Dicopper(II) Complexes of p-Cresol-2,6-Bis(dpa) Amide-Tether Ligands: Large Enhancement of Oxidative DNA Cleavage, Cytotoxicity, and Mechanistic Insight by Intracellular Visualization

Dicopper complexes of a new p-cresol-2,6-bis(dpa) amide-tether ligand (HL1), [Cu-2(mu-OH2)(mu-1,3-OAc)(L1)](ClO4)(2) (1) and [Cu-2(mu-1,1-OAc)(mu-1,3-OAc)(L1)]X (X = ClO4 (2a), OAc (2b)) were synthesized and structurally characterized. 2b rapidly cleaves supercoiled plasmid DNA by activating H2O2 at neutral pH to a linear DNA and shows remarkable cytotoxicity in comparison with related complexes. As 2b is more cytotoxic than HL1, the dicopper core is kept in the cell. A boron dipyrromethene (Bodipy)-modified complex of the p-cresol-2,6-bis(dpa) amide-tether ligand having a Bodipy pendant (HL2), [Cu-2(mu-OAc)(2)(L2)]( OAc) (3), was synthesized to visualize intracellular behavior, suggesting that 2b attacks the nucleolus and mitochondria. A comet assay clearly shows that 2b does not cleave nuclear DNA. The apoptotic cell death is evidenced from flow cytometry.

Automated summary

A series of new dicopper complexes of a p-cresol-2,6-bis(dpa) amide-tether ligand were synthesized, among which dicopper complex 2b exhibited remarkable cytotoxicity by rapidly cleaving DNA into linear form by activating H2O2 at neutral pH, as well as attacking the nucleolus and mitochondria.