A GFP Inspired 8‐Methoxyquinoline–Derived Fluorescent Molecular Sensor for the Detection of Zn2+ by Two–Photon Microscopy

An effective, GFP‐inspired fluorescent Zn2+ sensor is developed for two–photon microscopy and related biological application that features an 8‐methoxyquinoline moiety. Excellent photophysical characteristics including a 37‐fold fluorescence enhancement with excitation and emission maxima at 440 nm and 505 nm, respectively, as well as a high two–photon cross–section of 73 GM at 880 nm are reported. Based on the experimental data, the relationship between the structure and properties was elucidated and explained backed up by DFT calculations, particularly the observed PeT phenomenon for the turn–on process. Biological validation and detailed experimental and theoretical characterization of the free and the zinc–bound compounds are presented. New zinc sensor with 8‐methoxyquinoline moiety inspired by the green fluorescent protein chromophore was synthesized and characterized. The in vitro validation of the novel probe with two–photon microscopy was carried out successfully.