Arylethynyl‐Substituted Tristriazolotriazines: Synthesis, Optical Properties, and Thermotropic Behavior

Glang, Stefan; Rieth, Thorsten; Borchmann, Dorothee E.; Fortunati, Ilaria; Signorini, Raffaella; Detert, Heiner

doi:10.1002/ejoc.201400088

Cited by 31 publications

(36 citation statements)

References 88 publications

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“…A bromo derivative has been reported by Holst et al (2011). This compound combines our interest in perchloro hydrocarbons (Detert et al, 2009;Schollmeyer & Detert, 2017) and star-shaped discotic liquid crystals Glang et al, 2014).…”

Section: Structure Descriptionmentioning

confidence: 94%

1,3,5-Trichloro-2,4,6-tris(dichloromethyl)benzene

2017

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The asymmetric unit of the title compound, C 9 H 3 Cl 9 , contains one molecule. Two slightly different conformations with nearly C 3h symmetry are mutually disordered in a 1:1 ratio. This disorder enhances the overall structural symmetry to D 3h . Structure descriptionThe title compound (Fig. 1) is a central intermediate for star-shaped conjugated oligomers (Demenev et al., 2010;Detert et al., 2010). A bromo derivative has been reported by Holst et al. (2011). This compound combines our interest in perchloro hydrocarbons (Detert et al., 2009;Schollmeyer & Detert, 2017) and star-shaped discotic liquid crystals Glang et al., 2014).The asymmetric unit contains one molecule of the title compound and two very similar conformations with nearly C 3h symmetry occur in a 1:1 ratio (Fig. 2). This disorder enhances the symmetry of the overall structure to D 3h . Assuming the D 3h symmetry for one nondisordered molecule, the space group will rise from P4 3 to P4 3 2 1 2. However, then the refinement is not stable and the molecular symmetry is in contradiction to the chemistry. Distances between H atoms and ring-bound Cl atoms are 2.262 Å for H7Á Á ÁCl3 and also for H8Á Á ÁCl6, but the spacing between H9 and Cl9 is 2.43 Å . Similarly, two C-H bonds are nearly coplanar with the ring (H8-C8-C3-C4 = À3and H9-C9-C5-C6 = 3 ), whereas H7-C7-C1-C2 is twisted by À9 . Synthesis and crystallizationThe title compound was prepared according to Veciana et al. (1993) and Taerum et al. (2009) with the modification that a steel bomb (2.2 Â 25 cm) was used as reaction vessel. This allows scale-up to 3.0 g (16.5 mmol, 1.0 equivalent) 1,3,5-trichlorbenzene in 30 ml absolute chloroform with 2.7 g (19.8 mmol, 1.2 equivalents) AlCl 3 , and frequent pressure reduction was not necessary. The temperature was regulated with ISOHEAT

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Section: Structure Descriptionmentioning

confidence: 94%

1,3,5-Trichloro-2,4,6-tris(dichloromethyl)benzene

2017

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“…The original procedure is simple heating of the reactants in toluene; [4] addition of collidine as a base [6,18] or butanone/ potassium carbonate [7] are successful protocols for reactions with alkoxy-substituted tetrazoles (Scheme 1). The original procedure is simple heating of the reactants in toluene; [4] addition of collidine as a base [6,18] or butanone/ potassium carbonate [7] are successful protocols for reactions with alkoxy-substituted tetrazoles (Scheme 1).…”

Section: Synthesismentioning

confidence: 99%

“…The yield of this cascade of 12 reactions varies in a wide range, not only depending on the substituent on the tetrazole, but also on the temperature profile of the synthesis. [18] Scheme 1. [6] Two routes have been used for the synthesis of tetrazoles 58, the addition of azides or hydroazoic acid to nitriles [19] and the dehydration/azidination of benzamides.…”

Section: Synthesismentioning

confidence: 99%

“…tris-decyl t-TTT 15 has a maximum at λ max = 244 nm, slightly shifting bathochromic with increasing concentration and solvent polarity. [7,18,23] In highly polar solvents, increasing length of alkyl chains results in dramatic decrease of the molar absorptivity, e.g. [6] The UV absorption of p-alkoxyphenyl t-TTTs 16-21 has a maximum at λ max = 290 nm and shows a weak negative solvatochromism.…”

Section: Optical Propertiesmentioning

confidence: 99%

“…Later, Kaiser corrected Hofmann's structure to 13 (R = NH 2 ), since only this structure allows the formation of the oxidation products. Tartakovsky, in his seminal paper on TTTs, [5] presented the synthesis of triphenyl-TTT 2 and 14, the thermal properties and chemical behavior of these compounds; in the same year, some substituted aryl-and alkyl-TTTs (15,18) cules, when heated above 200°C, suffer a thermal isomerization. [4] TTTs regained attention only in 2005.…”

