Pt–S Bond-Enabled Temperature-Dependent Phosphorescence in S-Heteroaryl Tetradentate Pt(S^C^N^O) Complexes

This study presents the rare examples of S-heteroaryl tetradentate Pt(S^C^N^O) luminescent complexes ( PtSZ and PtSZtBu ) containing a Pt–S bond. The presence of the Pt–S bond allows the novel Pt(S^C^N^O) complexes to exhibit temperature-dependent phosphorescent emission behavior. The PtSZtBu exhibits dual-emission phenomena and biexponential transient decay spectra above 250 K, indicating the presence of two minimal excited states in the potential energy surface (PES) of the T 1 state. Through complementary experimental and computational studies, we have identified changes in orbital composition between Pt(d xy )–S(p x ) and Pt(d yz )–S(p z ) in excited states with increasing temperature. This results in two energy minima, enabling the excited states to decay selectively and radiatively at different temperatures. Consequently, this leads to remarkable steady-state and transient emission spectra changes. Our work not only provides valuable insights for the development of novel Pt–S bond-based tetradentate Pt(II) complexes but also enhances our understanding of the distinctive properties governed by the Pt–S bond.