Nematische systeme IV:

Steinsträßer, Ralf; Pohl, L.

doi:10.1016/s0040-4039(01)96743-7

Cited by 42 publications

(7 citation statements)

References 2 publications

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“…The g and A tensors of the TEMPONE molecule in the TPP nanochannels were determined from the spectrum of 4 at 86 K, as for 1 , and are given in Table . The calculated g and A tensors were consistent within the experimental error for several cases of TEMPONE or perdeuterated TEMPONE molecules confined in various organic matrixes or liquid crystals, ,,,− as shown in Table . In the simulation, the Gaussian and Lorentzian line-width components were 0.60 and 0.69 mT, respectively.…”

Section: Resultssupporting

confidence: 68%

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Molecular Orientation and Dynamics of Different Sized Organic Radicals Included in Organic 1D Nanochannels

2013

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The molecular orientation and dynamics of di-t-butylnitroxide (DTBN) and 4-oxo-2,2,6,6-tetramethyl-1-piperidinyl-1-oxyl (TEMPONE) radicals in the organic 1D nanochannels of tris(o-phenylenedioxy)cyclotriphosphazene (TPP) were investigated by examining inclusion compounds (ICs) diluted by the co-inclusion of nonradicals using electron spin resonance (ESR). Spectral simulation showed that the axial rotation of DTBN or TEMPONE molecules is excited in TPP nanochannels with activation energies of 3 and 10 kJ mol(-1), respectively. The rotation axes for both DTBN and TEMPONE were determined to be almost parallel to the principal y-axis of the g tensor, which agrees with the result reported for 2,2,6,6-tetramethyl-1-piperidinyl-1-oxyl (TEMPO) in TPP nanochannels, which has the activation energy of 5 kJ mol(-1). These results indicate that the molecular orientations of guest nitroxide radicals are almost independent of the molecular sizes of the guest radicals in TPP nanochannels, although the molecular dynamics are dependent on the molecular sizes.

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Section: Resultssupporting

confidence: 68%

“… e A low melting nematic eutectic composed of 65% phase IV and 35% of another phase; 83 K (refs and ). …”

Section: Resultsmentioning

confidence: 99%

Molecular Orientation and Dynamics of Different Sized Organic Radicals Included in Organic 1D Nanochannels

2013

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“…The compounds of series I have also been discussed in reference [9], but without explicit reference to the smectic phases. The transition temperatures given [24]). …”

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confidence: 99%

“…The mesophases of the p,p'-di-n-alkoxyazoxybenzenes are described in references [18] and [23]. The In order to investigate whether the asymmetric shape of the molecules affects certain mesophases, we finally consider the series (for n 7 from reference [24]). …”

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confidence: 99%

Molecular structure and the occurrence of smectic A and smectic c phases

Jeu

1977

J. Phys. France

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“…These results are somewhat surprising since the oxidation of unsymmetrical azobenzene derivatives generally gives rise to a mixture of the isomeric aand P-azoxybenzenes in a ratio of ca. 1: 1 (21)(22)(23)(24), except when a bulky substituent is present on one ring in which case one azoxy isomer is obtained predominantly (25).…”

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confidence: 99%

Studies of azo and azoxy dyestuffs. Part 17. Synthesis and structure determination of isomeric α and β phenylazoxypyridines, N-oxides, and methiodides. A reexamination of the oxidation of phenylazopyridines and X-ray structure analyses of 4-(phenyl-α-azoxy)pyridinium methiodide and 4-(phenyl-β-azoxy)pyridine-N-oxide

Buncel¹,

Keum²,

Cygler³

et al. 1984

Can. J. Chem.

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In an extension of Wallach rearrangement studies into the phenylazoxypyridine series, an investigation of 4-, 3-, and 2-phenylazoxypyridines, the N-oxides, and methiodides is reported. Oxidation of 4-and 3-phenylazopyridine with peracetic acid gives rise to the a and p phenylazoxypyridine-N-oxides, contrary to previous literature reports on the obtention solely of the a isomers. 2-Phenylazopyridine, however, yields only the 2-(phenyl-a-azoxy)pyridine-N-oxide. These results are rationalized on the basis of field, resonance, and steric effects. An unprecedented reactivity difference has been observed in the reactions of the a , p isomers of phenylazoxypyridines under conditions of the Wallach rearrangement. This reactivity difference permits the isolation of the a-azoxy isomers from the a,p mixtures. Unequivocal confirmation of the structures has been obtained from X-ray crystal structure determinations of two representative compounds in this series, viz. 4-(phenyl-P-azoxy)-pyridine-N-oxide (11) and 4-(phenyl-a-azoxy)pyridinium methiodide (12), which itself was formed by deoxygenation of 4-(phenyl-a-azoxy)pyridine-N-oxide, followed by methylation with methyl iodide. The crystal structure of 11 was solved by direct methods and refined by block-diagonal least squares to R = 0.041 for 2479 observed reflections. The asymmetric unit contains two independent molecules, both of which are planar. The structure of 1 2 was determined by the heavy-atom method and refined by full-matrix least squares to R = 0.043 for 1718 observed reflections. The molecules are not planar, the pyridine ring being rotated by 36.5" from the phenylazoxy plane. Evidence is presented for the existence of intramolecular C-H -. . O and C-H N bonds in crystal structures of trans-azoxyarenes. The carbon atoms involved in these hydrogen bonds are ortho to the azoxy group and can act as proton donors as a result of the inductive effect of the adjacent nitrogen.

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Nematische systeme IV:

Cited by 42 publications

References 2 publications

Molecular Orientation and Dynamics of Different Sized Organic Radicals Included in Organic 1D Nanochannels

Molecular Orientation and Dynamics of Different Sized Organic Radicals Included in Organic 1D Nanochannels

Molecular structure and the occurrence of smectic A and smectic c phases

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