Hydrogen-bonding effects on the fluorescence versus electron-transfer-initiated chemiluminescence spectra of the m-oxybenzoate ion derived from a bicyclic dioxetane

A comparative spectral study of the fluorescence of the m-oxybenzoate anion versus the electron-transfer-initiated chemiluminescence (CIEEL) of the same anion derived from the bicyclic dioxetanes in various solvents is reported. The present study reveals that the fluorescence of this oxyanion is blue-shifted in protic versus aprotic solvents, while the CIEEL-spectral maximum is independent of the medium. The same phenomenon has been recently observed for the m-oxybenzoate ion derived from CIEEL-active spiroadamantyl dioxetanes. The reported spectral differences between the fluorescence and chemiluminescence emissions cannot be attributed to exciplex formation in the CIEEL process, but result from the differences in hydrogen-bonding effects on the photo- and chemiexcited oxyanion species. The observed solvatochromism is qualitatively rationalized in terms of the semiempirical AM1 calculations.