Hybrid Host–Guest Complexes: Directing the Supramolecular Structure through Secondary Host–Guest Interactions

Abstract

A set of four hybrid host-guest complexes based on the inorganic crown ether analogue [H12W36O120]12- ({W36}) have been isolated and characterised. The cluster anion features a central rigid binding site made up of six terminal oxygen ligands and this motif allows the selective binding of a range of alkali and alkali-earth-metal cations. Here, the binding site was utilised to functionalise the metal oxide-based cavity by complexing a range of protonated primary amines within the recognition site. As a result, a set of four hybrid organic-inorganic host-guest complexes were obtained whereby the interactions are highly directed specifically within this cavity. The guest cations in these molecular assemblies range from the aromatic 2-phenethylamine (1) and 4-phenylbutylamine (2) to the bifunctional aromatic p-xylylene diamine (3) and the aliphatic, bifunctional 1,6-diaminohexane (4). Compounds 1-4 were structurally characterised by single-crystal X-ray diffraction, elemental analysis, flame atomic absorption spectroscopy, FTIR and bond valence sum calculations. This comparative study focuses on the supramolecular effects of the amine guest cations and investigates their structure-directing effects on the framework arrangement arising by locking the protonated amines within the cavity of the {W36} cluster. It was shown that parts of the organic guest cation protrude from the central binding cavity and the nature of this protruding organic "tail" directs the solid-state arrangement of compounds 1-4. Guest cations with a hydrophobic phenyl tail result in an antiparallel assembly of {W36} complexes arranged in a series of pillared layers. As a consequence, no direct supramolecular interactions between {W36} clusters are observed. In contrast, bifunctional guest cations with a secondary amino binding site act as molecular connectors and directly link two cluster units thus locking the supramolecular assembly in a tilted arrangement. This direct linking of {W36} anions results in the formation of an infinite supramolecular scaffold.

Structural and Electronic Properties of Polyoxovanadoborates Containing the [V12B18O60] Core in Different Mixed Valence States

“…Within the observed tendency of 3.34 to 3.83 emu K mol −1 , there is no clear correlation between the magnetic properties and the nature of the frameworks, which include different cations interacting with the polyanions, even though it is clear that the interactions between the different cations and the polyanion in the lattice affect the magnitude of the exchange phenomena in the cluster. It is interesting to point out that Hermosilla-Ibáñez et al reported in 2014 that it is possible to show by DFT calculations that the alkaline ions in compounds (18) and (19) quench the intracluster antiferromagnetic coupling, in comparison with compound (5) [57]. In this study, the results indicated that the presence of alkaline ions perturbs the extent of the spin density of the magnetic orbitals (dxy); this perturbation is dependent on the distance between the alkaline cation and the oxygen of the vanadyl groups.…”

“…From the χT(T) graph reported by Zhou et al [53] it is possible to infer that (27) is almost magnetically uncoupled at room temperature. On the other hand, the χT values of the rest of compounds, (5), (12), (15), (18), and (19) show that all of them are magnetically coupled at room temperature. Within the observed tendency of 3.34 to 3.83 emu K mol −1 , there is no clear correlation between the magnetic properties and the nature of the frameworks, which include different cations interacting with the polyanions, even though it is clear that the interactions between the different cations and the polyanion in the lattice affect the magnitude of the exchange phenomena in the cluster.…”

“…Among all the studied compounds included in this review, the magnetic properties of only (5), (11), (12), (15), (18), (19), (27), and (38) have been reported [53][54][55]57,63]. All of these systems have a mixed valence ratio of 10V IV /2V V , and present a bulk antiferromagnetic behavior.…”

“…The structural variety of these polyanionic clusters is generated by their interaction with or bonding to different cationic species such as protonated amines, ammonium and hydronium ions, alkaline, transition metal, and lanthanide ions. These cationic species can exist in the lattice as charge-compensating agents, or linked to the external oxygen atoms of the polyanionic species, and thus serve to increase the dimensionality of these systems [14][15][16][17][18][19]. The crystalline packing is stabilized by hydrogen bonds, in the case of ammonium cations, or by the formation of covalent bonds through the interaction of the external oxygen atoms of the polyanionic species with different metal cations, such as alkaline or transition metal ions.…”

Can Hydrophobic Interactions Influence Supramolecular Aggregation in Self‐Assembled Organic–Inorganic Hybrid Structures?

“…[12,13] In this initial study, the electrostatically-controlled formation of organic-inorganic hybrid systems was investigated with a range of experimental and theoretical analyses. The aim was to identify ways of directing the self-assembly so as to guide the resulting architecture into separate hydrophilic and hydrophobic regions.…”