Luminescent Ce(III) Complexes as Stoichiometric and Catalytic Photoreductants for Halogen Atom Abstraction Reactions
dataset
posted on 2015-07-29, 00:00 authored by Haolin Yin, Patrick J. Carroll, Jessica M. Anna, Eric J. SchelterLuminescent Ce(III)
complexes, Ce[N(SiMe<sub>3</sub>)<sub>2</sub>]<sub>3</sub> (<b>1</b>) and [(Me<sub>3</sub>Si)<sub>2</sub>NC(RN)<sub>2</sub>]Ce[N(SiMe<sub>3</sub>)<sub>2</sub>]<sub>2</sub> (R = <sup><i>i</i></sup>Pr, <b>1-</b><sup><i><b>i</b></i></sup><b>Pr</b>; R = Cy, <b>1-Cy</b>), with <i>C</i><sub>3<i>v</i></sub> and <i>C</i><sub>2<i>v</i></sub> solution symmetries
display absorptive 4f → 5d electronic transitions in the visible
region. Emission bands are observed at 553, 518, and 523 nm for <b>1</b>, <b>1-</b><sup><i><b>i</b></i></sup><b>Pr</b>, and <b>1-Cy</b> with lifetimes of 24, 67,
and 61 ns, respectively. Time-dependent density functional theory
(TD-DFT) studies on <b>1</b> and <b>1-</b><sup><i><b>i</b></i></sup><b>Pr</b> revealed the <sup>2</sup>A<sub>1</sub> excited states corresponded to singly occupied 5d<sub><i>z</i><sup>2</sup></sub> orbitals. The strongly reducing
metalloradical character of <b>1</b>, <b>1-</b><sup><i><b>i</b></i></sup><b>Pr</b>, and <b>1-Cy</b> in their <sup>2</sup>A<sub>1</sub> excited states afforded photochemical
halogen atom abstraction reactions from sp<sup>3</sup> and sp<sup>2</sup> C–X (X = Cl, Br, I) bonds for the first time with
a lanthanide cation. The dehalogenation reactions could be turned
over with catalytic amounts of photosensitizers by coupling salt metathesis
and reduction to the photopromoted atom abstraction reactions.
