Dual-Emissive Platinum(II) Metallacycles with Thiophene-Containing Bisacetylide Ligands

Three cis-diphosphino Pt(II) metallacycles with thiophene-containing bisacetylide ligands were synthesized and their absorption and emission properties examined. These properties are explained by DFT and TD-DFT analysis of ground-state as well as singlet- and triplet-state energies and geometries. Two of the metallacycles show room-temperature dual emission (fluorescence and phosphorescence) with different intensity ratios. Replacing the phenylene or ethynylene groups with thiophene rings in the bisacetylide ligand of the metallacycles results in modulation of the S-1 and T-1 states to show stronger fluorescence and weaker phosphorescence. More rigid and planar metallacycles suffer less from energy loss due to smaller degrees of structural reorganization and thermal deactivation. These are important factors to consider when designing single-component dual-emissive materials for applications such as white-emitting OLEDs, self-referencing oxygen sensors, and hypoxia contrast agents.