Electron-deficient moiety regulated structure: an efficient strategy for the design of a highly sensitive cyanide “turn-on” fluorescent probe

Developing fluorescent probes for the cyanide diagnosis is necessary as its extensive existence will seriously harm human health. Herein, the strategy for designing three novel probes came from our previously reported “turn-on” fluorescent probe, which was switched from a “turn-off” probe by inserting an electron-deficient benzothiadiazole (BTD) into a triphenylamine (TPA)-based dicyanovinyl (MT) compound with a phenyl group (Ph) as π-bridge (TPA-BTD-Ph-MT). To further investigate the effects of the electron-deficient group, BTD was firstly replaced by a stronger electron-deficient group of 2,3-diphenylquinoxaline (DPQ) to obtain TPA-DPQ-Ph-MT (P1). Based on P1 molecule, N-phenylcarbazole (PCZ), and thiophene (Th) were respectively used as a substitute to obtain PCZ-DPQ-Ph-MT (P2) and TPA-DPQ-Th-MT (P3) probes for investigating the effect of the electron donor and π-bridge on the fluorescent probe. P1 exhibited significant “turn-on” fluorescence response toward cyanide anion (CN−) with the best sensitivity and anti-interference performance. The sensing mechanism of P1 toward CN− was demonstrated and a good linearity was obtained in the wide concentration range of 0.025–40.0 μM with a low detection limit of 0.058 μM. Furthermore, P1 was successfully employed to determine CN– in food samples and image CN– in living cells and BALB/c mice, revealing its great practical potential for discriminative detection CN– in the fields of food and biological studies. Therefore, the strategy based on structure regulation provided good prospects for optimizing fluorescent probes.