双探针基团（DPG）聚氰分子对Al3+识别机理研究

Study on Recognition Mechanism of Al3+ by Cyanuric Chloride Molecules of Dual-Probe Group （DPG）

铝在人体中的代谢极其缓慢,摄入的铝会在体内不断积累,而异常浓度的Al^3+会破坏中枢神经系统,导致严重的神经性疾病,因此如何高效灵敏地检测Al^3+至关重要。荧光探针因具有携带方便、检测快速简单、价格低廉、选择性好等显著优点被广泛用于分析检测金属离子。大量研究中对于Al^3+的检测都是以单探针基团(single-probe group,SPG)分子以1∶1,2∶1,3∶1等进行配位。本文研究了一种活性三聚氯氰作为连接桥基团,罗丹明B酰胺和席夫碱衍生物对氨基苯甲酰水杨酸作为双探针基团(dual-probe group,DPG)的聚氰分子(RBCS),其采用易于控制的热动力学方法一步法制备得到。固定RBCS+Al^3+的浓度总和为20μmol·L^-1,改变二者的浓度比,通过Job-plot光学实验研究表明当离子占总浓度的比例在约0.68时578 nm处的荧光强度达到最高值,表明RBCS与Al^3+之间主要以1∶2进行配位。通过MALDI-TOF-MASS研究发现,相比无Al^3+的谱图,RBCS-Al^3+在900.07附近出现的新峰进一步验证了该DPG聚氰分子(RBCS)和Al^3+是以1∶2发生络合。通过探针RBCS(10 mg)中加入0,0.5,1,2,3当量Al^3+后的1H NMR滴定实验,对比特征H位置的变化,详细研究出RBCS对Al^3+的识别机理。研究表明当Al^3+存在时,Al^3+与RBCS上罗丹明酰胺部分羰基O,胺基N和三氰上N发生络合导致罗丹明酰胺开环,同时席夫碱部分的亚胺基团的N以及羧酸根和酚基的两个O也分别和Al^3+结合,使得CN键得到固化,整体的共轭性增加,从而产生荧光。综上所述,该聚氰分子(RBCS)可作为识别Al^3+的双探针基团分子。在365 nm紫外灯照射下RBCS-Al^3+表现出橙红色荧光,并随着Al^3+浓度的增加荧光逐渐增强。通过对RBCS光学性能测试条件的优化,最终选定在乙醇/水(99/1,V/V)溶液进行光学性能研究。通过荧光滴定实验测试了在激发波长557 nm,发射波长578 nm下RBCS(10μmol·L^-1)对不同浓度Al^3+(0.01~8 eq)的荧光强度变化,并对数据做线性回归处理,方程为y=32.3360+65.3641x,R2=0.9933,线性范围为1~10μmol·L^-1。通过3σ/k算得RBCS对Al^3+的检出限为15.0 nmol·L^-1。本研究可为设计DPG分子用于金属离子的检测提供参考。

The metabolism of aluminum in the human body is extremely slow,the ingested aluminum will accumulate in the body gradually,and the Al^3+of abnormal concentration will damage the central nervous system,leading to serious neurological diseases,so the detection of Al^3+efficiently and sensitively is very important.Fluorescent probes are widely used for analysis and detection of metal ion because of their advantages of convenient carrying,quick and easy detection,low price,good selectivity,etc.,and a large number of literature for the detection of Al^3+are based on being complexed with Single-Probe Group(SPG)molecules at 1∶1,2∶1,3∶1,etc.In this paper,an active cyanuric chloride as a bridging group,a rhodamine B amide and a Schiff base derivative,p-amino benzoyl salicylic acid,as a cyanuric chloride molecule(RBCS)of a dual-probe group(DPG)was studied.It is prepared in one step by an easily controlled thermodynamic method.The total concentration of immobilized RBCS+Al^3+was 20μmol·L^-1,and the experimental results of Job-plot show that the fluorescence intensity at 578 nm reaches the highest value when the ratio of ions to total concentration is 0.68,by adjusting the concentration ration of the two,the result indicates that RBCS and Al^3+are mainly coordinated by 1∶2.The MALDI-TOF-MASS study found that the new peak of RBCS-Al^3+at 900.07 compared to the spectrum without Al^3+,further verified that the DPG cyanuric chloride(RBCS)and Al^3+are complexed at 1∶2.The recognition mechanism of RBCS to Al^3+was studied in detail by the 1H NMR titration experiment with 0,0.5,1,2,3 equivalents of Al^3+added to the probe RBCS(10 mg)to compare the change of the characteristic H position.The results indicate that when Al^3+is present,the complexation of Al^3+with the carbonyl O,amino N and cyanuric chloride N on the rhodamine part of RBCS leads to the ring opening of rhodamine,at the same time,the imino group N of Schiff base and two O of carboxylic acid radical and phenol radical also bind with Al^3+respectively which solidifies the CN bond and increases the overall conjugation resulting in fluorescence.In conclusion,the cyanuric chloride molecule(RBCS)can be used as a Double-probe group molecule for the recognition of Al^3+ions.RBCS-Al^3+showed orange-red fluorescence under 365 nm ultraviolet lamp irradiation,and the fluorescence increased gradually with the increase of Al^3+concentration.After optimizing the testing conditions of RBCS optical properties,the optical properties of RBCS were studied in ethanol/water(99/1,V/V)solution.The RBCS(10μmol·L^-1)in the ethanol/water(99/1,V/V)solution was carried out by fluorescence titration experiments at an excitation wavelength of 557 nm and an emission wavelength of 578 nm finally.The fluorescence intensity changes of RBCS(10μmol·L^-1)for different concentrations of Al^3+(0.01~8 eq)were tested,and the data was linearly regressed.The equation was y=32.3360+65.3641x,R2=0.9933,and the linear range was 1~10μmol·L^-1.The detection limit of RBCS for Al^3+calculated by 3σ/k is 15.0 nmol·L^-1.The research in this study can provide a reference for the design of double probe group(DPG)molecules for the detection of metal ions.