Description
The integration of molecular photoswitches with fluorescent materials carves a promising pathway for the development of innovative, reversibly light-controlled fluorescent molecules with an array of possible applications. Due to their efficient bidirectional isomerization, tunability and high cis isomer stability, arylazopyrazoles (AAP) are an ideal selection for the photoswitch component of these investigational compounds. However, the incorporation of arylazopyrazoles into emissive organic fluorophores has been scarcely explored. In this work, the design and synthesis of a novel AAP-functionalized 1,8-Naphthalimide (NI) fluorescent photoswitch, with a hydrazide substituent serving as a metal binding unit, is described. The absorption and fluorescence properties of the compound were studied, and the results show that the new AAP-NI compounds undergo efficient reversible trans-to-cis photoisomerization upon alternating blue (405 nm) and green (530 nm) light irradiation. Moreover, the new AAP-NI derivatives display an intense fluorescence at around 525 nm, which is attributed to the 1,8-naphthalimide fluorophore. With a collection of metal ions, the sensing potential of the AAP-NI based fluorescent molecules was also studied. The observations following this series of testing reveal that this AAP-NI compound shows selective and sensitive sensing of Cu2+. In the presence of Cu2+ ions, the AAP-NI experienced significant fluorescence quenching and underwent a color change from orange-yellow to a bright green due to the paramagnetic nature of copper (II). As such, this novel compound could act as a highly selective colorimetric sensor for detecting the presence or absence of Cu2+ ions. In this respect, a sensor that detects Cu2+ could be used to alert that there is an unregulated concentration of copper (II) in the body. Since oxidative stress is known to onset the development of Alzheimer’s or Parkinson’s Disease, detection with this sensor may increase chances of these neurodegenerative diseases being caught, diagnosed, and treated early on.