Ligand-Centered Triplet Diradical Supported by a Binuclear Palladium(II) Dipyrrindione

Clayton J. Curtis, Andrei V. Astashkin, Jeanet Conradie, Abhik Ghosh, Elisa Tomat

Research output: Contribution to journalArticlepeer-review

7 Scopus citations


Oligopyrroles form a versatile class of redox-active ligands and electron reservoirs. Although the stabilization of radicals within oligopyrrolic πsystems is more common for macrocyclic ligands, bidentate dipyrrindiones are emerging as compact platforms for one-electron redox chemistry in transition-metal complexes. We report the synthesis of a bis(aqua) palladium(II) dipyrrindione complex and its deprotonation-driven dimerization to form a hydroxo-bridged binuclear complex in the presence of water or triethylamine. Electrochemical, spectroelectrochemical, and computational analyses of the binuclear complex indicate the accessibility of two quasi-reversible ligand-centered reduction processes. The product of a two-electron chemical reduction by cobaltocene was isolated and characterized. In the solid state, this cobaltocenium salt features a folded dianionic complex that maintains the hydroxo bridges between the divalent palladium centers. X-band and Q-band EPR spectroscopic experiments and DFT computational analysis allow assignment of the dianionic species as a diradical with spin density almost entirely located on the two dipyrrindione ligands. As established from the EPR temperature dependence, the associated exchange coupling is weak and antiferromagnetic (J ≈ -2.5 K), which results in a predominantly triplet state at the temperatures at which the measurements have been performed.

Original languageEnglish (US)
Pages (from-to)12457-12466
Number of pages10
JournalInorganic Chemistry
Issue number16
StatePublished - Aug 16 2021
Externally publishedYes

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry


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