Highly phosphorescent organopalladium() complexes with metal-metal-to-ligand charge-transfer excited states in fluid solutions

Dinuclear pincer-type cyclometalated Pd( ii ) complexes with foldable diacetylide ligands show crystallographically determined intramolecular Pd Pd contacts of 3.203-3.380 Å. In deoxygenated fluid solutions, these Pd( ii ) complexes are highly phosphorescent in the red region with emission quantum yields up to 48%, which has been ascribed to metal-metal-to-ligand charge-transfer (MMLCT) excited states in nature. Making Pd( ii ) brightly shining: mononuclear analogues are non-emissive, but folded dinuclear palladium( ii ) diacetylide complexes phosphoresce from MMLCT excited states with quantum yields up to 48%.