title: Impact of heterocirculene molecular symmetry upon two-dimensional crystallization.
abstract: Despite the development of crystal engineering, it remains a great challenge to predict the crystal structure even for the simplest molecules, and a clear link between molecular and crystal symmetry is missing in general. Here we demonstrate that the two-dimensional (2D) crystallization of heterocirculenes on a Au(111) surface is greatly affected by the molecular symmetry. By means of ultrahigh vacuum scanning tunneling microscopy, we observe a variety of 2D crystalline structures in the coverage range from submonolayer to monolayer for D(8h)-symmetric sulflower (C16S8), whereas D(4h)-symmetric selenosulflower (C16S4Se4) forms square and rectangular lattices at submonolayer and monolayer coverages, respectively. No long-range ordered structure is observed for C(1h)-symmetric selenosulflower (C16S5Se3) self-assembling at submonolayer coverage. Such different self-assembly behaviors for the heterocirculenes with reduced molecular symmetries derive from the tendency toward close packing and the molecular symmetry retention in 2D crystallization due to van der Waals interactions.
authors: 1] Empa, Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland [2] Institute of Physics, Chinese Academy of Sciences, 100190 Beijing, P.R. China.
authors: W D
authors: WD
authors: Xiao
authors: Institute of Physics, Chinese Academy of Sciences, 100190 Beijing, P.R. China.
authors: Y Y
authors: YY
authors: Zhang
authors: Institute of Physics, Chinese Academy of Sciences, 100190 Beijing, P.R. China.
authors: L
authors: L
authors: Tao
authors: 1] Empa, Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland [2] ICMP, Ecole Polytechnique Fédérale de Lausanne, Station 3, 1015 Lausanne, Switzerland.
authors: K
authors: K
authors: Aït-Mansour
authors: 1] Department of Chemistry, University of Helsinki, P.O. Box 55, 00014, Finland [2] Department of Chemistry, Moscow State University, Leninskiye Gory, 119992 Moscow, Russia.
authors: K Y
authors: KY
authors: Chernichenko
authors: Department of Chemistry, Moscow State University, Leninskiye Gory, 119992 Moscow, Russia.
authors: V G
authors: VG
authors: Nenajdenko
authors: Empa, Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland.
authors: P
authors: P
authors: Ruffieux
authors: Institute of Physics, Chinese Academy of Sciences, 100190 Beijing, P.R. China.
authors: S X
authors: SX
authors: Du
authors: Institute of Physics, Chinese Academy of Sciences, 100190 Beijing, P.R. China.
authors: H-J
authors: HJ
authors: Gao
authors: 1] Empa, Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland [2] Department of Chemistry and Biochemistry, Universität Bern, Freiestrasse 3, 3012 Bern, Switzerland.
authors: R
authors: R
authors: Fasel