Platinum squares with high selectivity and affinity for human telomeric G-quadruplexes.

Two new Pt(II) squares with quinoxaline-bridges selectively stabilize human telomeric G-quadruplexes with high binding constants (10(7)-10(9) M-1) and an unprecedented binding stoichiometric ratio of Pt(II) square/G-quadruplex (6 : 1). This selectivity is likely due to the Pt(II) squares' cube-like shape. Both Pt(II) squares also show significant telomerase inhibition and anticancer efficacy.