Reversible Intermolecular Energy Transfer between Chromium(III) Complexes in Fluid Solution.

摘要

Excitation energy transfer from Cr(en)3(3+), Cr(NH3)5(NCS)(2+), trans-CR(en)2(NCS)2(+), and cis-Cr(en)2(NCS)2(+) to Cr(CN)6(3-) is observed in room temperature solutions in water, dimethylsulfoxide, or dimethylformamide. The processes were observed by emission intensity measurements and, especially, by lifetime measurements on both the donor and the acceptor emission. The rate of energy transfer is essentially diffusion controlled in all cases and thus not very sensitive to the charge or ligation of the donor. In addition, evidence for reverse excitation energy transfer is presented; the lifetime of Cr(CN)6(3-) emission is dependent on the concentration of the Cr(III) ammine. It is shown that in this type of coupled system a full kinetic analysis is required to obtain correct bimolecular energy transfer rate constants as those obtained from conventional Stern-Volmer plots can be seriously in error. (Author)