Boron complexes of π-extended nitroxide ligands exhibiting three-state redox processes and near-infrared-II (NIR-II) absorption properties?

Dalton Transactions Pub Date: 2022-08-26 DOI: 10.1039/D2DT02545K

Abstract

Persistent radicals have attracted increasing attention owing to their fascinating properties, including multi-step redox and long-wavelength absorption characteristics. In this study, boron complexes with π-extended nitroxide ligands were synthesised via Buchwald–Hartwig amination reactions of the corresponding boron-nitroxide complex and diarylamines. These nitroxide complexes exhibited two-step and reversible one-electron oxidation processes, suggesting stable redox triads involving anionic aminoxide, neutral nitroxide-radical, and cationic oxoammonium ligands. Cationic boron complexes of the nitroxide radical ligands were obtained via chemical oxidation of the aminoxide complexes and structurally characterised. The cationic nitroxide-radical complexes exhibited strong absorptions at approximately 1100 nm, demonstrating their potential as near-infrared (NIR)-II-active functional dyes.

Graphical abstract: Boron complexes of π-extended nitroxide ligands exhibiting three-state redox processes and near-infrared-II (NIR-II) absorption properties
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