Section: Introductionmentioning

confidence: 99%

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Tristriazolotriazines: Luminescent Discotic Liquid Crystals

Detert

2018

Eur J Org Chem

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Tristriazolotriazines (TTT) are new tetracyclic and planar cores for discotic liquid crystals. Two symmetrical isomers are known, paddle‐wheel type t‐TTTs and r‐TTTs with the shape of a propeller. Cyclocondensation of chlorotriazoles gives r‐TTTs, Huisgen reaction of tetrazoles and cyanuric chloride yields t‐TTTs with tangentially attached substituents. Many alkoxyphenyl‐substituted t‐TTTs form broad mesophases, typically with a hexagonal columnar structure. These luminescent molecules, when heated above 200 °C, suffer a thermal isomerization. A threefold ring opening/ring closing mechanism transforms t‐TTTs via unsymmetrical isomers to r‐TTTs. Thermotropic properties are largely influenced by planarization and increase of molecular diameter. Increased melting points, even the complete loss of liquid crystallinity have been observed, but also the gain of mesomorphism.

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Isomerisation of Liquid‐Crystalline Tristriazolotriazines

Rieth

Röder

Lehmann

et al. 2017

Chemistry A European J

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Star-shaped discotic liquid crystals with columnar superstructures constitute ah ighly interesting class of organic materials. Phenyl-substituted tris [1,2,4]triazolo- [1,3,5]triazine, prepared by aH uisgen reaction of phenyltetrazole and cyanuric chloride, represents an excellent core for discotic liquid crystals (DLCs). The thermals tability is not perfect, at temperatures above the clearing point, as uccessive threefold isomerization leads to a highly planar, C 3 -symmetrical isomer,w hich mainly differs in the orientation of the aryl substituents to the centre of the molecule.Anew class of discotic liquid crystals has been obtained:E quipped with peripheral alkoxyc hains both isomers can form broad thermotropic mesophases. The optical, thermal,a nd physical properties were investigated by polarized optical microscopy,d ifferentials canning calorimetry,w ide-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 meltingp oints but also the loss or even gain of mesomorphism is observed.Organic p-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 ac olumnar arrangement resulting in anisotropic properties, for example, one-dimensional charge transport in the liquid-crystalline phase.[4] Typical DLCs consist of electron-rich polycyclic aromatic units,f or example, triphenylene or hexabenzocoronene, [5] whereas DLCs with an electron deficientc orea re rather scarce.[6] One of the youngest members of this group is the tris[1,2,4]triazolo-[1,3,5]triazine (TTT), at etracyclic, nitrogenrich, and C 3 -symmetrical analogue of triphenylene. The first TTT,t riphenyl-TTT 1 (R i = H), hasb een prepared by Huisgen, [7] its shape is at etracyclic plane with three phenylr ings sticking out of the bays. To avoid steric compression,t he substituents are twisted out of the plane with dihedral angles up to 808. [8,9] In 2008, Gallardo [8,10] and Glang [11] recognizedt he suitability of the TTT as ac ore for discotic liquid crystals. These propellers (e.g. 1b-1h)w ith six to nine alkoxy groups on the outer rim can form broad mesophases. Polarized optical microscopy (POM) revealed the characteristic textures of ac olumnar phase and wide and small-angle X-ray diffraction (WAXS and SAXS, respectively) on pre-orientated filaments confirmed ah exagonal arrangement of the columns in the mesophase and complex helical superstructures in the solid state. [12] All these TTTs with a 'tangential' orientation (t-TTT) of the alkoxyphenyl substituents wereo btained by the Huisgen route. An independent access to TTTsw as reported by Ta rtakovsky [13] in 2005:t hermocyclization of three 5-chloro-3-phenyl-1,2,4-triazole molecules resulted in a C 3 -symmetrical triphenyl tristriazolotriazine (2,R ...

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Arylethynyl‐Substituted Tristriazolotriazines: Synthesis, Optical Properties, and Thermotropic Behavior

Cited by 31 publications

References 88 publications

1,3,5-Trichloro-2,4,6-tris(dichloromethyl)benzene

1,3,5-Trichloro-2,4,6-tris(dichloromethyl)benzene

Tristriazolotriazines: Luminescent Discotic Liquid Crystals

Isomerisation of Liquid‐Crystalline Tristriazolotriazines

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