Isomerisation of Liquid-Crystalline Tristriazolotriazines

Article abstract of DOI:10.1002/chem.201705095

Star-shaped discotic liquid crystals with columnar superstructures constitute a highly interesting class of organic materials. Phenyl-substituted tris[1,2,4]triazolo-[1,3,5]triazine, prepared by a Huisgen reaction of phenyltetrazole and cyanuric chloride, represents an excellent core for discotic liquid crystals (DLCs). The thermal stability is not perfect, at temperatures above the clearing point, a successive threefold isomerization leads to a highly planar, C₃-symmetrical isomer, which mainly differs in the orientation of the aryl substituents to the centre of the molecule. A new class of discotic liquid crystals has been obtained: Equipped with peripheral alkoxy chains both isomers can form broad thermotropic mesophases. The optical, thermal, and physical properties were investigated by polarized optical microscopy, differential scanning calorimetry, wide-angle X-ray scattering, UV/Vis absorption and fluorescence spectroscopic measurements. The thermotropic properties are decisively affected by the molecular structure of the isomers, isomerisation leads to higher melting points but also the loss or even gain of mesomorphism is observed.

Full text of DOI:10.1002/chem.201705095

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Title: Isomerisation of Liquid-Crystalline Tristriazolotriazines
Authors: Heiner Detert, Thorsten Rieth, Nico Roeder, and Matthias
Lehmann
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Isomerisation of Liquid-Crystalline Tristriazolotriazines
Thorsten Rieth[a], Nico Röder[a], Matthias Lehmann,* [b] and Heiner Detert*[a]
Star-shaped
discotic
liquid
crystals
with
columnar
All these TTTs with a `tangential´ orientation (t-TTT) of the
alkoxyphenyl substituents were obtained via the Huisgen route.
An independent access to TTTs was reported by Tartakovsky[13]
in 2005: thermocyclization of three 5-chloro-3-phenyl-1,2,4-
superstructures constitute a highly interesting class of organic
materials. Phenyl substituted tris[1,2,4]triazolo-[1,3,5]triazine,
prepared by a Huisgen reaction of phenyl tetrazole and cyanuric
chloride, represents an excellent core for discotic liquid crystals
(DLCs). The thermal stability is not perfect, at temperatures
above the clearing point, a successive threefold isomerization
leads to a highly planar, C3-symmetrical isomer, which mainly
differs in the orientation of the aryl substituents to the centre of
the molecule. A new class of discotic liquid crystals has been
obtained: Equipped with peripheral alkoxy chains both isomers
can form broad thermotropic mesophases. The optical, thermal,
and physical properties were investigated by polarized optical
microscopy, differential scanning calorimetry, wide-angle X-ray
scattering, UV-Vis absorption and fluorescence measurements.
The thermotropic properties are decisively affected by the
molecular structure of the isomers, isomerisation leads to higher
melting points but also the loss or even gain of mesomorphism
is observed.
triazole molecules resulted in
a C3-symmetrical triphenyl
tristriazolotriazine (2, Ri = H) – but the different annulation
pattern brings the phenyl rings to distal positions. The molecule
adopts a star shape with phenyl rings as rays. This r-TTT with a
`radial´ orientation of the substituents to the core exhibits a very
high thermal stability, decomposition started only at 400 C (TGA).
Unfortunately, the scope of the synthetic method is very
small.[11f] The isomeric t-TTT 1 (Ri = H), when heated to 350 °C,
changed to an isomeric mixture of asymmetric (r,t-TTTs).[13]
Herein, we present the thermal isomerization of C3-symmetric
t-TTTs (1a-h) into C3-symmetric r-TTTs (2a-h, scheme 1, table
1), together with the impressive changes of their mesomorphous
behavior, structural investigations and some optical properties.
Organic -conjugated systems, small molecules[1] and
polymers,[2] are of great interest for sensing, optical and
electronic applications.[3] The group of discotic liquid crystals
(DLC) offers the additional feature of self-organization, often as
a columnar arrangement resulting in anisotropic properties, e.g.
one-dimensional charge transport in the liquid-crystalline
phase.[4] Typical DLCs consist of electron-rich polycyclic
aromatic units, e.g. triphenylene or hexabenzocoronene,[5]
whereas DLCs with an electron deficient core are rather
scarce.[6] One of the youngest members of this group is the
tris[1,2,4]triazolo-[1,3,5]triazine (TTT), a tetracyclic, nitrogen-rich,
and C3-symmetrical analogue of triphenylene. The first TTT,
triphenyl-TTT 1 (Ri = H), has been prepared by Huisgen[7], its
shape is a tetracyclic plane with three phenyl rings sticking out
of the bays. To avoid steric compression, the substituents are
twisted out of the plane with dihedral angles up to 80°.[8, 9] In
2008, Gallardo[8, 10] and Glang[11] recognized the suitability of the
TTT as a core for discotic liquid crystals. These propellers (e.g.
