Interactions of DNA with a New Platinum(IV) Azide Dipyridine Complex Activated by UVA and Visible Light: Relationship to Toxicity in Tumor Cells

7/abril/2012

Paulina Levario

The Pt^IV diazido complex trans,trans,trans-[Pt(N₃)₂(OH)₂(pyridine)₂] (1) is unreactive in the dark but is cytotoxic when photoactivated by UVA and visible light. We have shown that 1when photoactivated accumulates in tumor cells and binds strongly to nuclear DNA under conditions in which it is toxic to tumor cells. The nature of the DNA adducts, including conformational alterations, induced by photoactivated 1 are distinctly different from those produced in DNA by conventional cisplatin or transplatin. In addition, the observation that major DNA adducts of photoactivated 1 are able to efficiently stall RNA polymerase II more efficiently than cisplatin suggests that transcription inhibition may contribute to the cytotoxicity levels observed for photoactivated 1. Hence, DNA adducts of 1 could trigger a number of downstream cellular effects different from those triggered in cancer cells by DNA adducts of cisplatin. This might lead to the therapeutic effects that could radically improve chemotherapy by platinum complexes. The findings of the present work help to explain the different cytotoxic effects of photoactivated 1 and conventional cisplatin and thereby provide new insights into mechanisms associated with the antitumor effects of platinum complexes photoactivated by UVA and visible light.

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Interactions of DNA with a New Platinum(IV) Azide Dipyridine Complex Activated by UVA and Visible Light: Relationship to Toxicity in Tumor Cells

Jitka Pracharova, Lenka Zerzankova, Jana Stepankova, Olga Novakova, Nicola J. Farrer, Peter J. Sadler, Viktor Brabec, and Jana Kasparkova

Chemical Research in Toxicology Article ASAP

Department of Biophysics, Faculty of Science, Palacky University, 17. Listopadu 12, CZ-77146 Olomouc, Czech Republic

Institute of Biophysics, Academy of Sciences of the Czech Republic, v.v.i., Kralovopolska 135, CZ-61265 Brno, Czech Republic

Department of Chemistry, University of Warwick, Gibbet Hill Road, CV4 7AL, Coventry, United Kingdom

DOI: 10.1021/tx300057y

Publication Date (Web): March 15, 2012

Copyright © 2012 American Chemical Society

http://pubs.acs.org/doi/abs/10.1021/tx300057y

[Gallium(III) protoporphyrin IX]2: A Soluble Diamagnetic Model for Malaria Pigment

7/abril/2012

Paulina Levario

Gallium(III) protoporphyrin IX forms a dimeric propionate-bridged dimer, 2, that is a soluble diamagnetic analogue of hematin anhydride. The single-crystal structure of 2 corresponds to a nondisordered inversion-symmetric dimer similar to malaria pigment but, unlike it, has a six-coordinate metal and an intraporphyrin rather than an interporphyrin hydrogen bond. NMR NOE correlations demonstrate the presence of the propionate linkage in solutions with pyridine. Taken together, this is the first single-crystal X-ray diffraction study of a propionate-linked dimer as found in malaria pigment and the first evidence for its presence in solution.

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[Gallium(III) protoporphyrin IX]2: A Soluble Diamagnetic Model for Malaria Pigment

D. Scott Bohle and Erin L. Dodd

Inorganic Chemistry Article ASAP

Department of Chemistry, McGill University, Montreal H3A 2K6, Canada

DOI: 10.1021/ic2027303

Publication Date (Web): March 23, 2012

Copyright © 2012 American Chemical Society

http://pubs.acs.org/doi/abs/10.1021/ic2027303

Formation and Decomposition of CO2 Intercalated Graphene Oxide

7/Abril/2012

Paulina Levario

The formation, stability, and decomposition of CO₂ intercalated graphene oxide was analyzed by FTIR, TGA-MS, TGA-IR, AFM, and SEM for the first time. We found that the formation starts at 50 °C and develops up to 120 °C. The formation process can be best observed by FTIR spectroscopy, and the product is stable at ambient conditions. At higher temperatures, the decomposition of CO₂ intercalated graphene oxide occurs due to the release of water, CO₂, and CO that can be monitored by TGA-MS and TGA-IR analysis. AFM and SEM images can visualize the formation of blisters in GO films that become instable at 210 °C. We further prepared graphene oxide with a low water-content and found that the formation of CO₂ was significantly suppressed and CO became the major species responsible for the weight loss. In addition we prepared ¹⁸OH₂ treated graphene oxide to elucidate the formation process of CO₂ and found C¹⁶O¹⁸O by TGA-MS analysis that proves the crucial role of water during CO₂ formation. From these experiments we propose that hydrate species are key-intermediates for the formation of CO₂. Hence, it seems likely that rearrangement reactions that can proceed via hydrate intermediates, known from organic chemistry, are probably responsible for the formation of carboxylic acids at the edges of graphene oxide sheets after sonication of graphite oxide. Further, our investigations prove that graphene oxide is less stable than shown by TGA measurements. This has a high impact on the electronic properties of reduced graphene oxide, especially for all those using it for electronic applications.

