scholarly journals Near IR luminescent rare earth 3,4,5,6-tetrafluoro-2-nitrophenoxide complexes: Synthesis, X-ray crystallography and spectroscopy

Polyhedron ◽  
2008 ◽  
Vol 27 (5) ◽  
pp. 1503-1510 ◽  
Author(s):  
Youxuan Zheng ◽  
Majid Motevalli ◽  
Rendy H.C. Tan ◽  
Isaac Abrahams ◽  
William P. Gillin ◽  
...  
Keyword(s):  
Rare Earth ◽  
X Ray ◽  
X Ray Crystallography ◽  
Near Ir

scholarly journals Molecular cleft or tweezer compounds derived from trioxabicyclo[3.3.1]nonadiene diisocyanate and diacid dichloride

2015 ◽  
Vol 11 ◽  
pp. 1-8 ◽  
Author(s):  
Gert Kollenz ◽  
Ralf Smounig ◽  
Ferdinand Belaj ◽  
David Kvaskoff ◽  
Curt Wentrup
Keyword(s):  
Rare Earth ◽  
Crown Ether ◽  
Dft Calculations ◽  
Metal Ions ◽  
Rare Earth Metal ◽  
Alkaline Earth ◽  
Earth Metal ◽  
X Ray ◽  
X Ray Crystallography ◽  
Derivatives Of

The structures of two derivatives of the bisdioxine diisocyanate 1, the bisurea 4 and the biscarbamate 5, are established by X-ray crystallography and DFT calculations. These compounds possess endo,endo structures, in the case of the bisurea 4 with two nearly parallel pendant chains. The X-ray structures are reproduced very well by DFT calculations. Similar endo,endo conformations are calculated for the bisamide crown ether derivatives 7, where two proximate and nearly parallel crown ether units endow the molecules with a claw-like molecular cleft or tweezer structure as evidenced by an enhanced ability to extract some alkali, alkaline earth and rare earth metal ions.

Vicinal-diaryl interactions in stilbenoid hydrocarbons as observed in the through-space charge delocalization of their cation radicals

1999 ◽  
Vol 77 (5-6) ◽  
pp. 913-921 ◽  
Author(s):  
Rajendra Rathore ◽  
Jay K Kochi
Keyword(s):  
Space Charge ◽  
Cation Radical ◽  
Conformational Preference ◽  
Charge Delocalization ◽  
X Ray ◽  
X Ray Crystallography ◽  
Cation Radicals ◽  
Near Ir ◽  
Aromatic Interactions ◽  
Vis Spectroscopy

The conformational preference of vicinal or 1,2-phenyl groups is probed in two classes of ring-substituted 1,2-diphenylbicyclooctene (stilbenoid) hydrocarbons 1a-1d and 2a-2c. UV-vis spectroscopy reveals, and X-ray crystallography verifies, the intramolecular (edge-to-face) orientation for the phenyl-phenyl interaction in stilbenoids 1a-1d. Most importantly, when two pairs of ortho-methyl substituents are present, the cofacial phenyl groups in the stilbenoid donors are established by X-ray crystallography and spectrally observed in the cation radicals (2a+.-2c+.) by the appearance of new bands with strong absorptions in the near IR with λmax = 1100-1315 nm, analogous to those previously observed in intermolecular (aromatic) interactions of aromatic cation radicals.Key words: stilbenoid hydrocarbon, cation radical, aryl-aryl interaction.

scholarly journals Ligand influence on intramolecular cyclometalation in bis(phosphinimine) rare earth alkyl complexes

2016 ◽  
Vol 94 (4) ◽  
pp. 330-341 ◽  
Author(s):  
Kevin R.D. Johnson ◽  
Breanne L. Kamenz ◽  
Paul G. Hayes
Keyword(s):  
Rare Earth ◽  
Kinetic Analysis ◽  
Ancillary Ligand ◽  
X Ray ◽  
X Ray Crystallography ◽  
Alkyl Complexes ◽  
Ortho Metalation ◽  
Elimination Reactions ◽  
Alkane Elimination

