PNNL

Abstract

Size-selective, negative ion photoelectron spectroscopy in conjunction with quantum chemical calculations is employed to investigate the geometric and electronic structures of a protype system in catalytic olefin epoxidation research, i.e., deprotonated hexafluoroisopropanol ([HFIP-H]?) complexed with hydrogen peroxide (H2O2). Spectral assignments and molecular electrostatic surface analyses unveil a surprising prevalent existence of a high-lying isomer with asymmetric dual hydrogenbonding configuration that is preferably formed driven by influential directionspecific electrostatic interactions upon H2O2 approaching [HFIP-H]? anion. Subsequent inspections of molecular orbitals, charge and spin density distributions indicate the occurrence of partial charge transfer from [HFIP-H]? to H2O2 upon hydrogen bonding interactions. Accompanying with electron detachment, a proton transfer occurs to form the neutral complex of [HFIP •HOO?] structure. This work conspicuously illustrates the importance of directionality encoded in intermolecular interactions involving asymmetric and complex molecules, while the produced hydroperoxyl radical HOO? offers a possible new pathway in olefin epoxidation chemistry.