An Aza‐12‐crown‐4 Ether‐Substituted Naphthalene Diimide Chemosensor for the Detection of Lithium Ion

We synthesised aza‐12‐crown‐4 ether‐substituted naphthalene diimide (NDI‐12‐C‐4) and demonstrated its properties as an fluorescent and colorimetric sensor. The NDI‐12‐C‐4 uses the aza‐12‐crown‐4 moiety to bind Li + ion selectively over larger monovalent cation such as Cs + , Na + and K + . The sensor is chemically stable due to the crown‐ether, and the appended NDI fluorophore allows leads to optical changes exclusively for the monovalent Li + ion. UV–vis absorption, fluorescence, cyclic voltammetry (CV), 1H NMR and naked eye‐detection clearly demonstrate selective, sensitive binding of Li + ion with a detection limit of 5.0 μM. Importantly, reversible binding of Li + by NDI‐12‐C‐4 was also observed upon addition of EDTA, after which the sensor could be recovered via simple centrifugation, indicating suitability for use in a biological sensor device.