Synthesis Of Cis-TPE Macrocycle Diquaternary Ammonium Based On Rotation Restriction Of Double Bond,and Highly Sensitivitive Detection Of DNA

Aggregation-induced emission(AIE)has been receiving attention since its discovery and has great application value in many fields.Tetraphenylethylene(TPE)is the most studied AIE compound because of its simple structure,easy synthesis and modification.Previously,our group has proved that the free rotation restriction of TPE double bond in the excited state plays a key role to the AIE.Based on this,a series of cis-TPE macrocycle diquaternary ammonium and gem-TPE macrocycle diquaternary ammonium have been synthesized and used for DNA detection,then the sensitivity of DNA detection is greatly improved.At the same time,it was found that the cis-TPE macrocycle diquaternary ammonium has higher detection sensitivity than the gem-TPE macrocycle diquaternary ammonium.This is the first example for exploiting AIE mechanism of restriction of double bond rotation to significantly improve the sensitivity of AIE sensor.In addition,CD,CPL and other means were used to explore the mechanism of emission of these TPE macrocycle diquaternary ammonium caused by binded to DNA.(1)A variety of cis-TPE and gem-TPE quaternary ammonium were designed and synthesized,and characterized by nuclear magnetic resonance,melting point measurement,infrared spectroscopy and high resolution mass spectrometry.Fluorescence tests indicate that these TPE quaternary ammonium salts are typical AIE compounds.In addition,the synthesized TPE macrocycle diquaternary ammonium 8e was determined to be a cis-structure by X-ray single crystal diffraction.(2)Fish sperm DNA,calf thymus DNA and artificial 30 nt,20nt,10 nt DNA were detected respectively,using the synthetic series of TPE macrocycle diquaternary ammonium.It was found that cis-TPE macrocycle diquaternary ammonium have higher detection sensitivity than gem-TPE macrocycle diquaternary ammonium.The detection limit for fish sperm DNA can reach 64 pM(1.3 ng/mL),and the minimum detection limit reported in the literature is 20 ng/mL.The detection limit of calf thymus DNA can reach 1.6 ng/mL,and the detection limits of 30 nt DNA,20 nt DNA and 10 nt DNA can reach 32 pM(0.3 ng/mL),75 pM(0.5 ng/mL)and 387 pM(1.2 ng/mL),respectively.(3)A series of experiments were carried out to study the luminescence mechanism of TPE macrocycle diquaternary ammonium.The cis-TPE macrocycle diquaternary ammonium exhibits a stronger fluorescence enhancement effect than the gem-TPE macrocycle diquaternary ammonium when it is reacted with disodium terephthalate.The double CD signal peaks of cis-TPE macrocycle diquaternary ammonium 8a,8b,8c,cis-8e,8f,8g can be induced by calf thymus DNA,only single CD signals of gem-TPE macrocycle diquaternary ammonium 9,10 can be induced,and none CD signal of gem-TPE macrocycle diquaternary ammonium 35 can be induced,demonstrating that the cis-TPE macrocycle diquaternary ammonium are more rigid than the gem-TPE macrocycle diquaternary ammonium,and are easily induced to a single-directional helical structure.It is worth mentioning that the films prepared by the solutions of cis-TPE macrocycle diquaternary ammonium 8b and 8c and calf thymus DNA have strong CPL signals,and gem-TPE macrocycle diquaternary ammonium 9 and 10 do not show CPL signals.The results above prove that rotation restriction of the TPE macrocycle diquaternary ammonium double bond enhance the fluorescence emission.