Light induced exchange energy transfer reactions of micelle forming Ru(II) diimine complexes

Abstract

Photoinduced energy transfer from two surfactant Ru(II) diimine complexes of the type [(bpy) 2Ru(L)] 2+ (L=4-methyl-4′-heptadecyl-2,2′-bipyridine and 4,4′-diheptadecyl-2,2′-bipyridine) to anthracene-9-carboxylate (ANC) was investigated in aqueous solutions of the complexes. The luminescence quenching behavior of both complexes is strongly dependent on the complex concentration in solution and the ionic strength of the solution. The complexes exhibit a 20 nm red shift of the emission maximum upon micelle formation; the emission spectral changes illustrate the dependence of the critical micelle concentration (cmc) on the solution ionic strength. The quenching of the micellized complexes by ANC is dramatically enhanced relative to the complex in the aqueous phase. The dynamics of exchange energy transfer quenching of the micellized complex can be evaluated assuming a Poisson distribution of ANC quenchers among the micellized complex. The 3[ANC] formed in the quenching process can escape the micelle and react by electron transfer quenching with methyl viologen in the aqueous phase.