Macrocyclic Effects in the Mesomorphic Properties of Liquid-Crystalline Pillar[5]- and Pillar[6]arenes.

Nierengarten, Iwona; Guerra, Sebastiano; Holler, Michel; Karmazin‐Brelot, Lydia; Barberá, Joaquín; Deschenaux, Robert; Nierengarten, Jean‐François

Whereas the reaction of 1,4-bis(2-bromoethyloxy)benzene ( 4) with paraformaldehyde in the presence of BF3 ·Et2O afforded exclusively the cyclopentameric pillar[5]arene derivative ( 5), both cyclopenta- and cyclohexameric macrocycles 5 and 6 were obtained when the reaction of 4 with paraformaldehyde was performed at 45 °C in CHCl3 with FeCl3 as the catalyst. Treatment of compounds 4- 6 with sodium azide provided the corresponding polyazides, to which a cyanobiphenyl building block was subsequently grafted to generate model compound 1, pillar[5]arene 2, and pillar[6]arene 3, bearing two, ten and twelve mesomorphic subunits, respectively. The liquid-crystalline and thermal properties of the compounds were investigated by polarized optical microscopy (POM), differential scanning calorimetry (DSC), and X-ray diffraction (XRD). Comparison of the liquid-crystalline properties of macrocycles 2 and 3 with those of 1 revealed the strong influence of the macrocyclic pillar[ n]arene core on the mesomorphic properties. Whereas only a monotropic mesophase was observed for 1, a broad enantiotropic mesophase was evidenced for both pillar[ n]arene derivatives.

MACROCYCLIC compounds; LIQUID crystalline solvents; AROMATIC compounds; POLYOXYMETHYLENE; X-ray diffraction; MICROSCOPY

European Journal of Organic Chemistry, 2013, Vol 2013, Issue 18, p3675

1434-193X

Academic Journal

10.1002/ejoc.201300356