Electric-polarization and structure of molecular complexes of the metallic halides of group II of the periodic table

Dielectric measurements have been made on a number of molecular complexes of beryllium, zinc, cadmium and mercuric halides. The polarizations observed have been interpreted in terms of a tetrahedral configuration for the undissociated beryllium, zinc and cadmium halide complexes. In other cases the observed polarization has been shown to be due to the dissociation of the complex in solution.

Electric dipole moments and molecular structure of aliphatic nitro compounds and oximes

Using the treatment of Smith et al. charge distributions in and consequently the dipole moments of some aliphatic nitro compounds and oximes have been evaluated. The mesomeric moment derived as a difference between the calculated and the observed values gives a clear picture as to how the positive (+M) and the negative (-M) mesomeric effects operate in such systems.

Structure of Ce1-xSnxO2 and its relation to oxygen storage property from first-principles analysis

CeO2-SnO2 solid solution has been reported to possess high oxygen storage/release property which possibly originates from local structural distortion. We have performed first-principles based density functional calculations of Ce1-xSnxO2 structure (x=0, 0.25, 0.5, 1) to understand its structural stability in fluorite in comparison to rutile structure of the other end-member SnO2, and studied the local structural distortion induced by the dopant Sn ion. Analysis of relative energies of fluorite and rutile phases of CeO2, SnO2, and Ce1-xSnxO2 indicates that fluorite structure is the most stable for Ce1-xSnxO2 solid solution. An analysis of local structural distortions reflected in phonon dispersion show that SnO2 in fluorite structure is highly unstable while CeO2 in rutile structure is only weakly unstable. Thus, Sn in Ce1-xSnxO2-fluorite structure is associated with high local structural distortion whereas Ce in Ce1-xSnxO2-rutile structure, if formed, will show only marginal local distortion. Determination of M-O (M=Ce or Sn) bond lengths and analysis of Born effective charges for the optimized structure of Ce1-xSnxO2 show that local coordination of these cations changes from ideal eightfold coordination expected of fluorite lattice to 4+4 coordination, leading to generation of long and short Ce-O and Sn-O bonds in the doped structure. Bond valence analyses for all ions show the presence of oxygen with bond valence similar to 1.84. These weakly bonded oxygen ions are relevant for enhanced oxygen storage/release properties observed in Ce1-xSnxO2 solid solution. (C) 2010 American Institute of Physics.

Studies on the structure of the chromosomes - I. Allium cepa-Stain fixatives and their utility

The structure of the mitotic chromosomes of Allium cepa has been elucidated by controlling the temperature and time of exposure of fresh roots to stain fixatives. The details seen in material stained in N HCl-orcein for 8 min. at 60° C. and squashed after varying intervals of storage at room temperature were essentially similar to pictures obtained with 1% aceto-orcein and 1% aceto-orcein-N HCl (10:1) under identical conditions of handling. The chromosomes appear quadri-partite at metaphase and bi-partite at anaphase. A rare instance of the precocious assumption of a quadri-partite condition by two anaphase chromosomes is illustrated. Caduceus coiling of chromonemata was seen in chromosome bridges also. Chromosomes have material easily dissociable from the chromonemata and their removal does not affect the structural integrity of the chromosome.

Dipole moments and molecular structure of picrates of aromatic hydrocarbons and heterocyclic amines

Dipole moment measurements have been made in the case of a few aromatic hydrocarbon picrates, the values obtained being 2·18, 2·25, 2·97 (all in Debye units) for picrates of naphthalene, acenaphthene and phenanthrene respectively and the results discussed in terms of Mulliken's theory. Measurements have also been extended to include a few salt-like heterocyclic amine picrates.

Studies in sesquiterpenes-XVIII. The proton magnetic resonance spectra of some sesquiterpenes and the structure of humulene

The nuclear magnetic resonance spectra of longifolene, zerumbone, humulene, and their hydroderivatives have been studied in order to gauge the potentialities of this new tool in the field of sesquiterpenes. On the basis of present study, it has been possible to unequivocally fix the positions of the ethylene linkages in humulene and thus provide a straightforward solution of this hitherto unsolved problem.

Reaction of dialkyl 2-butynoate with aniline and formaldehyde: revision of the structure of the product

Dimethyl 3-(aryl)-3,6-dihydro-2H-1,3-oxazine4,5-dicarboxylate structure assigned for the products obtained in the Bronsted acid catalyzed reaction of dimethyl but-2-ynoates with anilines and an excess of formaldehyde in methanol has been revised to methyl 1-(aryl)-3-(methoxymethyl)-4,5-dioxopyrrolidine-3-carboxylate. (C) 2010 Elsevier Ltd. All rights reserved.

Crystal structure of an intermolecular 2:1 complex between adenine and thymine.Evidence for both Hoogsteen and `quasi-Watson-Crick' interactions

The titled complex, obtained by co-crystallization (EtOH/25 degrees C),is apparently the only known complex of the free bases. Its crystal structure, as determined by X-ray diffraction at both 90 K and 313 K, showed that one A-T pair involves a Hoogsteen interaction, and the other a Watson-Crick interaction but only with respect to the adenine unit. The absence of a clear-cut Watson-Crick base pair raises intriguing questions about the basis of the DNA double helix. (C) 2010 Elsevier Ltd. All rights reserved.

