Self-assembled half-sandwich Ir, Rh-based organometallic molecular boxes for reversible trapping of halocarbon molecules

Abstract

Reactions of [Cp*MCl(μ-Cl)]₂ (M = Ir or Rh) with 6,11-dihydroxy-5,12-naphthacenedione (H₂DHNA) in the presence of base, gave the corresponding binuclear complexes [Cp*₂M₂(μ-DHNA)Cl₂] (M = Ir (1a); M = Rh (1b)), respectively. Treatment of 1a or 1b with bidentate ligands (L) such as pyrazine, 4,4′-dipyridine (bpy), E-1,2-bis(4-pyridyl)ethene (bpe) or 2,5-bis(4-pyridyl)-1,3,5-oxadiazole (bpo) in the presence of AgOTf (OTf = CF₃SO₃) in CH₃OH, gave the corresponding tetranuclear complexes, general formula [Cp*₄M₄(μ-DHNA)₂(μ-L)₂](OTf)₄ (3a, 4a, 5a, 6a: M = Ir; 3b, 4b, 5b, 6b: M = Rh), respectively. X-Ray analyses of 3a, 3b, 4a, 4b, 5a and 5b revealed that each of the half-sandwich metal centers was connected by pyridyl ligands and bis-bidentate bridging ligands to construct a rectangular cavity with different dimensions, and strong π–π interactions between independent molecules to form rectangular channels in the solid-state. Complexes 3a and 3b based on H₂DHNA and pyrazine spacing ligands were found to exhibit selective and reversible small organic molecules adsorption properties. The example of C–H⋯Cl interactions served as a template by an interacted layer of monomeric complex for the creation of intercalated supramolecular arrays has been studied.