This is the author manuscript accepted for publication and has undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record.
This is the author manuscript accepted for publication and has undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record.
Understanding the processes by which porous solid-state materials adsorb and release guest molecules would represent a significant step towards developing rational design principles for functional porous materials. To elucidate the process of liquid exchange in these materials, dynamic in situ X-ray diffraction techniques have been developed which utilize liquid-phase chemical stimuli. Using these time-resolved diffraction techniques, the ethanol solvation process in a flexible metal-organic framework [Co(AIP)(bpy)(HO)]·2HO was examined. The measurements provide important insight into the nature of the chemical transformation in this system including the presence of a previously unreported neat ethanol solvate structure.
Singlet fission (k SF ) and excimer formation (k EXC ) rate constants along with other photophysical properties of thin solid layers of 1,3-diphenylisobenzofuran and 11 of its fluorinated derivatives have been determined. The molecular properties of these compounds are similar, but their crystal packing varies widely. Most of them undergo singlet fission whereas excitation in others is trapped in excimers. The trend in rate constants k SF agrees qualitatively with results of calculations by a simplified version of the frontier orbital model for a molecular pair. The main shortcoming of the model is discussed.
In situ X-ray diffraction techniques provide the ability to monitor the change in the structure of crystals, such as Metal-organic Frameworks (MOFs), in response to changes in the local chemical environment surrounding the material. These methods reveal the location and concentration of guest species as well as the reorganization of the host framework as the contents of the void spaces are exchanged. Previous work in our group examined the dehydration of a flexible cobalt-based framework in the single crystalline phase using dry nitrogen gas as well as the exchange of the lattice waters with ethanol. To examine the impact of grain size on the dehydration reaction, recent results from in situ powder X-ray diffraction measurements on the CoMOF system will also be presented. Finally, in situ single crystal Xray diffraction measurements performed on an isostructural nickel-based framework resulted in markedly different guest exchange behavior. Possible explanations for this change in reactivity as well as recent improvements to the environmental control cell to enable exciting new experiments will be discussed.
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