The dipyrrin-1,9-dione ligand, which is characteristic of the propentdyopent family of heme metabolites, behaves as an electron reservoir in transition metal complexes. We report the synthesis of a series of heteroleptic Pd(II) complexes featuring intramolecular hydrogen bonds between the redox-active dipyrrolic ligand and coordinated amine ligands. In each complex, the Pd(II) metal center is bound to one bidentate monoanionic propentdyopent ligand and monodentate or bidentate neutral amine ligands. The single-crystal structures and <sup>1</sup>H NMR spectra of these diamagnetic complexes demonstrate square-planar geometries, wherein intramolecular hydrogen-bonding between the acceptor terminal carbonyls of the propentdyopent ligand and the donor amine ligands are observed. Electrochemical analysis of the heteroleptic complexes revealed a quasi-reversible one-electron redox event, which was assigned to the reduction of the propentdyopent ligand and formation of a ligand-based radical. Although the reduction potentials are shifted anodically in comparison to those of the previously reported propentdyopent complexes the optical absorption spectra of the reduced species present similar features, including two long-wavelength bands (beyond 650 nm) that are characteristic of oligopyrrolic radicals. In summary, the propentdyopent framework can be incorporated in a series of heteroleptic complexes featuring hydrogen-bonding interactions within their primary coordination sphere. The effects of these interactions on the structural stability, ligand-based redox chemistry and overall reactivity of the complexes are currently under investigation.

Heteroleptic calladium(II) complexes of the redox-active propentdyopent scaffold supported by intramolecular hydrogen bonding

2019 Fall National Meeting

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