Short-lived intermediates, by their very nature, are difficult to fully characterize. Radicals are perhaps some of the best known chemical species that are short-lived and difficult to characterize, but many non-radicals share these qualities as well. Benzyne, for example, has been extensively characterized spectroscopically in matrices, but an isolated (non metal-bound) crystal structure remains elusive. Full structural characterization, especially the ultimate single crystal x-ray diffraction (SC XRD) structure determination, is important for comprehensive chemical understanding. Chemical x-ray photodiffraction is the specific SC XRD method used to characterize short-lived intermediates. It requires selecting intermediate precursors which are sensitive to UV radiation, and obtaining single crystals of the precursors. These single crystals are placed at very low temperatures (often using liquid helium) and exposed to strong UV radiation to trigger a partial chemical reaction that keeps the crystal structure intact on the whole. The partial reaction, though, is enough to detect with diffraction and make a determination of the crystal structure of the captured intermediate. Members of the Naumov Group at NYUAD’s Chemistry Department are making efforts to obtain the crystal structures of a wide variety of short-lived intermediates that will provide additional understanding to fundamental and long-standing problems in chemistry.

Chemical x-ray photodiffraction for structural characterization of short-lived intermediates

253rd National Meeting (2017)

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