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Formation and Decomposition of CO2 Intercalated Graphene Oxide

Siegfried Eigler, Christoph Dotzer, Andreas Hirsch, Michael Enzelberger, and Paul Müller

Chemistry of Materials Article ASAP

Department of Chemistry and Pharmacy, University Erlangen-Nürnberg and Institute of Advanced Materials and Processes (ZMP), Henkestrasse 42, 91054 Erlangen and Dr.-Mack Strasse 81, 90762 Fürth, Germany

^‡ Department of Physics, Universität Erlangen-Nürnberg, Erwin-Rommel-Strasse 1, 91058 Erlangen, Germany

DOI: 10.1021/cm203223z

Publication Date (Web): March 12, 2012

Copyright © 2012 American Chemical Society

http://pubs.acs.org/doi/abs/10.1021/cm203223z

Platinum(II) Diimine Complexes with Halide/Pseudohalide Ligands and Dangling Trialkylamine or Ammonium Groups

7/abril/2012
Paulina Levario Sánchez

A series of platinum(II) complexes with the formulas Pt(diimine)(pip₂NCNH₂)(L)²⁺[pip₂NCNH₂⁺ = 2,6-bis(piperidiniummethyl)phenyl cation; L = Cl, Br, I, NCS, OCN, and NO₂; diimine = 1,10-phenanthroline (phen), 5-nitro-1,10-phenanthroline (NO₂phen), and 5,5′-ditrifluoromethyl-2,2′-bipyridine (dtfmbpy)] were prepared by the treatment of Pt(pip₂NCN)Cl with a silver(I) salt followed by the addition of the diimine and halide/pseudohalide under acidic conditions. Crystallographic data as well as ¹H NMR spectra establish that the metal center is bonded to a bidentate phenanthroline and a monodentate halide/pseudohalide. The pip₂NCNH₂⁺ ligand with protonated piperidyl groups is monodentate and bonded to the platinum through the phenyl ring. Structural and spectroscopic data indicate that the halide/pseudohalide group (L^–) and the metal center in Pt(phen)(pip₂NCNH₂)(L)²⁺ behave as Brønsted bases, forming intramolecular NH···L/NH···Pt interactions involving the piperidinium groups. A close examination of the 10 structures reported here reveals linear correlations between N–H···Pt/L angles and H···Pt/L distances. In most cases, the N–H bond is directed toward the Pt–L bond, thereby giving the appearance that the proton bridges the Pt and L groups. In contrast to observations for Pt(tpy)(pip₂NCN)⁺ (tpy = 2,2′;6′,2″-terpyridine), the electrochemical oxidation of deprotonated adducts, Pt(diimine)(L)(pip₂NCN), is chemically and electrochemically irreversible.

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Platinum(II) Diimine Complexes with Halide/Pseudohalide Ligands and Dangling Trialkylamine or Ammonium Groups

Sayandev Chatterjee, Jeanette A. Krause, Kumudu Madduma-Liyanage, and William B. Connick

Inorganic Chemistry Article ASAP

Department of Chemistry, University of Cincinnati, P.O. Box 210172, Cincinnati, Ohio 45221-0172, United States

DOI: 10.1021/ic202462a

Publication Date (Web): April 2, 2012

Copyright © 2012 American Chemical Society

http://pubs.acs.org/doi/abs/10.1021/ic202462a

Exploring the coordination chemistry of MOF-graphite oxide composites and their applications as adsorbents.

Metal-organic frameworks (MOFs), besides being porous materials exhibit a very rich chemistry, which can be used for the synthesis of composites and/or the reactive adsorption of toxic gases. In this study, composites of MOFs (MOF-5, HKUST-1 or MIL-100(Fe)) and a graphitic compound (graphite or graphite oxide, GO) were synthesized and tested for the removal of NH(3), H(2)S and NO(2) under ambient conditions. The materials were characterized before and after exposure to the target gases by X-ray diffraction, thermogravimetric analysis, N(2) sorption measurement and FT-IR spectroscopy. The results indicate that strong chemical bonds exist between the MOF and GO as a result of the coordination between the GO oxygen groups and the MOFs' metallic centers. Depending on the structure of the MOF, such interactions induce the formation of a new pore space in the interface between the carbon layers and the MOF units, which enhances the physical adsorption capacity of the toxic gases. When unsaturated metallic sites are present in the MOFs, the target gases are also adsorbed via coordination to these centers. Further reaction with the framework leads to the formation of complexes. This is accompanied by the collapse of the MOF structure.

