Rings of Power: Controlling SOD Mimic Activity by the Addition of Pyridine Rings within the Pyridinophane Scaffold

Inorg Chem. 2024 Dec 16;63(50):23544-23553. doi: 10.1021/acs.inorgchem.4c02776. Epub 2024 Dec 3.

Abstract

Superoxide dismutase enzymes are a major defense against superoxide, which is a potent reactive oxygen species. Misregulation of reactive oxygen species and subsequent neuronal damage are etiological hallmarks of neurodegenerative disease. Macrocyclic small molecules have offered inroads toward functional SOD1 mimics. Herein, we report a series of five tetra-aza macrocyclic RPy2N2 ligands, varied by 4-position substitution of the pyridine ring with both electron-donating (R = OMe) and withdrawing groups (R = Cl, I, and CF3) to offer the first comparison to well-studied RPyN3 congeners and other mimics in the literature. New ligands have been characterized by NMR, mass spectrometry, elemental analysis, and potentiometric titrations (pKa). Cyclic voltammetry and X-ray diffraction analysis of the copper(II) complexes (CuII(RPy2N2)2+) demonstrate how pyridine substitution impacts the metal center. This data, and evaluation of the log βCu(II) and log βCu(I) within the series, indicates significant improvement to the binding affinity for Cu(I) without sacrifice of Cu(II) binding. The CuII(RPy2N2)2+ series yield the highest kcat for any Cu(II)-based small molecule functional SOD1 mimic (kcat = 45.36 M-1 s-1). Furthermore, the CuII(OMePy2N2)2+ and CuII(CF3Py2N2)2+ complexes were studied in FRDA cells to determine cell toxicity as a first step toward the application of these mimics as therapeutics for neurological disease.

MeSH terms

  • Biomimetic Materials / chemical synthesis
  • Biomimetic Materials / chemistry
  • Biomimetic Materials / pharmacology
  • Coordination Complexes / chemical synthesis
  • Coordination Complexes / chemistry
  • Coordination Complexes / pharmacology
  • Copper / chemistry
  • Humans
  • Ligands
  • Molecular Structure
  • Pyridines* / chemistry
  • Pyridines* / pharmacology
  • Superoxide Dismutase / chemistry
  • Superoxide Dismutase / metabolism

Substances

  • Pyridines
  • Coordination Complexes
  • Superoxide Dismutase
  • pyridine
  • Copper
  • Ligands