Naphthalimide-based fluorescent ‘turn-off’ probes for palladium ion: structure-activity relationships

Abstract

Palladium is extensively applied in many high-tech industries, but excessive residue in environment is harmful to human. Therefore, it is important to develop effective analysis methods for palladium ion. In this work, six naphthalimide-based fluorescent probes NPA-NPF were synthesized with ethylenediamine derivatives as the receptors. The experimental results show that the probes bearing flexible ethylenediamine exhibited excellent sensitivity and selectivity toward Pd2+, whereas NPC with rigid piperazine as the receptor displayed minimum response to Pd2+. The introduction of biotin and indomethacin enabled NPE and NPF to selectively bioimage Pd2+ in living cancer cells. Job’s plot results revealed that Pd2+ formed 1:1 complex with the probes having one receptor (NPA-NPC) or 2:1 complex with those bearing two receptors (NPD and NPE).