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 radical-anion state. The new stable radicals have an intense absorption at λmax∼1300 nm and can be either oxidized to regular [MII(MB-DIPY)]+ (M=Cu or Ni) or reduced to [MII(MB-DIPY)]− compounds. The radical nature of the stable [MII(MB-DIPY)] complexes was confirmed by EPR spectroscopy with additional insight into 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 density functional theory (DFT) and time-dependent DFT (TDDFT) calculations. These nickel(II) and copper(II) complexes represent the first stable radical compounds with a MB-DIPY ligand.
Bibliographical noteFunding Information:
Generous support by the NSF (CHE‐2153081), Minnesota Supercomputing Institute, University of Tennessee, and Canada WestGrid supercomputing facility to V.N.N. is greatly appreciated. We would like to acknowledge the help of Dr. Tanner Blessener and Dustin Nevonen with some of the data collection. M.S. and J.v.L. acknowledge funding from the Natural Sciences and Engineering Research Council of Canada (CGS−D program, and RGPIN‐2018‐05012) and the Canada Foundation for Innovation.
© 2022 Wiley-VCH GmbH.
- near-infrared absorption
- stable radicals
PubMed: MeSH publication types
- Journal Article