Identifying Structural Determinants of Mesomorphism from Focused Libraries of Tripedal Mesogens Prepared via the Passerini Three-Component Reaction

Heterolithic tripedal mesogens are branched, multifunctional molecules that exhibit liquid crystalline properties. The liquid crystalline phase behavior of heterolithic tripedal mesogens can be challenging to predict from the structures of the different branches. To elucidate the structural basis for smectic mesomorphism in the first examples of heterolithic ABC tripedal mesogens, we synthesized and characterized six homolithic, three heterolithic AB(2), and seven heterolithic ABC tripedes. The synthesis strategy took advantage of the Passerini three-component reaction to elaborate focused compound libraries in a combinatorial and high throughput manner. The phase behavior of the tripedes was characterized by a combination of polarized optical microscopy (POM), differential scanning calorimetry (DSC), and powder X-ray diffraction techniques. We show that one end-group of the heterolithic mesogens is responsible for the emergence of smectic mesomorphism in the presence of other groups that prefer nematic mesomorphism. Understanding how these structurally complex, non-conventional mesogens self-organize in liquid crystalline mesophases is significant for designing functional materials with predictable hierarchical order.