Supramolecular Materials

Research in our group falls under the theme of “supramolecular materials”. We are undertaking research to explore the supramolecular assembly of molecules into new materials, using coordination chemistry (usually) to fasten the molecules together. This “bottom up” approach to materials chemistry enables the synthesis of molecule-based materials with tuneable structures and properties. One of the chief assembly principles in our research has been the development and use of shape-persistent precursors for assembly to give porous structures. Our goal is to assemble new substances with interesting structures on the nanoscale: grids, tubes, 3-D networks, etc. On the way, we investigate the fundamental chemistry and the properties of the substances, including the role of the transition metals in the materials. Briefly, below is a list of the projects we are working on or have explored in the past few years:

• Schiff-base Macrocycles. We are investigating the synthesis and supramolecular assembly of macrocycles with conjugated backbones (e.g., Figure 1). Figure 2 illustrates the ion-induced tubular assembly that occurs upon binding of the macrocycles to alkali metals (Angew. Chem. 2003). Upon coordination to metal ions, these macrocycles form fascinating structures, such as the cluster-capped trimetallated macrocycle depicted in Figure 3 (Inorg. Chem. 2006).

 Figure 1 Figure 2  Figure 3

• Conjugated Metallopolymers. We are developing new soluble polymers that have a conjugated backbone, but transition metals incorporated into the structure. These polymers are promising for applications as new electronic materials and light emitting diode materials. Figure 4 shows a photograph of a polymer film containing metals in every repeat unit (from Macromolecules 2003).

Figure 4

• Self-Assembled Networks and Structures. We are developing new hydrogen-bonding motifs and coordination chemistry that will permit us to direct the assembly of new supramolecular assemblies and 3-D networks. We have discovered porous, 2-D and 3-D frameworks based on triptycenyl precursors that can be used to remove pollutants from water (Inorg. Chem. 2006).

We have other projects underway involving liquid crystals, modified cellulose, and metal-organic frameworks (MOFs). (For a more complete sampling of our projects, see the Publications list.) Students in our group learn synthetic methods of organic, inorganic, and polymer chemistry. We study our molecules and materials using NMR, fluorescence, IR, and UV-vis spectroscopies, mass spectrometry (ESI, EI, MALDI-TOF), transmission electron microscopy, thermogravimetric analysis, differential scanning calorimetry, and polarizing optical microscopy. We also collaborate to undertake other studies, such as magnetism.