Magnetic field effects on the phosphorescence of Pt(4,6-dFppy)(acac) – Tunability of the vibrational satellite structure

Effects of high magnetic fields on the properties of the lowest triplet state of the OLED emitter Pt(4,6-dFppy)(acac) are studied by site-selective high-resolution optical spectroscopy. Application of high fields strongly alters the pattern and magnitude of splitting of the triplet term, the oscillator strengths of the purely electronic 0–0 transitions between the T1 substates and the singlet ground state, and the vibrational satellite structures. In particular, the mechanism of radiative vibrational deactivation of the lowest triplet substate I changes with increasing field from a vibronically induced (Herzberg–Teller) to a Franck–Condon induced mechanism.