title: Self-organization of bent rod molecules into hexagonally ordered vesicular columns.
abstract: Bent-shaped rigid-core molecules with flexible chiral dendrons grafted to the outer side of the bend were synthesized and characterized by circular dichroism, differential scanning calorimetry, X-ray scatterings, and transmission electron microscopy in solution and the solid state. The bent aromatic rods based on hepta- and nonaphenylene with nitrile groups at both ends self-assemble into well-ordered hollow tubular structures in aqueous solution, while the bent rod based on heptaphenylene without nitrile groups showed no apparent aggregations in aqueous solution. In the solid state, the rigid-flexible molecules based on heptaphenylene rod without the nitrile group self-assemble into a 2D oblique columnar structure with the columnar cross-section containing two interlocked molecules. Remarkably, the rigid flexible molecules based on hepta-, nona-, and undecaphenylene with nitrile groups self-assemble into a hexagonal columnar structure with weak 3D order. A model of vesicular channel structure is proposed based on small- and wide-angle X-ray diffraction on oriented fibers, density measurement, reconstruction and simulation of electron density maps, and molecular dynamics simulation. In contrast to the hollow tubular structure found in solution, in the solid both the outside and the interior of the columns are filled by the pendant aliphatic coils. Filling of the interior of these vesicular channels is made possible by some bent rod molecules turning their obtuse apex inward. One in 7, 2 in 8, and 4 in 10 molecules are thus inverted in a column slice in compounds with hepta-, nona-, and undecaphenylene cores, respectively. These are new examples of vesicular double-segregated columnar structures recently discovered in some dendrons.
authors: Center for Supramolecular Nano-Assembly and Department of Chemistry, WCU Program of Chemical Convergence for Energy and Environment, Seoul National University, Seoul 151-747, Korea.
authors: Ho-Joong
authors: HJ
authors: Kim
authors: Feng
authors: F
authors: Liu
authors: Ja-Hyoung
authors: JH
authors: Ryu
authors: Seong-Kyun
authors: SK
authors: Kang
authors: Xiangbing
authors: X
authors: Zeng
authors: Goran
authors: G
authors: Ungar
authors: Jeong-Kyu
authors: JK
authors: Lee
authors: Wang-Cheol
authors: WC
authors: Zin
authors: Myongsoo
authors: M
authors: Lee
mesh_terms: D002942:Circular Dichroism; D050091:Dendrimers / Q000138:chemical synthesis / Q000737:chemistry*; D006841:Hydrocarbons, Aromatic / Q000138:chemical synthesis / Q000737:chemistry*; D046529:Microscopy, Electron, Transmission; D008958:Models, Molecular; D044367:Phase Transition; D011092:Polyethylene Glycols / Q000138:chemical synthesis / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D050091:Dendrimers; D006841:Hydrocarbons, Aromatic; D011092:Polyethylene Glycols