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Paper | Regular issue | Vol 45, No. 12, 1997, pp.2365-2379
Published online, 1st January, 1970
DOI: 10.3987/COM-97-7944
Synthesis and Complexation Behavior of N,N'-Bis(1-naphthylmethyl)-1,4,10,13-tetraoxa-7,16-diazacyclooctadecane

Kanji Kubo,* Ryoichi Ishige, Nobuo Kato, Emi Yamamoto, and Tadamitsu Sakurai

*Department of Applied Chemistry, Faculty of Engineering, Kanagawa University, 3-27-1 Rokkakubashi, Kanagawa-ku, Yokohama 221-8686, Japan


N,N’-Bis(1-naphthylmethyl)-4,13-diaza-18-crown-6 ether (2) gave intramolecular exciplex fluorescence, showing that the excited naphthalene chromophore was quenched by the azacrown unit. The azacrown ether (2) was found to display unique photophysical properties in the presence of metal salts. Complexation of 2 with Ba2+ increased the fluorescence intensity of the host by a factor of 40. 1H and 13C NMR analyses of this 1:1 complexation behavior revealed that Ba2+ strongly coordinates with the azacrown nitrogen to cause a dramatic decrease in an 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 exchange rate between the free host (2) and its complex with metal ions play a role in controlling the extent of the emission-intensity enhancement that was observed in the presence of a given metal ion.