Chemiluminescence behavior of fluorescent aromatics tethered 9-methylidene-10-methylacridans involving chemiluminescence resonance energy transfer (CRET) quenching

The chemiluminescence (CL) behavior, observed in the singlet oxygenation of three fluorescent aromatics tethered 9-methylidene-10-methylacridans bearing the pyrene, perylene, and stilbene moieties, was investigated. The CL spectrum of 9-(perylen-3′-ylidene)-10-methylacridan displayed a red-shifted emission different from the fluorescent products, while 9-(pyren-1′-ylidene)-10-methylacridan and 9-(4′-styrylbenzylidene)-10-methylacridan produced very weak CLs. A chemiluminescence resonance energy transfer (CRET) quenching of the excited aromatic aldehydes by the acridans remaining as the unreacted reactants was found to result in these unexpected CL behaviors.