Chlortetracycline (CTE) is a kind of tetracycline antibiotic against Gram-positive and negative bacteria. However, the overuse and excessive discharge of CTE would be harmful to the environment and human beings inevitably. Herein, to achieve sensitive and specific detection of CTE, an electron-deficient site (i.e., viologen segment) is incorporated into the construction of two isostructural multifunctional lanthanide-based complexes. Besides the distinct photochromism coupled with light-modulated typical Eu