Chemiexcitation Acceleration of 1,2-Dioxetanes by Spiro-Fused Six-Member Rings with Electron-Withdrawing Motifs

The chemiluminescent light-emission pathway of phenoxy-1,2-dioxetane luminophores attracts growing interest within the scientific community. Dioxetane probes undergoing rapid flash-type chemiexcitation exhibit higher detection sensitivity than those with a slow glow-type chemiexcitation rate. We discovered that dioxetanes fused to non-strained six-member rings, with hetero atoms or inductive electron-withdrawing groups, present both accelerated chemiexcitation rates and elevated chemical stability compared to dioxetanes fused to four-member strained rings. DFT computational simulations supported the chemiexcitation acceleration observed by spiro-fused six-member rings with inductive electron-withdrawing groups of dioxetanes. Specifically, a spiro-dioxetane with a six-member sulfone ring exhibited a chemiexcitation rate 293-fold faster than that of spiro-adamantyl-dioxetane. A turn-ON dioxetane probe for the detection of the enzyme β-galactosidase, containing the six-member sulfone unit, exhibited a S/N value of 108 in LB cell growth medium. This probe demonstrated a substantial increase in detection sensitivity towards E. coli bacterial cells expressing β-galactosidase, with an LOD value that is 44-fold more sensitive than that obtained by the adamantyl counterpart. The accelerated chemiexcitation and the elevated chemical stability presented by dioxetane containing a spiro-fused six-member ring with a sulfone inductive electron-withdrawing group, make it an ideal candidate for designing efficient turn-on chemiluminescent probes with exceptionally high detection sensitivity.