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
{[Co2(TTFTB)­(2,2′-Bpy)2­(H2O)2]·DMF·2H2O}n (1), {[Co2(TTFTB)­(4,4′-Bpy)­(H2O)6]·DMF}n (2), {[Cd­(H2TTFTB)­(Bpea)­(H2O)2]·DMF·3H2O}n (3), and {[Ba­(H2TTFTB)­(H2O)2]·DMF·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 (44.62)2­(48.64.816). The solid-state
electrochemical properties and gas adsorption behaviors of 3 and 4 were subsequently investigated. Due to the incorporation
of π-electron conjugated TTF rings into porous metal–organic
frameworks, complexes 3 and 4 exhibit two
reversible oxidation processes and adsorption selectivity for CO2 over N2. These compounds enrich the study of redox-active
porous materials.