The synthesis and reactivity of two new bis(phosphinimine)carbazole ligands (PippN=PMe2)2DMC (HLA, 3) and (PippN=P(C4H8))2DMC (HLB, 10), where Pipp = para-isopropylphenyl and DMC = 3,6-dimethylcarbazole, are reported. Dialkyl lutetium complexes of 3 and 10 were prepared in the presence of DMAP and THF by reaction of the proteo ligands with the new trialkyl reagent, Lu(CH2SiMe3)3(DMAP)2 (4) as well as Lu(CH2SiMe3)3(THF)2. For both ligands 3 and 10, the resulting lutetium complexes were prone to intramolecular cyclometalative alkane elimination reactions whereby the location of cyclometalation was influenced by the identity of the ancillary ligand coordinated to the metal. For ligand 3, cyclometalation of two PMe2 groups generated the complex (LA-κ3N,κ2C)Lu(DMAP)2 (5), whereas ligand 10 resulted in the single ortho-metalation of a para-isopropylphenyl ring to afford (LB-κ3N,κC)Lu(CH2SiMe3) (12). When complexed with scandium, ligand 10 behaved differently; double cyclometalation of two phospholane moieties resulted in the species (LB-κ3N,κ2C)Sc (15). The nature of the cyclometalation reactivity of ligands 3 and 10 is supported by X-ray crystallography and kinetic analysis, respectively.

Characterization of Erbium Doped SiO2 Layers Formed On Silicon By Spark Processing

1997 ◽  
Vol 486 ◽  
Author(s):  
John V. St. John ◽  
Jeffery L. Coffer ◽  
Young Gyu Rho ◽  
Patrick Diehl ◽  
Russell F. Pinizzotto ◽  
...  
Keyword(s):  
Rare Earth ◽  
Porous Silicon ◽  
Porous Si ◽  
Rare Earth Ion ◽  
Temperature Oxidation ◽  
X Ray ◽  
Near Ir ◽  
Erbium Doped ◽  
Er Doped

AbstractDeposition of a rare earth salt layer on a silicon substrate with subsequent spark processing yields a porous Si layer and SiO 2 cap doped with the rare earth ion. We have characterized luminescent Er-doped porous SiO2 on Si by scanning electron microscopy, energy dispersive Xray spectroscopy, as well as visible and near IR photoluminescence (PL) spectroscopies. Energydispersive x-ray maps indicate that the erbium concentration in the porous layer can be controlled by varying the molarity of the erbium solution deposited on the substrate prior to spark processing. Visible PL measurements reveal that the concentration of Er3+ is proportional to the resultant intensity of the visible fluorescence transitions; however, for the near IR fluorescence peak at 1.54 gim, self-quenching due to erbium clustering occurs at higher concentrations. Erbium-doped porous silicon layers can also be obtained by diffusion of an erbium salt into porous silicon formed by anodic etching of Si in hydrofluoric acid. Densification of the porous Si layers through high temperature oxidation after erbium diffusion forms erbium-doped SiO2 layers.

Synthesis and liquid crystal behavior of bis[3,4,12,13,21,22,30,31-octa(dodecylthio)-2,3-naphthalocyaninato] rare earth complexes

2006 ◽  
Vol 10 (09) ◽  
pp. 1132-1139 ◽  
Author(s):  
Ying Zhang ◽  
Na Pan ◽  
Qingbin Xue ◽  
Ming Bai ◽  
Jianzhuang Jiang
Keyword(s):  
Rare Earth ◽  
Liquid Crystal ◽  
Optical Microscope ◽  
Rare Earth Complexes ◽  
X Ray Diffraction ◽  
X Ray ◽  
Near Ir ◽  
Stable Temperature ◽  
Double Decker ◽  
Ionic Size

A series of novel bis[3,4,12,13,21,22,30,31-octa(dodecylthio)-2,3-naphthalocyaninato] rare earth(III) complexes M [ Nc ( SC 12 H 25)8]2( M = Nd , Eu , Gd , Tb , Y , Ho , Er ) have been prepared by tetramerization of 2,3-bis(dodecylthio)-6,7-dicyanonaphthalene with M ( acac )3·n H 2 O in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) in refluxing n-octanol. These sandwich double-decker complexes were characterized by elemental analysis and various spectroscopic methods including UV-vis, near IR, IR, and mass spectroscopies. Their liquid crystal behavior was studied by polarized optical microscope (POM), differential scanning calorimeter (DSC), and X-ray diffraction. These alkylthio-substituted bis(2,3-naphthalocyaninato) rare earth complexes yield a hexagonal columnar liquid crystal whose stable temperature range is between 42 and 243°C. The stable temperature domain of the mesophase shows a trend to be dependent on the central rare earth ionic size. In contrast, the molecular packing of these complexes as revealed by X-ray diffraction was found to be almost independent of the ionic size of the central rare earth.

