title: Two-dimensional porous molecular networks of dehydrobenzo[12]annulene derivatives via alkyl chain interdigitation.
abstract: The self-assembly of a series of hexadehydrotribenzo[12]annulene (DBA) derivatives has been scrutinized by scanning tunneling microscopy (STM) at the liquid-solid interface. First, the influence of core symmetry on the network structure was investigated by comparing the two-dimensional (2D) ordering of rhombic bisDBA 1a and triangular DBA 2a (Figure 1). BisDBA 1a forms a Kagomé network upon physisorption from 1,2,4-trichlorobenzene (TCB) onto highly oriented pyrolytic graphite (HOPG). Under similar experimental conditions, DBA 2a shows the formation of a honeycomb network. The core symmetry and location of alkyl substituents determine the network structure. The most remarkable feature of the DBA networks is the interdigitation of the nonpolar alkyl chains: they connect the pi-conjugated cores and direct their orientation. As a result, 2D open networks with voids are formed. Second, the effect of alkyl chain length on the structure of DBA patterns was investigated. Upon increasing the length of the alkyl chains (DBAs 3c-e) a transition from honeycomb networks to linear networks was observed in TCB, an observation attributed to stronger molecule-substrate interactions. Third, the effect of solvent on the structure of the nonpolar DBA networks was investigated in four different solvents: TCB as a polar aromatic solvent, 1-phenyloctane as a solvent having both aromatic and aliphatic moieties, n-tetradecane as an aliphatic solvent, and octanoic acid as a polar alkylated solvent. The solvent dramatically changes the structure of the DBA networks. The solvent effects are discussed in terms of factors that influence the mobility of molecules at the liquid-solid interface such as solvation.
authors.affiliation: Division of Frontier Materials Science, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan.
authors.forename: Kazukuni
authors.initials: K
authors.lastname: Tahara
authors.forename: Shuhei
authors.initials: S
authors.lastname: Furukawa
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Uji-i
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Uchino
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Ichikawa
authors.forename: Jian
authors.initials: J
authors.lastname: Zhang
authors.forename: Wael
authors.initials: W
authors.lastname: Mamdouh
authors.forename: Motohiro
authors.initials: M
authors.lastname: Sonoda
authors.forename: Frans C
authors.initials: FC
authors.lastname: De Schryver
authors.forename: Steven
authors.initials: S
authors.lastname: De Feyter
authors.forename: Yoshito
authors.initials: Y
authors.lastname: Tobe
mesh_terms: D000478:Alkylation; D000480:Alkynes / Q000138:chemical synthesis / Q000737:chemistry*; D016252:Microscopy, Scanning Tunneling / Q000379:methods; D008958:Models, Molecular; D015394:Molecular Structure; D010316:Particle Size; D011083:Polycyclic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D016062:Porosity; D012680:Sensitivity and Specificity; D013237:Stereoisomerism; D013499:Surface Properties
chemical_list: D000480:Alkynes; D011083:Polycyclic Compounds; C516931:dehydrobenzo(12)annulene