Manifesting Direction-Specific Complexation in [HFIP_-H·H₂O₂]^-: Exclusive Formation of a High-Lying Conformation

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, that is, 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 hydrogen-bonding configuration that is preferably formed driven by influential direction-specific 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. Accompanied 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.