title: Hexakis(4-iodophenyl)-peri-hexabenzocoronene- a versatile building block for highly ordered discotic liquid crystalline materials.
abstract: Hexakis (4-iodophenyl)-peri-hexabenzocoronene (5), a novel functionalizable mesogenic building block, was prepared by rational multistep synthesis. Although sparingly soluble in common solvents, it can be obtained in pure form and then functionalized via Hagihara-Sonogashira coupling to give a series of highly ordered columnar liquid crystalline molecules 14a-c. The total synthesis involves five 6-fold transformations, all in excellent to near quantitative isolated yields. Their thermotropic liquid crystalline behavior was studied by differential scanning calorimetry (DSC), polarized optical microscopy (POM) and wide-angle X-ray diffraction (WAXD). Compared to the normal alkyl-subsituted hexabenzocoronenes (HBCs), 14a-c exhibit more highly ordered columnar mesophases, including three-dimensionally ordered superstructures (helical columnar mesophase). These could arise from additional intracolumnar pi-pi interactions between, and space-filling requirements introduced by, the rigid-rod side groups. Atomic force microscopy (AFM) revealed self-assembled bundles of columnar aggregates in spin-coated films and isolated several-micron-long nanoribbons composed of a defined number of columns in drop cast films.
authors.affiliation: Max-Planck Institute for Polymer Research, Ackermannweg 10, D-55128, Mainz, Germany.
authors.forename: Jishan
authors.initials: J
authors.lastname: Wu
authors.forename: Mark D
authors.initials: MD
authors.lastname: Watson
authors.forename: Li
authors.initials: L
authors.lastname: Zhang
authors.forename: Zhaohui
authors.initials: Z
authors.lastname: Wang
authors.forename: Klaus
authors.initials: K
authors.lastname: Müllen