title: Synthesis and photophysical studies of bis-enediynes as tunable fluorophores.
abstract: We have synthesized a family of bis-enediynes by two complementary Pd/Cu-catalyzed Sonogashira cross-coupling methods. One is a modified Sonogashira reaction between the TMS-protected tetraalkyne 20 (or 21) and various aromatic bromides to afford bis-enediynes 22a-d and 23a-d bearing different peripheral aryl units. The other, the reaction of bifunctional 1,1-dibromo-1-alkenes with phenylacetylene, afforded a series of bis-enediynes 24-32 bearing various core aryl groups. These chemical modifications to the core and periphery of bis-enediynes induce dramatic changes in absorption and emission spectra. Bis-enediynes 22 and 23 show a large Stokes shift of about 50-110 nm when compared to the less-conjugated bis-enediynes 20 and 21. Absorptions and emissions of bis-enediynes 25, 27-29, and 31 were red-shifted relative to those of enediyne 35. Substantial increases in fluorescence quantum yields are observed as a result of extending the pi-conjugation. The emission wavelength of bis-enediynes was tailored from indigo blue to reddish-orange, suggesting that the color of emission can be tunable by modification of the core and/or peripheral units.
authors.affiliation: National Research Laboratory, Center for Integrated Molecular Systems, Department of Chemistry, Division of Molecular and Life Sciences, Pohang University of Science and Technology, Pohang 790-784, Korea.
authors.forename: Gil Tae
authors.initials: GT
authors.lastname: Hwang
authors.forename: Hyung Su
authors.initials: HS
authors.lastname: Son
authors.forename: Ja Kang
authors.initials: JK
authors.lastname: Ku
authors.forename: Byeang Hyean
authors.initials: BH
authors.lastname: Kim