Crystal Structures, Gas Adsorption, and Electrochemical Properties of Electroactive Coordination Polymers Based on the Tetrathiafulvalene-Tetrabenzoate Ligand

Four new polymeric metal compounds based on the redox-active tetrathiafulvalene-tetrabenzoate ligand and different divalent cations (Co(II), Cd(II), Ba(II)), including {[Co-2(TTFTB)(2,2'-Bpy)(2)(H2O)(2)]center dot DMF center dot 2H(2)O}(n) (1), {[Co-2(TTFTB)(4,4'-Bpy)(H2O)(6)]center dot DMF}(n) (2), {[Cd(H2TTFTB)(Bpea)(H2O)(2)]center dot DMF center dot 3H(2)O}(n) (3), and {[Ba(H2TTFTB)(H2O)(2)]center dot DMF center dot C2H5OH}(n) (4) (2,2'-Bpy = 2,2'-bipyridine, 4,4'-Bpy = 4,4'-bipyridine, Bpea = 1,2-bis(4-pyridyl)ethane), were synthesized and characterized. The versatile redox-active tetracarboxylate ligand was coordinated to divalent metal ions in a multidentate fashion, forming different structures for complexes 1-4. Complex 1 exhibits a one-dimensional chain structure, whereas the 3-fold interpenetrating 3,4L13 net was observed in complex 2. Importantly, complex 3 displays a (3,8)-connected tfz-d net and complex 4 features a new (4,8)-connected three-dimensional topological network with a point symbol of ((4)4.6(2))(2)(4(8).6(4).8(16)). The solid-state electrochemical properties and gas adsorption behaviors of 3 and 4 were subsequently investigated. Due to the incorporation of pi-electron conjugated TTF rings into porous metal-organic frameworks, complexes 3 and 4 exhibit two reversible oxidation processes and adsorption selectivity for CO2 over N-2. These compounds enrich the study of redox-active porous materials.