New chemiluminescent compounds, stable in aqueous buffers, for use in biological assaying include acridane-based compounds and 1,2-dioxetanes. Among the new acridane-based compounds are water-soluble acridanes, enhancer coupled acridanes, bis and tris-acridanes as well as acridane-1,2-dioxetanes. Among the new 1,2-dioxetanes are electron deficient group-containing dioxetanes and tethered bis-1,2-dioxetanes. The 1,2-dioxetanes are useful as substrates for various enzymes. The acridanes can be admixed with an oxidizing agent. an aqueous buffer and, optionally, a stabilizer to form a substrate or reagent formulation useful for assaying, inter alia, HRP.