Vaibhave Aggarwal

Synthesis and reactivity studies on new copper(II) complexes: DNA binding, generation of phenoxyl radical, SOD and nuclease activities

Tridentate ligand PhimpH binds to Cu(II) centre after deprotonation affording a new family of complexes [Cu(Phimp)(H(2)O)](2)(ClO(4))(2) (1), [Cu(Phimp)(2)] (2) and [Cu(Phimp)(L)] (3-5) where L are CH(3)COO(-), SCN(-) and NO(2)(-) respectively. The molecular structures of complexes 1 x CH(3)CN and 3 were determined by X-ray crystallography. Electrochemical studies depicted Cu(II)/Cu(I) couple in the range of -0.50 to -0.65 V vs. Ag/AgCl. EPR spectral studies for complexes 4 and 5 indicated the order of covalent character in 4 > 5 with d(x(2)-y(2)) ground state. Novel copper complexes were synthesized by a tridentate ligand having phenolato, pyridine and azomethine nitrogen donors. Phenoxyl radical complexes were generated; DNA interaction, SOD and nuclease activities were investigated. [corrected]

Hydrogen-bonding and π–π stacking inter­actions in tris­(1,10-phenanthroline-κ2N,N′)nickel(II) bis­{[1-tert-butyl­imidazole-2(3H)-thione-κS]trichloridonickelate(II)} acetonitrile disolvate

The asymmetric unit of the title complex, [Ni(C12H8N2)3][NiCl3(C7H12N2S)]2·2CH3CN, consists of one anion, one-half of a cation and one acetonitrile molecule. The NiII atom in the [Ni(phen)3]2+ cation (phen is 1,10-phenanthroline) lies on an inversion centre in an octahedral environment, whereas in the [NiCl3(tm)]− anion [tm is 1-tert-butylimidazole-2(3H)-thione], the geometry is distorted tetrahedral. In the crystal structure, intermolecular C—H⋯Cl hydrogen bonds and π–π stacking interactions (centroid–centroid distance = 3.52 Å) lead to the formation of a three-dimensional framework. One of the methyl groups of the tert-butyl group of N-tert-butyl-2-thioimidazole is disordered between two equally populated positions.

High-spin iron(III) complexes: structural, spectroscopic, and photochemical studies

Reaction of FeCl3 with one equivalent of acac (acac = pentane-2,4-dionate) and KTpMe2 (TpMe2 = hydrotris(3,5-dimethyl-pyrazol-1-yl)borate) yielded TpMe2Fe(acac)Cl (3), which upon reaction with methanolic solution of sodium azide resulted in the formation of a six coordinate compound TpMe2Fe(acac)N3 (4) with a single azide. When the reaction of FeCl3 and KTpMe2 was performed with two equivalents of sodium azide and one equivalent of 3,5-dimethylpyrazole (PzMe2H), a six coordinate cis azide compound [TpMe2Fe(PzMe2H)(N3)2] (5) was obtained. These compounds were characterized by spectroscopic methods and single crystal X-ray crystallography. Electrochemical studies of 5 show that it can be irreversibly reduced at relatively lower potential than 4. The photolysis of 5 was performed at 77 K at different wavelengths (480, 419, and 330 nm) showing that 5 was photoreduced to a high-spin Fe(II) species instead of photooxidized to Fe(V).