Daya Shankar Pandey

DNA Binding and Anti-Cancer Activity of Redox-Active Heteroleptic Piano-Stool Ru(II), Rh(III), and Ir(III) Complexes Containing 4-(2-Methoxypyridyl)phenyldipyrromethene

The synthesis of four novel heteroleptic dipyrrinato complexes [(η(6)-arene)RuCl(2-pcdpm)] (η(6)-arene = C6H6, 1; C10H14, 2) and [(η(5)-C5Me5)MCl(2-pcdpm)] (M = Rh, 3; Ir, 4) containing a new chelating ligand 4-(2-methoxypyridyl)-phenyldipyrromethene (2-pcdpm) have been described. The complexes 1-4 have been fully characterized by various physicochemical techniques, namely, elemental analyses, spectral (ESI-MS, IR, (1)H, (13)C NMR, UV/vis) and electrochemical studies (cyclic voltammetry (CV) and differential pulse voltammetry (DPV)). Structures of 3 and 4 have been determined crystallographically. In vitro antiproliferative and cytotoxic activity of these complexes has been evaluated by trypan blue exclusion assay, cell morphology, apoptosis, acridine orange/ethidium bromide (AO/EtBr) fluorescence staining, and DNA fragmentation assay in Dalton lymphoma (DL) cell lines. Interaction of 1-4 with calf thymus DNA (CT DNA) has also been supported by absorption titration and electrochemical studies. Our results suggest that in vitro antitumor activity of 1-4 lies in the order 2 > 1 > 4 > 3.

DNA/Protein Binding, Molecular Docking, and in Vitro Anticancer Activity of Some Thioether-Dipyrrinato Complexes

Syntheses and characterizations of the arene ruthenium [(η(6)-C6H6)RuCl(4-mtdpm)] (1), [(η(6)-p-MeC6H4Pr(i))RuCl(4-mtdpm)] (2), and structurally analogous rhodium/iridium complexes [(η(5)-C5Me5)RhCl(4-mtdpm)] (3) and [(η(5)-C5Me5)IrCl(4-mtdpm)] (4) [4-mtdpm = 5-(4-methylthiophenyl)dipyrromethene] have been reported. Their identities have been established by satisfactory elemental analyses, electrospray ionization-mass spectrometry (ESI-MS), FT-IR, NMR ((1)H, (13)C), UV/vis, emission spectral, and electrochemical studies. Structure of the representative complex 3 has been authenticated by X-ray single crystal analyses. The complexes 1-4 effectively bind with calf thymus DNA (CT DNA) through intercalative/electrostatic interactions. In addition, these exhibit significant cytotoxicity toward Dalton lymphoma (DL) cell line and cause static quenching of the bovine serum albumin (BSA) fluorophore. The antiproliferative activity, morphological changes, and apoptosis have been evaluated by MTT assay, acridine orange/ethidium bromide (AO/EtBr) fluorescence staining, and DNA ladder assay. Mode of interaction of the complexes with DNA/protein has also been supported by molecular docking. Various studies revealed remarkable decrease in the in vitro DL cell proliferation and induction of the apoptosis by 1-4, which lies in the order 2 > 1 > 4 > 3.

Stable mononuclear and binuclear ruthenium(II) arene complexes with multiple N-donor poly-pyridyl ligands: synthesis, spectroscopic and structural characterization. Single crystal X-ray structure of [(η6-C10H14)RuCl(bppz)]BF4

Abstract The reaction of 2,3-bis(2-pyridyl)-pyrazine (bppz) with dimeric chloro-bridged arene ruthenium complexes [{(η6-arene)RuCl2}2] (arene=p-cymene or hexamethyl benzene) gives highly stable cationic mono and binuclear complexes with the formulation [(η6-C10H14)RuCl(bppz)]+ and [{(η6-C10H14)RuCl}2(μ-bppz)]2+. On the contrary, reactions of the potential bridging ligand 2,4,6-tris(2-pyridyl)-1,3,5-triazine (tptz) or 3,6-bis(2-pyridyl)-1,2,4,5-tetrazine (bptz) with the chloro-bridged dimeric arene ruthenium complexes [{(η6-arene)RuCl2}2] under similar reaction conditions led to the formation of binuclear complexes with the formulation [{(η6-arene)RuCl}2(μ-L)]2+ (where η6-arene=p-cymene or hexamethyl benzene and L=tptz or bptz). The reaction products were characterized by various physico-chemical techniques, viz. elemental analyses, IR, 1H–1H COSY, 1H-, 13C-NMR, FAB mass spectroscopy and electronic spectral studies. Molecular structure of the representative mononuclear complex [(η6-C10H14)RuCl(bppz)]BF4 was determined by single crystal X-ray diffraction analysis. Crystal data: monoclinic, C2/c, a=16.103(5) A, b=16.207(2) A, c=19.124(2) A, β=91.61(2)°, Z=8, R=0.0714.

