Hydrogen Bonds and Self-Assembly to Direct Reactivity in the Solid State

In this presentation, we will describe our efforts to develop a general method to control chemical reactivity in the organic solid state. We use the method to provide access to complex organic molecules such as ladderanes and cyclophanes. In our method, we exploit hydrogen-bond-directed self-assembly with the use of small-molecule templates to assemble and preorganize olefins for intermolecular [2+2] photodimerizations. The templates assemble the olefins within discrete supramolecular assemblies for single and multiple photoreactions. By assembling the olefins within discrete assemblies, we overcome problems of long-range packing that have frustrated previous attempts to control the dimerization. We will also demonstrate how the approach provides a unique form of supamolecular catalysis that exploits fundamentals of mechanochemistry.

Capture of face-to-face π-interactions via solid-state [2+2] photodimerization

The use of principles of supramolecular chemistry to direct reactions in the crystalline state has emerged as a reliable means to facilitate highly selective reactions in a solvent-free environment. In this context, we exploit metal-organic complexes to fix spatial arrangements of molecules in crystal lattices to promote intermolecular [2+2] photodimerizations. Perfluorophenyl-perfluorophenyl interactions have recently emerged as a means to control supramolecular architectures and frameworks. However, it was not clear whether perfluorophenyl-perfluorophenyl interactions can be integrated in [2+2] photodimerizations in solids. In this presentation, we report a crystalline metal–organic complex with perfluorophenyl groups that adopt a well-defined face-to-face and head-to-head geometry in the solid state. Argentophilic forces are employed to enforce the face-to-face geometry. We demonstrate olefins of the solid to undergo a [2+2] photodimerization with UV-irradiation in a regiospecific and quantitative manner. In essence, we have employed the photoreaction as a means to covalently capture parallel perfluorophenyl-perfluorophenyl interactions in a solid.