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⩽T⩽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 3MLCT term of 3(Ir5d-ppyπ*) character. The energy separations and decay times are ΔEII,I=13.5 cm−1, ΔEIII,I=83 cm−1 and τI=145 μs, τII=11 μs, τIII=750 ns. All three substates are involved in the emission process at 300 K resulting in an average decay time of 2.1 μs. 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.