title: Monolayer structures of highly photoluminescent furan oligoaryls: an approach to improve packing crystallinity of dithiolated aromatics.
abstract: We demonstrated that mono- and dithiolated furan-containing oligoaryls (II-IV, see Chart 2) can be successfully synthesized via a one-pot strategy starting from propargylic dithioacetals. IRAS (infrared reflection-absorption spectroscopy) and STM (scanning tunneling microscopy) experiments revealed that single-component monolayers of II, III, and IV are essentially disordered, an important property that prevents excited photoluminescent molecules from self-quenching in the organic layers of an OLED device. Surprisingly, localized lattice packing of crystalline dithiolated furan oligoaryls on Au(111) can be assembled by immersing preadsorbed n-dodecanethiol SAMs in the corresponding deposition solutions. The discrepancy in the formation of disordered or localized crystalline structures is discussed. For single-component monolayers, the facile formation of S-Au bonds generates chaotically distributed monolayers in which the arched molecules hinge each other and block the desorptive pathways. The absence of crystalline packing is mainly attributed to the difficulty for the dithiols to simultaneously break two S-Au bonds, to desorb, and then to readsorb, the key step to improve the intermolecular attractions for crystalline SAMs. By preassembling n-dodecanethiol SAMs, the space for dithiolated compounds III and IV to adsorb is limited to domain boundaries or packing defects where crystalline packing of III and IV can grow.
authors.affiliation: Department of Chemistry, National Tsing Hua University, Hsinchu, Taiwan 30013.
authors.forename: Shu-Yi
authors.initials: SY
authors.lastname: Lin
authors.forename: I-Wen Peter
authors.initials: IW
authors.lastname: Chen
authors.forename: Chun-Hsien
authors.initials: CH
authors.lastname: Chen
authors.forename: Chin-Fa
authors.initials: CF
authors.lastname: Lee
authors.forename: Chih-Ming
authors.initials: CM
authors.lastname: Chou
authors.forename: Tien-Yau
authors.initials: TY
authors.lastname: Luh