Supramolecular architectures designed from iridium porphyrins via axial coordination and metal-metal bonded ruthenium corrole homodimers

Abstract

Unprecedent luminescent Iridium macrocycles, including the [n+n] type macrocycle, the tetranuclear [2+2] macrocycle and the hexanuclear [3+3] macrocycle were constructed stepwisely by metal-ligand interaction at the axial position of IrIIIttp. By reaction of IrIIIttp(CO)Cl with diverse organic phenyl linkers(Ar), dinuclear Irttp complexes were obtained initially as the building blocks. Then these five-coordinated iridium complexes could further self-assemble with bidentate diisocyanide ligands via the vacant axial coordination site of Irttp, giving rise to the formation of a series of supramolecular neutral macrocycle. The results showed that the dimension of theses supramolecules could vary notably by subtle modification of the organic linkers. All the metal complexes were well characterized by 1H NMR, MS and elemental analysis. Moreover, the photophysical studies exhibited that these neutral iridium metallamacrocycles displayed phosphorescent emission in the near-infrared region with quantum yield around 2% and microsecond emission lifetime.

The construction of supramolecular configurations from luninescent 2D iridium macrocycle to 3D iridium cages was achieved by carefully design of building blocks. Compared to phenyl groups, alkyl chains are much more flexible to adjust in the process of supramolecular self-assembly. Herein, alkyl chains were linked directly to the axial position of IrIIIttp, affording dinuclear and trinuclear five-coordinated iridium complexes. Vacant coordinating sites existing at the axial position of IrIIIttp drove the further self-assembly possible. Finally, the combination of dinuclear iridium complex with diisocyanide ligand gave rise to a tetranuclear macrocycle; while the self-assembly between tridentate iridium complexes and the flexible bipyridine ligand lead to the formation of hexanuclear cages. From the theoretic study, cage 4.3c adopted distorted trigonal bipyramidal structure with inner cavity of 3800 Å3. In addition, both the 2D macrocycle and 3D cages were phosphorescent emissive with emission λmax ranging from 711 to 733nm. Moreover, it was found that the subtle change of axial ligans on IrIIIttp could affect the photophysical properties obviously. A series of novel and air-stable metal-metal bonded ruthenium corrole homodimers were synthesized. All the metal complexes were well characterized by 1H NMR, mass spectrometry and elemental analysis. Moreover, their uv-vis and electrochemical properties were studied. Revealed by the single crystal x-ray analysis, the Ru-Ru bond distance in these homodimers is in the range of 2.1802-2.1844 Å, indicating the triple metal-metal bonding property. High resolution ESI-MS characterization revealed that the homodimer with two –OH units could polymerize based on the hydrogen bonding, the interaction of which could be easily viewed from single crystal structure. In addition, in the presence of Ru corrole homodimers, cyclopropanation of styrene with EDA and N–H insertion of aryl amines with EDA could be realized in mild condition.