Heteroleptic strontium complexes stabilized by donor-functionalized alkoxide and β-diketonate ligands

Based on the analysis of the crystal structure of the Ca2+ salt of ionomycin and the chemical and physical data on ionomycin, a number of ionomycin analogues have been synthesized to study the structural features affecting the Ca2+ binding and transport. Compounds 2, 3, and 4 were synthesized to study the effect of additional intramolecular oxygen coordination sites on Ca2+ transport. Compounds 5a–5d were prepared to study the effect of lipid solubility on Ca2+ binding and transport. Compounds 6a–6c were prepared to study the effect of the distance between the β-diketone and the carboxyl group on Ca2+ transport. A general synthetic route to these compounds has been developed. The key reactions in this route are the consecutive regioselective alkylations of the dianion of 2,4-pentanedione with the appropriate bromides.[Formula: see text]

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Intricacies of ligand coordination in tricarbonylchromium(0) complexes with ortho- and para-fluorobiphenyls

Acta Crystallographica Section C Structural Chemistry ◽

10.1107/s2053229617010774 ◽

2017 ◽

Vol 73 (8) ◽

pp. 638-644 ◽

Cited By ~ 1

Author(s):

Ilia A. Guzei ◽

Lara C. Spencer ◽

Sondra C. Buechel ◽

Leah B. Kaufmann ◽

Curtis J. Czerwinski

Keyword(s):

Solid State ◽

Structural Features ◽

Dihedral Angles ◽

Stable Isomer ◽

X Ray Diffraction ◽

Model Complexes ◽

Positional Disorder ◽

Ligand Coordination ◽

Solid State Structures ◽

Optimized Geometries

The steric and electronic factors that influence which of the two rings of a substituted biphenyl ligand coordinates to chromium are of interest and it has been suggested that haptotropic rearrangements within these molecules may be limited if the arene–arene dihedral angle is too large. Two tricarbonylchromium(0) complexes and their respective free ligands have been characterized by single-crystal X-ray diffraction. In the solid state, tricarbonyl[(1′,2′,3′,4′,5′,6′-η)-2-fluoro-1,1′-biphenyl]chromium(0), [Cr(C12H9F)(CO)3], (I), exists as the more stable isomer with the nonhalogenated arene ring ligated to the metal center. Similarly, tricarbonyl[(1′,2′,3′,4′,5′,6′-η)-4-fluoro-1,1′-biphenyl]chromium(0) crystallizes as the more stable isomer with the phenyl ring bonded to the Cr0 center. The arene–arene dihedral angles in these complexes are 55.77 (4) and 52.4 (5)°, respectively. Structural features of these complexes are compared to those of the DFT-optimized geometries of ten tricarbonyl[(η6-C6H5)(4-F-C6H4)]chromium model complexes. The solid-state structures of the free ligands 2-fluoro-1,1′-biphenyl and 4-fluoro-1,1′-biphenyl, both C12H9F, exhibit arene–arene dihedral angles of 54.83 (7) and 0.71 (8)°, respectively. The molecules of the free ligands occupy crystallographic twofold axes and exhibit positional disorder. Weak intermolecular C—H...F interactions are observed in all four structures.

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Structural and spectroscopic studies of transition metal nitrite complexes. VII. Crystal structures and spectra of two dinuclear and trinuclear species with stoichiometry [Ni(methylpyridine)2(NO2)2] containing bridging nitrite groups

Australian Journal of Chemistry ◽

10.1071/ch9812125 ◽

1981 ◽

Vol 34 (10) ◽

pp. 2125 ◽

Cited By ~ 9

Author(s):

AJ Finney ◽

MA Hitchman ◽

CL Raston ◽

GL Rowbottom ◽

AH White

Keyword(s):

