title: Superstructure-dependent optical and electrical properties of an unusual face-to-face, pi-stacked, one-dimensional assembly of dehydrobenzo[12]annulene in the crystalline state.
abstract: To develop a novel pi-conjugated molecule-based supramolecular assembly, we designed and synthesized trisdehydrotribenzo[12]annulene ([12]DBA) derivative 2 with three carboxyl groups at the periphery. Recrystallization of 2 from DMSO gave a crystal of the solvate 23 DMSO. Crystallographic analysis revealed, to our surprise, that a face-to-face pi-stacked one-dimensional (1D) assembly of 2 was achieved and that the DMSO molecule played a significant role as a "structure-dominant element" in the crystal. This is the first example of [12]DBA to stack completely orthogonal to the columnar axis. To reveal its superstructure-dependent optical and electrical properties, 2 and its parent molecule 1, which crystallizes in a herringbone fashion, were subjected to fluorescence spectroscopic analysis and charge-carrier mobility measurements in crystalline states. The 1D stacked structure of 2 provides a red-shifted, broadened, weakened fluorescence profile (lambda(max) = 545 nm, phi(F) = 0.01), compared to 1 (lambda(max) = 491 nm, phi(F) = 0.12), due to strong interactions between the p orbitals of the stacked molecules. The charge-carrier mobility of the single crystal of 23 DMSO, as well as 1, was determined by flash photolysis time-resolved microwave conductivity (FP-TRMC) measurements. The single crystal of 23 DMSO revealed significantly-anisotropic charge mobility (sigma(mu) = 1.5x10(-1) cm(2) V(-1) s(-1)) along the columnar axis (crystallographic c axis). This value is 12 times larger than that along the orthogonal axis (the a axis).
authors.affiliation: Department of Material and Life Science, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka, 565-0871, Japan. hisaki@mls.eng.osaka-u.ac.jp
authors.forename: Ichiro
authors.initials: I
authors.lastname: Hisaki
authors.forename: Yuu
authors.initials: Y
authors.lastname: Sakamoto
authors.forename: Hajime
authors.initials: H
authors.lastname: Shigemitsu
authors.forename: Norimitsu
authors.initials: N
authors.lastname: Tohnai
authors.forename: Mikiji
authors.initials: M
authors.lastname: Miyata
authors.forename: Shu
authors.initials: S
authors.lastname: Seki
authors.forename: Akinori
authors.initials: A
authors.lastname: Saeki
authors.forename: Seiichi
authors.initials: S
authors.lastname: Tagawa