1b-1h) with six to nine alkoxy groups on the outer rim can form
broad mesophases. Polarized light revealed the characteristic
textures of a columnar phase and X-ray diffraction (WAXS and
SAXS) on pre-orientated filaments confirmed a hexagonal
arrangement of the columns in the mesophase and complex
helical superstructures in the solid state.[12]
Scheme 1. Thermal isomerisation of tristriazolotriazines
Table 1: Substitution pattern and isomerization yields of r-TTTs
Comp.
1a/2a
1b/2b
1c/2c
1d/2d
1e/2e
1f/2f
R1
R2
R3
Yield.
65 %
43 %
38 %
18 %
21 %
26 %
22 %
32 %
OC3H7
H
H
OC10H21
OC12H25
OC14H29
OC16H33
OC8H17
OC10H21
OC12H25
OC14H29
OC16H33
OC8H17
H
H
H
H
OC8H17
OC10H21
4-ethyloctyloxy
1g/2g
1h/2h
OC10H21
4-ethyloctyloxy
OC10H21
4-ethyloctyloxy
Heating alkoxy-substituted t-TTTs like 1a to 350 °C results in
mixtures with varying composition of non-symmetric isomers and
decomposition products. The latter are drastically reduced if the
reaction is performed in an inert solvent and below 300 °C, the
time required for a complete transformation increases to four to
six days. Isomerization of the t-TTTs was achieved by heating
solutions of 1a-h in octadecane for several days at 235 °C under
exclusion of oxygen. Time-dependent 1H-NMR (figure 1)
revealed a stepwise process; the first rearrangement was fast,
starting material vanished within 14 h, but it took 4 days to
complete the cascade of rearrangements to C3-symmetrical 2a.
[a]
[b]
Dr. T. Rieth, Dipl.-Chem. N. Röder, Prof. Dr. H. Detert*
Institute for Organic Chemistry
Johannes Gutenberg-University Mainz
Duesbergweg 10–14, 55099 Mainz (Germany)
Fax: (+49) 6131-39-25338
E-mail: detert@uni-mainz.de
Prof. Dr. M. Lehmann
Julius-Maximilians-Universität
Institut für Organische Chemie
Am Hubland, 97074 Würzburg
Supporting information for this article is given via a link at the end of
the document.
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For the mechanism (scheme S1), a heterolytic bond fission
of a triazine bond, rotation of one ring around the triazole-
triazole bond and recombination was proposed[13] for each
isomerization step.
Single crystals of p-propyloxyphenyl substituted r-TTT (2a)
were obtained via slow evaporation of a solution in toluene. X-
ray scattering verified the postulated isomeric arrangement of
the atoms in the triazole rings (figure 2.) and provides
information about the molecular packing in the solid state.
Crystallographic data exhibit a nearly planar molecule: The
dihedral angles between the central TTT core and the peripheral
phenyl rings are below 5° whereas the phenyl substituents in
crystalline p-alkoxy phenyl t-TTT are twisted up to 80°.[8,9] The
organization of the molecules in the solid state is based on π-π
interactions between the electron-rich alkoxyphenyl substituents
and the electron-poor TTT cores. A distance of 3.3 Å between
adjacent molecules is in the typical range of π-π interactions.
Investigations of the di- and trialkoxyphenyl substituted t-TTTs
and r-TTTs (1b-g, 2d-g) with a polarized optical microscope
show the typical fan-shaped and dendritic textures of columnar
mesophases. The fluid nature of the materials was confirmed
by shear experiments, which resulted in a planar alignment of
the phases. Only r-TTT 2h with branched side chains diplays
banana-leaf like textures (Figure 3., right). While dialkoxy-t-TTTs
1b, 1c are mesomorphous over a broad temperature range, their
radial isomers 2b and 2c crystallize upon cooling from the
isotropic melt. Noteworthy, thermal isomerization of 1h
remarkably converted an originally non-mesomorphous t-TTT
into the liquid-crystalline isomer 2h (figure 3.).
