Some 5- and 6-coordinate base adducts of Bis(acetylacetonato)manganese(II)

1964 ◽  
Vol 17 (10) ◽  
pp. 1119 ◽  
Author(s):  
DP Graddon ◽  
GM Mockler
Keyword(s):  
Molecular Weight ◽  
Magnetic Moments ◽  
Donor Atom ◽  
Dark Colour ◽  
Anhydrous Compound ◽  
Coordinate Base ◽  
Lower Moment

From diaquobis(acetylacetonato)manganese(II) we have obtained mono- and bis(pyridine)acetylacetonatomanganese(II), corresponding 4-methylpyridine compounds, bis-2-methylpyridine-, aquo-2-methylpyridine-, and o-phenanthroline- derivatives and some compounds in which all or part of the water is replaced by ethanol. All these compounds have magnetic moments which are normal for spin-free d5 complexes, but anhydrous bis(acetylacetonato)manganese(II) has a slightly lower moment. Molecular weight determinations show that the anhydrous compound is trimeric; the adducts with one molecule of base, though monomeric and 5-coordinate in freshly prepared benzene solutions, slowly decompose in solution, probably to condensed 6-coordinate species; the bispyridine, bis-4-methylpyridine, and o-phenanthroline adducts also dissociate in solution, an indication that manganese(II) forms unstable complexes with nitrogen as donor atom. The dark colour of these solutions appears to be due to manganese(IV) oxide.

The anomalous paramagnetism of iron(III) NN-dialkyldithiocarbamates

1964 ◽  
Vol 17 (3) ◽  
pp. 294 ◽  
Author(s):  
AH White ◽  
R Roper ◽  
E Kokot ◽  
H Waterman ◽  
RL Martin
Keyword(s):  
Molecular Weight ◽  
Thermal Equilibrium ◽  
Room Temperature ◽  
Chemical Nature ◽  
Magnetic Moments ◽  
Chloroform Solution ◽  
Exchange Interactions ◽  
Magnetic Behaviour ◽  
Antiferromagnetic Exchange ◽  
Molecular Type

The magnetic moments of a series of 19 NN-disubstituted dithiocarbamates of iron(III), [Fe(S2C.NR?R")3], are anomalous in that their behaviour is neither "high-" nor "low-spin". Values of μeff. at room temperature lie between 2.62 and 5.83 B.M., the datum for each compound depending on the chemical nature of the substituents R' and R". This anomalous situation persists in benzene or chloroform solution. Cryoscopic and ebullioscopic molecular weight determinations establish that all the compounds are monomeric, which excludes the possibility that the magnetic behaviour arises from the presence of antiferromagnetic exchange interactions of either the inter- or intra-molecular type. These observations strongly support the early and generally overlooked work of Cambi who in 1932 proposed a thermal equilibrium between "magnetic isomers" of spins S = � and S = 5/2 to account for the origin of the magnetic anomaly.

Studies in the Stereochemistry of Zinc(II). I. Derivatives of Bis(acetyl-acetonato)zinc(II)

1963 ◽  
Vol 16 (6) ◽  
pp. 980 ◽  
Author(s):  
DP Graddon ◽  
DG Weeden
Keyword(s):  
Molecular Weight ◽  
Crystal Field ◽  
Predominant Species ◽  
Anhydrous Compound ◽  
Derivatives Of

The compound melting at 138� and for long supposed to be anhydrous bis(acetylacetonato)zinc(II) is shown to be the monohydrate. The anhydrous compound has also been obtained, melting at 152�; and adducts are described with one and two molecules of pyridine or 4-methylpyridine, one molecule of 2-methylpyridine, and two molecules of ammonia. Molecular weight determinations in benzene and triphenylmethane show that with the exception of the anhydrous compound which is monomeric, the predominant species in solution are five-coordinate. Differences in the stereochemical behaviour of zinc in these compounds from the behaviour of cobalt(II) and nickel(II) in corresponding compounds are interpreted in terms of crystal-field stabilization of octahedral complexes of the latter ions.

Coordination compounds of substituted 1,10-Phenanthrolines and related dipyridyls. VI. Complexes of copper(II) and 4,6,4',6'-Tetramethyl-2,2'-bipyridine

1965 ◽  
Vol 18 (9) ◽  
pp. 1331 ◽  
Author(s):  
JR Hall ◽  
MR Litzow ◽  
RA Plowman
Keyword(s):  
Molecular Weight ◽  
Coordination Compounds ◽  
Magnetic Moments ◽  
Spectral Measurements

The following complexes of copper(II) and 4,6,4',6'-tetramethyl-2,2'-bipyridine (tmb) have been prepared: CuX2tmb, where X = NO3,Cl,Br, and �SO4; Cu(tmb)2X2, nH2O, where X = NO3 (n = 1) and ClO4, (n = 0, 1, and 2); and Cu(tmb)2X(ClO4), nH2O, where X = NO3 (lz = 1) and Cl (n = 0). The magnetic moments of the compounds range from 1.89 to 2.05 B.M. The results of conductivity, molecular weight, and spectral measurements suggest the occurrence of four-, five-, and six-coordinate copper(II).

