Seminar,G. Calzaferri, D*(0’) + A(0)  D(1) + A*(1’) D*(0’) + A(0)  D(0) + A*(2’) etc. D*(0’) + A(0)  D(2) + A*(0’) The energy transfer rate constant k EnT for electronic excitation energy of the type: k EnT can be expressed by means of Fermi’s golden rule:  is related to the overlap between the emission spectrum of the donor and the absorption spectrum of the acceptor.  = measure of the density of the iner- acting initial D*…A and final D…A* states. Electronic excitation energy transfer. The Förster radius R 0.

Seminar,G. Calzaferri, The formula is correct if the dimension of [J] is chosen to be cm 6 mol -1 For chemists the more natural way to choose the dimension of the spectral overlap integral is: [J] = [cm 3 M -1 ], [M] =[mol L -1 ].

Seminar,G. Calzaferri, At a specific D*….A distance, the rate at which D* emits light is equal to the rate at which it transfers its excitation energy A. At this distance R 0 we can write: From this we find the Förster radius R 0 for electronic excitation energy transfer. Inserting k EnT : Luminescence rate of D*: Energy transfer rate: Förster energy transfer radius R 0

Seminar,G. Calzaferri, Förster radius R 0 for electronic excitation energy transfer: Distance dependence of the energy transfer rate constant: R 0 is equal to the donor- acceptor distance at which the probability for energy transfer is equal to 0.5.

Seminar,G. Calzaferri, Dyes: donor/acceptor J / cm 3 M -1 R 0 / Å  0,D / ns k EnT / ns -1 R=R0R=R0 R=15 Å Ox / Ox4.4× / Py / Py1.1× / Py / Ox2.3× / K. Lutkouskaya, G. Calzaferri J. Phys. Chem. B 2006, 110, 5633

Seminar,G. Calzaferri, The probability P for energy transfer is: cancelling Luminescence rate of D*: Energy transfer rate: FRET

Seminar,G. Calzaferri, D:  = 6; 2D:  = 4, 1D:  = 2

Seminar,G. Calzaferri, ns 0.45 ns 0.89 ns 0.13 ns One-dimensional electronic excitation energy migration C. Minkowski, G. Calzaferri, Angew. Chem. 2005, 44, 5325