METAL-ION DETECTION BY THE MAGNETIC-FIELD-SENSITIVE FLUORESCENCE OF INTRAMOLECULAR EXCIPLEXES CONTAINING AZA-CROWN-ETHER MOIETIES AS ELECTRON-DONOR

Magnetic field effects (MFE) detected by intramolecular exciplex fluor escence have been studied in acetonitrile solutions for new donor-acce ptor compounds in which pyrene is Linked to aza-15-crown ether by a po lymethylene chain with 3, 9, and 16 CH2 units. It was found that addit ion of alkali and alkaline-earth ions to the solutions decreases the o bservable MFE. The longer the chain and the greater the stability cons tants of the aza-crown complexes with metal ions, the more pronounced is the influence of the added metal ions. The data obtained are ration alized on the basis of a kinetic scheme that specifically includes pho toejection of metal ions from the crown-ether complexes, accompanied b y Coulombic interaction of the ions released with the solvent-separate d radical ion pairs, the so-called special salt effect.