Difference Fourier Analysis of Glucose Embedded and Frozen Hydrated Purple Membrane

1982 ◽  
Vol 40 ◽  
pp. 74-75
Author(s):  
Jules S. Jaffe ◽  
Robert M. Glaeser
Keyword(s):  
Purple Membrane ◽  
Data Set ◽  
High Resolution Data ◽  
X Ray ◽  
X Ray Crystallography ◽  
Fourier Techniques ◽  
Versus Protein ◽  
The Difference ◽  
Difference Fourier ◽  
Ideal Method

Although difference Fourier techniques are standard in X-ray crystallography it has only been very recently that electron crystallographers have been able to take advantage of this method. We have combined a high resolution data set for frozen glucose embedded Purple Membrane (PM) with a data set collected from PM prepared in the frozen hydrated state in order to visualize any differences in structure due to the different methods of preparation. The increased contrast between protein-ice versus protein-glucose may prove to be an advantage of the frozen hydrated technique for visualizing those parts of bacteriorhodopsin that are embedded in glucose. In addition, surface groups of the protein may be disordered in glucose and ordered in the frozen state. The sensitivity of the difference Fourier technique to small changes in structure provides an ideal method for testing this hypothesis.

3-D reconstruction of molecular shape from microcrystal thin sections

1983 ◽  
Vol 41 ◽  
pp. 748-749
Author(s):  
S. Cusack ◽  
J.-C. Jésior
Keyword(s):  
Three Dimensional ◽  
Molecular Shape ◽  
Biological Molecules ◽  
Fourier Space ◽  
Single Particles ◽  
Thin Sections ◽  
Standard Methods ◽  
X Ray ◽  
X Ray Crystallography ◽  
Dimensional Reconstruction

Three-dimensional reconstruction techniques using electron microscopy have been principally developed for application to 2-D arrays (i.e. monolayers) of biological molecules and symmetrical single particles (e.g. helical viruses). However many biological molecules that crystallise form multilayered microcrystals which are unsuitable for study by either the standard methods of 3-D reconstruction or, because of their size, by X-ray crystallography. The grid sectioning technique enables a number of different projections of such microcrystals to be obtained in well defined directions (e.g. parallel to crystal axes) and poses the problem of how best these projections can be used to reconstruct the packing and shape of the molecules forming the microcrystal.Given sufficient projections there may be enough information to do a crystallographic reconstruction in Fourier space. We however have considered the situation where only a limited number of projections are available, as for example in the case of catalase platelets where three orthogonal and two diagonal projections have been obtained (Fig. 1).

Electron microscopy of rabbit FC crystals

1983 ◽  
Vol 41 ◽  
pp. 730-731
Author(s):  
Robert A. Grant ◽  
Laura L. Degn ◽  
Wah Chiu ◽  
John Robinson
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
High Resolution Electron Microscopy ◽  
Molecular Replacement ◽  
X Ray ◽  
X Ray Crystallography ◽  
Resolution Electron ◽  
Replacement Technique ◽  
Hydrated Crystal ◽  
Molecular Structure Analysis

Proteolytic digestion of the immunoglobulin IgG with papain cleaves the molecule into an antigen binding fragment, Fab, and a compliment binding fragment, Fc. Structures of intact immunoglobulin, Fab and Fc from various sources have been solved by X-ray crystallography. Rabbit Fc can be crystallized as thin platelets suitable for high resolution electron microscopy. The structure of rabbit Fc can be expected to be similar to the known structure of human Fc, making it an ideal specimen for comparing the X-ray and electron crystallographic techniques and for the application of the molecular replacement technique to electron crystallography. Thin protein crystals embedded in ice diffract to high resolution. A low resolution image of a frozen, hydrated crystal can be expected to have a better contrast than a glucose embedded crystal due to the larger density difference between protein and ice compared to protein and glucose. For these reasons we are using an ice embedding technique to prepare the rabbit Fc crystals for molecular structure analysis by electron microscopy.

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