©Sutter Jean-Pascal & Roques Nans/LCC Toulouse

Figure. (Top) H-bonds donnor carrying R groups (H, CH3, OH or OCH2Ph) and H-bonds acceptor implied in formation of SPA-1(R), with single crystal structure of SPA-1(CH3), (down) I2 absorption (from diode solution in hexane) by SPA-1(R) as a function of R group (photos realised after 4h, 1 and 14 days) and single crystal structure of SPA-1(CH3) after adsorption of I2.

Microporous solids formed from molecules associated by hydrogen bonds (H-bonds) are a class of molecular materials of growing interest. Typical properties of porous solids, such as permanent porosity, selective adsorption and sequestration of adsorbates or even detection, have been obtained for such supramolecular architectures.

Our approach to develop such materials involves negatively charged coordination complexes, typically metal-oxalate complexes, and pyridinium-type organic cations. The former act as H-bond acceptors and the latter as H-bond donors. The resulting ionic H-bonds are stronger than classical H-bonds. This particularity, which makes our approach original, has allowed access to new series of iso-structural porous structures called SPA-1(R), whose channels are decorated by polar, apolar R groups or a mixture of both (see figure). These modifications has allowed adjustment of sorption characteristics for the solids while maintaining very similar porosities. As an illustration, for R = CH₃, rapid adsorptions of carbon dioxide or iodine are obtained whereas they are much less efficient (or even non-existent) when R = OH. However, this last group is ideal for rapid water adsorption at low saturating vapor values and for sequestering its adsorbate more strongly.

These exceptional results in the field of porous supramolecular architectures are linked to the robustness of the synthons association involved in the formation of SPA-1(R), forcing an identical structure for each SPA-1(R) independently of the R group carried by the cation.

@Pichon Céline et Sutter Jean-Pascal / LCC Toulouse

Molecular magnets are molecules that behave similarly to traditional magnets using daily. These molecules could serve as a support for data recording (“North-South” or “South-North” magnetization direction inducing a magnetic bistability). Recording medium made of these molecules would lead to storage densities unmatched by our current hard drives. Today, the very low operating temperatures of such magnet molecules are the main drawback to overcome to favor applications, and significant work on the design mobilize chemists in the field.

Our study reveals that deformations within such molecule lead to a reduction in its operating temperature. Supported by theoretical calculations, our observations show that the linearity of the bonds between the active constituents of the molecule (Fe^II and Cr^III for the studied system) guarantees not only optimal communication between the metallic centers but also the greatest magnetic anisotropy. This work will help to better design of magnet molecular with improved properties.

Concomitant Emergence of Circularly Polarized Luminescence and Single-Molecule Magnet Behavior in Chiral-at-Metal Dy Complex.
B. El Rez, J. Liu, V. Béreau, C. Duhayon, Y. Horino, T. Suzuki, L. Coolen, J.-P. Sutter.
Inorg. Chem. Front., 2020, 7, 4527-4534.
https://doi.org/10.1039/D0QI00919A