Multifaceted half-sandwich arene–ruthenium complexes: interactions with biomolecules, photoactivation, and multinuclearity approach

Biological properties of the arene–ruthenium complexes have attracted substantial current interest. Their activity is appreciably defined and controlled by the arene moieties, organic ligands and the metal center. In this review, we discuss the interaction of arene–ruthenium complexes with significant biomolecular targets (DNA and enzymes). Principally, active complexes may interact with the biomolecular targets DNA or nucleobases either by direct coordination facilitated by aquation of the complex or by intercalation/stacking of the pendant planar part of the complex, usually from the planar ancillary ligands or arenes with extended rings, between the DNA base pairs. On the other hand, kinetically inert metal complexes can also provide a potential tool (as enzyme inhibitors) for the targeting of important biomolecules (other than DNA), such as protein kinases. At the same time, coordination with a metal facilitates the outreach of the organic molecules in the intracellular region. This review also highlights the photodriven activation of arene–ruthenium complexes, important metal–drug interactions and the potential of multinuclear scaffolds as important drug candidates (e.g., metallodendrimers) and drug carriers (e.g. metallacages) for targeted delivery and activity.

Interaction of ferrocene appended Ru(II), Rh(III) and Ir(III) dipyrrinato complexes with DNA/protein, molecular docking and antitumor activity

Efficacy of the ferrocene appended piano-stool dipyrrinato complexes [(η(6)-C6H6)RuCl(fcdpm)] (1), [(η(6)-C10H14)RuCl(fcdpm)] (2), [(η(6)-C12H18)RuCl(fcdpm)] (3) [(η(5)-C5Me5)RhCl(fcdpm)] (4) and [(η(5)-C5Me5)IrCl(fcdpm)] (5) [fcdpm = 5-ferrocenyldipyrromethene] toward anticancer activity have been described. Binding of the complexes with calf thymus DNA (CT-DNA) and BSA (bovine serum albumin) have been thoroughly investigated by UV-Vis and fluorescence spectroscopy. Binding constants for 1-5 (range, 10(4)-10(5) M(-1)) validated their efficient binding with CT-DNA. Molecular docking studies revealed interaction through minor groove of the DNA, on the other hand these also interact through hydrophobic residues of the protein, particularly cavity in the subdomain IIA. In vitro anticancer activity have been scrutinized by MTT assay, acridine orange/ethidium bromide (AO/EtBr) fluorescence staining, and DNA ladder (fragmentation) assay against Daltons Lymphoma (DL) cells. Present study revealed that rhodium complex (4) is more effective relative to ruthenium (1-3) and iridium (5) complexes.

Heteroleptic Dipyrrinato Complexes Containing 5-Ferrocenyldipyrromethene and Dithiocarbamates as Coligands: Selective Chromogenic and Redox Probes

