FLUORESCENCE QUENCHING OF N,(N)OVER-BAR-BIS(2,5-DI-TERT-BUTYLPHENYL)-3,4-9,10-PERYLENEBIS(DICARBOXIMIDE) (DBPI) BY CO2+ ION

Energy transfer from the singlet excited state of DBPI (N, NBAR-bis(2,5-di-tert-butylphenyl)-3,4:9,10-perylenebis(dicarboximide)) dye to Co2+ ions as acceptor has been studied in methanol, ethylene glycol and glycerol as well as in anionic and cationic micelles by steady state emission measurements. It was found that the bimolecular quenching rate constant k(q) is viscosity and temperature dependent' An increase in k(q) by a factor of 3.4 is observed on using glycerol instead of methanol. This is accompanied by a decrease in the diffusion rate constant k(d) by a factor of about 1.6 x 10-(3). This is a clear indication of a Forster-type long-range energy transfer mechanism in viscous media. The experimental critical transfer distances R0 have been calculated as 14, 19 and 17 angstrom in methanol, ethylene glycol and glycerol respectively. It was also found that the fluorescence quenching increases with increasing SDS (sodium dodecyl sulphate) concentration but decreases with increasing CTAC (cetyltrimethylammonium chloride) concentration in aqueous media.