Elastic and bright assembly-induced luminescent crystals of platinum(ii) 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)pi pi* emission with an emission quantum yield of 0.40, the co-crystal exhibited bright, triplet metal-metal-to-ligand charge transfer ((MMLCT)-M-3) emission owing to PtMIDLINE HORIZONTAL ELLIPSISPt interactions, thereby achieving a significantly higher emission quantum yield of 0.94.

Automated summary

Molecular crystals of Pt(ii) complexes with metallophilic interactions can exhibit bright assembly-induced luminescence with colour tunability. However, their brittleness hinders their application in flexible optical materials. In this study, the elastic deformation of crystals of polyhalogenated Pt(ii) complexes was achieved, resulting in bright luminescence. The crystal of [Pt(bpic)(dFppy)] showed ligand-centred emission, while the co-crystal of [Pt(bpic)(dFppy)] and [Pt(bpic)(ppy)] exhibited metal-metal-to-ligand charge transfer emission with a significantly higher emission quantum yield.