title: Visualization of various supramolecular assemblies of oligo(para-phenylenevinylene)-melamine and perylene bisimide.
abstract: A melamine derivative has been covalently equipped with two oligo(para-phenylenevinylene) (OPV) chromophores. This procedure yields a bifunctional molecule with two hydrogen-bonding arrays available for complementary binding to perylene bisimide derivatives. Depending on the solvent, hydrogen-bonded trimers, tetramers, and dimers on a graphite surface are observed for pure OPV-melamine by using scanning tunneling microscopy (STM). Upon the addition of perylene bisimide, linear tapes of perylene bisimide, 12-membered rosettes that consist of alternating hydrogen-bonded OPV-melamine and perylene bisimide moieties are visualized. These results provide direct evidence for the possible modes of hydrogen bonding within a supramolecular co-assembly in solution. Subsequently, the optical properties of pure OPV-melamine and co-assemblies with a perylene bisimide derivative were characterized in solution. In an apolar solvent, OPV-melamine self-assembles into chiral superstructures. Disassembly into molecularly dissolved species is reversibly controlled by concentration and temperature. Complementary hydrogen bonding to a perylene bisimide derivative in an apolar solvent yields multicomponent, pi-stacked dye assemblies of enhanced stability that are characterized by fluorescence quenching of the constituent chromophores. Titration experiments reveal that a mixture of hydrogen-bonded oligomers is present in solution, rather than a single discrete assembly. The solution experiments are consistent with the STM results, which revealed various supramolecular assemblies. Our system is likely not to be optimally programmed to obtain a discrete co-assembled structure in quantitative yield.
authors.affiliation: Laboratory of Macromolecular and Organic Chemistry Eindhoven University of Technology, Eindhoven, The Netherlands.
authors.forename: Freek J M
authors.initials: FJ
authors.lastname: Hoeben
authors.forename: Jian
authors.initials: J
authors.lastname: Zhang
authors.forename: Cameron C
authors.initials: CC
authors.lastname: Lee
authors.forename: Maarten J
authors.initials: MJ
authors.lastname: Pouderoijen
authors.forename: Martin
authors.initials: M
authors.lastname: Wolffs
authors.forename: Frank
authors.initials: F
authors.lastname: Würthner
authors.forename: Albertus P H J
authors.initials: AP
authors.lastname: Schenning
authors.forename: E W
authors.initials: EW
authors.lastname: Meijer
authors.forename: Steven
authors.initials: S
authors.lastname: De Feyter