The di-copper(ii) cation, [Cu 2(μ-terephthalate)(1,10-phen) 4] 2+, is a powerful, non-sequence-specific, minor-groove oxidizer of duplex DNA which, unlike copper(ii) bis-1,10-phenanthroline chloride, operates independently of exogenous reagents. The agent displays excellent in vitro cytoxicity towards cisplatin-resistant ovarian cancer cells, producing intracellular reactive oxygen species upon nano-molar exposure. © 2012 The Royal Society of Chemistry.