Selective and Sensitive Fluorescent Chemosensors for Cu2＋ Ion Based upon Bis-1,8-naphthalimide Dyads

A series of new fluorescent chemosensors 5a--5e, composed of two aminonaphthalimide fluorophores and 2,6-bis（（N-aminoalkyl）aminocarboxy）pyridines, were prepared, characterized, and their fluorescent properties to- wards heavy and transition metal （HTM） ions were investigated. Chemosensors 5e--Se exhibited high selectivity and sensitivity for Cu2＋ ion over other HTM ions with fluorescent quenching （green to colourless）. It clearly demonstrated that the length of the linkers （diamines） between the aminonaphthalimides and 2,6-dicarboxypyridine of 5a--Se was very important for their sensitivity and selectivity for Cu2~ ion over other HTM ions.