Laser-pulsed phosphorescence studies of the distance dependence for triplet–triplet energy transfer

Publisher Website
Google Scholar
Abstract
The distance dependence for the rate of triplet–triplet energy transfer between aromatic chromophores is established from time‐dependent phosphorescence measurements. The phosphorescence decay of carbazole which serves as the energy donor is followed as a function of time in the presence of increasing concentrations of naphthalene (acceptor) in a rigid glass of 2:1 (v/v) ethanol–diethyl ether at 77 °K. A 10 nsec pulse at 337 nm from a N2 laser is used to selectively excite the donor. The nonexponential phosphorescence decays of the donor in the presence of acceptor can be interpreted in terms of an exponential (Dexter) variation of the rate of triplet–triplet energy transfer with intermolecular separation. Interpretation of the distance dependence for transfer in terms of donor–acceptor wavefunction overlap emphasizes the extension of molecular wavefunctions from the nuclei resulting in transfer over distances of greater than 10 Å. Transfer over these distances with the efficiencies observed can be understood in terms of a decrease in the effective nuclear charge of the carbon atoms of the donor and acceptor to a value of +1.0.