Emission of Ir(ppy)3.: Temperature dependence, decay dynamics, and magnetic field properties

Emission spectra and decay times of fac-Ir(ppy)(3) dissolved in THF were registered for 1.2 K less than or equal to T less than or equal to 300 K and magnetic fields (at T = 1.5 K) up to B = 10 T. Three emissive triplet substates I, II, and III could be identified and classified as substates of a (MLCT)-M-3 term of (3)(Ir5d-ppypi*) character. The energy separations and decay times are DeltaE(II.I) = 13.5 cm(-1), DeltaE(III.I) = 83 cm(-1) and tau(I) = 145 mus, tau(II) = 11 mus, tau(III) = 750 ns. All three substates are involved in the emission process at 300 K resulting in an average decay time of 2.1 mus. Magnetic field application at T = 1.5 K alters the dominant radiative deactivation process from a forbidden to a significantly allowed process. The magnetic field-induced change of the emission decay rate can be described by a first-order perturbation approach. (C) 2003 Elsevier B.V. All rights reserved.