• Megha S Deshpande

      Articles written in Journal of Chemical Sciences

    • Mixed-ligand complexes of ruthenium(II) incorporating a diazo ligand: Synthesis, characterization and DNA binding

      Megha S Deshpande Avinash S Kumbhar

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      Mixed-ligand complexes of the type [Ru(N-N)2(dzdf)]Cl2, where N-N is 2,2′-bipyridine (bpy), 1,10-phenanthroline (phen) and 9-diazo-4,5-diazafluorene (dzdf), have been synthesized and characterized by elemental analysis, UV-Vis, IR and NMR spectroscopy. Binding of these complexes with calf thymus DNA (CT-DNA) has been investigated by absorption spectroscopy, steady-state emission spectroscopy and viscosity measurements. The experimental results indicate that the size and shape of the intercalating ligands have marked effect on the binding affinity of the complexes to CT-DNA. The complex [Ru(phen)2(dzdf)]Cl2 binds with CT-DNA through an intercalative binding mode, while the complex [Ru(bpy)2(dzdf)]Cl2 binds electrostatically.

    • Synthesis, structural, and DFT studies of mixed ligand copper(II) malonates


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      The synthesis, spectra, electrochemical studies, single crystal structures and DFT studies of twonew mixed ligand copper(II) malonates viz. [Cu(H2O)(bpy(OH)2)(mal)].H2O 1 and [Cu(H2O)(dmp)(mal)].2H2O 2 (bpy(OH)2) = 2,2Ꞌ-bipyridine-6,6Ꞌ-diol; dmp = 6,6Ꞌ-dimethyl-1,10-phenanthroline; H2mal =malonic acid) are reported. The malonate, bpy(OH)2 (in 1), dmp (in 2) function as bidentate ligands in thedistorted square pyramidal Cu(II) compounds while the aqua ligand occupies the axial site in 1. In contrast, oneNof dmp occupies the axial site in 2. ESR studies reveal the distorted coordination geometry of Cu(II) in 1 and 2.Extensive hydrogen bonding (O-H···O and C-H···O) is observed between the malonate oxygens, oxygens ofwater and the monomeric Cu(II) species resulting in the formation of hydrogen bonded network structure in 1 and2. The neutral monomeric Cu(II) species and lattice water molecules in 2 are linked viaO-H···Ohydrogen bondforming a water dimer. Both compounds exhibit π···π stacking and carbonyl(lp)···π interactions (in 2) stabilizethe structure. DFT studies reveal stronger hydrogen bond energy for 2 compared to 1, while π···π stacking energyis larger in 1 than in 2 and carbonyl(lp)···π interactions in 2 are found to be moderate. In a series of fivecoordinated mixed ligand Cu(II) malonates, compound 2 exhibits maximum deviation of the {CuN2O3}polyhedron from square pyramidal towards trigonal bipyramidal geometry.

      The supramolecular network structures of [Cu(H2O)(bpy(OH)2)(mal)]·H2O 1 and [Cu(H2O)(dmp)(mal)]·2H2O 2 are directed by O–H⋅⋅⋅O and C–H⋅⋅⋅O interactions. Additionally π⋅⋅⋅π stacking in 1 and π⋅⋅⋅π /carbonyl(lp)⋅⋅⋅π interactions in 2 contribute to the structure stabilization. 2 is an unique example showing severe distortion of the {CuN2O3} polyhedron.

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