| Summary: | A set of mesomorphic materials in which the <i>o</i>-carborane cluster is covalently bonded to a cholesteryl benzoate moiety (mesogen group) through a suitably designed linker is described. The olefin cross-metathesis between appropriately functionalized styrenyl-<i>o</i>-carborane derivatives and a terminal alkenyl cholesteryl benzoate mesogen (all type I terminal olefins) leads to the desired <i>trans</i>-regioisomer, which is the best-suited configuration to obtain mesomorphic properties in the final materials. The introduction of different substituents (R = H (<b>M2</b>), Me (<b>M3</b>), or Ph (<b>M4</b>)) to one of the carbon atoms of the <i>o</i>-carborane cluster (C<sub>cluster</sub>) enables the tailoring of liquid crystalline properties. Compounds <b>M2</b> and <b>M3</b> show the chiral nematic (N*) phase, whereas <b>M4</b> do not show liquid crystal behavior. Weaker intermolecular interactions in the solid <b>M3</b> with respect to those in <b>M2</b> may allow the liquid crystallinity in <b>M3</b> to be expressed as enantiotropic behavior, whereas breaking the stronger intermolecular interaction in the solid state of <b>M2</b> leads directly to the isotropic state, resulting in monotropic behavior. Remarkably, <b>M3</b> also displays the blue phase, which was observed neither in the chiral nematic precursor nor in the styrenyl-cholesterol model (<b>M5</b>) without an <i>o</i>-carborane cluster, which suggests that the presence of the cluster plays a role in stabilizing this highly twisted chiral phase. In the carborane-containing mesogens (<b>M2</b> and <b>M3</b>), the <i>o</i>-carborane cluster can be incorporated without destroying the helical organization of the mesophase.
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