A circular dichroism study uncovers a two-step interaction of antitumor azolato-bridged dinuclear platinum(II) complexes with calf thymus DNA.

The interactions of four antitumor azolato-bridged dinuclear platinum(II) complexes, [{cis-Pt(NH(3))(2)}(2)(μ-OH)(μ-azolato)](2+), with calf thymus DNA were monitored dose- and time-dependently, by using circular dichroism. Complexes 1-4 reacted with DNA via a two-step interaction that comprised a prompt diffusion-controlled reaction, which induced a B- to C-form transition, and a relatively slow temperature-dependent reaction.