Crystallographic and N.M.R.-Relaxation Studies on Bis [{N,N'-(1,3-dimethylpropanediylidene)dianilinato}(1 - )]nickel(II)

1979 ◽  
Vol 32 (4) ◽  
pp. 727 ◽  
Author(s):  
PC Healy ◽  
MR Bendall ◽  
DM Doddrell ◽  
BW Skelton ◽  
AH White
Keyword(s):  
Theoretical Calculation ◽  
Relaxation Times ◽  
Nickel Atom ◽  
Intramolecular Interactions ◽  
Bidentate Ligands ◽  
X Ray ◽  
The Mean ◽  
Independent Molecules ◽  
Relaxation Studies

A single-crystal X-ray structure determination of bis[{N,N'-(1,3-dimethylpropanediyldene)dianilinato)(1-)]nickel(II) at 295 K shows that, within each of the two independent molecules of the complex within the structure, the nickel atom is chelated by two of the bidentate ligands and is thus four-coordinate. Because of the intramolecular interactions between the phenyl substituents of the ligands, the metal atom environments are highly irregular, although consistent between the two molecules. There are no significant deviations in the Ni-N distances from the mean of 1.965�; but the interligand N-Ni-N angles about the nickel range from 110.4 to 134.7�. A theoretical calculation of the 13C and 1H nuclear relaxation times using the X-ray-determined metal-nuclear separations reproduces the experimentally observed relaxation times for selected positions within the complex, provided ligand-centred effects are taken into account. Mathematical complexity prevents a complete theoretical calculation of the relaxation times for ligand atoms with varying distances from the nickel atom.

scholarly journals Syntheses and Structures of Ni(II) Complexes Containing 2‑alkyliminomethyl Pyrene Ligands

2018 ◽  
Vol 34 (4) ◽  
Author(s):  
Xuan Dien Luong ◽  
Truong Xuan Nguyen ◽  
Quan Duc Ngo
Keyword(s):  
Mixed Solvent ◽  
Nickel Atom ◽  
Bidentate Ligand ◽  
Coordination Geometry ◽  
X Ray Diffraction ◽  
X Ray ◽  
Square Planar ◽  
The Mean ◽  
Independent Molecules ◽  
Step Distance

The N,O-bidentate ligand 2-((methylimino)methyl)pyren-1-ol (1) gives with nickel acetate in a mixed solvent of toluene and ethanol in the presence of NaOAc the nickel(II) complex 1(Ni). It was characterized by elemental analysis, IR, NMR, MS spectroscopy and single crystal X-ray diffraction. With respect to the nickel atom the complex 1(Ni) adopts a distorted square planar trans-coordination geometry. Concerning the ligand arrangement, complex 1(Ni) has a step configuration with the angle of 35.5o between the mean planes of the pyrene rings in the two independent molecules and step distance S = 1.93 Å, whereas the referent nickel(II) bis(salicylaldiminato) takes a much smaller step configuration with an angle of 17.6o and the step distance S = 0.845 Å (chart 1). 

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.

The Use of the Pseudo-Voigt Function in the Variance Method of X-ray Line-Broadening Analysis

1997 ◽  
Vol 30 (4) ◽  
pp. 427-430 ◽  
Author(s):  
F. Sánchez-Bajo ◽  
F. L. Cumbrera
Keyword(s):  
Crystallite Size ◽  
Original Form ◽  
Line Broadening ◽  
X Ray Diffraction ◽  
Stabilized Zirconia ◽  
X Ray ◽  
Variance Method ◽  
The Mean ◽  
Voigt Function

A modified application of the variance method, using the pseudo-Voigt function as a good approximation to the X-ray diffraction profiles, is proposed in order to obtain microstructural quantities such as the mean crystallite size and root-mean-square (r.m.s.) strain. Whereas the variance method in its original form is applicable only to well separated reflections, this technique can be employed in the cases where there is line-profile overlap. Determination of the mean crystallite size and r.m.s. strain for several crystallographic directions in a nanocrystalline cubic sample of 9-YSZ (yttria-stabilized zirconia) has been performed by means of this procedure.

