Radical complexes of nickel(II)/copper(II) and redox non-innocent MB-DIPY ligands: unusual stability and strong near-infrared absorption at lmax ~1300 nm

• Published in: Chemistry : a European journal
• Main Authors: Zatsikha, Yurii V, Shamova, Liliya I, Shepit, Michael, Berry, Steven M, Thomas, Fabrice, Herbert, David E, van Lierop, Johan, Nemykin, Victor N
• Format: Journal Article
• Language: English
• Published: Germany 08.06.2022
• Subjects: aza-BODIPY azadipyrromethene stable radical nickel copper near-infrared absorption
• ISSN: 1521-3765

The preparation of radicals with intense and redox-switchable absorption beyond 1000 nm is a long-standing challenge in the chemistry of functional dyes. Here we report the preparation of a series of unprecedented stable neutral nickel(II) and copper(II) complexes of "Manitoba-dipyrromethenes" (MB-DIPYs) in which the organic chromophore is present in the anion-radical state. The new stable radicals have an intense absorption at l max ~ 1300 nm and can be either oxidized to a regular [M II (MB-DIPY)] + (M = Cu or Ni) or reduced to [M II (MB-DIPY)] - compounds. The radical nature of the stable [M II (MB-DIPY)] . radicals was confirmed by EPR spectroscopy with additional insight on their electronic structure obtained by UV-Vis spectroscopy, electro- and spectroelectrochemistry, magnetic measurements, and X-ray crystallography. The electronic structures and spectroscopic properties of the radical-based chromophores were also probed by the Density Functional Theory (DFT) and time-dependent DFT (TDDFT) calculations. These nickel(II) and copper(II) complexes represent the first stable radical compounds with an MB-DIPY ligand.