It is still remained as a big challenge to modulate the structures of supramolecular architectures in spite of tremendous researches on supramolecular chemistry. The coordination-driven self-assembly of metal ions with electron donating groups such as pyridine has been considered as one of most convenient methods. However, the assembly is reversible and researches have tried to use more strong interactions for the formation of concrete supramolecules. Herein, we used the bridging mode of tetrazolyl groups which bind two half sandwich Ir complexes. They provided stronger bonds toward Ir metal centers and the ligands containing multiple tetrazoles could modulate the structures of supramolecular assemblies by changing the numbers and the positions of tetrazole ligands.
In this study, we synthesized Ir(Ⅲ) supramolecules from 1,2-, 1,3-ditetrazolyl benzene and 1,3,5-tritetrazolyl benzene via bridge-driven self-assembly. These complexes were characterized by IR, 1H NMR, 13C NMR, Electrospray ionization mass spectrometry. Their solid state structures were also confirmed by single crystal X-ray diffraction study. The types of tetrazolyl ligands highly influence to the assemblies of Ir supramolecules, producing different architectures such as the rectangle, truncated trigonal pyramid, truncated tetrahedron. The rectangular structure was obtained from the reaction of 1,2-ditetrazolyl benzene, [Cp*IrCl2]2, AgOTf in molar ratio of 1:1:3. By changing 1,2-ditetrazolyl benzene to 1,3-one, truncated trigonal pyramidal hexa-iridium supramolecule was obtained. Even more interesting truncated tetrahedral structure was achieved by the reaction of 1,3,5-tritetrazolyl benzene, [Cp*IrCl2]2, AgOTf in molar ratio of 2:3:9. This bridge-driven self-assembly concept provides a simple new strategy and can be used in the various homo- or hetero-metallic three-dimensional self-assemblies.