a dioxetane that includes a fluorescent chromophore spiro - bound at the 4 - carbon of the dioxetane . the dioxetane has the formula ## str1 ## where x is cr 7 r 8 , o , s , or n - r , and each r 1 , r 2 , r 3 , r 4 , r 5 , andr 6 , independently , is h , an electron - withdrawing group , an electron - donating group , heteroaryl , or an enzyme cleavable group , or groups r 1 - r 6 together form a ring , and t is a substituted or unsubstituted aryl , polyaryl , cycloalkylidene or polycycloalkylidene group spiro - bound at the 3 - carbon of the dioxetane . the dioxetane can be decomposed by direct cleavage of the dioxetane 0 -- 0 bond or by cleavage of an enzyme cleavable group bonded to the dioxetane to form a luminescent substance that includes the coumarin portion of the dioxetane . the dioxetanes are used in an assay to detect a member of a specific binding pair or an enzyme .