Synthesis and optical characterization of novel azacrown ethers containing an acridinone or an N-methylacridinone unit as potential fluorescent chemosensors

Four new achiral and four new chiral monoazacrown ethers containing an acridinone or an N-methylacridinone fluorescent signalling unit were prepared by reacting chloromethyl-substituted acridinone derivatives with achiral monoazacrown ethers with different cavity sizes and enantiopure monoaza-18-crown-6 ethers having two methyl and two isobutyl groups on their chiral centres, respectively. The operation of these chemosensors is based on the photoinduced electron transfer (PET) process, thus they show fluorescence enhancement in the presence of cationic guests. Their fluorescent behaviour as well as their complexation properties towards selected metal ions and the enantiomers of α-(1-naphthyl)ethylammonium perchlorate and potassium mandelate were examined.