Crystal Structures ◽

Visible Region ◽

Spectroscopic Studies ◽

Coordination Sites ◽

Ligand Coordination ◽

Amine Ligands ◽

Single Oxygen Atom ◽

Single Oxygen ◽

Species Being ◽

Oxygen Bond

The crystal structures of the dimer [Ni(γmpy)2(NO2)2]2,2C6H6 and the trimer [Ni(βmpy)2(NO2)2]3,- C6Hs (γmpy = 4-methylpyridine, βmpy = 3-methylpyridine) are reported, the latter being the redetermination of a structure described previously. The ligand coordination geometry in each oligomer is essentially octahedral, with neighbouring nickel(II) ions being bridged by two nitrite groups, one through a single oxygen atom and the second through an oxygen and the nitrogen atom. The amine ligands occupy trans coordination sites with the terminal bond positions in both species being taken up by chelating nitrite ions. In both compounds the oligomers pack so that the amine rings form sheets with potential voids in the lattice being filled by clathrated benzene molecules. The electronic spectra of the complexes in the visible region are unusual, showing peaks centred at c. 17500 and c. 20500 cm-1, and the assignment of these is discussed. The infrared stretching frequencies of the nitrite groups in these and other compounds are found to correlate well with the observed nitrogen-oxygen bond lengths.

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Electron microscopy and diffraction studies of polyimides

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100074069 ◽

1983 ◽

Vol 41 ◽

pp. 28-29

Author(s):

O.C. de Hodgins ◽

K. R. Lawless ◽

R. Anderson

Keyword(s):

Electron Microscopy ◽

Electron Microscope ◽

Structural Features ◽

Inert Atmosphere ◽

Polyimide Films ◽

Resolution Electron ◽

The Matrix ◽

High Resolution Electron Microscope ◽

Diffraction Patterns ◽

Polymeric Samples

Commercial polyimide films have shown to be homogeneous on a scale of 5 to 200 nm. The observation of Skybond (SKB) 705 and PI5878 was carried out by using a Philips 400, 120 KeV STEM. The objective was to elucidate the structural features of the polymeric samples. The specimens were spun and cured at stepped temperatures in an inert atmosphere and cooled slowly for eight hours. TEM micrographs showed heterogeneities (or nodular structures) generally on a scale of 100 nm for PI5878 and approximately 40 nm for SKB 705, present in large volume fractions of both specimens. See Figures 1 and 2. It is possible that the nodulus observed may be associated with surface effects and the structure of the polymers be regarded as random amorphous arrays. Diffraction patterns of the matrix and the nodular areas showed different amorphous ring patterns in both materials. The specimens were viewed in both bright and dark fields using a high resolution electron microscope which provided magnifications of 100,000X or more on the photographic plates if desired.

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Skeletal elements of crinoid echinoderms: High-resolution structural and microanalytical results

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100074768 ◽

1983 ◽

Vol 41 ◽

pp. 194-195

Author(s):

D. F. Blake ◽

L. F. Allard ◽

D. R. Peacor

Keyword(s):

High Resolution ◽

Marine Invertebrates ◽

Sea Urchins ◽

Structural Features ◽

Sea Stars ◽

High Resolution Tem ◽

Relationship Of ◽

The Relationship ◽

Insight Into

Echinodermata is a phylum of marine invertebrates which has been extant since Cambrian time (c.a. 500 m.y. before the present). Modern examples of echinoderms include sea urchins, sea stars, and sea lilies (crinoids). The endoskeletons of echinoderms are composed of plates or ossicles (Fig. 1) which are with few exceptions, porous, single crystals of high-magnesian calcite. Despite their single crystal nature, fracture surfaces do not exhibit the near-perfect {10.4} cleavage characteristic of inorganic calcite. This paradoxical mix of biogenic and inorganic features has prompted much recent work on echinoderm skeletal crystallography. Furthermore, fossil echinoderm hard parts comprise a volumetrically significant portion of some marine limestones sequences. The ultrastructural and microchemical characterization of modern skeletal material should lend insight into: 1). The nature of the biogenic processes involved, for example, the relationship of Mg heterogeneity to morphological and structural features in modern echinoderm material, and 2). The nature of the diagenetic changes undergone by their ancient, fossilized counterparts. In this study, high resolution TEM (HRTEM), high voltage TEM (HVTEM), and STEM microanalysis are used to characterize tha ultrastructural and microchemical composition of skeletal elements of the modern crinoid Neocrinus blakei.

