Elastic and bright assembly-induced luminescent crystals of platinum() complexes with near-unity emission quantum yield

Molecular crystals of Pt( ii ) complexes with metallophilic interactions can provide bright assembly-induced luminescence with colour tunability. However, the brittleness of many of these crystals makes their application in flexible optical materials difficult. Herein, we have achieved the elastic deformation of crystals of polyhalogenated Pt( ii ) complexes exhibiting bright assembly-induced luminescence. A crystal of [Pt(bpic)(dFppy)] (Hbpic = 5-bromopicolinic acid, HdFppy = 2-(2,4-difluorophenyl)pyridine) and a co-crystal of [Pt(bpic)(dFppy)] and [Pt(bpic)(ppy)] (Hppy = 2-phenylpyridine) were found to exhibit significant elastic deformation due to their highly anisotropic interaction topologies. While the crystal of [Pt(bpic)(dFppy)] exhibited monomer-based ligand-centred 3 ππ* emission with an emission quantum yield of 0.40, the co-crystal exhibited bright, triplet metal-metal-to-ligand charge transfer ( 3 MMLCT) emission owing to Pt Pt interactions, thereby achieving a significantly higher emission quantum yield of 0.94. Molecular crystals composed of platinum( ii ) complexes exhibited elastic deformation without cracking and bright assembly-induced emission with an extremely high emission quantum yield of 0.94.