Interlaboratory Study of Blood Selenium Determinations

1987 ◽  
Vol 70 (4) ◽  
pp. 664-667
Author(s):  
Tee-Siaw Koh
Keyword(s):  
Hydride Generation ◽  
Atomic Absorption Spectrophotometry ◽  
Bovine Blood ◽  
Blood Samples ◽  
X Ray ◽  
Absorption Spectrophotometry ◽  
Coefficients Of Variation ◽  
The Mean ◽  
Se Deficiency

Abstract Fifty-one laboratories from 14 countries participated in a survey on the determination of selenium (Se) in 8 bovine blood samples with Se concentrations ranging from 0.2 μmol/L (0.016 μg/mL) to 14 μmol/L (1.1 μg/mL). The methods used (and the percentage of participants using each method) were fiuorometry (61), hydride-generation atomic absorption spectrophotometry (AAS) (23), graphitefurnace AAS (6), gas chromatography (4), neutron activation analysis (4), and X-ray fiuorometry (2). There was little difference in the mean Se results obtained by fiuorometry or hydride-generation AAS (P &gt; 0.05). Mean intralaboratory coefficients of variation (CVs) from known replicates ranged from 4 to 14% for all samples. Interlaboratory CVs were related to blood Se concentration and increased to 55% at Se levels below 0.4 μmol/L (0.032 μg/mL). Laboratories that used quality control (QC) schemes had lower interlaboratory CVs than those that did not, but the advantage began to diminish at blood Se concentration below 0.4 μmol/L (0.032 μg/mL). The high interlaboratory CVs, coupled with the false assurance from the low intralaboratory CVs and the ineffectiveness of the QC schemes at blood Se concentrations below 0.4 μmol/L (0.032 μg/mL), are of concern in diagnosis of marginal Se deficiency in livestock where the concentrations of interest are in the range 0.15-0.5 μmol/L (0.012-0.039 μg/mL).

Determination of X-ray Elastic Constants in a Ti-14Al-21Nb Nb Alloy and a Ti-14Al-21Nb/SiC Metal Matrix Composite

1990 ◽  
Vol 34 ◽  
pp. 689-698 ◽  
Author(s):  
J. Jo ◽  
R. W. Hendricks ◽  
W. D. Brewer ◽  
Karen M. Brown
Keyword(s):  
Residual Stress ◽  
Plastic Deformation ◽  
Elastic Constant ◽  
Theoretical Calculation ◽  
Metal Matrix Composite ◽  
Elastic Constants ◽  
Metal Matrix ◽  
Intrinsic Value ◽  
X Ray

Residual stress values in a material are governed by the measurements of the atomic spacings in a specific crystallographic plane and the elastic constant for that plane. It has been reported that the value of the elastic constant depends on microstructure, preferred orientation, plastic deformation and morphology [1], Thus, the theoretical calculation of the elastic constant may deviate from the intrinsic value for a real alloy.

Determination of Heavy Metals in Damascus Drinking Water Using Total Reflection X-Ray Fluorescence

1999 ◽  
Vol 34 (2) ◽  
pp. 305-316 ◽  
Author(s):  
E.H. Bakraji ◽  
J. Karajo
Keyword(s):  
Trace Elements ◽  
Drinking Water ◽  
Total Reflection ◽  
World Health ◽  
X Ray ◽  
Quality Guidelines ◽  
The World ◽  
The Mean ◽  
Health Organization

Abstract Total reflection X-ray fluorescence spectrometry and chemical preconcentration have been applied for multi-elemental analysis of Damascus drinking water. Water was taken directly from taps of several city sectors and analyzed for the following trace elements: Ti, V, Cr, Fe, Co, Ni, Cu, Zn, Se and Pb. The detection limits were found to be in the range of 0.1 to 0.4 µg/L. The mean levels of trace elements in the Damascus drinking water were below the World Health Organization drinking water quality guidelines.

