The formation of heterobimetallic complex [Co(bpy)2(ODHIP)Zn]5+ by [Co(bpy)2ODHIP]3+ and Zn2+ was investigated. The luminescent property of complex was also studied. The results indicated that the nonluminescent monometallic complex [Co(bpy)2ODHIP]3+ could coordinated with Zn2+ to form the luminescent heterobimetallic complex [Co(bpy)2(ODHIP)Zn]5+, the emission intensity increased as increasing the amounts of Zn2+. The luminescence became the strongest at the ratio of CZn / CCo of 1. After binding to DNA, [Co(bpy)2ODHIP]3+ must change its binding mode from partial intercalation to intercalation to make the peripheral coordination site on the ODHIP ligand accessible for Zn2+, the coordination occurred from the opposite side of helix with respect to the intercalated [Co(bpy)2ODHIP]3+, and the luminescent heterobimetallic complex [Co(bpy)2(ODHIP)Zn]5+ was formed. On the other hand, [Co(bpy)2(ODHIP)Zn]5+ bound to DNA by intercalation and situated the region of the intercalated [Co(bpy)2ODHIP]3+ between the base pairs of DNA, while the remained monometallic complex [Co(bpy)2ODHIP]3+ bound to DNA by partial intercalation.