Figure 1. Stepwise rearrangement of 1a to 2a, monitored by time-dependent
1H-NMR-spectroscopy (grey: signals of non-symmetrical intermediates)
NMR-Spectroscopy clearly reveals the three steps of the
cascade of rearrangements. Asymmetric isomers (ttr-TTT and
trr-TTT) generate different sets of signals for the protons of any
phenyl substituent (gray) whereas C3-symmetrical t-TTT 1a and
r-TTT 2a provoke only one set of signals each. Resonances of
ortho-protons from radially orientated phenyl rings are
significantly shifted towards lower field while the meta-protons
appear at slightly higher field. The impact on the chemical shift is
caused by different overlap of the anisotropy cones of the phenyl
substituents and the isomeric TTT-cores due to planarization.
Furthermore, 13C-NMR signals of phenyl substituted triazole
carbons are strongly shifted to lower field (t-TTT: 151 ppm, r-
TTT: 165 ppm). Likewise 15N-NMR confirmed the complete
isomerization of the core (t-TTT:[8] δ= -69.2, -99.8, - 226.6; r-TTT
2b: δ= -119.7, -116.1, -192.2 ppm). DFT calculations show that
the transformation of 1 (R1 = OCH3, R2,3 = H) to the first isomer
(ttr) is exothermic by 8.3 kcal/mol, the following rearrangements
reduce the energy by 12,3 kcal/mol each - the final product r-
TTT 2 is about 32.9 kcal/mol lower in energy than the t-isomer.
Figure 3. POM-textures (crossed-polarizers) of t-TTT 1h at 120 °C (left) and
r-TTT 2h at 210 °C (right)
Mesomorphous behaviour was also studied by differential
scanning calorimetry (DSC), the transition temperatures are
summarized in table 2. DSC of t-TTTs 1 confirms the broad
mesophases and reveals that compounds 1d, 1e with longer
side chains display a second mesophase. But the prime result of
the caloric measurements on t-TTTs 1 is their thermal instability
above 200 °C! Repeated DSC scans up to 260 °C clearly reveal
a shift of phase transitions to lower temperatures (fig. S43) by
some degrees per scan. It appears that even this short exposure
to thermal stress is sufficient to initiate the rearrangement.
Transition temperatures and the resulting widths of the
mesophases are not only dependent on number and length of
the alkoxy chains; the orientation of the alkoxyphenyl
substituents plays a pivotal role. DSC and POM revealed that
the width of the enantiotropic mesophases of dialkoxyphenyl
substituted TTTs 1d ( TM = 113 C) and 1e (TM = 103 C)
drastically shrinked upon isomerization to 2d, 2e (2d:TM
=
Figure 2. Molecular structure[14] of tris(p-propoxyphenyl)-r-TTT (2a).
8 C) or even vanished completely (2c). The opposite effect, an
astonishing broadening of the mesophases was observed upon
isomerization of trialkoxyphenyl TTTs: t-TTTs 1f ( TM = 58 C),
1g ( TM = 39 °C) were transformed to r-TTTs with significantly
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higher clearing points and mesophase ranges 2f ( TM = 170 °C), diffraction pattern (fig. 4; at 115 °C: arec = 34.7 Å, brec = 29.5 Å).
2g ( TM > 165 °C). These highly viscous LC phases of 2f and
2g do not show crystallization peaks on cooling and the second
heating scans reveal only one endothermic transition with very
low transition enthalpies. Whereas star-shaped TTT 1h is not
mesomorphous, its radial isomer 2h provokes two endothermic
transitions (DSC: Cr  Col: 75 °C; Col  I: 207 °C, H = 4.8
kJmol-1,  TM = 132 °C). Cooling with 10°/min shifted the
crystallization peak to 38 °C. This supercooling by T = -40 °C
and the puny enthalpy of fusion (H = 2.8 kJmol-1) are attributed
to a very slow and incomplete crystallization from the highly
viscous mesophase.
Two broad meridional reflexes located on the layer line (hk3)
correspond to a periodicity with c = 43.2 Å along the columns.
