Homochiral Self-Sorted and Emissive IrIII Metallo-Cryptophanes

Abstract

The racemic ligands (±)-tris(isonicotinoyl)-cyclotriguaiacylene (L1), or (±)-tris(4-pyridyl-methyl)-cyclotriguaiacylene (L2) assemble with racemic (Λ,Δ)-[Ir(ppy)2(MeCN)2]+, in which ppy=2-phenylpyridinato, to form [{Ir(ppy)2}3(L)2]3+ metallo-cryptophane cages. The crystal structure of [{Ir(ppy)2}3(L1)2]⋅3BF4 has MM-ΛΛΛ and PP-ΔΔΔ isomers, and homochiral self-sorting occurs in solution, a process accelerated by a chiral guest. Self-recognition between L1 and L2 within cages does not occur, and cages show very slow ligand exchange. Both cages are phosphorescent, with [{Ir(ppy)2}3(L2)2]3+ having enhanced and blue-shifted emission when compared with [{Ir(ppy)2}3(L1)2]3+.