Synthesis and complexation behavior of N-(1-naphthylmethyl)-1,4,7,10,13-pentaoxa-16-azacyclooctadecane.

A fluorescent photoinduced electron transfer (PET) sensor (3) that consists of 1-aza-18-crown-6 and a 1-naphthyl pendant shows a fluorescent increase with bivalent metal ions and a fluorescent decrease with monovalent metal ions. (1)H and (13)C NMR analyses of this 1:1 complexation behavior revealed that Ba(2+) strongly coordinates with the azacrown nitrogen to cause a dramatic decrease in the intramolecular charge-transfer character. In addition, it was suggested that not only the metal ion-dependent coordinated structure of the resulting complex but also the interaction between the thiocyanate anion and the naphthyl group play a role in controlling the extent of the emission-intensity increase and decrease that was observed in the presence of a given metal salt.