Photophysical properties of Re(pbt)(CO)₄ studied by high resolution spectroscopy

Abstract

Photophysical properties of Re(pbt)(CO)₄ are investigated at cryogenic temperatures and high magnetic fields. The highly resolved spectra show that the zero field splitting of the lowest triplet T₁ into three substates is smaller than 2 cm⁻¹. With this result, the T₁ state can be classified as only slightly MLCT-perturbed ³LC (³ππ*) state. Consistently, spin-lattice relaxation times are slow at T = 1.2 K and emission decay times with τ(I) = 960 μs, τ(II) = 320 μs, and τ(III) = 24 μs are long due to only small singlet admixtures. The vibrational satellite structures observed reflect different vibrational deactivation mechanisms and reveal similar geometries of the emitting triplet and the ground state.