Synthesis and Photophysical Studies of Bis-enediynes as Tunable Fluorophores

• Published in: Journal of the American Chemical Society 2003-09, Vol.125 (37), p.11241-11248
• Main Authors: Hwang, Gil Tae, Son, Hyung Su, Ku, Ja Kang, Kim, Byeang Hyean
• Format: Article
• Language: English
• Subjects: Chemistry; Condensed benzenic and aromatic compounds; Exact sciences and technology; Organic chemistry; Preparations and properties
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja0349148

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 π-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.