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Inverse Kinetic Solvent Isotope Effect in TiO 2 Photocatalytic Dehalogenation of Non‐adsorbable Aromatic Halides: A Proton‐Induced Pathway
Author(s) -
Chang Wei,
Sun Chunyan,
Pang Xibin,
Sheng Hua,
Li Yue,
Ji Hongwei,
Song Wenjing,
Chen Chuncheng,
Ma Wanhong,
Zhao Jincai
Publication year - 2015
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201409392
Subject(s) - chemistry , halide , halogenation , protonation , photocatalysis , kinetic isotope effect , adsorption , methanol , photochemistry , solvent , inorganic chemistry , catalysis , organic chemistry , ion , physics , deuterium , quantum mechanics
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 TiO 2 in a [D 0 ]methanol/[D 4 ]methanol solution. Combined with in situ ATR‐FTIR spectroscopy investigations, a previously unknown pathway for the transformation of these aromatic halides in TiO 2 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 TiO 2 surface and an ET reaction to form dehalogenated products follows.