Author(s):  
A. I. Egorov ◽  
L. P. Kablna ◽  
I. A. Kondurov ◽  
E. M. Korotkikh ◽  
V. V. Martynov ◽  
...  
Keyword(s):  
Heavy Metals ◽  
Critical Angle ◽  
Environmental Water ◽  
Total Reflection ◽  
Angular Deviation ◽  
Narrow Beam ◽  
X Ray ◽  
Order Of Magnitude ◽  
Elemental Contents

The total reflection x-ray fluorescence (TXRF) method of analyzing elemental contents Is based on the small angle irradiation of thin samples placed on a total reflecting backing with a narrow photon beam. Two instrumental problems are to be solved here. The first is to form the narrow beam with a small angular deviation. The usual way to solve this problem is to use collimators with small solid angles. These angles must be less than the critical angle for x-ray total reflection, which, in the energy range 10 - 20 keV has an order of magnitude around 10−3 rad.

Some Observations on the Use of Certain Analyzing Crystals for the Determination of Silicon and Aluminum*

1965 ◽  
Vol 9 ◽  
pp. 515-527 ◽  
Author(s):  
Frank L. Chan
Keyword(s):  
Count Rate ◽  
Limit Of Detection ◽  
Fluorescence Analysis ◽  
Organic Crystals ◽  
Background Count ◽  
X Ray ◽  
Pure Silicon ◽  
Order Of Magnitude ◽  
Constant Potential

AbstractDuring the past several years, a number of analyzing crystals have been prepared in the U.S. Air Force Aerospace Research Laboratories. Crystals such as alkaline acid malonates, sucrose, pentaerythritol (PET), and several others have been grown with the sole purpose of application in X-ray fluorescence analysis of silicon, aluminum, and other elements of low atomic number. Crystals from natural sources, such as quartz, mica, and gypsum, have also been procured from different parts of the world for this purpose.Among the analyzing crystals so prepared, pentaerythritol gave the highest count rate for silicon and aluminum. However, since this crystal is organic in nature, great care must be exercised in handling this type of crystal in order to obtain constant count rates. For the analysis of silicon and aluminum, a-quartz crystal gave a somewhat low count rate, but this crystal has certain advantages over the organic crystals, and can be used for analysis of materials having high silicon and aluminum content.For instance, when using a conventional X-ray emission vacuum spectrograph of standard make, with the latest alterations, one of the PET crystals attained a count rate of 101,870 cps for pure silicon when the instrument was operated at 60 kVP and SO m A with a negligible background count. With a constant potential attachment and operated at 60 kVP and 34 mA, 1.15,600 cps with negligible background count was obtained for silicon. The count rate for aluminum was of the same order of magnitude with somewhat higher background count.Several sets of standards have been procured and small amounts of silicon and aluminum in these standards have been analyzed by the latest modified vacuum spectrograph. These results are under study and the limit of detection calculated. Procedures and results are described and discussed.

Accurate determination of the As(v) coordination environment at the surface of ferrihydrite using synchrotron extended X-ray absorption fine structure spectroscopy and ab initio Debye–Waller factors

2019 ◽  
Vol 6 (8) ◽  
pp. 2441-2451
Author(s):  
Shaofeng Wang ◽  
Guoqing Zhang ◽  
Jinru Lin ◽  
Xin Wang ◽  
Yongfeng Jia
Keyword(s):  
Fine Structure ◽  
Ab Initio ◽  
Accurate Determination ◽  
Coordination Environment ◽  
X Ray ◽  
Absorption Fine ◽  
Mononuclear Complexes ◽  
X Ray Absorption

The synchrotron EXAFS fitting using ab initio Debye–Waller factors suggests that ferrihydrite adsorbs arsenate dominantly via monodentate mononuclear complexes.

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