Synthesis, photophysical and metal ion signalling behaviour of mono- and di-azacrown derivatives of 4-aminophthalimide

Abstract

Synthesis, photophysical behaviour and metal ion signalling ability of 3-component systems, I and II, comprising a 4-aminophthalimido moiety as fluorophore, a dimethylene spacer and two different azacrown receptors, are reported. The fluorescence quantum yields and lifetimes of both the systems have been found to be significantly lower than that of the parent fluorophore indicating the occurrence of photoinduced electron transfer (PET) between the terminal moieties. PET is found to be more efficient in II, presumably due to the presence of more than one electron-donating centre in the receptor moiety. Fluorescence decay behaviour of the systems suggests a through-space nature of PET. The systems exhibit off-on fluorescence signalling in the aprotic media in the presence of several metal ions, some of which are well known for their fluorescence quenching abilities. Diazacrown derivative, II, appears to be a somewhat better signalling system than the monoazacrown derivative, I.