A small molecular fluorescent sensor for highly selectivity of zinc ion

A new fluorescent sensor for Zn2+ based on 2-methylquinoline has been designed and synthesized. The sensor (1) demonstrates a Zn2+-specific emission enhancement linearly by a factor of 14 with a 1:1 binding ratio even in the presence of a wide range of biological cations. This can be correlated to the efficient Zn2+ binding of 1 and to the participation of relevant amine functions in the metal coordination which promotes a good chelation-enhanced fluorescence (CHEF) effect and prevents the photoinduced electron transfer (PET) effect. Although the addition of Cd2+ also induced an emission enhancement to a certain extent, this enhancement was less pronounced as compared to that of Zn2+, which was further demonstrated by DFT calculations.