Microporous, Homochiral Structures Containing Iron Oxo-Clusters Supported by Antimony(III) Tartrate Scaffolds

Abstract

A chiral cluster compound, dipotassium bis-(μ-tartrato)-diantimony(III), K2Sb2L2 (H4L = l-tartaric acid), was used as a secondary building unit to react with Fe(III) perchlorate and Fe(II) sulfate in water and DMF (DMF = dimethylformamide) in the presence of NaN(CN)2 or 4,4′-bipyridine. Three distinct homochiral structures have been obtained: H3Na7[Fe4Sb6(μ4-O)6(μ3-O)2(l-tartrate)6]·14H2O (1), H5K3[(CH3)2NH2]2[Fe7Sb6(μ4-O)6(μ3-O)2(l-tartrate)6]2·28H2O (2), and Na3K5[(CH3)2NH2]4[Fe6Sb6(μ4-O)6(μ3-O)2(l-tartrate)6]2·30H2O (3). All of these compounds contain iron oxo-clusters sandwiched by Sb3(μ3-O)(l-tartrate)3 SBUs. 1 consists of isolated [Fe4Sb6(μ4-O)6(μ3-O)2(l-tartrate)6]10– clusters, which are interconnected by Na+ ions into 2D homochiral layers. The structure of 2 features [Fe7Sb6(μ4-O)6(μ3-O)2(l-tartrate)6]5– clusters; the clusters are further linked into negatively charged honeycomb layers. Both types of clusters are found in 3 and are also assembled into negatively charged honeycomb layers. The accessibility of the microporosity of 2 was demonstrated by adsorption of 2-butanol. The magnetic properties of the compounds were measured from 5 to 300 K and indicate predominantly antiferromagnetic exchange interactions.