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Magnetic sustentation experiments are employed to monitor the adsorption process of a supramolecularly assembled MOF in solution.

The synergistic combination of a zirconium metal–organic cluster and a Keggin type polyoxotungstate led to a chemically stable and photoactive porous material.

Clustering chemistry is a key point in the design and synthesis of the secondary building units that comprise metal-organic frameworks (MOFs) based on group IV metals. In this work, the first stages of the zirconium-carboxylate clustering process in alcohol/water mixtures are studied in detail using the monocarboxylic benzoic and hydroxybenzoic acids to avoid the polymerization. Mass spectroscopy measurements performed on the reactions revealed the presence of hexa- and pentanuclear species even at low pH values and also evidenced the acid-base nature and pH dependence of the transformation between both species. The control on the chemistry governing the equilibria between these species has allowed us to isolate six new compounds in the solid state. The single-crystal X-ray diffraction analysis revealed that they are closely related to the well-known [Zr

Correction for ‘An in solution adsorption characterization technique based on the response to an external magnetic field of porous paramagnetic materials: application on supramolecular metal–adenine frameworks containing heterometallic heptameric clusters’ by Jon Pascual-Colino et al., Inorg. Chem. Front., 2023, https://doi.org/10.1039/d2qi01994a.

This work is aimed at the analysis of the interactions that drive the assembling of coordination metal-organic polymers based on biological molecules. Single-crystal X-ray diffraction data show that the compound 1D-{[Cu2(μ-ade)4(H2O)2]·2[Cu(theoph)2]·∼10H2O}n (1) contains neutral rhomboid shaped chains sustained by the tridentate μ3-κN3:κN7:κN9 coordination mode of the adenine nucleobase. These chains are formed by dimeric copper/adeninato (ade) cores doubly bridged by monomeric copper/theophyllinato (theoph) entities with the alkaloid acting as peripheral ligand. The lack of direct intermolecular nucleobase···nucleobase interactions, due to their disruption by the crystallization water molecules, does not provide a highly porous material, but the irregular shape of the polymeric chain hinders their packing and allows the presence of a moderate amount of voids (16% of the unit cell volume) in good accordance with its adsorption capacity of 0.38 mmol CO2/g at 273 K. Thermogravimetric and variable temperature X-ray diffraction analyses show that the compound retains its structure up to 110 °C whereas above this temperature the release of the coordination water molecules produces a significant loss of crystallinity. Magnetic measurements indicate an overall antiferromagnetic behavior with a J value of −267 cm−1 within the dimeric entity.

This work is aimed at the analysis of the π–π stacking interactions as the driving force to develop porous supramolecular metal–organic frameworks (SMOFs) as an alternative to more directional hydrogen bonding interactions. Four compounds based on the interaction between rigid copper/adenine entities and theobromine/caffeine molecules have been synthesized: [Cu7(μ-ade)6(μ3-OH)6(μ-H2O)6](theo)2·∼28H2O (1), [Cu2(μ-ade)4(H2O)2]·3Htheo·∼7H2O (2), [Cu2(μ-ade)4(H2O)2]·2Htheo·∼18H2O (3), and [Cu2(μ-ade)4(H2O)2]·(caf)·∼6H2O (4). The blue compound 1 is formed by wheel-shaped cationic heptameric units where the copper atoms are bridged by hydroxide anions, water molecules, and adeninato ligands with a μ-κN3:κN9 coordination mode. The assembly of the heptameric entities and the theobrominate anions takes place mainly through π–π stacking interactions involving the adeninato ligands and theobrominate moieties. Although compound 1 exhibits an open-framework with voids representing 37% of the unit cell, the plasticity ...

Nucleobases are known as suitable builders of porous materials not only due to their high number of heteroatoms leading to different coordination modes, but also because they establish strong and predictable supramolecular interactions. In this contribution, nucleobases (adenine and guanine), functionalized nucleobases (9-methyladenine) and nucleobase derivatives (6-chloropurine) have been evaluated as ligands for the construction of metal–nucleobase building blocks which can afford supramolecular porous materials, analyzing in detail the requirements that these entities must fulfill and pointing out the relevance of accomplishing the suggested requisites. More concisely, we have evaluated a paddle-wheel shaped dimeric entity, [Cu2(μ-Hade)4Cl2]Cl2·8H2O (1) (where Hade: adenine), a trimeric unit, [Co3(μ-Hade)2(μ-Cl)4Cl2(H2O)4]·2H2O (2), a dimeric entity, [Cu2(Hgua)2(H2gua)2(μ-Cl)2Cl2(H2O)][CuCl4] (3) (where Hgua: guanine, H2gua: guaninium), a monomeric unit with 9-methyladenine as the pendant ligand, [Co(9-Meade)2(H2O)4]Cl2·2H2O (4), zigzag chains, [Cu2(μ-CH3COO)4(μ-9-Meade)]n·nCH3OH (5), and a monomeric unit with 6-chloropurinato ligands, [Co(6-Clpur)2(H2O)4]·4H2O (6).

Two planar organic anions, benzoate and benzene-1,4-dicarboxylate (terephthalate), have been selected as potential π-stacking intercalators among ferrimagnetic [Cu7(μ-adeninato)6(μ3-OH)6(μ-H2O)6]2+ heptameric discrete entities. The resulting supramolecular architecture is highly dependent on the negative charge density distribution, mainly located in the carboxylate groups of the organic anions. In this sense, the benzoate anion, with just one carboxylate group, does not allow its intercalation between the adeninato ligands as it would imply a high steric hindrance among the heptameric entities. As a consequence, these benzoate anions are located inside the voids of the crystal structure reducing the accessible volume of compound [Cu7(μ-adeninato)6(μ3-OH)6(μ-H2O)6](benzoate)2·~17H2O (1). On the contrary, the terephthalate anion, containing two carboxylate groups at opposite sites, adopts a π-stacking sandwich arrangement between two adeninato ligands that affords the porous open structure of formula [Cu7(μ-adeninato)6(μ3-OH)6(μ-H2O)6](terephthalate)·nH2O (2a, 2b; n: 12 and 24, respectively). In addition to that, the less directional nature of the π-stacking interactions in comparison to the complementary hydrogen bonding based supramolecular metal-organic frameworks (SMOFs), suits them with a flexible architecture able to reversibly adsorb/desorb water (up to a 25–30% at 20 °C) altogether with the expansion/shrinkage of the crystal structure. The bridging adeninato and hydroxido ligands are effective magnetic exchange mediators to provide a ST = 5/2 ferrimagnetic state for the heptanuclear entity.