Tristriazolotriazines (TTTs) with a threefold alkoxyphenyl substitution were prepared and studied by DSC, polarized optical microscopy (POM) and X-ray scattering. Six pentyloxy chains are sufficient to induce liquid-crystalline behavior in these star-shaped compounds. Thermotropic properties of TTTs with varying substitution patterns and a periphery of linear chains of different lengths, branching in the chain and swallow-tails, are compared. Generally, these disks display broad and stable thermotropic mesophases, with the tangential TTT being superior to the radial isomer. The structure–property relationships of the number of alkyl chains, their position, length and structure were studied.

Tristriazolotriazines with azobenzene substitution and peripheral alkoxy‐ or alkylamino chains were prepared from the corresponding aryltetrazoles and cyanuric chloride. These star‐shaped dyes are highly acidochromic. Alkoxy‐substitution allows reversible trans‐cis photoswitching. Compounds with a 3,4‐dialkoxy substitution are discotic liquid crystals that form broad and stable thermotropic mesophases. The thermal behavior was studied by DSC and polarizing optical microscopy.

The synthesis of tris(aryloxadiazolyl)triazines (TOTs), C 3‐symmetrical star‐shaped mesogenes with a 1,3,5‐triazine center, 5‐phenyl‐1,3,4‐oxadiazole arms, and various peripheral alkoxy side chains is reported. Threefold Huisgen reaction on a central triazine tricarboxylic acid and suitable aryltetrazoles yields the title compounds. Selected analogues with a benzene center are included in this study and allow for an evaluation of the impact of the central unit on the physical properties. Thermal (differential scanning calorimetry, DSC; polarization optical microscopy, POM), optical (UV/Vis, fluorescence), electric (time of flight, TOF), and structural (single crystal; wide‐angle X‐ray scattering, WAXS) properties of these compounds were investigated. The modification of alkoxy chain length and substitution pattern allows for a tuning of the physical properties. TOTs emit blue to yellow light, depending on conjugation length, donor–acceptor substitution, and solvent polarity, whereas concentration quenches and aggregation enhances the emission. The width of the mesophases is typically around ΔT=100–150 K but can even exceed 220 K. Polarization optical microscopy and X‐ray diffraction on oriented filaments reveal that TOTs are highly ordered liquid crystals (LCs) with long‐range hexagonal columnar structure.

C3‐symmetrical, alkoxyphenyl substituted 2,5,8‐(tris‐1,3,4‐oxadiazol‐2‐yl)benzo [1,2‐b; 3,4‐b′; 5,6‐b′′]trithiophenes (OXD‐BTT) are synthesized via threefold Huisgen‐reaction. A broad variation of alkoxy substitution pattern and chain lengths is reported. The thermal behavior was investigated via differential scanning calorimetry (DSC), polarized optical microscopy (POM) and thermogravimetry (TGA). Optical properties were studied via UV‐Vis and fluorescence spectroscopy. Structural information of the LC phases was gained from X‐ray diffraction on oriented fibers. OXD‐BTT provide enormous phase widths (ΔT≥289 K) with clearing points close to thermal decomposition. Most of the derivatives exhibit two different mesophases, the lower phase with a rectangular 3D‐structure and a hexagonal 2D‐lattice at higher temperature. The variation of the chain length allows a tuning of melting and clearing points. OXD‐BTT emit blue light with fluorescence quantum yields up to 30 % in good solvents. The emission is very sensitive to aggregation, thus, in poor solvents the emission intensity decreases, and red shift of maxima occurs.

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