Milan Maji

Synthesis and bio-catalytic activity of isostructural cobalt(III)-phenanthroline complexes

AbstractWe have synthesized two isostructural mononuclear cobalt(III) complexes [1]NO3⋅3H2O and [1]NO3⋅CH3CO2H⋅H2O {[1]+ = [Co(1,10-phenanthroline)2Cl2]+} and characterized by single crystal X-ray structural analyses. Mass spectral studies of the complexes indicate both the compounds to produce identical cationic species viz., [Co(phen)2Cl2]+ in methanol solution. [1]+ has been evaluated as model system for the catechol oxidase enzyme by using 3,5-di-tert-butylcatechol (3,5-DTBC) as the substrate in methanol medium, which revealed that the cationic complex efficiently inhibits catalytic activity with kcat value 9.65 ×102 h−1. [1]+ cleaved pBR 322 DNA without addition of an activating agent. Further, the anti-cancer activity of [1]+ on human hepatocarcinoma cell line (HepG2) has been examined. The induction of apoptosis induced in the cell line was assessed base on the changes in cell morphology, which showed the efficacy of [1]+ to induce apoptosis in 53% of cells during 24 h treatment. Interestingly, the observed IC50 values reveal that [1]+ brings about conformational change on DNA strongly and exhibits remarkable cytotoxicity. The cationic cobalt(III) complex exhibits good catalytic activity in saturated oxygen environment towards 3,5-ditertbutylcatechol with kcat value 9.65×102 h-1. It also exhibits important cytotoxicity against human hepatocarcinoma cell line (HepG2).

Synthesis, structural characterization, and solution properties of a 1-D Pb(II)-bipyridine coordination polymer

A new one-dimensional (1-D) Pb(II) coordination polymer, [Pb(2,2′-bpy)(NO3)2(H2O)]n (1) (2,2′-bpy = 2,2′-bipyridine), has been synthesized and characterized by different spectroscopic techniques and X-ray single-crystal analysis. From the X-ray crystal structure of 1, the Pb2+ can be best described as a highly distorted pentagonal bipyramid with O4 (water) and O6 (nitrate) at apical positions (O4–Pb–O6 of 143.7(1)°). Variability in bond distances reveals that Pb2+ is unsymmetrically surrounded by two nitrates, one 2,2′-bpy and one water. Nitrates bridge between monomers. The molecule crystallizes in the monoclinic P21/n (14) space group. This is the first example of a 1-D Pb(II) polymer in which nitrates show three different coordination motifs (terminal, chelating, and bridging). Solid state as well as solution phase UV–vis spectral analysis and mass spectrometric studies clearly reveal instability with breakdown of Pb(II) polymer in aqueous solution. The arrangement of the 2,2′-bpy, water, and nitrates leaves a coordination gap at the Pb(II) occupied probably by a stereo-active lone pair of electrons.

Unprecedented hetero-geometric discrete copper(II) complexes: Crystal structure and bio-mimicking of Catecholase activity

AbstractAn unprecedented solid of coper(II) complexes, [Cu(dpa)2NCS]2[Cu(dpa)2(NCS)2](ClO4)2 (1) [dpa = 2,2′-dipyridylamine; SCN = thiocyanate], has been synthesized and crystallographically characterized with the aim to study the catecholase activity. The Cu(II) complex mimics the full catalytic cycle of the active site of catechol oxidase enzyme in acetonitrile medium with a turnover number of 4.788×103 h −1 along with the production of semiquinone radical and hydrogen peroxide. In situ generation of Cu(I) species in the catalytic pathway of catechol oxidation was established by electrochemical study and further confirmed by electron paramagnetic resonance (EPR) spectroscopy. Graphical AbstractThis paper reports an X-ray crystallographically characterized Cu(II) complexes which mimics the full catalytic cycle of functional model of catechol oxidase enzyme with significant turnover number (4.788×103 h-1) along with the production of semiquinone radical and hydrogen peroxide.

Recognition of self-assembled water-nitrate cluster in a Co(III)-2,2′-bipyridine host: Synthesis, X-ray structure, DNA cleavage, molecular docking and anticancer activity

AbstractA mononuclear cobalt(III) complex [Co(bpy)2Cl2]NO3⋅2H2O (1) (bpy = 2,2′-bipyridine) has been synthesized and crystallographically characterized. Self-assembly of the lattice water molecules from rectangular tetrameric water cluster interacts with nitrate anion along the c-axis forming a six membered hexagonal water-nitrate cluster. It presents a new mode of association of water molecules with nitrate molecules which is not predicted theoretically or found experimentally. The molecule effectively cleaves bacterial genomic DNA and shows important cytotoxicity against human hepatocarcinoma cell (HepG2). Graphical AbstractThis paper reports an X-ray crystallographic characterization of a Co(III)-bpy complex which also presents a new mode of association of water molecules with nitrate molecules which was not predicted theoretically or found experimentally or reported in literature. The molecule effectively cleaves bacterial genomic DNA and shows important cytotoxicity against human hepatocarcinoma cell (HepG2).

Catalytic aspects of a copper(II) complex: biological oxidase to oxygenase activity

A coper(II) complex,

Binary, Ternary, and Quarternary Complexes of Ruthenium(II) Involving the Flexidentate ONNS Donor Mono(4-(4-tolyl)thiosemicarbazone) of 2,6-Diacetylpyridine (L(2)H). First Report on Ruthenium Complexes of a Mono(thiosemicarbazone) of a Diketone: Crystal Structure of [Ru(L(2))(PPh(3))(2)]ClO(4).

\hbox {[Cu(dpa)}_{2}\hbox {(OAc)](ClO}_{4})

Synthesis, crystal structure determination, spectroscopic and electrochemical studies of trans-[Ru(PPh3)2(bbpH2)Cl]Cl·CHCl3·H20 (bbpH2=2,6-bis(benzimidazolyl) pyridine) – an infinite double columnar supramolecule in the solid state

[Cu(dpa)2(OAc)](ClO4) (1) [dpa =