Versatility in Templated Solid-State Reactions

University Of Iowa, Iowa City IA

Investigators

Abstract

Technical Summary: The general goal of this project is to increase the versatility of small-molecule templates in controlling chemical reactivity in the organic solid state. With support from the Solid-State and Materials Chemistry program in the Division of Materials Research, the research aims to increase versatility by determining the ability of the templates to: (i) serve as supramolecular catalysts of [2+2] photodimerizations of olefins, (ii) make available cross-photodimerizations, and (iii) direct the construction of paddlanes. The research is motivated by the fact that although small molecule templates have, in recent years, provided a high level of control of bimolecular reactivity in organic solids, there remains a need for the templates to go beyond previous methodologies. Being able to control reactivity in the organic solid state is attractive for applications in molecular and polymer synthesis (e.g. products unavailable in solution, stereocontrolled reactivity), green chemistry (e.g. solvent-free synthesis), inorganic chemistry (e.g. ligand design), and materials science (e.g. data storage). Effects of crystal packing have largely prevented chemists from achieving a degree of control of reactivity in solids akin to solution. The templates circumvent the packing problem by preorganizing olefins within supramolecular assemblies for reaction. We expect to generalize a grinding method based on principles of mechanochemistry that facilitates supramolecular catalysis in solids to hydrogenbond-donor and -acceptor catalysts, as well as different molecular recognition groups. We plan to use the templates to direct cross-photodimerizations within co-crystal solid-solutions and ternary co-crystals. We also aim to employ templates to direct the supramolecular construction of polyhedral molecules in the form of [23](1,3,5)- and [24](1,2,4,5)cyclophanes, or paddlanes. The approach will take advantage of the ability of the templates to enforce reactive alignment of multiple C=C bonds to make available the new target molecules. Non-Technical Summary With support from the Solid-State and Materials Chemistry program in the Division of Materials Research, the general goal of this project is to increase the versatility of small-molecules to serve as templates to control the reactivity of organic molecules in crystals. Being able to control reactivity is attractive for applications in molecular and polymer synthesis (e.g. products unavailable in solution, stereocontrolled reactivity), green chemistry (e.g. solvent-free synthesis), inorganic chemistry (e.g. ligand design), and materials science (e.g. data storage). The broad training experienced by the undergraduate and graduate students, which will involve underrepresented groups and minorities, will continue to enable the participants to immediately enter the workforce. The proposed activities will result in a new undergraduate laboratory at the University of Iowa that employs computational chemistry to assess the stability of reactive supramolecular complexes derived from the solid state. An annual "Career Day" for undergraduates will be developed, which will integrate a "Working Weekend" workshop on X-ray crystallography and powder diffraction developed by the PI. The PI will also develop a website to support the Midwest Organic Solid State Chemistry Symposium (MOSSCS), which is an annual meeting in the Midwest region of the United States that supports undergraduate and graduate student presentations. Our proposed laboratory experiment, along with our previously reported and recently developed experiments on solid-state reactions, will be published and disseminated electronically with access from the MOSSCS website. That our research encapsulates many core principles of green chemistry (e.g catalysis, solvent-free synthesis) means that we can use organic solid-state chemistry as a vehicle to positively impact the perception of the role of synthetic chemistry in society.