Fluorescence sensors from pyreno[4,5-d]imidazole derivatives

Abstract

Herein, The five fluorescent probes (P1, P2, P3, P4 and P5) based on pyreno[4,5-d]imidazole were successfully prepared in two steps from pyrene in 26 – 40% overall yields. After that, all of the compounds were studied the photophysical properties and selectivity for sensing metal ions. The results showed compound P5 was not selective to metal ions while the others (P1, P2, P3 and P4) were selective to detection of trivalent metal ions such as Bi3+, Al3+, Cr3+ and Fe3+ in CH3CN. However, only compound P2 with 2-hydroxyl phenyl substituent on imidazole ring formed complexation reaction selectively towards bismuth (III) ions and provided fluorescence enhancement signal attributing to the excited state intramolecular proton transfer (ESIPT) process. Compound P2 exhibited selective fluorescence turn-on at 447 nm. The sensing mechanism was determined by 1H-NMR, and UV-VIS and fluorescence titrations, and the Job’s plot indicated a 1:1 binding between P2 and bismuth (III) ions. The detection limit was 1.20 µM in CH3CN-DMSO (8:2, v/v) mixture and 3.40 µM in 10% aqueous in the mixed 80% CH3CN-DMSO (pH =5). Moreover, the sensor was applied to quantitative analysis of spiked Bi3+ in real water samples from different sources. The recovery of Bi3+ was completed at 91-97%.