Self-Assembly of Four Coordination Polymers in Three-Dimensional Entangled Architecture Showing Reversible Dynamic Solid-State Structural Transformation and Color-Changing Behavior upon Thermal Dehydration and Rehydration

Abstract

A unique three-dimensional (3D) supramolecular compound, [Co(dpe)(BTC)(H 2 O)][Co(dpe)(BTC)(H 2 O) 3 ]-[Co(dpe)(HBTC)(H 2 O)][Co(dpe) 2 (H 2 O) 3.5 (EtOH) 0.5 ]•1.5H 2 O (1; dpe = 1,2-bis(4-pyridyl)ethane and H 3 BTC = benzenetricarboxylic acid), has been synthesized and structurally characterized by the single-crystal X-ray diffraction method. Compound 1 consists of four coordination polymers (CPs), two are two-dimensional (2D) layered metal−organic frameworks (MOFs) with (4,4) topology of [Co(dpe)(BTC)(H 2 O)] − and [Co(dpe)(HBTC)(H 2 O)], whereas the other two are onedimensional (1D) polymeric chains of [Co(dpe)(BTC)(H 2 O) 3 ] − and [Co(dpe)(H 2 O) 3.5 (EtOH) 0.5 ] 2+ . The 3D supramolecular architecture of 1 is constructed via the penetration of interdigitated double-layered 2D rectangular-grid frameworks by two 1D coordination polymeric chains and entangled tightly by the subtle combination of intermolecular hydrogen bonding and π−π interactions among the four CPs. Controlled heating of the as-synthesized crystal 1 at ∼160 °C produces a desolvated 1 and accompanying color-changing behavior from pink to deep-blue, and the deep-blue desolvated 1 regenerates the pink rehydrated crystal with the chemical formula of [Co(dpe 2) upon exposure to water vapor. The structural determination of 2 shows almost the same structural characteristics as that of 1 with the only difference being the replacement of disordered coordinated solvent (half H 2 O and half EtOH molecules) by H 2 O and the numbers of solvated water molecules. The cyclic thermogravimetric analysis and powder X-ray diffraction measurements of desolvated 1 demonstrate a reversible rehydration/dehydration property, which is associated with solid-state structural transformation and thermally induced UV−vis absorption properties.

Synthesis, Structures, and Water Adsorption of Two Coordination Polymers Constructed by M(II) (M = Ni (1) and Zn (2)) with 1,3-Bis(4-Pyridyl)Propane (bpp) and 1,2,4,5-Benzenetetracarboxylate (BT4−) Ligands

“…Recently, MOFs with high porosity have been examined for their water capture properties and found to be highly promising materials [ 42 , 43 , 44 ]. However, water capture properties applied to 3D supramolecular architectures assembled via CPs or MOFs are seldom detected and only a few cases have been investigated [ 45 , 46 , 47 ]. The water sorption isotherm with large hysteresis loops found in 1 is interesting and may be exploited as a water harvesting material.…”

Sponge-Like Water De-/Ad-Sorption versus Solid-State Structural Transformation and Colour-Changing Behavior of an Entangled 3D Composite Supramolecuar Architecture, [Ni4(dpe)4(btc)2(Hbtc)(H2O)9]·3H2O

“…Two or more CPs with different dimensionality—such as 1D plus 1D, 1D plus 2D, 2D plus 2D, and 2D plus 3D—within the crystal were found in the formation of their appealing interpenetrated or catenated 3D supramolecular networks [37,38,39,40,41,42,43,44,45,46,47,48]. Recently, a entangled 3D architecture composed of four CPs in a Co 4 system with chemical formula [Co 4 (dpe) 4 (BTC) 2 (HBTC)(H 2 O) 8.5 (EtOH) 0.5 ]·3H 2 O (dpe = 1,2-bis(4-pyridyl)ethane and H 3 BTC = 1,3,5-benzenetricarboxylic acid) has been reported in our groups, which shows a composite combination of two 1D chains plus two 2D layers, extending to a 3D entangled supramolecular network [49]. Benzene-1,3,5-tricarboxylic acid (H 3 btc) is a rigid, planar molecule, and has been widely used as a bridging ligands on the construction of multi-dimensional MOFs in the form of its three benzene-1,3,5-triboxylate anions, H 2 btc − , Hbtc 2− , and btc 3− [50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80,81,82,83,84,85,86,87,88,89,90,91].…”

Two-Dimensional Metal-Organic Framework Materials: Synthesis, Structures, Properties and Applications

“…Wang and co-workers also reported a 3D framework, 668 Here, two rectangular anionic and neutral 2D grids with distorted octahedral Co(II) centers and anti-dpe are mutually interdigitated with each other via the uncoordinated carboxylate group from lateral btc 3− and Hbtc 2− and form double-layered networks arranged in parallel ABAB fashion to generate 1D rectangular channels. These channels get further threaded by the 1D linear chains containing distorted octahedral Co(II) centers and anti-dpe arranged in an alternate fashion to generate a 3D supramolecular framework which is strongly entangled via both hydrogen bonding as well as π•••π interactions.…”

“…Wang and co-workers also reported a 3D framework, [Co­(dpe)­(btc)­(H 2 O)]­[Co­(dpe)­(btc)­(H 2 O) 3 ]­[Co­(dpe)­(Hbtc)­(H 2 O)]­[Co­(dpe) 2 (H 2 O) 3.5 (EtOH) 0.5 ]·1.5H 2 O (dpe = 1,2-bis­(4-pyridyl)­ethane), comprised multidimensional polymers, i.e. , two (4,4)-connected 2D MOFs of anionic [Co­(dpe)­(btc)­(H 2 O)] − and neutral [Co­(dpe)­(Hbtc)­(H 2 O)] and two 1D polymeric chains of anionic [Co­(dpe)­(btc)­(H 2 O) 3 ] − and cationic [Co­(dpe)­(H 2 O) 3.5 (EtOH) 0.5 ] 2+ . Here, two rectangular anionic and neutral 2D grids with distorted octahedral Co­(II) centers and anti -dpe are mutually interdigitated with each other via the uncoordinated carboxylate group from lateral btc 3– and Hbtc 2– and form double-layered networks arranged in parallel ABAB fashion to generate 1D rectangular channels.…”