The density is 0.97 g/cm3, equivalent to 14 mesogens in two
columns. Again, such a large periodicity can only be explained
by a helical stacking of seven tilted mesogens along one colum
with a mean distance of 6.2 Å.A tilt of 53° allows a mean
distance of the aromatic rings of 3.7 Å. This and the relatively
poor correlation along the column are reasons for only few
meridional reflexes and the lack of the typical π-stacking
reflection. A fibre diffraction simulation of the pattern on a
geometry-optimized model is in perfect agreement with the
experimental data (fig. 4). The helical arrangement in the liquid
crystal state allows best the filling of the void space between the
arms of the star mesogens by simultaneous optimization of the
nanosegregation and is found recently for many star LC
systems.[17, 18]
Table 2: Phase transitions of t-TTTs 1 and r-TTTs 2
TTT
1b
1c
1d
1e
1f
transitions
Cr 89 M 207 I
TTT
2b
2c
transitions
Cr 136 I
Cr 92 Colh 208 I[8]
Cr -11 M1 68 M2 181 I
Cr 19 M1 68 M2 171 I
Cr 126 M 184 I
Cr 126 M 165 I
Cr 124 I
Cr1 90 Cr2 131 I
Cr 128 Col 136 I
Cr 36 M1 97M2 125 Colh 132 I
Cr 35 Colh 205 I
Colh 181 I
Cooling below the melting transition results in crystallization
of 2e, 2f, and 2h to form higher ordered phases with preserved
orientation of the colums (SI). Only 2g maintains the columnar-
hexagonal structure of the LC phase Lower temperatures
provoke increasing diameters ahex of the columns due to a
stretching of the aliphatic chains - thereby reducing the π-π-
distances of the coplanar aromatic nuclei to 3.3 Å.
2d
2e
2f*
2g
2h
1g
1h
10
150 °C
Cr 75 Colr 207 I
meridian
equator
π-stack
* only visible in the first heating scan
halo
150 °C
93 °C
The self organization of the discotic mesogens was studied
in detail by X-ray diffraction on oriented filaments, obtained by
extrusion of 2e,f,g,h in the LC phase. Figure 4 exemplifies the
typical diffraction pattern found for the two different columnar LC
phases in 2f and 2h. Main signal is the halo (4.5 Å) that
corresponds to the mean distance of the liquid aliphatic chains.
Furthermore, a broad meridional signal and a small number of
intense equatorial reflexes were observed. The latter can be
indexed for hexagonal unit cells of 2e-f with cell parameters ahex
according to the diameter of the columns. ahex increases with
the number and length of the side chains: 2f: ahex = 29.8 Å
(150 °C), 2g: ahex = 31.5 Å (115 °C), and 2e: ahex = 36.3 Å
(130 °C). Intracolumnar distances of the discotic mesogens
provoke broad meridional signals at 3.3 Å (25 °C) to 3.6 Å
(167 °C), these distances correspond to attractive interactions
between π-systems. Correlation lengths range up to 3-10
molecules within the π-stack, thus showing the LC character of
the phase.[15] Interestingly, a set of weak and diffuse intensities
very close to the reflections 10 along the meridian indicates a
correlation along the columnar axis, with a correlation length of
1-2 repeating units. Closer inspection of these signals could be
successfully done for compound 2f, which reveal a c-parameter
of 51 Å in which 14 molecules stack along the column at 150 °C.
This large repeating distance can be explained only by helical
stacking of the radial star mesogens. Contrary to the hexagonal
phases formed from TTTs with linear side chains, the branched
chains in 2h result in a different volume ratio. Tilting of the
mesogens allows to maintain a strong interaction of the aromatic
units, but the structure of the mesophase changes to centered
rectangular with two columns in the unit cell, as confirmed by the
20
11
21
25 °C
equator
5
10
20
25
15 2 / °
11
20
115 °C
meridional
reflection
02
115 °C
halo
13
5
10
15
20
25
2/ °
Figure 4. Diffraction pattern of 2f at 150 °C (top left) and of 2h at 115 °C
(bottom left), Inset: simulated fibre diffraction pattern (Clearer).[16] Top right:
2θ-Scan along equator and meridians with indexing of the reflexes according
to a hexagonal phase (2f). Bottom right: 2θ-Scan along equator and meridian
with indexing of the reflexes according to a cetered rectangular phase (2h).
The isomeric TTTs are colorless and fluorescent compounds,
in solution, in the solid state, and in their mesophases.
