Journal of Physical Chemistry A, Vol.124, No.10, 2036-2045, 2020
Probing Orientation-Specific Charge-Dipole Interactions between Hexafluoroisopropanol and Halides: A Joint Photoelectron Spectroscopy and Theoretical Study
The interactions between hexafluoroisopropanol (HFIP) and halogen anions X- (F-, Cl-, Br-, and I-) have been investigated using negative ion photoelectron (NIPE) spectroscopy and ab initio calculations. The measured NIPE spectrum of each [HFIP center dot X](-) (X = Cl, Br, and I) complex shows a pattern identical to the corresponding X- by shifting to the high electron binding energy side, indicative of the formation of the [HFIP center dot center dot center dot X-] structure in which X- interacts with HFIP via charge-dipole interactions. However, the spectrum of [HFIP center dot F](-) appears completely different from that of F- and is more similar to the spectrum of the deprotonated HFIP anion (HFIP-H-). The geometry and electron density calculations indicate that a neutral HF molecule is formed upon HFIP interacting with F- via proton transfer, rendering a stable structure of [HFIP-H center dot center dot center dot HF](-). Two conformers of [HFIP-H center dot HF](-) with HFIP being in synperiplanar and antiperiplanar configurations, respectively, are observed, providing direct experimental evidences to show the distinctly different and orientation-specific interactions between HFIP and halide anions.