Supramolecular Frameworks Built up from Red-Phosphor­escent trans-Re6 Cluster Building Blocks: One Pot Synthesis, Crystal Structures, and DFT Investigations†

The reaction of a K4[\Re6Si8\(OH)a6]·8H2O rhenium cluster salt with 4,4'-bipyridine (bpy) or 4-aminopyridine (apy) in an aq. soln. at mild temp. and pressure conditions lead to cluster functionalization and to the formation of two new compds. [\Re6Si8\(OH)a2(bpy)a4]·bpy·4H2O (1) and [\Re6Si8\(OH)a2(apy)a4]·2apy·2H2O (2). Their crystal structures are built up from trans-[\Re6Si8\(OH)a2(L)a4] neutral units and the cohesions of both supramol. frameworks are based on π-π stacking as well as hydrogen bonds, involving the cluster units trans-[\Re6Si8\(OH)a2(L)a4], interstitial L ligands and water mols. 1 and 2 present 2D and 3D cluster frameworks, resp. Both compds. show red-NIR luminescence in the solid states. DFT calcns. demonstrate that assocn. of face capped Re6 clusters with bpy and apy ligands enabled to form supramol. frameworks that retain luminescent properties of the cluster units.