To investigate the relationship between the molecular structure and biological 
activity of polypyridyl Ru(II) complexes, such as DNA binding, photocleavage 
ability, and DNA topoisomerase and RNA polymerase inhibition, six new 
[Ru(bpy)(2)(dppz)](2+) (bpy=2,2'-bipyridine; 
dppz=dipyrido[3,2-a:2,',3'-c]phenazine) analogs have been synthesized and 
characterized by means of (1)H-NMR spectroscopy, mass spectrometry, and 
elemental analysis. Interestingly, the biological properties of these complexes 
have been identified to be quite different via a series of experimental methods, 
such as spectral titration, DNA thermal denaturation, viscosity, and gel 
electrophoresis. To explain the experimental regularity and reveal the 
underlying mechanism of biological activity, the properties of energy levels and 
population of frontier molecular orbitals and excited-state transitions of these 
complexes have been studied by density-functional theory (DFT) and time-depended 
DFT (TDDFT) calculations. The results suggest that DNA intercalative ligands 
with better planarity, greater hydrophobicity, and less steric hindrance are 
beneficial to the DNA intercalation and enzymatic inhibition of their complexes.