Coordination of di- and triimine ligands at ruthenium(II) and ruthenium(III) centers: structural, electrochemical and radical scavenging studies

Herein, we explore the coordination of di- and triimine chelators at ruthenium(II) and ruthenium(III) centers. The reactions of 2,6-bis-((4- tetrahydropyranimino)methyl)pyridine (thppy), N1,N2-bis((3-chromone) methylene)benzene-1,2-diamine (chb), and tris-((1H-pyrrol-2-ylmethylene) ethane)amine (H3pym) with trans-[RuIICl2(PPh3)3] afforded the diamagnetic ruthenium(II) complex cis-[RuCl2(thppy)(PPh3)] (1) and the paramagnetic complexes [mer-Ru2(μ-chb)Cl6(PPh3)2] (2), and [Ru(pym)] (3), respectively. The complexes were characterized by IR, NMR, and UV–vis spectroscopy and molar conductivity measurements. The structures were confirmed by single crystal X-ray diffraction studies. The redox properties of the metal complexes were probed via cyclic- and squarewave voltammetry. Finally, the radical scavenging capabilities of the metal complexes towards the NO and 2,2-di(4-tert-octylphenyl)-1-picrylhydrazyl (DPPH) radicals were investigate

Ruthenium complexes with Schiff base ligands containing benz(othiazole/imidazole) moieties: Structural, electron spin resonance and electrochemistry studies

Novel ruthenium(II/III) complexes of Schiff bases containing benzimidazole (bz) or benzothiazole (bs) moieties were isolated: the diamagnetic ruthenium complex, cis-[RuIICl2(bzpy)(PPh3)2] (1) was formed from the 1:1 M reaction between N-((pyridine-2-yl)methylene)-1H-benzimidazole (bzpy) and metal precursor, trans-[RuCl2(PPh3)3]. The same metal precursor, when reacted with the benzimidazole-derived Schiff bases [N-(2-hydroxybenzylidene)-benzothiazole (Hbsp) and N-(2-hydroxybenzylidene)-benzimidazole (Hbzp)], afforded the paramagnetic ruthenium(III) complexes [RuCl(bsp)2(PPh3)] (2) and trans-[RuCl(bzp)(PPh3)2] (3), respectively. These metal complexes were characterized via IR, mass and UV–Vis spectroscopy, elemental analysis, single crystal XRD analysis as well as conductivity measurements. Their redox properties were probed by voltammetry and accompanying UV–Vis spectroelectrochemistry experiments. Structural features of complex 1 were further investigated by multinuclear (1H and 31P) NMR spectroscopy

4′-[2-(Trifluoro­meth­yl)phen­yl]-2,2′:6′,2′′-terpyridine

The title compound, C22H14F3N3, is a versatile tridentate N-donor ligand consisting of a terpyridyl (terpy) molecule substituted in the 4′-position by a phenyl group, itself substituted in an ortho-position by a bulky trifluoro­methyl group. The phenyl ring is twisted as a result of steric inter­actions involving the bulky trifluoro­methyl substituent. This is reflected in the dihedral angle between the mean plane through the C atoms of the phenyl ring and the terpyridyl unit being 69.2 (1)°. The crystal structure contains no short van der Waals contacts. However, the terpy units stack in a head-to-tail orientation perpendicular to the c axis. The structure is is loosely stabilized by π–π inter­actions between the terminal pyridine rings of adjacent mol­ecules along the stack. The perpendicular distance between the mean planes through the terpy moieties of adjacent mol­ecules is 3.4 (1) Å

Redox behaviour of cymantrene Fischer carbene complexes in designing organometallic multi-tags

Please read abstract in the article.This work is supported by the National Research Foundation (NRF) of South Africa, (D.I.B., Grant number 76226;J.C.S., Grant number 81829). I. F. acknowledges the Spanish MICINN and CAM (Grants CTQ2010-20714-CO2-01/BQU, Consolider-Ingenio 2010, CSD2007-00006, S2009/PPQ-1634). O.Q.M. acknowledges financial support from the University of KwaZulu-Natal and the NRF.http://onlinelibrary.wiley.com/journal/10.1002/(ISSN)1521-37652015-04-30hb201

Cancer molecular biology and strategies for the design of cytotoxic gold(i) and gold(iii) complexes:a tutorial review

Abstract This tutorial review highlights key principles underpinning the design of selected metallodrugs to target specific biological macromolecules (DNA and proteins). The review commences with a descriptive overview of the eukaryotic cell cycle and the molecular biology of cancer, particularly apoptosis, which is provided as a necessary foundation for the discovery, design, and targeting of metal-based anticancer agents. Drugs which target DNA have been highlighted and clinically approved metallodrugs discussed. A brief history of the development of mainly gold-based metallodrugs is presented prior to addressing ligand systems for stabilizing and adding functionality to bio-active gold(I) and gold(III) complexes, particularly in the burgeoning field of anticancer metallodrugs. Concepts such as multi-modal and selective cytotoxic agents are covered where necessary for selected compounds. The emerging role of carbenes as the ligand system of choice to achieve these goals for gold-based metallodrug candidates is highlighted prior to closing the review with comments on some future directions that this research field might follow. The latter section ultimately emphasizes the importance of understanding the fate of metal complexes in cells to garner key mechanistic insights

Gold(Iii) Complexes Of Pyridyl- And Isoquinolylamido Ligands: Structural, Spectroscopic, And Biological Studies Of A New Class Of Dual Topoisomerase I And Ii Inhibitors

The structures, spectroscopy, and cytotoxicity of four novel nominally square-planar gold(III) chelates 1-4 with the general formula cis-AuCl 2(X), where the ligand X is an anionic bidentate pyridyl- or isoquinolylamido chelating agent, are described. The Au-Namido, Au-Npyridyl, and Au-Nisoquinolyl distances are 2.002(9)-2.016(3), 2.01(1)-2.037(3), and 2.037(3) Å, respectively. Density functional theory simulations afforded accurate gold(III) coordination geometries for 1-4 (bond distances and angles to within 5% of the X-ray values), while accurate transition energies were limited to those calculated in the UV spectral region. The complexes had variable stability in dimethyl sulfoxide: compound 3 (relatively rigid) was indefinitely stable, compounds 1 and 2 (conformationally flexible) slowly demetalated over 30 days, and 4 (extensively aromatic) formed an insoluble precipitate after 10 days (72 h in an aqueous buffer). The isoquinolylamido derivative 4 was sufficiently cytotoxic in the NCI-60 screen to undergo full five-dose testing. Notably low GI50 (1.8, 2.3, and 3.2 μM) and IC50 (4.0, 9.8, and 15 μM) values were recorded for the OVCAR-3, IGROV1, and SW-620 cell lines, respectively. Hierarchical cluster analysis employing the National Cancer Institute (NCI) data for known anticancer drugs and 4 revealed that compound 4 is mechanistically identical with the topoisomerase IIα (Top2) poison zorubicin and statistically similar to the topoisomerase IB (Top1) poisons camptothecin and 9-methoxycamptothecin. The Top2-catalyzed decatenation reaction of kinetoplast DNA was studied as a function of the concentration of 4: the compound acts as an interfacial poison of Top2 at low concentrations (\u3c1 μM) and a catalytic inhibitor of the enzyme above 5 μM. Gel mobility shift assays (plasmid DNA substrate) showed that the catalytic inhibition of Top2 likely correlates with DNA binding by 4 at concentrations \u3e5 μM. Compound 4 is also a catalytic inhibitor of Top1 at higher concentrations, consistent with DNA binding by the complex. © 2013 American Chemical Society