Synthesis and Structural characterization of half-sandwich iridium macro-metallacycles containing 1,5-dihydroxy-9,10- anthraquinone ligand

Treatment of binuclear complex [Cp*2Ir2(μ-dhaq)Cl2] (H2dhaq = 1,5-dihydroxy-9,10-anthraquinone) with pyrazine or bifuncational pyridyl-based ligands (4,4′-bipyridine (bpy), E-1,2-bis(4′-pyridyl)ethene (bpe), and 2,5-bis(4′-pyridyl)- 1,3,4-oxadiazole (bpo)) in the presence of AgOTf (OTf = CF3SO3) in CH3OH, gave the corresponding tetranuclear complexes, with a general formula of [Cp*4Ir4(μ-dhaq)2(μ-L)2](OTf)4 (2a–2d), respectively. The molecular structure of [Cp*4Ir4(μ-dhaq)2(μ-pyrazine)2](OTf)4 (2a) has been determined by single-crystal X-ray analysis, revealing that the metal centers were connected by pyrazine and bis-bidentate dhaq2− ligands to construct a “slope” rectangular cavity with the dimension of 7.4 × 8.8 × 6.9 Å. 2a also exhibited unique properties in host–guest behavior.

Graphical abstractBinuclear complex [Cp*2Ir2(μ-dhaq)Cl2] (1) and tetranuclear complexes [Cp*4Ir4(μ-dhaq)2(μ-L)2](OTf)4 (2a–2d) (L = pyrazine, 4,4′-bipyridine, E-1,2-bis(4′-pyridyl)ethene and 2,5-bis(4′-pyridyl)-1,3,4-oxadiazole) are reported. Crystal structure and host–guest behavior of 2a have been investigated.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Novel half-sandwich iridium metallarectangles were synthesized. ► Structure of these metallarectangles was confirmed by X-ray crystallography. ► Such metallarectangles could display interesting host–guest properties.