Synthesis And Ion Relay Recognition Research Of Fluorescent Probes Based On2-(2-aminophenyl)Benzimidazole Derivatives

As one of the imidazole compounds, benzimidazole palys a crucial role inbiological and environmental systems, and, it was widely used in the field ofbiomedicine. Along with the deepening of research, people find that imidazolecompounds have a good quantum yield. Not only can this fluorescence characteristicbe used in organic environment, but also it has a good broad application prospect inwater environment. More and more attention has been paid to the imidazolecompounds and it is constantly used in ion recognition in recent years. We designedand synthesized a series of fluorescent sensors based on2-(2′-aminophenyl)benzimidazole derivative in this thesis and get some meaningfulresults. The details are as follows:1. Briefly introducted to the conception of supramolecular and new sensingmechanisms of fluorescent chemosensors emerged in recent years. In addition,Summarized the progress of ion recognition with probes derived fromphenylbenzimidazole.2. A new fluorescent2-(2′-aminophenyl)benzimidazole derivatized sensor BMD1was synthesized. Probe BMD1exhibits highly selective and sensitive recognitionproperties to Cu2+in CH3OH/H2O (1/1, v/v, HEPES10mM, pH=7.0) solution with a1:1binding stoichiometry. The in situ prepared BMD1-Cu(II) complex solutiondisplays highly selectivity to cyanide through Cu2+displacement approach andpossesses excellent tolerance to other common interference anions. The detectionlimits of sensor BMD1to Cu2+and BMD1-Cu(II) complex to cyanide were estimatedto be1.82×10-8M and1.62×10-6M, respectively.3. A new fluorescent2-(2′-aminophenyl)benzimidazole derivatized sensor BMD2was designed and synthesized. Sensor BMD2exhibits quickly, highly selective and sensitive recognition properties to Cu2+in HEPES buffered (pH=6.0) water solutionwith a1:1binding stoichiometry. The in situ formed BMD2-Cu(II) complex solutionexhibits fast response and high selectivity to sulfide anion via Cu2+displacementapproach and possesses excellent tolerance to other common interference anions. Thedetection limits of sensor BMD2to Cu2+and BMD2-Cu(II) complex to sulfide anionwere estimated to be3.5×10-7M and1.35×10-6M, respectively. Proof-of-conceptexperiments with some natural water samples were performed and demonstrated thatsensor BMD2has potential utilities for Cu2+and sulfide ion concentration evaluationin real water samples.4. A new fluorescent2-(2′-aminophenyl)benzimidazole derivatized sensor BMD3was designed andsynthesized. In CH3CN/H2O (2︰8, v/v, HEPES10mM, pH7.4)solution, sensor BMD3displays two emission bands and exhibits a highly selectiveand ratiometric response to Zn2+ions with a distinctly longerwavelengthemission blueshifted through the inhibition of the excited-state intramolecular protontransfer(ESIPT) process. BMD3can clearly discriminate Zn2+from Cd2+and other metal ions.Moreover, the in situ generated BMD3-Zn（II） solution exhibits a highly selectiveand ratiometric response to S2-among various anions and thiol-containing amino acidsvia Zn2+displacement approach, which results in a revival.of the ESIPT phenomenonof free BMD3. These results demonstrate that BMD3can serve as a ratiometricsensor for sequential recognition of Zn2+and S2-in aqueous solution throughinhibition and turn-on of ESIPT process.5. A new fluorescent2-(2′-aminophenyl)benzimidazole derivatized sensor BMD4with2-picolylamine as Zn2+chaltor was designed andprepared. In buffered watersolution(HEPES10mM, pH=7.4), sensor BMD4displays highly selective, sensitiveand ratiometric fluorescent recognition to Zn2+based on inhibition of excited-stateintramolecular protontransfer(ESIPT). In addition, the resultant BMD4-Zn（II）complex exhibits ratiometric responses to S2-with excellent selectivity via S2-inducedZn2-displacement approach. The results demonstrate that BMD4can serve as aratiometric fluorescent sensor for relay recognition of Zn2-and S2-in wateratphysiological pH. 6. A new fluorescent2-(2′-aminophenyl)benzimidazole derivatized sensor BMD5that behaves as a ratiometric fluorescent receptor for Zn2+in water has been described.In HEPES buffer at pH=7.4, sensor L displays a weak fluorescence emission band at367nm. Upon addition of Zn2+, the emission intensity at367nm is decreased,concomitantly, a new emission band centered at426nm is developed, thus facilitatesa ratiometric Zn2+sensing behavior. Sensor BMD5binds Zn2+through a1︰1bindingstoichiometry with high selectivity over other metal cations. Sensor L displays a linearresponse to Zn2+concentration from0to6.0×10-5M, sensor BMD5also exhibits highsensitivity to Zn2+with a detection limit of3.31×10-7M.