Solid-state reactions in co-crystals: Applications in synthetic chemistry and materials science

Chemistry is on the verge of a new era where the attention of chemists has shifted from covalent bonds to noncovalent interactions and their use as a reliable tool to design functional materials and to control the outcome of organic reactions. Although covalent synthesis in fluidic medium via supramolecular control has been achieved with limited success, the organic solid state has been of particular interest since it is not affected by solvent effects, thus enabling the formation of unique materials with remarkable stereoselectivity under environment-friendly conditions. Although reactions in solids have resulted in a number of remarkable discoveries in chemistry and materials science, solid-state synthesis is generally not considered as a mainstream synthetic medium and solid-state reactions are seldom appreciated as an efficient way to access molecular targets. Owing to the limited number of solid-state reactions and the uncontrollable nature of crystal packing, the solid state has not been utilized readily as a primary synthetic medium. In this context, reactions conducted in multi-component molecular assemblies or co-crystals have been recently recognized as a general way of controlling reactivity in the solid state. In recent years, our group has demonstrated that small organic molecules can be incorporated into organic solids to alter the crystal packing of olefins and semiconducting molecules, thereby controlling their physicochemical properties. The [2+2]photodimerization of olefins is a successful demonstration how templated solid state synthesis can efficiently synthesize complex targets that are synthetically challenging via conventional routes. In this dissertation, the generality and synthetic applicability of the templated synthetic approach in solid state will be described. How supramolecular interactions in molecular co-crystals precisely guide covalent bond formation in order to construct complex molecular targets will be demonstrated. Finally, co-crystallization will be shown as a general way to control chromic properties in crystals.