Crystal engineering of organic and metal-organic solids: design, structure and properties

Crystal engineering has recently emerged as a method of choice for the design and the construction of both organic and metal-organic functional materials. Solid-state synthesis, of the most commonly studied aspects of crystal engineering, has been shown to provide access to molecular targets that are hardly obtainable using principles of conventional (i.e. solution-based) organic synthesis. Reactions in the solid state, however, are not routinely used in organic synthetic chemistry. The scarce use of solid-state reactions can be attributed to the difficulty of predicting molecular arrangements in the solid state, as well as to the lack of methodologies to control crystal packing. Templatedirected solid-state synthesis is a recently developed modus operandi that enables control over reactivity within multi-component crystals. This thesis is partially focused on the application of template-directed solid-state approach to [2+2] photocycloaddition reactions in the solid state, as well as on the understanding of intermolecular interactions in crystals. Synthetic templates have been utilized to construct cocrystals that enable a class of hitherto underdeveloped organic solid-state reactions, namely [2+2] crossphotoaddition reactions. In addition, products derived form templated solid state reactions, namely tetrapyridylcyclobutanes, have been utilized to generate exceptional materials, such as thixothropic hydrogels based on nano-dimensional metal-organic particles. The utility of crystal engineering has also been expanded to the nano-science and the development of nanomaterials. A crystallization method for the preparation of nano-dimensional cocrystals has been developed. The method has been shown to enable single-crystal-to-single-crystal [2+2] photodimerizations of olefins. In addition, nanodimensional cocrystals have been shown to exhibit distinctive mechanical properties upon single-crystal-to-single-crystal transformations. In addition to solid-state reactions and materials derived therefrom, we systematically studied hierarchies of supramolecular synthons in pharmaceutical