In contrast to the fluorescent response of ZTRS to metal ionsin aqueous solutions, in 100% CH3CN Zn2+ and Cd2+ result inblue-shifted emissions with the maximum wavelength changefrom 481 to 430 and 432 nm, respectively (Supporting Information,Figures S4, S5); however, the addition of Zn2+ and Cd2+to ZTRS in 100% DMSO cause red-shifted emissions with themaximum wavelength change from 472 to 512 and 532 nm,respectively (Supporting Information, Figures S6, S7). TheFigure 1. Influence of pH on the fluorescence of ZTRS in acetonitrile/water (50:50, v/v). Excitation wavelength: 360 nm. [ZTRS] ) 10 μM. (a) . Inset: The fluorescence intensity at 483 nm as a function of pH; (b) pH . Inset: The ratiometric fluorescence changes as a function of 2. (a) Fluorescence spectra of 10 μM ZTRS in the presence of various metal ions in aqueous solution (CH3CN/ M HEPES (pH ) ) 50:50).Excitation at 360 nm. (b) Fluorescence spectra of ZTRS in the presence of different concentrations of Zn2+. The inset shows the Job plot evaluated fromthe fluorescence with a total concentration of 10 μ of other HTM ions results in blue-shift in emissionsin both CH3CN and DMSO (Supporting Information, FiguresS8, S9). However, a small blue-shift of the absorption maximumof ZTRS in CH3CN, DMSO, and aqueous solution uponaddition of Zn2+ and Cd2+ (Supporting Information, FiguresS10-S15) indicates that the red-shifted emission does not resultfrom the deprotonation of amide NH group, because thedeprotonation of the NH group conjugated to 1,8-naphthalimidewould cause a red-shift in absorption spectra. 18h,25a Thesespectral data suggest that ZTRS binds Zn2+ and Cd2+ indifferent tautomeric forms, depending on the solvent and metalions (Scheme 3); ZTRS complexes both Zn2+ and Cd2+ in theamide tautomer in CH3CN, and the imidic acid tautomer inDMSO predominantly. However, other HTM ions bind to theamide tautomer in both CH3CN and evidence for the amide and imidic acid tautomericbinding modes (Scheme 3) is provided by 1H NMR titrationexperiments of ZTRS with Zn2+ and Cd2+ in CD3CN (SupportingInformation, Figures S16, S17) and DMSO-d6 (SupportingInformation, Figures S18, S19), 2D NOESY of ZTRS/Zn2+ (1:1 complex) in CD3CN (Figures 3, Supporting Information,Figures S20, S21) and DMSO-d6 (Figures 3, S22-23),and IR spectra of ZTRS/Zn2+ (1:1 complex) in CH3CN(Supporting Information, Figure S24) and DMSO (SupportingInformation, Figure S25). As a reference, the binding propertiesof ZTF with Zn2+ were also examined by means of 1H NMRand IR spectra.与ZTRS与含水溶液中金属离子的荧光响应相反,在100%CH3CN中,Cd2+和Zn2+产生最大波长从481分别变化到430和432nm的蓝移发射(支持信息的图S4和S5);然而,向100%DMSO中的ZTRS添加Cd2+和Zn2+会引起最大波长从472分别变化到512和532nm的红移发射(支持信息的图S6和S7)。添加其他HTM离子会引起在CH3CN和DMSO中发射的蓝移(支持信息的图S8、S9)。不过,在添加Cd2+和Zn2+时,在CH3CN、DMSO以及含水溶液中的ZTRS的吸收谱小的蓝移(支持信息的图S10-S15)表明,红移发射不是因为酰胺NH基团去质子化的结果,因为与1,8萘二甲酰亚胺共轭的NH基团的去质子化会引起吸收谱的红移18h,25a。这些光谱数据告诉我们,ZTRS根据溶剂和金属离子(方案3)以不同的互变异构形式与Cd2+和Zn2+结合;ZTRS主要与CH3CN中酰胺互变异构体中的Cd2+和Zn2+络合,以及与DMSO中亚氨酸互变异构体中的Cd2+和Zn2+络合。可是,其他离子与CH3CN和DMSO中的酰胺互变异构体结合。 关于酰胺和亚胺酸互变异构结合模式(方案3)的进一步证据由ZTRS的氢核磁共振(1H NMR)滴定实验,用CD3CN(支持信息的图S16、S17)和DMSO-d6(支持信息的图S18、S19)中的Cd2+和Zn2+,CD3CN(图3,支持信息的图S20/S21)和DMSO-d6(图3,S22、S23)中的ZTRS/Zn2+(1:1络合物)的2维相关核磁共振谱(2D NOESY),以及CH3CN(支持信息的图S24)和DMSO(支持信息的图25)中ZTRS/Zn2+(1:1络合物)的红外光谱提供。作为参考,ZTF与Zn2+的结合性质也用1H NMR和红外光谱进行了研究。