title: Inverse kinetic solvent isotope effect in TiO2 photocatalytic dehalogenation of non-adsorbable aromatic halides: a proton-induced pathway.
abstract: An efficient redox reaction between organic substrates in solution and photoinduced h(+) vb /e(-) cb on the surface of photocatalysts requires the substrates or solvent to be adsorbed onto the surface, and is consequentially marked by a normal kinetic solvent isotope effect (KSIE ≥ 1). Reported herein is a universal inverse KSIE (0.6-0.8 at 298 K) for the reductive dehalogenation of aromatic halides which cannot adsorb onto TiO2 in a [D0 ]methanol/[D4 ]methanol solution. Combined with in situ ATR-FTIR spectroscopy investigations, a previously unknown pathway for the transformation of these aromatic halides in TiO2 photocatalysis was identified: a proton adduct intermediate, induced by released H(+) /D(+) from solvent oxidation, accompanies a change in hybridization from sp(2) to sp(3) at a carbon atom of the aromatic halides. The protonation event leads these aromatic halides to adsorb onto the TiO2 surface and an ET reaction to form dehalogenated products follows.
authors.affiliation: Key Laboratory of Photochemistry, Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190 (China).
authors.forename: Wei
authors.initials: W
authors.lastname: Chang
authors.forename: Chunyan
authors.initials: C
authors.lastname: Sun
authors.forename: Xibin
authors.initials: X
authors.lastname: Pang
authors.forename: Hua
authors.initials: H
authors.lastname: Sheng
authors.forename: Yue
authors.initials: Y
authors.lastname: Li
authors.forename: Hongwei
authors.initials: H
authors.lastname: Ji
authors.forename: Wenjing
authors.initials: W
authors.lastname: Song
authors.forename: Chuncheng
authors.initials: C
authors.lastname: Chen
authors.forename: Wanhong
authors.initials: W
authors.lastname: Ma
authors.forename: Jincai
authors.initials: J
authors.lastname: Zhao
keywords: electron transfer; isotope effects; photocatalysis; surface chemistry; titanium