The Crystal and Molecular Structure and Properties of Diaqua[N-salicylidene – (S) – (+) – glutamato]copper(II) Monohydrate

1991 ◽  
Vol 46 (10) ◽  
pp. 1323-1327 ◽  
Author(s):  
J. Krätsmár-Šmogrovič ◽  
F. Pavelčík ◽  
J. Soldánová ◽  
J. Sivy ◽  
V. Seressová ◽  
...  
Keyword(s):  
Molecular Structure ◽  
Crystal And Molecular Structure ◽  
Magnetic Behaviour ◽  
Title Complex ◽  
Donor Atom ◽  
Structure And Properties ◽  
X Ray Diffraction ◽  
X Ray ◽  
Anhydrous Compound ◽  
Tridentate Schiff Base

The crystal and molecular structure of the title complex was determinated by single crystal X-ray diffraction (R = 0.066 for 1059 observed reflections). The approximately square-pyramidal coordination of Cu(II) results from donor atoms O(12), O(1), N(1), O(5) of one H2O molecule as well as the tridentate Schiff base dianion ligand and from the weakly bonded O(1) donor atom of one other H2O molecule in the apical site.The magnetic behaviour of the complex studied obeys the Curie—Weiss law in the temperature range 94—309 K with a small value of the Weiss constant, θ = 1.4 Κ. A similar cryomagnetic behaviour is also characteristic for the anhydrous compound, [N-salicylidene—(S)—(+)-glutamato]copper(II), obtained by thermal dehydration of the title complex.

Evaluation of the dark field method for large association of spread DNA

1978 ◽  
Vol 36 (2) ◽  
pp. 190-191
Author(s):  
Douglas C. Barker
Keyword(s):  
Electron Microscopy ◽  
Molecular Weight ◽  
Mitochondrial Dna ◽  
Extraction Method ◽  
Field Method ◽  
Dark Field ◽  
Kinetoplast Dna ◽  
Field Electron ◽  
Field Electron Microscopy ◽  
Dark Field Electron

A number of satisfactory methods are available for the electron microscopy of nicleic acids. These methods concentrated on fragments of nuclear, viral and mitochondrial DNA less than 50 megadaltons, on denaturation and heteroduplex mapping (Davies et al 1971) or on the interaction between proteins and DNA (Brack and Delain 1975). Less attention has been paid to the experimental criteria necessary for spreading and visualisation by dark field electron microscopy of large intact issociations of DNA. This communication will report on those criteria in relation to the ultrastructure of the (approx. 1 x 10-14g) DNA component of the kinetoplast from Trypanosomes. An extraction method has been developed to eliminate native endonucleases and nuclear contamination and to isolate the kinetoplast DNA (KDNA) as a compact network of high molecular weight. In collaboration with Dr. Ch. Brack (Basel [nstitute of Immunology), we studied the conditions necessary to prepare this KDNA Tor dark field electron microscopy using the microdrop spreading technique.

Introduction

1978 ◽  
Vol 36 (3) ◽  
pp. 543-544
Author(s):  
W. Bernard
Keyword(s):  
Molecular Weight ◽  
Electron Microscope ◽  
Nucleic Acid ◽  
Gene Mapping ◽  
Molecular Genetics ◽  
Cell Biology ◽  
Gene Activity ◽  
Close Connection ◽  
Basic Information ◽  
Simple Systems

In comparison to many other fields of ultrastructural research in Cell Biology, the successful exploration of genes and gene activity with the electron microscope in higher organisms is a late conquest. Nucleic acid molecules of Prokaryotes could be successfully visualized already since the early sixties, thanks to the Kleinschmidt spreading technique - and much basic information was obtained concerning the shape, length, molecular weight of viral, mitochondrial and chloroplast nucleic acid. Later, additonal methods revealed denaturation profiles, distinction between single and double strandedness and the use of heteroduplexes-led to gene mapping of relatively simple systems carried out in close connection with other methods of molecular genetics.

The External Shape of Human γ GI Immunoglobulin from Crystal Sections

1971 ◽  
Vol 29 ◽  
pp. 428-429
Author(s):  
L. W. Labaw
Keyword(s):  
Molecular Weight ◽  
Sodium Phosphate ◽  
Osmium Tetroxide ◽  
Unit Cell ◽  
Monoclinic Space Group ◽  
X Ray ◽  
Large Molecular Weight ◽  
Cell Dimensions ◽  
Unit Cell Dimensions ◽  
Crystallographic Axes

Crystals of a human γGl immunoglobulin have the external morphology of diamond shaped prisms. X-ray studies have shown them to be monoclinic, space group C2, with 2 molecules per unit cell. The unit cell dimensions are a = 194.1, b = 91.7, c = 51.6Å, 8 = 102°. The relatively large molecular weight of 151,000 and these unit cell dimensions made this a promising crystal to study in the EM.Crystals similar to those used in the x-ray studies were fixed at 5°C for three weeks in a solution of mother liquor containing 5 x 10-5M sodium phosphate, pH 7.0, and 0.03% glutaraldehyde. They were postfixed with 1% osmium tetroxide for 15 min. and embedded in Maraglas the usual way. Sections were cut perpendicular to the three crystallographic axes. Such a section cut with its plane perpendicular to the z direction is shown in Fig. 1.This projection of the crystal in the z direction shows periodicities in at least four different directions but these are only seen clearly by sighting obliquely along the micrograph.

