Perylene bis-n-dodecyl diimide is found to quench fluorescenc emissions of naphthalene, phenanthrene and dihydrocarbazolocarbazole molecules at rates of 4.4 x 10(11), 2.8 x 10(12) and 2.5 x 10(4) M-1 sec(-1), in respective order of aromaticity. These unusulally high rates of fluorecence quenchings are attributed to Perrin model static quenching and presence of electron transfer through singlet excited state of perylene diimide. Calculated free energy of electron transfer, Delta G(ET)=-120.5 kJ/mol, between perylene diimide and dihydro carbazolocarbazole is taken as evidence for observation of high fluorescence quenching rate for carbazolocarbazole molecule.