Bicyclic dioxetanes bearing an inden-2-yl or a benzo(b)thiazol-2-yl moiety as a CIEEL-active chemiluminescent substrate emitting red light.

Bicyclic dioxetanes bearing 5-(t-butyldimethylsiloxy)inden-2-yl, 3, or 5-(t-butyldimethylsiloxy)benzo(b)thiazol-2-yl, 4, were synthesized. On treatment with large excess of tetrabutylammonium fluoride in DMSO, dioxetane, 3, decomposed rapidly with accompanying emission of red (vermilion) light (lambda(max) (CL) = 637 nm). Comparing the chemiluminescent properties for 3 with those for related dioxetane, 1, in which pi-conjugation system is not fixed in plane, both CIEEL-decay rate and chemiluminescent efficiency were found to be improved for 3. Chemiluminescent decomposition of dioxetane, 4, was similarly induced to emit crimson light (lambda(max) (CL) = 725 nm), though the chemiluminescent efficiency was low.