A boron-dipyrrin-mercury(II) complex as a fluorescence turn-on sensor for chloride and applications towards logic gates

摘要

Chloride (CP) plays an important role in many cellular responses, including control of membrane potential, neurotransmission, regulation of cell volume and charge balance. Due to its physiological relevance, there is a growing need for improved optical sensors that can detect Cl~- ions in biological and environmental samples. Herein, we have developed new N-acylhydrazone substituted BODIPY-mercury(II) based fluorescent turn-on sensors 1-Hg~(2+) and 2-Hg~(2+), which showed remarkable selectivity and specificity towards Cl~- ions under physiological conditions. The new BODIPY compounds 1 and 2 were synthesized by treating their corresponding 3,5-diformyl BODIPYs 3 and 4 with isonicotinohydrazide in one step under simple reaction conditions. Compounds 1 and 2 absorb in 615-650 nm and emit in 625-660 nm regions. BODIPYs 1 and 2 showed exclusive sensing towards Hg~(2+) and formed I-Hg~(2+) and 2-Hg~(2+) complexes, respectively, which resulted in the quenching of fluorescence. Job's plot analyses and HR-MS studies supported the formation of 1-Hg~(2+) and 2-Hg~(2+) complexes. Complexes 1-Hg~(2+) and 2-Hg~(2+) were found to be exclusive fluorescence turn-on sensors for chloride ions. Upon addition of Cl~- ions to 1-Hg~(2+) and 2-Hg~(2+) complexes, the mercury(II) ions were extracted from the complexes by releasing the free BODIPYs 1 and 2 which reflected in the significant enhancement of fluorescence intensity (22-fold) with a detection limit of 108 nM. The reversibility and reusability of sensors for the detection of Hg~(2+) and Cl~- ions were tested for six cycles. Interestingly, the sensor can be used to construct an IMPLIES logic gate system as demonstrated in this paper. Furthermore, the probe is cell membrane-permeable and can readily be used to detect the intracellular Cl~- ions.