Self-Assembled Monolayers of Alkoxy-Substituted Octadehydrodibenzo[12]annulenes on a Graphite Surface: Attempts at peri-Benzopolyacene Formation by On-Surface Polymerization

• Published in: Chemistry : a European journal Vol. 16; no. 28; pp. 8319 - 8328
• Main Authors: Tahara, Kazukuni, Inukai, Koji, Hara, Noritaka, Johnson II, Charles A., Haley, Michael M., Tobe, Yoshito
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 26.07.2010; WILEY‐VCH Verlag; Wiley Subscription Services, Inc
• Subjects: Chemistry; dehydrobenzoannulene; Formations; interfaces; Lamella; Molecular structure; monolayers; Networks; Polymerization; scanning probe microscopy; Scanning tunneling microscopy; Self-assembled monolayers; self-assembly; Two dimensional
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201000711

Self‐assembled monolayers of a series of tetraalkoxy‐substituted octadehydrodibenzo[12]annulene (DBA) derivatives 1 c–g possessing butadiyne linkages were studied at the 1,2,4‐trichlorobenzene (TCB) or 1‐phenyloctane/graphite interface by scanning tunneling microscopy (STM). The purpose of this research is not only to investigate the structural variation of two‐dimensional (2D) monolayers, but also to assess a possibility for peri‐benzopolyacene formation by two‐dimensionally controlled polymerization on a surface. As a result, the formation of three structures, porous, linear, and lamella structures, were observed by changing the alkyl chain length and the solute concentration. The formation of multilayers of the lamella structure was often observed for all compounds. The selection of molecular networks is basically ascribed to intermolecular and molecule–substrate interactions per unit area and network density. The selective appearance of the linear structure of 1 d is attributed to favorable epitaxial registry matching between the substrate lattice and the overlayer lattice. Even though the closest interatomic distance between the diacetylenic units of the DBAs in the lamella structure (≈0.6 nm) is slightly larger compared to the typical distances necessary for topochemical polymerization, the reactivity toward external stimuli (electronic‐pulse irradiation from an STM tip and UV irradiation) was investigated. Unfortunately, no evidence for polymerization of the DBAs on the surface was observed. The present results indicate the necessity for further designing a suitable system for the on‐surface construction of structurally novel conjugated polymers, which are otherwise difficult to prepare. Pull yourself together: Monolayers of tetraalkoxy‐substituted octadehydrobenzo[12]annulene (DBA) derivatives (see picture), which have butadiyne linkages, were studied by STM at the liquid/solid interface. The reactivity of DBA in the monolayer toward external stimuli was also investigated to assess the possibility for peri‐benzopolyacene formation by two‐dimensionally controlled polymerization on a surface.