Isolating in-crystallo reaction intermediates during 4+4 light-driven cycloaddition

Pentiptycene-anthracene (PAn-OCn) crystals are an ideal platform for delving into the fundamental aspects of in crystallo photochemical processes due to their light-driven [4+4] cycloadditive chemistry. In our previous experiments at the ESRF we used the unusual setup at the FIP2 (BM07) beamline, where an online microspectrophotometer is built perpendicularly to the X-ray beamline, to conduct simultaneous fluorescence and X-ray diffraction experiments with a time-resolution of ~30 seconds. From these, and based on a variety of analytical techniques, we observed the structural/kinetic features of PAn-OCn chemistry. Most importantly, our data suggested the presence of a reaction intermediate, which, due to low occupancy and short life-time, we could not structurally characterize. Thus, we propose to repeat our PAn-Ocn experiments at the ESRF at a higher time-resolution to determine the nature of the reaction intermediate.