Crystal And Molecular-Structure Of 8-Acetoxy-6-(2,4-Dimethoxy-5-Bromophenyl)-3-Methyl-Tricyclo[5,2,1,03,8 ]Decan-2-One

The crystal and molecular structure has been determined by the heavy-atom method and refined by the least-squares procedure to R= 8"3 % for 2033 photographically observed reflexions. The compound crystallizes in the space group P]" with two molecules in a unit cell of dimensions a = 11"68 + 0-02, b = 12"91 +0"02, c= 10"43+0"02/~, e= 114"7+ 1, fl=90-2+ 1 and 7,= 118.3+ 1 °. The unit cell also contains one molecule of the solvent, benzene. The 'cage' part of the molecule exhibits a large number of elongated bonds and strained internal valency angles. The bridgehead angle in the bicyclic heptane ring system is 89 °. The acetate group at C(16) and the methyl group at C(15) are cis to each other.

Crystal And Molecular Structure Of A Dimethyl Sulphoxide Complex With Lanthanum Nitrate, La(No3)34.(Ch3)2so

The crystal structure of the complex La(NO3)3.4(CH3)2SO has been solved by the heavy-atom method. The complex crystallizes in the monoclinic space group C2/e with four formula units in a unit cell of dimensions a= 14.94, b= 11.04, c= 15.54 A and fl= 109 ° 10'. The parameters have been refined by threedimensional least-squares procedures with anisotropic thermal parameters for all atoms except hydrogen. The final R index for 1257 observed reflexions is 0.094. The La 3 + ion is coordinated by ten oxygen atoms with La-O distances varying from 2.47 to 2.71 A. The geometry of the coordination polyhedron is described.

Structural Studies Of Analgesics And Their Interactions .1. Crystal And Molecular-Structure Of Antipyrine

The complex crystallizes in the space group P21/c with four formula units in a unit cell of dimensionsa= 12.747, b= 7.416, c= 17.894 A and/3= 90.2 °. The structure has been solved by the symbolic addition procedure using three dimensional photographic data and refined to an R value of 0.079 for 2019 observed reflexions. The pyramidal nature of the two hetero nitrogen atoms in the antipyrine molecule is inter:nediate between that observed in free antipyrine and in some of its metal complexes. The molecule is more polar than that in crystals of free antipyrine but less so compared with that in metal complexes. In the salicylic acid molecule, the hydroxyl group forms an internal hydrogen bond with one of the oxygen atoms in the carboxyl group. The association between the salicylic acid and the antipyrine molecules is achieved through an intermolecular hydrogen bond with the other carboxyl oxygen atom in the salicylic acid molecule as the proton donor and the carboxyl oxygen atom of the antipyrine molecule as the acceptor

A Device to Crystallize Organic Solids: Structure of Ciprofloxacin, Midazolam, and Ofloxacin as Targets

The crystal structure determination of the anhydrous form of any organic compound has been a challenge because of solvent incorporation during crystallization. A device to grow anhydrous forms of low melting organic solids based on vaporization and condensation by a gradient cooling technique has been designed. Its utility has been evaluated by growing anhydrous forms of ciprofloxacin, midazolam, and ofloxacin. Ciprofloxacin crystallizes in triclinic P (1) over bar, midazolam in monoclinic P2(1)/n, and ofloxacin in the C2/c space group. Comparative studies on the conformational features with solvated structure show no significant variation in the aromatic moieties.

Synthesis, structure, transformation studies and catalytic properties of open-framework cadmium thiosulfate compounds

Five new thiosulfate based inorganic-organic hybrid open-framework compounds have been synthesized employing mild reaction conditions. Of the five compounds, [Na-2(H2O)(8)][Cd(C10H8N2)( S2O3)(2)]center dot 2H(2)O, I and [Cd-2(C10H8N2)(2)(HS2O3)(2)(S2O3)(2)][(C10H9N2)(2)(C10H8N2)(2)]center dot 8H(2)O, II have one-dimensional (1D) structures and [Cd(C10H8N2)(H2O)(2)(S2O3)]center dot 2H(2)O, III, [Cd-2(C10H8N2)(3)(S2O3)(2)], IV and [Cd-2(C10H8N2)(2.5)(S2O3)(2)], V have three- dimensional (3D) structures. The 1D structures are somewhat related, formed by the bonding between tetrahedral Cd centers (CdN2S2) and 4,4'-bipyridine (bpy) units. The inter-chain spaces are occupied by the hanging thiosulfate units in both the cases along with Na(H2O)(6) chains in I and free bpy units in II. The three 3D structures have one-dimensional cadmium thiosulfate chains linked by bpy units. Interpenetration has been observed in all the 3D structures. The 3D structures appear to be related and can be derived from fgs net. Transformation studies on the 1D compound, [Na-2(H2O)(8)][Cd(C10H8N2)(S2O3)(2)]center dot 2H(2)O, I, indicated a facile formation of [Cd(C10H8N2)(H2O)(2)(S2O3)]center dot 2H(2)O, III. Prolonged heating of I gave rise to a 3D cadmium sulfate phase, [Cd-2(C10H8N2)(2)(H2O)(3)(SO4)(2)]center dot 2H(2)O, VI. Compound VI has one-dimensional cadmium sulfate chains formed by six-membered rings connected by bpy units to form a 3D structure, which appears to resemble the topological arrangement of III. Transformation studies of III indicates the formation of IV and V, and at a higher temperature a new 3D cadmium sulfate, [Cd(C10H8N2)(SO4)], VII. Compound VII has a 4 x 4 grid cadmium sulfate layers pillared by bpy units. All the compounds were characterized by PXRD, TGA, IR and UV-visible studies. Preliminary studies on the possible use of the 3D compounds (III-VII) in heterogeneous cyanosilylation of imines appear to be promising.