Tris(5-aryl-1,3,4-oxadiazolyl)benzotrithiophenes : discotic liquid crystals with enormous mesophase ranges

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Der Wert und die Bedeutung popularer Musik werden in westlichen Gegenwartsgesellschaften durch drei Instanzen bestimmt: durch die Musikproduzierenden selbst, durch intermediare Instanzen wie Musikkritiker und andere Medienakteure und durch die Rezipienten. Kunstler nehmen bei der Produktion von Musik eine formale und inhaltliche Positionierung vor und versehen ihr Material mit Bedeutung. Musikkritiker ordnen ausgewahlte Neuerscheinungen in die kunstlerische Biographie und das musikalische Feld ein, schreiben ihnen Wert zu und fungieren als Filterinstanz fur den Output am Musikmarkt.

Synthesis, Thermal, and Optical Properties of Tris(5‐aryl‐1,3,4‐oxadiazol‐2‐yl)‐1,3,5‐triazines, New Star‐Shaped Fluorescent Discotic Liquid Crystals

Abstract 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‐…

Star-shaped conjugated compounds forming nematic discotic systems

Abstract Star-shaped compounds, having a benzene ( 9a,b ) or a 1,3,5-triazine ( 11a,b ) core and stilbenoid arms were prepared. Hexyloxy chains, attached in the middle of the arms, provide nematic discotic phases ND, which are unusual for such systems. The position of the sidechains prevents the micro-segregation, which is valid for star-shaped discs of columnar phases. The stilbenoid character of 9a,b and 11a,b guarantees a high light sensitivity. Apart from the statistical CC bond formation by irradiation in solution or in the LC phases, a topochemically controlled chemo-, regio- and stereoselective photocyclodimerization 11a → 12 was found in the crystalline state. The structure determin…

Photoreactive Liquid Crystals in the Series of Dendritic and Cyclic Stilbenoid Compounds

The dendrimers 1 and 2 and the areno-condensed annulenes 3 and 4 represent new mesogens for the generation of discotic mesophases. The stilbenoid building blocks of these compounds provide the molecular basis for interesting photochemical and photophysical effects like dimerisation, oligomerisation or the formation of charge carriers.

Supramolecular order of stilbenoid dendrons: importance of weak interactions

Stilbenoid dendrons with various donor and acceptor groups on the focal unit were synthesised by a Wittig–Horner reaction, starting from an aldehyde functionalised dendron and various substituted phosphonic acid esters. The target molecules are composed of meta-branched arms, two of them with extended conjugation (distyrylbenzene) and three flexible dodecyloxy chains; the focal group consists of a donor or acceptor substituted styryl unit. The cross-conjugation of the arms prevents the strong electronic influence of substituents on the two extended oligophenylenevinylene chromophores. However, intermolecular interactions mediated by the focal unit allow control of the supramolecular stackin…

Guest-Host Systems of 1,3,5-Tristyrylbenzenes

(E,E,E)-1,3,5-Tris(3,4,5-trimethoxystyryl)benzene (1a) forms monoclinic crystals of the space group P21/c. Incorporation of three transoid diacetyl guest molecules between the three arms leads to triclinic crystals of the space group P1. The styryl groups, originally present in a nonsymmetrical conformation, are simultaneously transformed to a C3 arrangement. (E,E,E)-1,3,5-Tris- (3,4,5-tripropoxystyryl)benzene (1b) forms monoclinic crystals of the space group P21/c. The C3 arrangement of the styryl groups is present in the first, the unsymmetrical arrangement in the second modification. Incorporation of two acetone guests in the largest and the middle-sized angle space between the styryl ar…

Dendrimers consisting of stilbene or distyrylbenzene building blocks synthesis and stability

Abstract On the basis of Wittig-Horner reactions and protection group techniques compound 7 for the core and the components 9a-c and 11a-c for the dendrons were prepared and linked in the final step. The convergent synthesis yielded constitutionally and configurationally pure dendrimers ( 2a-c, 2a'-c' ) which consist of distyrylbenzene units. Their thermo-oxidative stability in the presence of air was studied by chemiluminescence and compared to the dendrimers 1 consisting of stilbene units.

Shape-persistent V-shaped mesogens—formation of nematic phases with biaxial order

A homologous series of shape-persistent V-shaped molecules has been designed to form the biaxial nematic phase. Phenyleneethynylene moieties are attached to a bent fluorenone unit to create an apex angle of about 90°, which is determined from the single crystal structure. Two mesogens, one symmetric and another unsymmetric, have been synthesized by attaching a cyano group to one or both of the peripheral phenyl units, respectively. These groups introduce local dipoles essential for the formation of the nematic phases. The tendency to form a crystalline phase is reduced by laterally substituted hexyloxy chains which allow the nematic phase to be supercooled to a glassy state. Two of the thre…

Isomerisation of Liquid-Crystalline Tristriazolotriazines

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, C

Star-Shaped Conjugated Systems

The present review deals with the preparation and the properties of star-shaped conjugated compounds. Three, four or six conjugated arms are attached to cross-conjugated cores, which consist of single atoms (B, C+, N), benzene or azine rings or polycyclic ring systems, as for example triphenylene or tristriazolotriazine. Many of these shape-persistent [n]star compounds tend to π-stacking and self-organization, and exhibit interesting properties in materials science: Linear and non-linear optics, electrical conductivity, electroluminescence, formation of liquid crystalline phases, etc.

CCDC 1539528: Experimental Crystal Structure Determination

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