DIPOLE FORBIDDEN ENERGY-TRANSFER BETWEEN HOST AND GUEST IN FLUORENE - DIZENZOFURAN MIXED-CRYSTALS

Energy transfer from fluorene host to dizenzofuran guest singlet states has been investigated at 1.3 K. By polarized fluorescence measurements after host and selective guest excitation the transfer efficiency has been found to be about two orders of magnitude smaller than in mixed crystals so far investigated. The reduced efficiency observed in the range of guest concentrations between 0.002% and 2%, can be related to the fact that the S1 ⇌ S0 transition dipoles of host and guest molecules are polarized perpendicular to one another. Energy transfer constants obtained from relative quantum efficiencies of host and guest are explicable in terms of the dipole-dipole interaction. © 1979.