Design And Recognition Properties Of Several Novel Fluorescent Sensors For Transition Metal Ions

The advantages of fluorescent sensors for transition metal ions include convenience, highsensitivity and selectivity, observation in situ, etc. The coumarin dyes have excellentphotophysics and photochemistry properties such as high stability against light, highfluorescence quantum yields and big Stokes shift, etc. Therefore, coumarin dyes are oftenused for the design of fluorescent sensors for transition metal ions.The fluorescent sensors S1-3for Cu²⁺bearing hydrazide and imine unit based on coumarinhave been designed and synthesized. Their structure are identified by1HNMR and MS, andtheir recognition effects for metal ions have been investigated in neutral buffer. S1exhibitsCu²⁺-only sensitive among metal ions such as alkali （K⁺, Na⁺）, alkaline earth (Ca²⁺, Mg²⁺),and transition metal ions(Cd²⁺, Ag+, Fe3+, Pb²⁺, Cr3+, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺). Upon theaddition on of Cu²⁺, there are a38nm blue-shift in absorbance maximum，a17nm red-shift inemission maximum, a8.2-fold intensity enhancement in fluorescence and an obviousfluorescence change from almost colorless to blue. S1is pH-insensitive and may be used forCu²⁺detection in neutral and weakly alkaline pH span. S2exhibits Cu²⁺-only sensitive amongmetal ions. Upon the addition of Cu²⁺, there are a64nm blue-shift in absorbance maximum，a60nm red-shift in emission maximum, a60.1-fold intensity enhancement in fluorescence and17-fold increase in fluorescence quantum yield. S3exhibits Hg²⁺-only sensitive among metalions. Upon the addition of Hg²⁺, there are a26nm blue-shift in absorbance maximum，a29.5-fold intensity enhancement in fluorescence. S3may detect Hg²⁺in relatively wide pHspan.