Back electron transfer in electron-exchange chemiluminescence of oxyaryl-substituted spiroadamantyl dioxetane, an analog of firefly bioluminescence

The viscosity dependence of the excitation yield of the singlet oxybenzoate anion, an emitter of electron-exchange chemiluminescence of oxyaryl-substi tuted spiroadamantyl dioxetane. a chemical analog of firefly bioluminescenc e, was studied. At 299 K the excitation yield increases from 8 to 23% as th e content of diphenylmethane in its mixture with benzene increases to 97%. This effect was quantitatively interpreted in terms of a probabilistic mode l of the solvent-cage effect, assuming that the chemiexcitation results fro m the back electron transfer between the products of chemically initiated d ecomposition of the starting reagent.