Molecular parameters and mesomorphism of discotic polysubstituted benzene derivatives

Abstract

The previously developed approach to prediction of columnar and nematic mesophases for compounds with disc-shaped molecules was applied to low-molecular-weight polysubstituted benzene derivatives. The molecular parameters were calculated for 39 new compounds: derivatives of 1,3,5-tri(4-hydroxybenzoyloxy)benzene, 1,3,5-tri(4-cyclohexylbenzoyloxy)benzene, 1,3,5-tri(4-hydroxyphenylcarboxy)benzene, 1,2,3-tri(4-cyclohexylbenzoyloxy)benzene, etc. The prediction results were checked by the synthesis of certain compounds from the test sample and examination of their mesomorphic behavior. The prediction of the mesomorphism is negative for only three of the 39 compounds considered. The majority of the molecules under consideration tend to form columnar supramolecular packings, and the capability to form a nematic phase is predicted for only eight compounds. For a number of structures, the capability and incapability to form a nematic phase are equally probable. Synthesis and examination of the mesomorphic behavior of seven repesentatives of the series considered showed good agreement with the prediction results. 1,3,5-Tri(4-heptyloxybenzoyloxy)benzene, 1,3,5-tri(4-cyclohexylbenzoyloxy)benzene, 1,3,5-tri(4-nonyloxyphenylcarboxy)-benzene, and 1,2,3-tri(4-cyclohexylbenzoyloxy)benzene pass into the liquid crystal state forming mainly columnar supramolecular packings. 1,3,5-Tri(4-octyloxybenzoyloxy)benzene and 1,3,5-tri(4-nonyloxybenzoyloxy)benzene melt at 55 and 48°C, respectively, without forming a mesophase, which is also well consistent with the prediction results.