ORGN 98 |
| Zig-zag type pi-conjugated oligomers i.e. ortho-substituted oligoaryleneethynylenes have not been widely explored as versatile and useful pi-conjugated building blocks to construct functional molecular materials. By using electron-donating dibenzothiophene and electron-accepting dibenzothiophene dioxide as arenes, novel series of well-defined zig-zag type multi-dipolar oligoaryleneethynylenes, DA(n) having up to six charge-transfer units (dipoles) have been designed, synthesized by palladium-catalyzed Sonogashira coupling reactions and investigated. The functional properties of these multi-dipolar oligoaryleneethynylenes can easily be modified/ enhanced by incorporating/ extending with various central aryleneethynyl group such as phenylethynyl, fluorenylethynyl, bifluorenylethynyl, bithienylethynyl, terthienylethynyl within the donor–acceptor units, yielding D-Ar-A(n). Although the absorption and emission of these zig-zag type oligoaryleneethynylenes are not greatly dependent of the number of extending dipolar chromophores linked, the fluorescence quantum efficiencies consistently decrease with increased number of covalently linked dipolar units. Remarkably, these zig-zag type oligoaryleneethynylenes exhibit an increase in the two-photon absorption cross-sections (TPA) with increased number of covalently linked dipolar units. Our results suggest that the TPAs can be enhanced without causing the red-shift of absorption and emission which could provide a means to enhance the TPA at a specific wavelength. The detailed structure-property relationships of these zig-zag type multi-dipolar oligoaryleneethynylenes will be presented.
|
|
Materials, Devices, and Switches
1:00 PM-5:00 PM, Sunday, 10 September 2006 Moscone Center -- Room 132, Oral
Division of Organic Chemistry |