Conformation of eukaryotic ribosomal RNAs

1983 ◽  
Vol 41 ◽  
pp. 592-593
Author(s):  
M. Boublik ◽  
G. Thornton ◽  
G. Oostergetel ◽  
J.F. Hainfeld ◽  
J.S. Wall
Keyword(s):  
Molecular Weight ◽  
Mass Measurement ◽  
Carbon Film ◽  
Structural Complexity ◽  
Scanning Transmission Electron Microscope ◽  
Electron Microscopic ◽  
Pure Nitrogen ◽  
Freeze Dried ◽  
Scanning Transmission ◽  
Partially Unfolded

Understanding the structural complexity of ribosomes and their role in protein synthesis requires knowledge of the conformation of their components - rRNAs and proteins. Application of dedicated scanning transmission electron microscope (STEM), electrical discharge of the support carbon film in an atmosphere of pure nitrogen, and determination of the molecular weight of individual rRNAs enabled us to obtain high resolution electron microscopic images of unstained freeze-dried rRNA molecules from BHK cells in a form suitable for evaluation of their 3-D structure. Preliminary values for the molecular weight of 28S RNA from the large and 18S RNA from the small ribosomal subunits as obtained by mass measurement were 1.84 x 106 and 0.97 x 106, respectively. Conformation of rRNAs consists, in general, of alternating segments of intramolecular hairpin stems and single stranded loops in a proportion which depends on their ionic environment, the Mg++ concentration in particular. Molecules of 28S RNA (Fig. 1) and 18S RNA (not shown) obtained by freeze-drying from a solution of 60 mM NH+4 acetate and 2 mM Mg++ acetate, pH 7, appear as partially unfolded coils with compact cores suggesting a high degree of ordered secondary structure.

The Structure of Radiation Cross-Linked Poly (ethylene oxide) Gels

1971 ◽  
Vol 29 ◽  
pp. 76-77
Author(s):  
C. E. Cluthe ◽  
G. G. Cocks
Keyword(s):  
Molecular Weight ◽  
Ethylene Oxide ◽  
Parallel Plate ◽  
Average Molecular Weight ◽  
Radical Reaction ◽  
Free Radical Reaction ◽  
Nitrogen Gas ◽  
Poly Ethylene Oxide ◽  
Poly Ethylene ◽  
Initial Viscosity

Aqueous solutions of a 1 weight-per cent poly (ethylene oxide) (PEO) were degassed under vacuum, transferred to a parallel plate viscometer under a nitrogen gas blanket, and exposed to Co60 gamma radiation. The Co60 source was rated at 4000 curies, and the dose ratewas 3.8x105 rads/hr. The poly (ethylene oxide) employed in the irradiations had an initial viscosity average molecular weight of 2.1 x 106.The solutions were gelled by a free radical reaction with dosages ranging from 5x104 rads to 4.8x106 rads.

The Collagenic Molecular Structural Unit of Solid State Complexes

1971 ◽  
Vol 29 ◽  
pp. 478-479
Author(s):  
Kenneth M. Richter ◽  
John A. Schilling
Keyword(s):  
Molecular Weight ◽  
Solid State ◽  
Structural Unit ◽  
X Ray Diffraction ◽  
X Ray ◽  
Naoh Treatment

The structural unit of solid state collagen complexes has been reported by Porter and Vanamee via EM and by Cowan, North and Randall via x-ray diffraction to be an ellipsoidal unit of 210-270 A. length by 50-100 A. diameter. It subsequently was independently demonstrated by us in dog tendon, dermis, and induced complexes. Its detailed morphologic, dimensional and molecular weight (MW) aspects have now been determined. It is pear-shaped in long profile with m diameters of 57 and 108 A. and m length of 263 A. (Fig. 1, tendon, KMnO4 fixation, Na-tungstate; Fig. 2a, schematic of unit in long, C, and x-sectional profiles of its thin, xB, and bulbous, xA portions; Fig. 2b, tendon essentially unmodified by ether and 0.4 N NaOH treatment, Na-tungstate). The unit consists of a uniquely coild cable, c, of ṁ 22.9 A. diameter and length of 2580-3316 A. The cable consists of three 2nd-strands, s, each of m 10.6 A.

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