Substituted tetrabenzocyclophanes as mesogenic units of new polycondensates exhibiting columnar mesophases

Kranig, Wolfgang; Spiess, Hans Wolfgang; Zimmermann, Herbert

doi:10.1080/02678299008029199

Cited by 17 publications

(11 citation statements)

References 7 publications

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“…Yet, there are certain classes of discotic mesogens in which the molecular core is not flat (for example, derivatives of tribenzocyclononene 2,3 ) and not even rigid. To the latter class belong the mesogens derived from tetrabenzoorthocyclophanes [4][5][6][7][8][9] (Figure 1a).…”

Section: Introductionmentioning

confidence: 99%

“…The mesomorphic properties of several homologues of these series were studied by differential scanning calorimetry (DSC), optical polarizing microscopy, X-ray diffraction, and deuterium NMR. [4][5][6][7][8][9] The latter work 9 describes a detailed analysis of the deuterium NMR spectrum of one member (octa-heptyloxy) of the series in terms of the motional and ordering characteristics in the mesophase region. It confirms that the core conformation in the mesophase is most likely that of a sofa and that in the columns the molecules are stacked on top of each other in a locked form, like in a pile of chairs (see Figure 2a).…”

Section: Introductionmentioning

confidence: 99%

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Dynamics and Ordering in the Columnar Mesophases of Octa-alkyloxy Orthocylophane: A Carbon-13 NMR Investigation

et al. 2003

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Octa-alkyloxy tetrabenzo-orthocyclophanes (TBC-n where n is the number of carbons in the side chains) exhibit columnar mesophases of various symmetries, depending on the length of the side chains. The conformation of the orthocylophane core in these mesophases is that of a sofa, with the molecules stacking on top of each other to form columns. Within these columns, the molecules undergo reorientation via a combined pseudorotation/rotation mechanism. In the present work, carbon-13 NMR is used to study the mechanism and the kinetic parameters of this process, as well as the ordering characteristics in two homologues of the series, viz. TBC-9, which exhibits a single rectangular mesophase (Dr), and TBC-12, which is polymorphic with two mesophases, a low-temperature Dr and a high-temperature hexagonal columnar phase, Dh. Using 1D and 2D dynamic carbon-13 MAS NMR, the pseudorotation/rotation mechanism suggested earlier by Kuebler et al. on the basis of deuterium NMR studies (Liq. Cryst. 1995, 18, 300) is confirmed and kinetic parameters for the process are derived. Where comparable, the results are consistent with the earlier measurements. The results also indicate the presence of fast high-amplitude librations of the sofa conformation within the columns. The NMR lines of the MAS spectra within the mesophases are inhomogeneously broadened due to the distribution of isotropic chemical shifts. The latter probably reflects packing heterogeneity along the columns. Dynamic measurements of the sofa-sofa pseudorotation of TBC-9 in chloroform solutions are also reported.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Dynamics and Ordering in the Columnar Mesophases of Octa-alkyloxy Orthocylophane: A Carbon-13 NMR Investigation

et al. 2003

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“…The value of ,( , + 2)-1, 0.75 ± 0.15, reported earlier" is not convincingly different from the value, 0.90 ± 0.01, found in the present work. «,(«, + a2yl =/ir2[r, -/,( , -t2)]-' (5) The results reported here for procyanidins Bl, B2, B3, B4, and B5 do modify in a significant way the qualitative picture of the conformational characteristics of the family of procyanidin polymers. The values of a,(at + a2)~' obtained for procyanidins Bl and B7 by Bergmann et al" were 0.75 ± 0.15 and 0.85 ± 0.08, respectively.…”

Section: Discussionmentioning

confidence: 62%

“…In the present paper we extend the above conformational and dynamic studies of the cyclotetraveratrylene to a more highly substituted derivative, i.e., 3,4,5,10,11,12,17,18,19,24,25,26dodecamethoxy [ 1.1.1.1 ]orthocyclophane (DCP) (or, according to our previous nomenclature,3 1,2,3,5,6,7,9,10,11,13,14,15dodecamethoxytetrabenzo [adgj] cycledodecatetraene). We find from the NMR spectra at low and room temperatures that in this derivative the stability of the sofa and boat conformations are very nearly equal.…”

Section: Introductionmentioning

confidence: 86%

Variations in the heterogeneity of the decay of the fluorescence in six procyanidin dimers

Cho¹,

Tian²,

Porter³

et al. 1990

J. Am. Chem. Soc.

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“…Calorimetric analysis was carried out using a Perkin-Elmer DSC 7 calorimeter calibrated against the melting temperature of indium. Transition temperatures were taken from the DSC traces of samples on cooling from the isotropic liquid and on the subsequent reheating cycle at a heating/cooling rate of 10°C min-l.…”

Section: Techniquesmentioning

confidence: 99%

Discotic liquid-crystal behaviour of some multinuclear phthalocyanine derivatives

Bryant¹,

Cook²,

Haslam³

et al. 1994

J. Mater. Chem.

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The liquid-crystal properties are reported for a series of multinuclear phthalocyanines containing either two or three macrocyclic ring units. All but one of the compounds, the 'dimer' with the shortest spacer group between the two rings, exhibit discotic columnar mesophase behaviour. On cooling from the isotropic liquid the liquid-crystalline dimers show two distinct mesophases and the trimers one. Phase-transition temperatures are dependent upon the length of the linkages and whether or not copper is inserted into the macrocycle. The materials become very viscous, if not glass-like, when cooled to room temperature but retain the mesophase features defined by X-ray diffraction measurements.

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Substituted tetrabenzocyclophanes as mesogenic units of new polycondensates exhibiting columnar mesophases

Cited by 17 publications

References 7 publications

Dynamics and Ordering in the Columnar Mesophases of Octa-alkyloxy Orthocylophane: A Carbon-13 NMR Investigation

Dynamics and Ordering in the Columnar Mesophases of Octa-alkyloxy Orthocylophane: A Carbon-13 NMR Investigation

Variations in the heterogeneity of the decay of the fluorescence in six procyanidin dimers

Discotic liquid-crystal behaviour of some multinuclear phthalocyanine derivatives

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