Browsing by Author "Krishna Kumar Manar"

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Homoleptic d10 metal complexes containing ferrocenyl functionalized dithiocarbamates as sensitizers for TiO2 based dye-sensitized solar cells
(Elsevier Ltd, 2018) Neetu; Krishna Kumar Manar; Pankaj Srivastava; Nanhai Singh
Four synthesized d10 metal complexes, namely, ferrocenyl based pyridyl functionalized dithiocarbamates macro-cyclic metal-organic coordination polymers, [M(L)2]∞ (M = Zn(II), L = (N-ferrocenyl-methyl-N-pyridin-4-ylmethyl)dithiocarbamate Zn-2; Cd (II), L = (N-ferrocenyl-methyl-N-pyridin-3-ylmethyl) dithiocarbamate Cd-3 and dimers [M(L)2]2 (M = Zn(II), Hg(II), L = (N-ferrocenyl-methyl-N-pyridin-3-ylmethyl) dithiocarbamate, Zn-1 and Hg-4 were studied for their sensitization activities when anchored on TiO2 thin film electrode and employed as photoanode in dye-sensitized solar cells (DSSC). The absorption spectra of test dyes in dichloromethane solution indicated absorption in 400–500 nm range for all complexes, revealing the possibility of their use as photosensitizers for TiO2. The cyclic voltammetry (CV) demonstrated quasi-reversible behavior for all the complexes. All the dye sensitizers showed significant light harvesting properties with an exceptionally high light-to-electrical energy conversion efficiency (6.23%) shown by Zn-1 complex which was close to that obtained with standard Ru dye, N719 (6.96%) under similar experimental conditions. The better performance of Zn-1 complex compared to other studied dye sensitizers were attributed to its structural features. The extent of interfacial charge recombination and electron lifetime were evaluated by the electrochemical impedance spectroscopy (EIS). © 2018 Elsevier Ltd
New planar trans-copper(II) β-dithioester chelate complexes: synthesis, characterization, anticancer activity and DNA-binding/cleavage studies
(Taylor and Francis Ltd., 2017) Manoj Kumar Yadav; Akhilendra Kumar Maurya; Gunjan Rajput; Krishna Kumar Manar; Manjula Vinayak; Michael G. B. Drew; Nanhai Singh
New planar trans-copper(II) β-dithioester complexes, [Cu(L)2] (L = methyl-3-hydroxy-(3-pyridyl)-2-propenedithioate (L1 in 1), methyl-3-hydroxy-(2-naphthyl)-2-propenedithioate (L2 in 2), methyl-3-hydroxy-3-(p-methoxyphenyl)-2-propenedithioate (L3 in 3), methyl-3-hydroxy-3-(p-fluorophenyl)-2-propenedithioate (L4 in 4), and methyl-3-hydroxy-3-(p-bromophenyl)-2-propenedithioate (L5 in 5)), have been synthesized and characterized by elemental (C, H, N and S) analysis, ESI-MS, IR, and UV-vis spectra. The structures of HL3 and its corresponding complex 3 have been determined by X-ray crystallography. Electrochemical behavior of all complexes has been studied by cyclic voltammetry. All five planar complexes show efficient DNA-binding and DNA (PBR322)-cleavage in a concentration-dependent manner (1 > 3 > 5 > 2 > 4). Cleavage efficiency is enhanced in the presence of H2O2 as well as ascorbic acid. However, the order of increased efficiency of Cu(II) chelates differs in the presence of H2O2 as 4 > 1 > 2 > 3 > 5. Among these complexes, the pyridyl- and methoxy-functionalized 1 and 3 have shown higher self-activating capability in DNA-cleavage. All complexes show significant variation in IC50 on MCF-7 cell line. Additionally, treatment with the complexes gradually increases apoptotic cell death in dose-dependent manner in RAW 264.7 cell line. These findings highlight potential cancer protective nature of these complexes. © 2017 Informa UK Limited, trading as Taylor & Francis Group.
Synthesis, characterization, DNA binding and cleavage activity of homoleptic zinc(II) β-oxodithioester chelate complexes
(Taylor and Francis Ltd., 2017) Manoj Kumar Yadav; Akhilendra Kumar Maurya; Gunjan Rajput; Krishna Kumar Manar; Manjula Vinayak; Michael G. B. Drew; Nanhai Singh
New homoleptic zinc(II) complexes, [Zn(L)2], where L = methyl-3-hydroxy-(3-pyridyl)-2-propenedithioate L1 1, and methyl-3-hydroxy-(4-pyridyl)-2-propenedithioate L2 2, have been synthesized and characterized by elemental (C, H, and N) analysis, ESI-MS, and (IR, UV–vis, NMR) spectroscopy; the structure of 1 has been deduced by X-ray crystallography. The DNA binding and cleavage activity of the complexes have been studied. The cleavage potential of pBR322 DNA by 1 and 2 has been checked. Complex 1, which contains nitrogen of the pyridine group in the 3-position enhances DNA cleavage potential in the presence of ascorbic acid; however, the complex is protective against DNA cleavage in the presence of DMSO or H2O2. Also, 1 causes cytotoxicity against the MCF-7 breast cancer cell line. The efficient cytotoxic activity and DNA cleavage ability of 1 in the presence of ascorbic acid shows its potential anticancer properties and the need for further investigations of its potential as an anticancer drug. © 2017 Informa UK Limited, trading as Taylor & Francis Group.