The synthesis and study of the liquid crystalline, photophysical, and aggregation behavior of novel octupolar oxadiazole derivatives are reported. These molecules formed columnar mesophases at elevated temperatures which transformed into a glassy state at ambient temperatures wherein the columnar order was retained. Their spontaneous concentration dependent hierarchical self-assembly from spheres to fibrous gels has been investigated using TEM, SEM, and XRD. Retention ofthe hexagonal columnar (Col h ) order was also observed in the fibrous aggregates. Concentration dependent luminescence spectral studies indicated that the change in morphology from spheres to fibrous aggregates was associated with a shift in chromophore packing from predominantly H-type to J-type aggregates. Time resolved anisotropic investigations revealed that the columnar stacking of molecules in the aggregated state provided a pathway for excitation energy migration to the lower energy J-traps.

Formation of Highly Luminescent Supramolecular Architectures Possessing Columnar Order from Octupolar Oxadiazole Derivatives: Hierarchical Self‐Assembly from Nanospheres to Fibrous Gels

The design of programmedmolecules capable of organizing in a predictable way to form complex superstructures is an attractive target of contemporary research. Supramolecular chemistry and crystal engineering have advanced largely by using the node and spacer approach for the construction of polygonal frames and infinite 2D or 3D nets by means of coordination chemistry. Chevron-shaped bidentate ligands have been used for the design of discrete supramolecular hexagons and polyhedra either in solution or in the crystalline state. In contrast to solid-state structures, which, once formed, cannot be modified, liquid crystals (LCs) can easily respond to external stimuli by changing their organization. In recent years chevron-shaped (bent-core) LC molecules have attracted significant interest, owing to their ability to exhibit ferroelectric and antiferroelectric properties. Herein we use polyphilic molecules with a bent aromatic core to design two new types of honeycomb-like LC phases with hexagonal, and for the first time, also with trigonal symmetry. For this purpose, p-conjugated bent aromatic cores were functionalized at the ends with glycerol units, capable of forming cooperative hydrogen bonds, and with a long, flexible nonpolar chain (either alkyl or semiperfluoroalkyl) attached to the bay region, that is, to the 2-position of the central benzene ring of the bent core. This approach resulted in a new type of LC molecule with anchor-like shape. Two types of molecules were synthesized as shown in Scheme 1, according

Liquid-Crystal Engineering with Anchor-Shaped Molecules: Honeycombs with Hexagonal and Trigonal Symmetries Formed by Polyphilic Bent-Core Molecules

We have synthesized three new molecules that have three thienylethynyl arms substituting a central benzene core and different electron donor/acceptor groups in the three remaining phenyl positions. The absorption, fluorescence, phosphorescence, and transient triplet–triplet spectra are analyzed in the light of the electronic structure of the ground and excited states obtained from quantum-chemical calculations. From the above, the relevant photophysical data (including quantum yields, lifetimes, and rate constants) could be derived. It was found that the major deactivation pathway is internal conversion, which competes with the fluorescence and intersystem crossing processes. For the three investigated compounds, we provide convincing theoretical support corroborating these findings and further conclusions based on the theoretical information obtained. These molecules are one of the very few cases in which the depolarization ratios, obtained from the NLO optical measurements, clearly reflect the octopolar configuration. Molecular hyperpolarizabilities have been measured and display a typical dependence on the donor–acceptor substitution pattern.

Synthesis, Spectroscopy, Nonlinear Optics, and Theoretical Investigations of Thienylethynyl Octopoles with a Tunable Core

A straightforward access to a hitherto unknown C3 -symmetric tricyclic triol both in racemic and enantiopure forms has been developed. Treatment of 7-tert-butoxynorbornadiene with peroxycarboxylic acids provided mixtures of C1 - and C3 -symmetric 3,5,7-triacyloxynortricyclenes via transannular π-cyclization and replacement of the tert-butoxy group. By refluxing in formic acid, the C1 -symmetric esters were converted to the C3 -symmetric formate. Hydrolysis gave diastereoisomeric triols, which were separated by recrystallization. Enantiomer resolution via diastereoisomeric tri(O-methylmandelates) delivered the target triols on a gram scale. The pure enantiomers are useful as core units of dopants for liquid crystals.

C3‐Symmetric Tricyclo[2.2.1.02,6]heptane‐3,5,7‐triol

Controlling the Macroscopic Chirality of Organic Materials Based on 1,3,5-Trialkynylbenzenes†

Flssigkristalle aus C3-symmetrischen Mesogenen fr nichtlineare Optik zweiter Ordnung**

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Flssigkristalle aus C3-symmetrischen Mesogenen fr nichtlineare Optik zweiter Ordnung**