Georges Mouchaham

Tetradihydrobenzoquinonate and Tetrachloranilate Zr(IV) Complexes: Single-Crystal-to-Single-Crystal Phase Transition and Open-Framework Behavior for K4Zr(DBQ)4

The molecular complexes K4[Zr(DBQ)4] and K4[Zr(CA)4], where DBQ(2-) and CA(2-) stand respectively for deprotonated dihydroxybenzoquinone and chloranilic acid, are reported. The anionic metal complexes consist of Zr(IV) surrounded by four O,O-chelating ligands. Besides the preparation and crystal structures for the two complexes, we show that in the solid state the DBQ complex forms a 3-D open framework (with 22% accessible volume) that undergoes a crystal-to-crystal phase transition to a compact structure upon guest molecule release. This process is reversible. In the presence of H2O, CO2, and other small molecules, the framework opens and accommodates guest molecules. CO2 adsorption isotherms show that the framework breathing occurs only when a slight gas pressure is applied. Crystal structures for both the hydrated and guest free phases of K4[Zr(DBQ)4] have been investigated.

Tubular crystals growth for a nanoporous hydrogen-bonded metal–organic framework

A supramolecular architecture formed by H-bonded assemblage of ditopic bisimidazoliumbenzene cations with anionic metal-oxalate modules shows permanent porosity upon guests release; the reversible sorption process being accompanied by crystal-to-crystal transformations. Additional macroporosity for the material was achieved by controlled growth of crystals with tubular morphology.

Extended H-bond networks based on guanidinium H-donors and [Zr(A)4]4− H-acceptor units: modulation of the assemblage and guest accessible volume by chemical design (A = oxalate, dihydrobenzoquinonate, chloranilate)

Supramolecular assemblages between three different [Zr(A)4]4− metallotectons (A stands for oxalate, Ox2−; dihydrobenzoquinonate, DBQ2−; or chloranilate CA2−) and three different guanidinium cation analogues (guanidinium, H-Guan+; 2-amino-imidazolium, H-AIm+; and N,N-dimethylguanidinium, H-DmG+) have been envisioned to investigate how the anionic and/or cationic building-block characteristics influence the connectivity and/or the dimensionality of frameworks based on charge-assisted H-bonds. Added to the benchmark material, {(H-Guan)4[Zr(Ox)4]}, (1), the crystal structures of six architectures of formula {(H-AIm)4[Zr(Ox)4]}·5H2O (2), {(H-DmG)4[Zr(Ox)4]}·0.5H2O (3), {(H-Guan)4[Zr(DBQ)4]}·1.5H2O (4), {(H-Guan)4[Zr(CA)4]}·5.85H2O (5), {(H-AIm)4[Zr(CA)4]}·H2O (6), and {K2(H2O)3(H-DmG)2[Zr(DBQ)4]}·H2O (7) have been characterized. While 1 consists of a two dimensional (2D) H-bonded network with compact structure, four out of the six supramolecular architectures (2–7) form 3D H-bonded networks, and three of these materials (namely, 2, 4 and 5) present open-framework architectures with solvent accessible voids ranging from 8 to 13%. Compounds 4–7 are the first examples of H-bonded frameworks constructed from [Zr(DBQ)4]4− and [Zr(CA)4]4− metallotectons.

Hydrogen-Bonded Open-Framework with Pyridyl-Decorated Channels: Straightforward Preparation and Insight into its Affinity for Acidic Molecules in Solution

A hydrogen-bonded open framework with pores decorated by pyridyl groups was constructed by off-charge-stoichiometry assembly of protonated tetrakis(4-pyridyloxymethyl)methane and [Al(oxalate)3 ]3- , which are the H-bond donor and acceptor of ionic H-bond interactions, respectively. This supramolecular porous architecture (SPA-2) has 1 nm-large pores interconnected in 3D with large solvent-accessible void (53 %). It demonstrated remarkable affinity for acidic organic molecules in solution, which was investigated by means of various carboxylic acids including larger drug molecules. Competing sorption between acetic acid and its halogenated homologues evidenced good selectivity of the porous material for the halogenated acids. The gathered results, including a series of guest@SPA-2 crystal structures and HRMAS-NMR spectra, suggest that the efficient sorption exhibited by the material relies not only on an acid-base interaction. The facile release of these guest molecules under neutral conditions makes this SPA a carrier of acidic molecules.

Supramolecular open-framework architectures based on dicarboxylate H-bond acceptors and polytopic cations with three/four N–H+ donor units

Supramolecular assemblages based on anionic H-acceptors and cationic H-donors have been envisioned to elaborate open frameworks maintained by ionic H-bonds. Combinations of di-anionic chloranilate (CA2−), oxalate (Ox2−), or terephthalate (BDC2−) and trisimidazolium or tetrapyridinium derivatives (three and four N–H+ donors, respectively) yielded five architectures of formulae [{(H3TrIB)(CA)1.5}·2DMF·2.5H2O] (1), [{(H4Tetrapy)(CA)2}·3DMF] (2), [{(H3TrIB)(HOx)(Ox)}·5H2O] (3), [{(H4Tetrapy)(Ox)2}·5H2O] (4), and [{(H4Tetrapy)(BDC)2(H2O)}·1DMF·3H2O] (5) (with TrIB = 1,3,5-trisimidazolylbenzene and Tetrapy = tetrakis[(pyridine-4-yloxy)methyl]methane). Four of these, i.e.1, 2, 4 and 5, show an open framework. Their assembling patterns and framework dimensionalities are mainly governed by the chemical features of the cation. 1D (3) and 2D (1) networks are found with [H3TrIB]3+, whereas 3D diamond-type networks (2, 4, 5) are systematically formed with [H4Tetrapy]4+. While the individual adamantanoid cages exhibit large voids in all 3D structures, net catenations (with a total degree of interpenetration up to 19) reduce the potential porosities of the solids to 17–32%. The largest solvent accessible void (42%) is found for the 2D supramolecular organization of 1, for which net interpenetration does not take place. Crystal structures for all five architectures are reported. Framework robustness upon guest departure and gas sorption properties have been explored for materials 1 and 2 with the highest potential accessible voids.

CCDC 1537659: Experimental Crystal Structure Determination

Related Article: Georges Mouchaham, Nans Roques, Walid Khodja, Carine Duhayon, Yannick Coppel, Stephane Brandes, Tamas Fodor, Michel Meyer and Jean-Pascal Sutter|2017|Chem.-Eur.J.|23|11818|doi:10.1002/chem.201701732

CCDC 1537663: Experimental Crystal Structure Determination

Related Article: Georges Mouchaham, Nans Roques, Walid Khodja, Carine Duhayon, Yannick Coppel, Stephane Brandes, Tamas Fodor, Michel Meyer and Jean-Pascal Sutter|2017|Chem.-Eur.J.|23|11818|doi:10.1002/chem.201701732