Answer:

Unlike the metal complexes of phen or bpy

(bpy=2,2’-bipyridine), the mixed-ligand metal com-

plexes of phen and dppz have been unambiguously

shown to intercalate into the BASE PAIRS of DOUBLE

helical DNA [8, 18 – 23]. The mixed-ligand ruthe-

nium(II) complex [Ru(phen)2(dppz)]2+ has so far been

most extensively used for the DNA-binding studies

and reported to be an avid binder of DNA [18 –

23]. However, DNA-binding studies of mixed-ligand

metal complexes with the central metal ions other

than ruthenium(II) have attracted much less atten-

tion except for recent reports on rhodium [7], os-

mium(II) [8], cobalt(II) and nickel(II) [10] and rhe-

nium(I) [11] complexes. Clearly, further studies of the

mixed-ligand complexes of central metal ions other

than the above mentioned metal ions are needed to

investigate the influence of the changes in geometry,

charge, spin state, redox potential etc. on the DNA-

binding process and mechanism of the mixed-ligand

complexes. These studies also serve as complemen-

tary ones to those of mixed-ligand complexes con-

taining ruthenium(II) and other metal ions mentioned

above. In the present study, the DNA-binding proper-

ties of bis(1,10-phenanthroline)(dipyrido[3,2-a:3’,2’-

c]phenazine)iron(II), [Fe(phen) 2(dppz)]2+ (Fig. 1)

have been fully characterized by means of equilib-

rium binding constant (Kb), melting temperature (TM)

of double helical DNA upon binding to the metal

complex, thermodynamic parameter of the DNA bind-

ing, and enantioselectivity of the DNA binding of the

iron(II) mixed-ligand complex.