Benzo-15-crown-5 (2,3,5,6,8,9,11,12-octahydrobenzo[b][1,4,7,10,13]pentaoxacyclopentadecine) and dibenzo-15-crown-5 (6,7,9,10,17,18-hexahydrodibenzo[b,h][1,4,7,10,13]pentaoxacyclopentadecine as fluorescent probes for physiologically important potassium ion

A pictorial representation of two benzo crown ethers assembling together to accommodate a potassium ion to form 2:1 ligand-metal ion complex. The cation is held in the cavity by ion-dipole interactions. The coordination number of the potassium ion is ten. Complexation enhanced fluorescence produced by suppression of PET mechanism is masked by FRET.