Crystal structure of fac-Tris(pentane-2,3,4-trione 3-oximato)cobalt(III)

1978 ◽  
Vol 31 (11) ◽  
pp. 2437 ◽  
Author(s):  
BN Figgis ◽  
CL Raston ◽  
RP Sharma ◽  
AH White
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Least Squares ◽  
Title Compound ◽  
Bidentate Ligands ◽  
X Ray Diffraction ◽  
X Ray ◽  
Independent Molecules

The crystal structure of the title compound has been determined by single-crystal X-ray diffraction at 295 K and refined by least squares to a residual of 0.058 for 2363 'observed' reflections. Crystals are triclinic, Pī, Z 4, a 15.517(8), b 11.772(7), c 11.282(7) Ǻ, α 112.10(4), β 94.80(3), γ 90.60(4)°. <Co-N, O>| distances are 1.883, 1.925 Ǻ respectively, the disposition of the three bidentate ligands within each of the two independent molecules being fac.

An X-Ray Structure Determination of the Twinned Crystals of Dinitrato-2,2′-dipyridylsilver(II)

1972 ◽  
Vol 50 (3) ◽  
pp. 315-323 ◽  
Author(s):  
G. W. Bushnell ◽  
M. A. Khan
Keyword(s):  
Silver Atom ◽  
Unit Cell ◽  
Planar Geometry ◽  
X Ray ◽  
Square Planar ◽  
Distorted Octahedral ◽  
Cell Dimensions ◽  
The Mean ◽  
Unit Cell Dimensions

The crystal structure of dinitrato-2,2′-dipyridylsilver(II) has been solved and refined to an R-value of 0.070. Four circle diffractometer measurements were obtained from the twinned triclinic crystals. The unit cell dimensions at 22 °C are: a = 697.5 ± 0.2 pm, b = 999.4 ± 0.2 pm, c = 1032.2 ± 0.2 pm, α = 113.46 ± 0.02°, β = 100.71 ± 0.02°, γ = 95.28 ± 0.02°. The space group is [Formula: see text] (No. 2) with two molecules per unit cell. The density is 2.06 ± 0.04 g cm−3 (measured), 2.02 g cm−3 (calculated). The four shortest bond lengths to silver are: Ag—O(1), 214.8 ± 1.5 pm; Ag—O(4), 213.6 ± 1.5 pm; Ag—N(1), 212.4 ± 1.6 pm; Ag—N(2), 220.7 ± 1.6 pm. These four bonds are distorted from square planar geometry with the silver atom lying 19.90 ± 0.17 pm out of the mean plane of the other four atoms. There are also long bonds to the nitrato groups of neighboring molecules: Ag—O(1′), 275.3 ± 1.3 pm; Ag—O(2″), 276.3 ± 1.6 pm. Inclusion of these bonds gives a distorted octahedral silver coordination. Though predominantly unidentate, there is a slight tendency toward bidentate bonding in both nitrato ligands: Ag—O(2), 305.8 ± 1.4 pm; Ag—O(5), 295.0 ± 1.7 pm. O(2) and O(5) approach the convex side of the distorted square planar coordination. The deviation from planarity of the closely bonded square, and angular distortions in the above mentioned octahedral coordination can be rationalized by considering the silver as eight coordinate. The bonds to silver may be grouped 4:2:2 by length or 4:3:1 by angular disposition.

Theoretical Calculation of Background in X-Ray Spectrometry for the Determination of Some Heavy Trace Elements

1991 ◽  
Vol 35 (B) ◽  
pp. 755-756
Author(s):  
Jean-Jacques Gruffat
Keyword(s):  
Trace Elements ◽  
Theoretical Calculation ◽  
Spectral Distribution ◽  
Geological Samples ◽  
X Ray ◽  
Correct Calculation ◽  
The Continuum

AbstractThe Kulenkampff-Kramers formula giving the spectral distribution of the continuum as a function of wavelength allows a correct calculation of background under the peak. It is only necessary to measure two backgrounds, one on each side of the peak, The true background under the peak is given by multiplying them by adequate coefficients and adding them up. This method has been applied to the determination of low amounts of Ce, La, Ba and Cs in geological samples.

Sign in / Sign up

Export Citation Format

Share Document