Design and Synthesis of Highly Photostable Yellow–Green Emitting 1,8-Naphthalimides as Fluorescent Sensors for Metal Cations and Protons

摘要

Abstract Two highly photostable yellow–green emittingud1,8-naphthalimides 5 and 6, containing both N-linkedudhindered amine moiety and a secondary or tertiary cationudreceptor, were synthesized for the first time. Novel compoundsudwere configured as “fluorophore–spacer–receptor”udsystems based on photoinduced electron transfer. Photophysicaludcharacteristics of the dyes were investigated inudDMF and water/DMF (4:1, v/v) solution. The ability of theudnew compounds to detect cations was evaluated by theudchanges in their fluorescence intensity in the presence ofudmetal ions (Cu2+, Pb2+, Zn2+, Ni2+, Co2+) and protons. Theudpresence of metal ions and protons was found to disallow audphotoinduced electron transfer leading to an enhancementudin the dye fluorescence intensity. Compound 5, containingudsecondary amine receptor, displayed a good sensor activityudtowards metal ions and protons. However the sensorudactivity of dye 6, containing a tertiary amine receptor anduda shorter hydrocarbon spacer, was substantially higher. Theudresults obtained indicate the potential of the novel compoundsudas highly photostable and efficient “off–on” pHudswitchers and fluorescent detectors for metal ions withudpronounced selectivity towards Cu2+ ions.