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Study of the Molecular Architecture of Keratin Filaments by Electron Microscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100053310 ◽

1982 ◽

Vol 40 ◽

pp. 118-119

Author(s):

U. Aebi ◽

P. Rew ◽

T.-T. Sun

Keyword(s):

Electron Microscopy ◽

Structural Organization ◽

Cell Types ◽

Structural Features ◽

Molecular Architecture ◽

The Past ◽

Keratin Filaments ◽

Different Types ◽

10 Nm Filaments ◽

Different Cell Types

Various types of intermediate-sized (10-nm) filaments have been found and described in many different cell types during the past few years. Despite the differences in the chemical composition among the different types of filaments, they all yield common structural features: they are usually up to several microns long and have a diameter of 7 to 10 nm; there is evidence that they are made of several 2 to 3.5 nm wide protofilaments which are helically wound around each other; the secondary structure of the polypeptides constituting the filaments is rich in ∞-helix. However a detailed description of their structural organization is lacking to date.

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Measurement and Reduction of Radiation Damage in Frozen Hydrated Crystalline Specimens

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100069867 ◽

1978 ◽

Vol 36 (3) ◽

pp. 70-77 ◽

Cited By ~ 1

Author(s):

R.M. Glaeser ◽

S.B. Hayward

Keyword(s):

Diffraction Pattern ◽

Structural Information ◽

Structural Disorder ◽

Structural Features ◽

Biological Macromolecules ◽

Diffraction Intensity ◽

Object Structure ◽

Specimen Material ◽

Unit Cells ◽

Identical Unit

Highly ordered or crystalline biological macromolecules become severely damaged and structurally disordered after a brief electron exposure. Evidence that damage and structural disorder are occurring is clearly given by the fading and eventual disappearance of the specimen's electron diffraction pattern. The fading and disappearance of sharp diffraction spots implies a corresponding disappearance of periodic structural features in the specimen. By the same token, there is a oneto- one correspondence between the disappearance of the crystalline diffraction pattern and the disappearance of reproducible structural information that can be observed in the images of identical unit cells of the object structure. The electron exposures that result in a significant decrease in the diffraction intensity will depend somewhat upon the resolution (Bragg spacing) involved, and can vary considerably with the chemical makeup and composition of the specimen material.

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Some Structural Features of Metaphase Chromosomes of Mice and Men

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100060969 ◽

1967 ◽

Vol 25 ◽

pp. 190-191

Author(s):

Godfrey C. Hoskins ◽

Betty B. Hoskins

Keyword(s):

Electron Microscopy ◽

Electron Micrographs ◽

Structural Features ◽

Metaphase Chromosomes ◽

The Future ◽

Of Mice And Men ◽

Mouse Cells ◽

Human And Mouse

Metaphase chromosomes from human and mouse cells in vitro are isolated by micrurgy, fixed, and placed on grids for electron microscopy. Interpretations of electron micrographs by current methods indicate the following structural features.Chromosomal spindle fibrils about 200Å thick form fascicles about 600Å thick, wrapped by dense spiraling fibrils (DSF) less than 100Å thick as they near the kinomere. Such a fascicle joins the future daughter kinomere of each metaphase chromatid with those of adjacent non-homologous chromatids to either side. Thus, four fascicles (SF, 1-4) attach to each metaphase kinomere (K). It is thought that fascicles extend from the kinomere poleward, fray out to let chromosomal fibrils act as traction fibrils against polar fibrils, then regroup to join the adjacent kinomere.

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