Absorption maxima of tangential and radial isomers in
cyclohexane peak at nearly identical positions (1b: max 310 nm,
2b:max 312 nm) but the more planar r-isomers 2 show
structured spectra and higher extinction coefficients (1b: log  =
4.63, 2b: log  = 4.77, and not the negative solvatochromism of
the t-isomers 1. The structured emission bands of r-TTTs appear
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[5]
[6]
a) S. Kumar, Liq. Cryst. 2005, 32, 1089–1113; b) S. Kohmoto, E. Mori,
K. Kishikawa, J. Am. Chem. Soc. 2007, 129, 13364–13365; c) M. G.
Schwab, T. Qin, W. Pisula, A. Mavrinskiy, X. Feng, M. Baumgarten, H.
Kim, F. Laquai, S. Schuh, R. Trattnig, E. J. W. List, K. Müllen, Chem.
Asian J. 2011, 6, 3001–3010; d) D. Adam, P. Schumacher, J. Simmerer,
L. Häusling, K. Siemensmeyer, K.H. Etzbach, H. Ringsdorf, D. Haarer,
Nature 1994, 371, 141-143.
at significantly higher energies than those of their t-isomers (in
cyclohexane: 1b: Fmax= 370 nm, 2b:Fmax= 348 nm). Large
Stokes shifts of t-TTTs and blurred spectra indicate substantial
geometrical changes after excitation. Both series display a
positive solvatofluorochromism with
a
remarkably higher
sensitivity of the r-isomers 2.
a) G. Kestemont, V. de Halleux, M. Lehmann, D. A. Ivanov, M. Watson,
Y. H. Geerts, Chem.Commun. 2001, 2074-2075; b) M. Lehmann, G.
Kestemont, R. G. Aspe, C. Buess-Herman, M. J. H. Koch, M. G. Debije,
J. Piris, M. P. de Haas, J. M. Warman, M. D. Watson, V. Lemaur, J.
Cornil, Y. H. Geerts, R. Gearba, D. A. Ivanov, Chem. Eur. J. 2005, 11,
Summary
Thermal rearrangements of tristriazolotriazines convert the
all-tangential form in three steps to the all-radial form. An
increase of the molecular diameter and planarization are
responsible for changes of the thermotropic properties:
increased melting points and even loss of mesomorphism
appear, but also the gain of liquid crystallinity has been
observed.
3349-3362.
[7]
[8]
R. Huisgen, H.J. Sturm, M. Seidel, Chem. Ber. 1961, 94, 1555-1562.
R. Cristiano, H. Gallardo, A. J. Bortoluzzi, I. H. Bechtold, C. E. M.
Campos, R. L. Longo, Chem. Commun. 2008, 5134-5136.
K. Herget, D. Schollmeyer, H. Detert, Acta Cryst. 2013, E69, o365–
o366;
[9]
[10] R. Cristiano, J. Eccher, I. H. Bechtold, C. N. Tironi, A. A. Vieira, F.
Molin, H. Gallardo, Langmuir 2012, 28, 11590-11598.
[11] a) S. Glang, V. Schmitt, H. Detert, Proc. 36th Ger. Top. Meeting on LCs,
2008, 125-128; b) S. Glang, D. Borchmann, T. Rieth, H. Detert, Adv.
Sci. Technol. 2013, 77, 118-123; c) S. Glang, T. Rieth, D. Borchmann, I.
Fortunati, R. Signorini, H. Detert, Eur. J. Org. Chem. 2014, 3116–3126;
e) T. Rieth, S. Glang, D. Borchmann, H. Detert, Mol. Cryst. Liq. Cryst,
2015, 610, 89-99; f) S. Glang, H. Detert, to be published.
Acknowledgements
The authors thank the Deutsche Forschungsgemeinschaft
(DFG) for generous financial support, M. Müller (DSC) and Dr. D.
Schollmeyer (XRD) for many measurements.
[12] T. Rieth, T. Marszalek, W. Pisula, H. Detert, Chem. Eur. J. 2014, 20,
5000-5006.
[13] V. A. Tartakovsky, A. E. Frumkin, A. M. Churakov, Yu. A. Strelenko,
Russ. Chem. Bul. Int. Ed. 2005, 54, 719-725.
[14] Crystal structure: Mercury 3.3. One propyl chain disordered.
CCDC1539528 contains the supplementary crystallographic data.
These data can be obtained free of charge from The Cambridge
Crystallographic Data Centre via www.ccdc.cam.ac.uk/datarequest/cif.
