Trimethine cyanine dyes with an indole nucleus: Synthesis and spectral properties studies

A series of trimethine quinoline cyanine dyes with an indole nucleus were designed and synthesized based on the chemical structures of Cy-3 and TO. The structures of all dyes were confirmed by (HNMR)-H-1 and MS. Studies on their spectral properties showed that the trimethine cyanine dyes had properties of both the embedded dye TO and the bonded dye Cy-3. The maximum fluorescence wavelength of the final cyanine dyes shifted red compared with those of Cy-3 and TO alone. When we changed the substituent groups on the indole ring of the dye, both the fluorescence intensity and wavelength exhibited corresponding changes. The fluorescence wavelength of indole quinoline with an electron donor group shifted red and the fluorescence intensity was enhanced with good photostability. When labeled with BSA, a significant fluorescence enhancement could be observed. (c) 2012 Elsevier B.V. All rights reserved.