Ultra Pseudo-Stokes Shift Near Infrared Dyes Based on Energy Transfer

Abstract

Novel fluorescent dyes with ultra pseudo-Stokes Shift were prepared based on intramolecular energy transfer between a fluorescent donor and a Cyanine-7 acceptor. The prepared dyes could be excited at ~ 320 nm and emit fluorescence at ~ 780 nm. The energy transfer efficiencies of the system are found to be > 94 %.

Figure 1

Two known types of large Stokes shift Cy-7

Figure 2

a) Absorption spectra of equimolar (1.0 μM) 1a–b, 2a–b in MeOH. b) Fluorescence spectra of equimolar (1.0 μM) 1a–b, 2a–b excited at 306, 318, 307 and 315 nm respectively in MeOH. c) Fluorescence spectra of equimolar (1.0 μM) 1a–b, 2a–b and IR-775 excited at 306, 318, 307, 315 and 315 nm respectively in MeOH.

Scheme 1

Structure of Cy-7 dyes, and synthetic scheme of UPSS dyes1a–b, and 2a–b. Donors and acceptors are in blue and black, respectively.