2,2’-二乙酰色氨酸甲酯对Cu^(2＋)的识别传感

Methyl 2,2′-bis(N-acetyltryptophan) as a Highly Sensitive and Selective Chemosensor for Cu^(2+)

设计合成了化学传感分子2,2’-二乙酰色氨酸甲酯(bATM),应用吸收光谱考察了其对金属离子(Cu2+,Hg2+,Pb2+,Zn2+,Cd2+和Ni2+)的响应.结果表明,bATM的吸收光谱仅对Cu2+响应显著,光谱红移102nm,溶液由无色转变为黄色,实现了Cu2+的高选择性高灵敏裸眼识别.对Cu2+的响应线性范围为5.0×10-8～1.8×10-5 mol/L,检测限为5.5nmol/L.初步探讨了传感分子与Cu2+的结合模式和光谱传感机制.

A 2,2′-bistryptophan derivative（bATM） was designed as a selective and sensitive chemosensor for Cu2＋among heavy metal ions（Cu2＋,Hg2＋,Pb2＋,Zn2＋,Cd2＋ and Ni2＋） in acetonitrile and water-acetonitrile binary solvents.Absorption spectrum of bATM in acetonitrile peaked at 320 nm was found to exhibit a huge red-shift to 420 nm in the presence of Cu2＋,together with the appearance of two isosbestic points at 270 nm and 350 nm.In water-acetonitrile binary solvents however the absorption spectral evolution becomes weaker and the spectral variation is less with increasing water content,suggesting that the hydration of Cu2＋plays a role.The red-shift in water-acetonitrile binary solvents was found to be smaller too,now from 314 nm to 360 nm,despite the observation of two isosbestic points.In acetonitrile the absorbance of bATM at 420 nm is linear to Cu2＋concentration over 5.0×10-8 mol/L to 1.8×10-5 mol/L,with a detection limit of 5.5 nmol/L（3σ/k）.Job plot indicates that bATM coordinates with Cu2＋in a 2∶1 stoichiometry.CD spectral titrations in acetonitrile suggest a conformation change in bATM upon coordinating Cu2＋that it takes a cis-conformation in terms of its two tryptophan moieties and becomes more planar in the Cu2＋-complex.Although detailed sensing mechanism remains to be clarified,the observed high sensitivity and selectivity of bATM in its absorption spectral response toward Cu2＋suggests that the structural framework of bATM deserves further effort for developing sophisticated chemosensors for transition metal ions,for example by modifying its structure in the amino acid moiety.