Topoisomerase I inhibitory and photocleavage activity of non-dppz DNA ‘light switches’ based on ruthenium complexes containing nitro group

A new polypyridyl ligand containing a nitro group and two new ruthenium complexes of it were synthesized. The two complexes exhibited non-dppz DNA ‘light switch’ effects after interaction with calf thymus DNA. Introducing both electron-withdrawing group (─ NO 2 ) and electron-donating group (─ CH 3 ) may be the reason that the two complexes display DNA ‘light switch’ behaviors. Furthermore, one of the complexes showed higher photocleavage activity, topoisomerase I inhibition activity and DNA affinity than the other. The present work shows that the more active complex can be employed as a non-dppz DNA ‘light switch’, DNA photocleaver and topoisomerase I inhibitor. In addition, the two complexes have no or weak cytotoxic activities against Eca-109 and A549 cells.