[15] P. Scherrer, Nachr. Ges. Wiss. Göttingen, Math.-Phys. Kl. 1918, 2, 98.
[16] O. S. Makin, P. Sikorski, L. C. Serpell, J. Appl. Crystallogr. 2007, 40,
966.
Keywords: Tristriazolotriazine • Discotic Liquid crystal •
Isomerization• X-ray diffraction • Fluorescence
[1]
a) S. Jhulki, I. Neogi, J.N. Moorthy, Jarugu in Organic Structures
Design: Application in Optical and Electronic Devices (Ed.: T. J. Chow)
Pan Stanford Publishing, Singapore, 2015, pp. 327-398; b) J. Roncali,
P. Leriche, P. Blanchard, Adv. Mater. 2014, 26, 3821-3838; c) E. Orgiu,
P. Samori, Adv. Mater. 2014, 26, 1827-1845; d) H. Detert, M. Lehmann,
H. Meier, Materials 2010, 3, 3218-3330.
[17] M. Lehmann, M. Hügel, Angew. Chem. Int. Ed. 2015, 54, 4110–4114.
[17] [18] M. Lehmann, P. Maier, Angew. Chem. Int. Ed. 2015, 54, 9710 –9714.
[2]
[3]
a) J. L. Bredas, Adv. Mater. 1995, 7, 263-74; b) N. Allard, M. Leclerc in
Functional Materials (Eds.:M. Leclerc, R. Gauvin), de Gruyter, Berlin,
2014, pp.- 121-138.
a) H. Usta, W. C. Sheets, M. Denti, G. Generali, R. Capelli, S. Lu, X. Yu,
M. Muccini, A. Facchetti, Chem. Mater. 2014, 26, 6542-6556; b) W.
Pisula, X. Feng, K. Müllen, Chem. Mater. 2011, 23, 554–567; c) B. R.
Kaafarani, Chem. Mater. 2011, 23, 378– 396; d) J. Zaumseil, in Organic
Electronics II (Ed.: H. Klauk), Wiley-VCH, Weinheim, 2012, pp. 353-
386; e) E.-K. Fleischmann, R. Zentel, Angew. Chem. Int. Ed. 2013, 52,
8810-8827; f) A. Pron, P. Gawrys, M. Zagorska, D. Djurado, R.
Demadrille, Chem. Soc. Rev. 2010, 39, 2577-2632; f) A. Boländer, D.
Kieser, C. Voss, S. Bauer, C. Schön, S. Burgold, T. Bittner, J. Hölzer,
R. Heyny-von Haußen, G. Mall, V. Goetschy, C. Czech, H. Knust, R.
Berger, J. Herms, I. Hilger, B. Schmidt, J. Med. Chem. 2012, 55,
9170−9180.
[4]
a) S. Laschat, A. Baro, N. Steinke, F. Giesselmann, C. Haegele, G.
Scalia, R. Judele, E. Kapatsina, S. Sauer, A. Schreivogel. M. Tosoni,
Angew. Chem. 2007, 119, 4916-4973, Angew. Chem. Int. Ed. 2007, 46,
4832-4887; b) S. Kumar: The Chemistry of Discotic Liquid Crystals,
CRC Press, Boca Raton, 2010; c) W. Pisula, K. Muellen in Handbook of
Liquid Crystals 2nd ed. (Ed.: J. W. Goodby), Wiley-VCH, Weinheim,
2014, 8, pp. 627-673; d) S. Sergeyev, W. Pisula, Y. H. Geerts, Chem.
Soc. Rev. 2007, 36, 1902–1929; e) T. Wöhrle, I. Wurzbach, J. Kirres, A.
Kostidou, N. Kapernaum, J. Litterscheidt, J. C. Haenle, P. Staffeld, A.
Baro, F. Giesselmann, S. Laschat, Chem. Rev. 2016, 116, 1139-1241.
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Entry for the Table of Contents (Please choose one layout)
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Thorsten Rieth, Nico Röder,
Matthias Lehmann and Heiner Detert*
Page No. – Page No.
Isomerisation of Liquid-Crystalline
Tristriazolotriazines
A thermal rearrangement of discotic tristriazolotriazines converts Huisgen type all-
tangential, C3-symmetrical TTTs in three steps via two non-symmetrical isomers to
also C3-symmetrical but all-radial isomers. According to the substitution pattern,
liquid crystallinity is changed, destroyed, or even gained.
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