THE MECHANISM OF THE 9,10-DIBROMOANTHRACENE MEDIATED TRIPLET-SINGLET ENERGY TRANSFER IN THE TETRAMETHYL-1,2-DIOXETANE ENERGIZED RUBRENE LUMINESCENCE*

Abstract— The ternary chemiluminescent system consisting of tetramethyl-dioxetane (TMD), 9 ,10-dibromoanthracene (DBA) and rubrene (Ru) has been investigated in benzene solution and in polystyrene matrices. DBA has been found to mediate the energy transfer between excited triplet acetone (³K), generated from TMD, and rubrene resulting in the enhancement of the Ru emission and reduction in the DBA emission. A detailed kinetic analysis confirms that ca. 50% of the enhanced chemilumines-cence involves triplet-singlet (TS) energy transfer from ³K to DBA, followed by singlet-singlet (SS) energy transfer from DBA to Ru, the remainder ca. 50% being due to reabsorption of DBA fluorescence by rubrene. It is concluded that the TS energy transfer is of the resonance type, occurring with a rate of k^TS_K.DBA= (1.4 ± 0.4) ± 10⁹M^-1s^-1 and an efficiency of ø^TS_K.DBA= 0.3 ± 0.1. As expected, the SS energy transfer is also of the resonance type, taking place at comparable rates in benzene solution and in polystyrene matrices, is. k^SS_DBARU= 1.5 ± 10¹⁰ M^-1 and (2.2 ± 0.2) ± 10¹⁰M^-1s^-1, respectively.