Organic and metal-organic materials chemistry have undergone unprecedented development in the past decade. The field of organic materials was marked with advances in synthesis of multicomponent solids, such as cocrystals, based on a variety of interactions, including recently emerged halogen bonds. In metal-organic materials, attention has been given to metal-organic frameworks (MOFs), microporous solids of technological importance for gas storage and separation, catalysis etc. Common to these fields is a need for better, fundamental understanding of principles guiding their synthesis, transformations and structure-property relationships. While experimental techniques, such as X-ray diffraction and solid-state NMR spectroscopy are indispensable, theoretical methods have gained ground in evaluating energies of polymorphs, calculating enthalpies and free energies of solid-state transformations and characterizing crystal energy landscapes. This presentation will outline our recent efforts in using periodic density functional theory (DFT) to characterize and even predict MOF and cocrystal systems. Specifically, I will describe full ab-initio screening for a previously not reported class of microporous materials, based on the recently isolated pentazolate (pnz-) ligand. The structure of pentazolate anion, with five nitrogen atoms available for creation of coordination bonds, makes it an excellent ligand for exploring topological diversity. Our search has revealed several previously not described topologies, one of which represents the putative lowest-energy structure of the Cd(pnz)2 framework system. While demonstrating, for the first time, the use periodic DFT to predict the potential structures of not yet synthesized MOFs, this work also revealed a potential route to design MOF structures that are inherently thermodynamically stable, but at the same time exhibit a low-density structure. I will also outline the use of periodic DFT to study thermodynamics of cocrystal formation, with a focus on systems based on halogen bonds. Particular attention will be given to the use of phonon calculations to probe lattice energies and free energies, enabling a theoretical rationalization of the effect of temperature on solid-state reactivity of cocrystals.

Periodic DFT calculations for predicting structures, properties and reactivity of organic and metal-organic materials

256th National Meeting (2018)

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