An investigation of energy transfer between coumarin 35 and xanthene derivatives in liquid medium

The energy transfer between coumarin 35 (C35) and pyronin compounds, which are xanthene derivatives, i.e. pyronin B (PyB) and pyronin Y (PyY), in methanol was investigated at room temperature by using steady-state absorption, emission, and time-resolved fluorescence spectroscopy. Fluorescence energy transfer rate constants (k_T ) and critical radius (R_0) were determined for C35-PyB and C35-PyY molecular pairs in methanol. The obtained values of kT and R_0 indicated that the dipole-dipole interaction between C35-PyB and C35-PyY molecular pairs accounted for the energy transfer mechanism. The energy transfer efficiency and the distance between the donor and acceptor (r) were also calculated for donor-acceptor pairs using Forster’s theory.