Triplet state properties of a red light emitting [Pt(s-thpy)(acac)] compound

A photophysical characterization based on optical high-resolution spectra and emission decay properties at low temperatures and at high magnetic fields is carried out for [Pt(s-thpy)(acac)] (s-thpy = 5,2-bis(2-thienyl)pyridinate and acac = acetylacetonate). The electronic 0–0 transition between the lowest triplet state and the ground state lies at 16 150 cm−1 (619 nm). The zero-field splitting (ZFS) of T1 is smaller than 1 cm−1. Thus, the emitting excited state is mainly of ligand-centered 3LC (3ππ∗) character and experiences only weak spin–orbit couplings to higher lying singlet states. The compound does not fulfill important requirements for OLED applications, but strategies for improvements are pointed out.