Chemiexcitation efficiency for the charge-transfer-induced chemiluminescent decomposition of 3-hydroxyphenyl-substituted dioxetanes in an aqueous system

The decomposition of 3-oxyphenyl-3-methoxy-4-(2′-spiroadamantane)-1,2-dioxetane (A) and 5-tert-butyl-4,4-dimethyl-1-(3-oxyphenyl)bicyclo[3.2.0]heptane (B) in NaOH/H2O gives light in poor yield, which is several orders of magnitude lower than that in aprotic solvents. To understand the poor chemiluminescence efficiency in NaOH/H2O, we investigated the behaviors of the authentic emitters, methyl 3-oxidobenzoate (C) and 2,2,4,4-tetramethyl-3-oxopentyl 3-oxidobenzoate (D). We found that D was weakly fluorescent though hydrolyzed in NaOH/H2O, and estimated that the singlet-chemiexcitation efficiency ΦS was 6.1×10−3 for the decomposition of B in NaOH/H2O. On the other hand, ΦS for A could not be estimated, since C was hydrolyzed too rapidly to observe its fluorescence.