π-Expanded benzothiazole dyes with excited-state intramolecular proton-transfer process: Synthesis, photophysical properties, imaging in cells and zebrafish

In this paper, we have designed and synthesized HBT-fused aryl-imidazole derivatives HBTA, HBTB, HBTC and HBTD through pi-expanded system, which have large absorption extinction coefficients, relatively high quantum yields, large Stokes shifts. The dyes HBTB, HBTC and HBTD still retained excited state intramolecular proton-transfer property (E* and K* emission). They also exhibited good ESIPT properties in serum. The experimental results and theoretical calculations verified that the nonplanar and nitrogen heterocyclic structure of pi-expanded rings was beneficial for the k* emission under the same conditions. Moreover, The HBTA, HBTB, HBTC and HBTD were successfully applied for the imaging in living cells and zebrafish. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

In this paper, HBT-fused aryl-imidazole derivatives with large absorption extinction coefficients, high quantum yields, and large Stokes shifts were designed and synthesized. These dyes exhibited good ESIPT properties in serum and were successfully applied for imaging in living cells and zebrafish. The nonplanar and nitrogen heterocyclic structure of the pi-expanded rings was found to be beneficial for emission under the same conditions.