Debashree Mandal

Self-assembly of an azido-bridged [NiII6] cluster featuring four fused defective cubanes.

The cluster [Ni6(H2L)2(HL1)2(N3)8].2C2H5OH.2H2O [1.2C2H5OH.2H2O], featuring four fused defective cubanes, has been obtained via azido-bridge-driven dimerization of two phenolate-centered trinuclear Ni3 fragments.

Interaction with DNA of a heteronuclear [Na2Cu4] coordination cluster obtained from the assembly of two hydroxo-bridged [CuII2] units by a dimeric sodium nitrate template

The heteronuclear [Na(2)Cu(4)(bemp)(2)(OH)(2)(NO(3))(2)(OH(2))(4)] x 5 H(2)O (1 x 5H(2)O; H(3)bemp: 2,6-bis-[(2-hydroxyethylimino)-methyl]-4-methyl-phenol) cluster has been synthesized in aqueous-methanol at room temperature and structurally characterized. The water soluble complex is obtained from the template assembly of two [Cu(2)(bemp)(OH)] neutral fragments through their weak oxophillic interactions with two interconnected NaNO(3) units as core. Four [Na(2)Cu(4)] units form a metal-organic cage arrangement in the crystal lattice that traps a (H(2)O)(7) cluster. Variable-temperature magnetic susceptibility measurements (2-300 K) reveals a strong antiferromagnetic coupling between the Cu(II) ions within the dimers with J = -124.1 cm(-1) (in the H = -2JS(1)S(2) convention). The interaction of complex 1 x 3H(2)O with calf thymus DNA (binding constant K(b), 4.6 x 10(4) M(-1)) in Tris buffer was studied by UV-visible and emission titration, and cyclic voltammetry. The hexanuclear Na(2)Cu(4) complex also binds double-stranded supercoiled plasmid pBR322 DNA and displays efficient hydrolytic cleavage. The hydrolytic mechanism is supported by evidence from DNA relegation employing T4 ligase assay and reactive oxygen species (ROS) quenching cleavage experiments.

A ketone oximate based cyclic cationic [NiII4] inverse metallacrown from simultaneous chelation and bridging of two ligands

The Ni(4) inverse metallacrown (NHEt(3)) [Ni(4)(bmo)4(Hael)2(ael)2](ClO(4))3 [(NHEt(3)).1.(ClO(4))3], with the inverse 12-MC-4 motif, has been assembled via simultaneous chelation and bridging of butan-2,3-dionemonoxime (Hbmo) and 2-amino ethanol (Hael).