A New Nitrosyl-bridged Bimetallic Nitroprusside Complex: Synthesis, Crystal Structure, Supramolecular Self-assembly and Spectral Behavior of Interactions with DNA

A new nitrosyl-bridged bimetallic nitroprusside complex, [Ba(phen)3(H2O)][Fe(CN)5NO]·1.5phen·2H2O (phen = 1,10-phenanthroline) (1), has been synthesized and characterized by elemental analysis and single crystal X-ray diffraction. The crystal structure analysis reveals that complex 1 crystallizes in the triclinic space group Pī. The asymmetric structural unit is comprised of one [Ba(phen)3(H2O)]2+ complex cation, one [Fe(CN)5NO]2– complex anion, 1.5-uncoordinated phenanthroline molecules and two lattice water molecules. The complex ions are linked into a 1D chain-like arrangement by the trans CN and NO groups in nitroprusside. The six-coordinated Fe-atom forms a distorted octahedral coordination configuration, and the Ba-atom has a nine-coordinate monocapped antiprismatic geometry. Five types of π–π stacking interactions of phenanthroline and some intra- and intermolecular hydrogen bonds are observed in the 3D supramolecular self-assembly. Absorption spectroscopy, fluorescence titration and viscometry studies of the interaction between complex 1 and calf thymus DNA indicate that complex 1 is a moderate metallo-intercalator with the intrinsic binding constant of 3.70 × 104 M−1 and the linear Stern–Volmer quenching constant of 5.98 × 104 M−1.