Towards tetrazine-based near-infrared fluorogenic dyes: Is there a wavelength limit?

Abstract

Tetrazine-based fluorogenic dyes have been broadly applied in the studies of many biomolecules in live cells via wash-free imaging. While near-infrared (NIR) dyes are much preferred in these scenarios, few tetrazine-based NIR fluorogenic dyes have been reported to date. In this work, we developed three tetrazine-based cyanine dyes with emission wavelengths of up to ~790 nm and fluorescence turn-on ratios of ~4. We also performed quantum chemical calculations to rationalize the low turn-on ratio in these dyes. Our results show that based on the dark-state quenching mechanism, the tetrazine moiety is intrinsically not suitable for developing NIR fluorogenic dyes with emission wavelengths of >~710 nm.