Auto-oligomerization and hydration of pyrrole revealed by x-ray absorptionspectroscopy

摘要

Near edge x-ray absorption fine structure spectra have been measured at the carbon and nitrogenK-edges of the prototypical aromatic molecule, pyrrole, both in the gas phase and when solvated inwater, and compared with spectra simulated using a combination of classical molecular dynamicsand first principles density functional theory in the excited state core hole approximation. Theexcellent agreement enabled detailed assignments. Pyrrole is highly reactive, particularly in water,and reaction products formed by the auto-oligomerization of pyrrole are identified. The solvatedspectra have been measured at two different temperatures, indicating that the final states remainlargely unaffected by both hydration and temperature. This is somewhat unexpected, since thenitrogen in pyrrole can donate a hydrogen bond to water.