Intermolecular energy transfer in rigid matrices at 77 K. Part 1.—Quenching of triphenylene phosphorescence by aquated terpositive lanthanide ions

Abstract

Electronic energy transfer from the lowest triplet state of triphenylene to the terpositive aquated lanthanide ions, Pr³⁺, Nd³⁺, Sm³⁺, Er³⁺ and Tm³⁺ in alcohol glasses at 77 K was investigated. On the basis of spectral overlap calculations and the fitting of the observed donor phosphorescence decays to the decay functions predicted for exchange and multipolar transfer mechanisms it was found that exchange is the dominant transfer mechanism. The average Bohr radii and critical radii for these systems were evaluated. A discussion is given which relates the average Bohr radii to the lanthanide contraction, the nephelauxetic effect, the 2p, 3d or 4ƒ nature of the interacting orbitals, and the spin degeneracies of the associated states. The critical radii for these systems were found to be, for the most part, independent of quencher. The effect of making allowance for the finite volume of the donor and acceptor molecules was also investigated, and was found to be unimportant in the systems studied; reasons for this are suggested.