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

Abstract

Four new polymeric metal compounds based on the redox-active tetrathiafulvalene-tetrabenzoate ligand and different divalent cations (Co(II), Cd(II), 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 three-fold interpenetrating 3,4L13 net was observed in complex 2. Importantly, complex 3 displays (3,8)-connected tfz-d net and complex 4 features 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 π-electron conjugated TTF rings into porous metal-organic frameworks, complexes 3 and 4 exhibit two reversible oxidation processes and adsorption selectivity for CO 2 over N 2 .These compounds enrich the study of redox-active porous materials.

Novel Topology in Semiconducting Tetrathiafulvalene Lanthanide Metal‐Organic Frameworks

“…Each group of five TTFs consists of two sets of dimers (TTF1 and TTF2) and an orthogonal TTF (TTF3). Though this arrangement contrasts with the parallel π‐stacking modes of other TTFTB MOFs, it is somewhat reminiscent of the κ packing arrangement, consisting of orthogonal TTF dimers, found in many organic metals and superconductors ,. Close S⋅⋅⋅S contacts as short as 3.72 Å are present between all S atoms within the dimers in Tm 6 (TTFTB) 5 .…”

“…Whereas the assembly of most MOFs is driven by the formation of inorganic secondary building units (SBUs), our group has recently shown that the organic ligands can also direct structure through the formation of supramolecular π interactions that define an organic SBU, as demonstrated with the isolation of an unprecedented topology in MIT‐25 . The latter is based on the tetrathiafulvalene tetrabenzoate (TTFTB) linker, which forms MOFs with diverse topologies, all of which exhibit strong π interactions . In addition to their structure‐defining roles, these interactions lead to several desirable physical properties, including electrical and proton conductivity, and redox‐switchable breathing behavior .…”

Electronic, Structural and Functional Versatility in Tetrathiafulvalene‐Lanthanide Metal–Organic Frameworks

“…The selectivity of MUV-5a towards the adsorption of CO2 over N2 likely arises from the higher quadrupole moment of CO2, which makes it capable of interacting more strongly with the framework. [29,30] This feature opens the way for the utilization of this type of materials in gas separation or sensing applications. As far as the arrangement of the organic linkers is concerned, we note that in MUV-5 solids the TTF units are forming onedimensional segregated stacks of slightly slipped moieties running along the a-axis (Figures 1 and 3).…”

“…N2 adsorption-desorption isotherms performed at 77 K reveals a minimum uptake of N2, in line with other previously reported TTFbased coordination polymers. [29] Interestingly, MUV-5a is able to adsorb CO2 with a modest CO2 uptake of 65 cm 3 ·g -1 (12.8 wt. %) at 273 K ( Figure S15), which is higher than that observed in other similar TTF-based MOFs at 195 K [29] , and a total uptake of 2.1 mmol·g -1 at 12 bar and 273 K ( Figure 2).…”

“…[29] Interestingly, MUV-5a is able to adsorb CO2 with a modest CO2 uptake of 65 cm 3 ·g -1 (12.8 wt. %) at 273 K ( Figure S15), which is higher than that observed in other similar TTF-based MOFs at 195 K [29] , and a total uptake of 2.1 mmol·g -1 at 12 bar and 273 K ( Figure 2). The selectivity of MUV-5a towards the adsorption of CO2 over N2 likely arises from the higher quadrupole moment of CO2, which makes it capable of interacting more strongly with the framework.…”