Electronically Divergent Triscyclometalated Iridium(III) 2-(1-naphthyl)pyridine Complexes and Their Application in Three-Component Methoxytrifluoromethylation of Styrene

Rachael E.N. Njogu; Peter Fodran; Yuxi Tian; Lydia W. Njenga; David K. Kariuki; Amir O. Yusuf; Ivan Scheblykin; Ola F. Wendt; Carl-Johan Wallentin

doi:10.1055/s-0037-1611716

Synlett, Table of Contents

Synlett 2019; 30(07): 792-798
DOI: 10.1055/s-0037-1611716

letter

Electronically Divergent Triscyclometalated Iridium(III) 2-(1-naphthyl)pyridine Complexes and Their Application in Three-Component Methoxytrifluoromethylation of Styrene

Rachael E.N. Njogu

^aCentre for Analysis and Synthesis, Department of Chemistry, P.O. Box 124, SE-22100 Lund University, Sweden Email: ola.wendt@chem.lu.se

^dDepartment of Chemistry, University of Nairobi, P.O Box 30197, KE-00100 Nairobi, Kenya

,

Peter Fodran

^bDepartment of Chemistry and Molecular Biology, P.O. Box 462, SE-40530 University of Gothenburg, Sweden Email: carl.wallentin@chem.gu.se

,

Yuxi Tian

^cChemical Physics, Department of Chemistry, Lund University, P.O Box 124, SE-22100, Sweden

,

Lydia W. Njenga

^dDepartment of Chemistry, University of Nairobi, P.O Box 30197, KE-00100 Nairobi, Kenya

,

David K. Kariuki

^dDepartment of Chemistry, University of Nairobi, P.O Box 30197, KE-00100 Nairobi, Kenya

,

Amir O. Yusuf

^dDepartment of Chemistry, University of Nairobi, P.O Box 30197, KE-00100 Nairobi, Kenya

,

Ivan Scheblykin

^cChemical Physics, Department of Chemistry, Lund University, P.O Box 124, SE-22100, Sweden

,

Ola F. Wendt*

^aCentre for Analysis and Synthesis, Department of Chemistry, P.O. Box 124, SE-22100 Lund University, Sweden Email: ola.wendt@chem.lu.se

,

Carl-Johan Wallentin *

^bDepartment of Chemistry and Molecular Biology, P.O. Box 462, SE-40530 University of Gothenburg, Sweden Email: carl.wallentin@chem.gu.se

› Author Affiliations

Abstract

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^◊ These authors contributed equally.

Published as part of the Special Section 10th EuCheMS Organic Division Young Investigator Workshop

Abstract

A systematic study of the photophysical and electrochemical properties of triscyclometalated homoleptic iridium(III) complexes based on 2-(1-naphthyl)pyridine (npy) ligands is presented. A systematic investigation of ligand substitution patterns showed an influence on the lifetime of the excited state, with slight changes in the absorption and emission spectral features. Specifically, the emission lifetime of a complex of an npy ligand substituted with a strongly electron-withdrawing trifluoromethyl group was longer than that of the corresponding complex with the electronically nonperturbed ligand (3.7 μs versus 1.5 μs). Electronically complementary ligands and complexes with orthogonal configurations showed slightly shorter excited state lifetimes compared with unsubstituted npy (1.4–3.0 μs). All complexes displayed reversible or quasireversible redox-couple processes, with the complex of the trifluoromethylated ligand showing the highest ground-state oxidation potential E_1/2 ^ox [Ir(III)/Ir(IV) = 0.95 V vs. SCE in CH₂Cl₂]. This study showed that these complexes can be used as efficient photoredox catalysts, as demonstrated by their application in a regioselective methoxytrifluoromethylation in which the npy complexes showed equal or better performance compared with the archetypical photoredox catalyst tris[2-phenylpyridinato]iridium(III).

Key words

photoredox catalysis - iridium catalysis - oxytrifluoromethylation - styrene - naphthylpyridines - ligands

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References

References and Notes
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