Research Laboratory - Wolfgang Schmitt

We are developing methodologies for engineering hybrid organic-inorganic coordination compounds. The concept of hybrid organic-inorganic materials presents a means for customizing physical and chemical properties by reducing the dimensionality and by influencing the devolution pattern of classical inorganic materials within organic matrices. This approach allows a combination of the superior properties of inorganic and organic materials. Our investigations include the synthesis, self-assembly and physicochemical characterization of coordination polymers, cluster compounds, biominerals and bioinorganic enzyme models. Key research areas under this purview include gas storage materials (e.g. for hydrogen), catalysis, separation science and magnetic materials. Furthermore, we use coordination polymers as templates for the synthesis of nanostructured materials by thermolysis, pyrolysis and intra-crystal polymerization resulting in organic-inorganic composites, pure inorganic or carbon-based materials.

Posted by edc on March 10, 2012 • Comments (64)

Supramolecular Approaches to Influence the Symmetry on Mn Coordination Clusters

Angew. Chem. Int. Ed., 2012, DOI: 10.1002/anie.201107358:

A supramolecular approach using chlorides as structure-directing ligands to prepare high-nuclearity, mixed-valent Mn coordination clusters which are characterized by {Mn(II)Mn(III)12}, {Mn(II)3Mn(III)10} and {Mn(II)3Mn(III)11} core structures is reported. The {Mn(II)Mn(III)12} complex is the first structurally characterized Mn-based Keplerate and has one of the highest symmetries of the high-nuclearity Mn coordination clusters reported so far. The applied synthetic approach was used to influence the symmetry of the species and to generate supramolecular chirality. The reported complexes are stable in solution and stabilize high-spin ground states induced by intra-molecular ferromagnetic interactions.

Posted bynjc on March 8, 2008 • Comments (64)

Extending the Family of Zn-Based MOFs Containing Large Pores and Channels

Chem. Commun. 2012, DOI: 10.1039/C2CC17357C:

Tri- and pentanuclear, kinetically stable SBUs were exploited for the preparation of the novel MOFs [Zn3(BTEB)2(DMF)2] and (Me2NH2)[Zn5(BTEB)33-OH)2(DMF)2]. The applied synthetic approach results in topologies that are stabilised by tritopic benzene-trisethynylbenzoic acid (BTEB) linkers giving rise to chiral frameworks with large pores or channels.

Posted by edc on March 8, 2008 • Comments (64)

Hybrid Polyoxovanadates - Supramolecular Cages & Networks

Inorg. Chem. 2012, 51, 19. and Dalton. Trans. 2012, 41, 2918.

Our applied synthetic approach results in hybrid polyoxovanadate structures: unprecedented cage structures and rather unsymmetrical condensed vanadates that self-organise in the solid state into hexagonal supramolecular assemblies. We show that condensation reactions in 4-aminophenyl arsonic acid-stabilized reaction mixtures are governed by vanadium/arsonate ratios. Chloride ions and water molecules stabilize the cavitand cagesthat accommodate these guests as an octahedral assembly within their capsular entity. The exclusion of chlorides and use of HNO3(aq) to acidify the reaction mixture, significantly influences the underlying condensation reactions and results in the formation of an unusually asymmetric, condensed clusters with remarkable supramolecular packing structures.

Posted by tfc on March 8, 2008 • Comments (2) •

From Platonic Templates to Archimedean Solids: Successive Construction of Nanoscopic Polyoxovanadate Cages

J. Am. Chem. Soc.. 2011, 133, 11240.

we describe a successive build-up of highly symmetrical nanoscopic coordination cages. Our synthetic approach takes advantage of a supramolecular template effect which involves octahedral {halide/H2O} assemblies that form during the cage formation and reside in the cluster cavity. The halide ions are associated with the formation and assembly of tetranuclear {V4} secondary building units whilst the encapsulated H2O molecules relate to the stabilisation of dinuclear {V2} units. In our regime, the molar ratio between V(V)/V(IV) provides us with a tool to influence the involved condensation reactions and control the template and cage formation. Octahedral {X2(H2O)4} (X = Cl- and Br-) aggregates stabilise two constitutional {V16As10} isomers, whose conformations are influenced by the nature of the halide involved. {Cl4(H2O)2} promotes the formation of the {V16As8} and {V20As8} cluster cores whilst the platonic {Cl6} template leads to a {V24As8} core structure. The latter is the largest hybrid vanadate cluster reported to date and its formation replicates and agrees with the mathematical relationship between an Archimedean truncated octahedron and an encapsulated Platonic octahedron.