Supramolecular Frameworks Based on Rhenium Clusters Using the Synthons Approach

• Main Authors: Nathalie Audebrand, Antoine Demont, Racha El Osta, Yuri V. Mironov, Nikolay G. Naumov, Stéphane Cordier
• Format: Article
• Language: English
• Published: MDPI AG 2021-05-01
• Series: Molecules
• Subjects: rhenium sulfide cluster; crystal engineering; synthon; topology; supramolecular framework
• Online Access: https://www.mdpi.com/1420-3049/26/9/2662

The reaction of the K₄[{Re₆Sⁱ₈}(OH)^a₆]·8H₂O rhenium cluster salt with pyrazine (Pz) in aqueous solutions of alkaline or alkaline earth salts at 4 °C or at room temperature leads to apical ligand exchange and to the formation of five new compounds: [<i>trans-</i>{Re₆Sⁱ₈}(Pz)^a₂(OH)^a₂(H₂O)^a₂] (<b>1</b>), [<i>cis-</i>{Re₆Sⁱ₈}(Pz)^a₂(OH)^a₂(H₂O)^a₂] (<b>2</b>), (NO₃)[<i>cis-</i>{Re₆Sⁱ₈}(Pz)^a₂(OH)^a(H₂O)^a₃](Pz)·3H₂O (<b>3</b>), [Mg(H₂O)₆]_0.5[<i>cis-</i>{Re₆Sⁱ₈}(Pz)^a₂(OH)^a₃(H₂O)^a]·8.5H₂O (<b>4</b>), and K[<i>cis</i>-{Re₆Sⁱ₈}(Pz)^a₂(OH)^a₃(H₂O)^a]·8H₂O (<b>5</b>). Their crystal structures are built up from <i>trans</i>- or <i>cis</i>-[{Re₆Sⁱ₈}(Pz)^a₂(OH)^a_4−x(H₂O)^a_x]^x−2 cluster units. The cohesions of the 3D supramolecular frameworks are based on stacking and H bonding, as well as on H₃O₂₋bridges in the cases of (<b>1</b>), (<b>2</b>), (<b>4</b>), and (<b>5</b>) compounds, while (<b>3</b>) is built from stacking and H bonding only. This evidences that the nature of the synthons governing the cluster unit assembly is dependent on the hydration rate of the unit.