Selective fluorescent recognition of Zn²⁺ by using chiral binaphthol-pyrene probes

The bis-binaphthol-pyrene derivative 1 (R isomer) and 2 (S isomer) selectively sense Zn²⁺ by undergoing a reversible fluorescent emission enhancement at 550 nm. Moreover, upon addition of Zn²⁺, the magnitude of the peak in the CD spectrum of 1 at 289 nm increases and the intensity of the peak at 272 nm decreases. Opposite changes were observed for 2 upon the addition Zn²⁺. The distinctive fluorescence and ratiometric CD spectral changes are attributed to a change in the dihedral angle between the binaphthol groups in 1 and 2 caused by Zn²⁺ binding. Probe 1 was further employed to image Zn²⁺ in cells.