Structure-switching ML Ir(iii) coordination cages with photo-isomerising azo-aromatic linkers.

Cyclotriguaiacylene has been functionalised with 3- or 4-pyridyl-azo-phenyl groups to form a series of molecular hosts with three azobenzene-type groups that exhibit reversible photo-isomerisation. Reaction of the host molecules with [Ir(C^N)(NCMe)] where C^N is the cyclometallating 2-phenylpyridinato, 2-(4-methylphenyl)pyridinato or 2-(4,5,6-trifluorophenyl)pyridinato results in the self-assembly of a family of five different [{Ir(C^N)}(L)] coordination cages. Photo-irradiation of each of the cages with a high energy laser results in → photo-isomerisation of the pyridyl-azo-phenyl groups with up to 40% of groups isomerising.

Homochiral Self-Sorted and Emissive Ir Metallo-Cryptophanes.

The racemic ligands (±)-tris(isonicotinoyl)-cyclotriguaiacylene (L1), or (±)-tris(4-pyridyl-methyl)-cyclotriguaiacylene (L2) assemble with racemic (Λ,Δ)-[Ir(ppy) (MeCN) ] , in which ppy=2-phenylpyridinato, to form [{Ir(ppy) } (L) ] metallo-cryptophane cages. The crystal structure of [{Ir(ppy) } (L1) ]⋅3BF 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.