Copper(II) Complexes of 2,2'- Bis dipyrrins: Synthesis, Characterization, Cell Uptake, and Radiolabeling with Copper-64

Inorg Chem. 2023 Dec 18;62(50):20666-20676. doi: 10.1021/acs.inorgchem.3c01551. Epub 2023 Aug 8.

Abstract

Complexes prepared with positron-emitting copper-64 are of interest as imaging agents for positron emission tomography (PET). This work investigates the potential of using acyclic tetrapyrrolic 2,2'-bisdipyrrins as ligands to prepare charge-neutral, lipophilic, cell-permeable, redox active complexes with positron-emitting copper-64. The synthesis and characterization of a series of tetrapyrrolic 2,2'-bisdipyrrin copper(II) complexes are reported. Four 2,2'-bisdipyrrin copper(II) complexes were prepared with different functional groups in the meso-position of the ligands. Two of the new copper(II) complexes, one palladium(II) complex, and one nickel(II) complex were characterized by X-ray crystallography, which demonstrated that the copper(II) is in a distorted square planar environment. An investigation of the electrochemical properties of the complexes by cyclic voltammetry revealed that the complexes undergo multiple quasi-reversible processes. A comparison of the cyclic voltammetry of the copper complexes with their palladium(II) analogues suggests that these redox processes are ligand-based and not metal-based. The copper(II) complexes are cell-permeable in A431 mammalian cells and are nontoxic at concentrations of 50 μM. The ligands can be radiolabeled with copper-64 at room temperature.

MeSH terms

  • Coordination Complexes* / chemistry
  • Copper Radioisotopes*
  • Crystallography, X-Ray
  • Ligands
  • Oxidation-Reduction
  • Palladium

Substances

  • Copper-64
  • Copper Radioisotopes
  • Palladium
  • Ligands
  • Coordination Complexes