Fluorescent Zn^II Chemosensor Mediated by a 1,8-Naphthyridine Derivative and It's Photophysical Properties

One of the greatest challenges in using fluorescent chemosensors for highly selective and sensitive transition-metal ions is finding an efficient and simple method for its synthesis. In this study, a highly efficient fluorescence chemosensor for Zn^II was developed from N-Boc-L-proline modified 1,8-naphthyridine. The fluorescence intensity of the chemosensor was increased significantly only in the presence of Zn^II ion which provided a perceived color change for rapid visual sensing, while other metal ions showed fluorescence quenching or little changes. It was worth noting that the chemosensor L distinguished Zn^II from Cd^II commonly having similar properties. The solvent effect and possible bonding mode for fluorescence enhancement have been also discussed. Results of this study indicated that the Boc-group in l-proline significantly improved the sensitivity and selectivity for Zn^II detection performance, as confirmed by comparison experiments and time dependent-density functional theory (TD-DFT) calculations.