Self-assembly directed by C–H activation: Synthesis and characterization of [(Cp∗Ir)2(R–NC–Ph–CNR)]2(4,4-bipyridine)2·(OTf)4 (R = Ph, Me)

Self-assembly of a novel class of bis-imine-cyclometalated macrocycles [(Cp∗Ir)2(Ph–NC–Ph–CN–Ph)]2(4,4′-bipyridine)2·(OTf)4 (3a) and [(Cp∗Ir)2(Me–NC–Ph–CN–Me)]2(4,4′-bipyridine)2·(OTf)4 (3b) was directed by double-site C–H activations of aromatic bis-imine substrates. Two synthetic routes were established, using either (i) binuclear cyclometalated complexes (Cp∗Ir)2L1Cl2 (1a) and (Cp∗Ir)2L2Cl2 (1b) or (ii)4,4′-bipyridine(bpy)-bridged complex (Cp∗IrCl2)2(bpy) (2) as starting materials. All the products were characterized by IR, 1H NMR and EA. Isomers were found in macrocyclic complexes, which were thermodynamically stable from reversible transformation in days. Highly robust structure of the cyclometalated macrocycles was indicated by the existence of stable isomer pairs. One isomer of 3b was determined by single-crystal X-ray diffraction. It was a rare case for half-sandwich metallosupramolecular macrocycles that weak interactions between macrocycles and OTf ions were fully captured in detail, and were demonstrated to be essential for the maintenance of tunnel structures of macrocycles in crystal packing.

Graphical abstractA novel class of bis-imine-cyclometalated macrocycles [(Cp∗Ir)2Ph–NC–Ph–CN–Ph]2(4,4′-bipyridine)2·(OTf)4 and [(Cp∗Ir)2Me–NC–Ph–C=N–Me]2(4,4′-bipyridine)2·(OTf)4 was constructed. Isomers were found in solution. 1-Dimensional extended tunnel was observed in crystal stacking of 3b.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Assembly of bis-imine-cyclometalated macrocycles was directed by C-H activation. ► Thermodynamically stable isomers of macrocycles were captured. ► Weak interactions between cyclic cation and counter anion were characterized.