Six heteroleptic dipyrrinato complexes [Ni(fcdpm)(dedtc)] (1), [Ni(fcdpm)(dipdtc)] (2), [Ni(fcdpm)(dbdtc)] (3), [Pd(fcdpm)(dedtc)] (4), [Pd(fcdpm)(dipdtc)] (5), and [Pd(fcdpm)(dbdtc)] (6) (fcdpm = 5-ferrocenyldipyrromethene; dedtc = diethyldithiocarbamate; dipdtc = diisopropyldithiocarbamate; dbdtc = dibutyldithiocarbamate) have been synthesized and characterized by elemental analyses and spectral (ESI-MS, IR, (1)H, (13)C NMR, UV-vis) and electrochemical studies. Crystal structures of 1, 2, 4, and 5 have been authenticated by X-ray single-crystal analyses. Nickel-based complexes 1-3 display selective chromogenic and redox sensing for Hg(2+) and Pb(2+) ions, while palladium complexes 4-6 display selective chromogenic and redox sensing only for Hg(2+). Electronic absorption, ESI-MS, and electrochemical studies indicated that sensing arises from interaction between 1-3 and Hg(2+)/Pb(2+) through sulfur of the coordinated dithiocarbamates, while it arises from the pyrrolic nitrogen of fcdpm and dithiocarbamate sulfur from 4-6 and Hg(2+). Different modes of binding between Ni and Pd complexes have further been supported by theoretical studies. The receptor-cation binding constants (K(a)) and stoichiometry between probes and Hg(2+)/Pb(2+) have been estimated by the Benesi-Hildebrand method and Jobs plot analysis. Detection limits for 1-3 toward Hg(2+)/Pb(2+) and 4-6 for Hg(2+) have been found to be reasonably high.

Synthetic, spectral and structural aspects of some mono- and binuclear (homo/hetero) Ru(II) hydrido carbonyl complexes

Abstract Reactions of the poly-pyridyl bridging ligand 2,4,6-tris(2-pyridyl)-1,3,5-triazine; 2,3-bis(2-pyridyl)-pyrazine and 3,6-bis(2-pyridyl)-1,2,4,5-tetrazine (referred hereafter as tptz, bppz and bptz respectively) with [RuH(CO)Cl(PPh3)3] in methanol, gave highly stable cationic complexes with the formulation [RuH(CO)(PPh3)2(L)]+. Further, the mononuclear complex [RuH(CO)(PPh3)2(bppz)]PF6 reacted with K2PtCl4, [PdCl2(benzonitrile)2], [{Ru(η6-C10H14)(μ-Cl)Cl}2], [{Ru(η6-C6Me6)(μ-Cl)Cl}2], [RuCl(η5-C5H5)(PPh3)2] and [{Rh(η5-C5Me5)(μ-Cl)Cl}2] in methanol under refluxing conditions to give bppz bridged binuclear complexes with the formulation [RuH(CO)(PPh3)2(bppz)PtCl2]PF6, [RuH(CO)(PPh3)2(bppz)PdCl2]PF6, [RuH(CO)(PPh3)2(bppz)(η6-C10H14)RuCl](PF6)2, [RuH(CO)(PPh3)2(bppz)(η6-C6Me6)Cl2Ru](PF6)2, [RuH(CO)(PPh3)2(bppz)(η5-C5H5)(PPh3)Ru](PF6)2 and [RuH(CO)(PPh3)2(bppz)Rh(η5-C5Me5)Cl](PF6)2 in quantitative yield. The reaction products have been characterized by elemental analyses, IR, 1H-, 1H–1H-COSY, 13C-, 31P-NMR, ESMS, FAB mass spectroscopy, electronic spectra and cyclic voltammetry. Molecular structure of the representative mononuclear complex [RuH(CO)(PPh3)2(tptz)]BF4 has been confirmed by X-ray crystallography. Crystal structure determination revealed η2-coordination of the ligand tptz with the metal center. Crystal data: monoclinic, P21/n, a=17.810(6) A, b=22.233(9) A, c=12.156(4) A, β=90.06(3)°, Z=4, R=0.078.

Magnetoresistance behavior of ferromagnetic shape memory alloy Ni 1.75 Mn 1.25 Ga

A negative-positive-negative switching behavior of magnetoresistance (MR) with temperature is observed in a ferromagnetic shape memory alloy

Ruthenium(II) Polypyridyl Complexes: Potential Precursors, Metalloligands, and Topo II Inhibitors

{\text{Ni}}_{1.75}{\text{Mn}}_{1.25}\text{Ga}

Synthesis and spectroscopic properties of cationic Ru(II) arene complexes [Ru(η6-arene)(P)Cl(L)]+. (P=PPh3, PEt3, MePPri2 and L=4-cyanopyridine or 1,4-dicyanobenzene)

. In the austenitic phase between 300 and 120 K, MR is negative due to