Camille Petit, Teresa J Bandosz.

The Department of Chemistry, The City College of New York and the Graduate School of the City University of New York, 160 Convent Avenue, New York, USA.

Journal Article: Dalton Transactions (impact factor: 4.08). 02/2012; DOI: 10.1039/c2dt12017h

Towards a New Family of Photoluminescent Organozinc 8-Hydroxyquinolinates with a High Propensity to Form Noncovalent Porous Materials.

We report on investigations of reactions of tBu(2) Zn with 8-hydroxyquinoline (q-H) and the influence of water on the composition and structure of the final product. A new synthetic approach to photoluminescent zinc complexes with quinolinate ligands was developed that allowed the isolation of a series of structurally diverse and novel alkylzinc 8-hydroxyquinolate complexes: the trinuclear alkylzinc aggregate [tBuZn(q)](3) (1(3) ), the pentanuclear oxo cluster [(tBu)(3) Zn(5) (μ(4) -O)(q)(5) ] (2), and the tetranuclear hydroxo cluster [Zn(q)(2) ](2) [tBuZn(OH)](2) (3). All compounds were characterized in solution by (1) H NMR, IR, UV/Vis, and photoluminescence (PL) spectroscopy, and in the solid state by X-ray diffraction, TGA, and PL studies. Density functional theory calculations were also carried out for these new Zn(II) complexes to rationalize their luminescence behavior. A detailed analysis of the supramolecular structures of 2 and 3 shows that the unique shape of the corresponding single molecules leads to the formation of extended 3D networks with 1D open channels. Varying the stoichiometry, shape, and supramolecular structure of the resulting complexes leads to changes in their spectroscopic properties. The close-packed crystal structure of 1(3) shows a redshifted emission maximum in comparison to the porous crystal structure of 2 and the THF-solvated structure of 3.

Kamil Sokołowski, Iwona Justyniak, Witold Sliwiński, Katarzyna Sołtys, Adam Tulewicz, Arkadiusz Kornowicz, Robert Moszyński, Janusz Lipkowski, Janusz Lewiński.

Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw (Poland), Fax: (+48) 22-3433333.

Journal Article: Chemistry (impact factor: 5.38). 03/2012; DOI: 10.1002/chem.201104028

Hydrogen Bonding Patterns and Supramolecular Structure of 4,4′-Bipyrazolium Salts

12/marzo/2012
Maximiliano De La Higuera Macías

The crystal structures of 18 inorganic salts of 4,4′-bipyrazolium [H2bpz]2+ and 3,3′,5,5′-tetramethyl-4,4′-bipyrazolium [H2Me4bpz]2+ (bpz = 4,4′-bipyrazole; Me4bpz = 3,3′,5,5′-tetramethyl-4,4′-bipyrazole) involving Cl−, I−, I3−, PdCl42−, Cu2Cl62−, Re2Cl82−, SiF62−, TaF6−, Zr2F124−, (BeF3−)n, IO3−, ClO4−, S2O62−, HSO4−, and H2PO4− ions were determined by X-ray diffraction. Primary supramolecular organization of the bipyrazolium salts originates in strong hydrogen bonding between multiple NH cationic donors and O, F, Cl, I anionic acceptors following three main modes, which support linear joints of the cationic moieties: {(Hpz+)2(A−)2}, {(Hpz+)2(AX2−)2}- two pyrazolium moieties joined by a one-atom and three-atom bridging fragment respectively, and {(Hpz+)(AX2−)} - a single pyrazolium moiety “capped” by a three-atom anionic fragment. These modes provide suitable and characteristic supramolecular synthons for the rational design of hydrogen bonded pyrazolium frameworks. The control over dimensionality of the structure is feasible through proper choice of the anion, its charge, and configuration of the acceptor atoms. A relatively high number of hydrogen bond acceptor atoms of the anions (TaF6−, Zr2F124−, ClO4−) results in bifurcation of NH···X bonding. Weaker CH···X hydrogen bonding and slipped π/π interactions are relevant for the secondary supramolecular organization.

Ishtvan Boldog (et al). Hydrogen Bonding Patterns and Supramolecular Structure of 4,4′-Bipyrazolium Salts Inorganic Chemistry Department, Kiev University, Volodimirska Street 64, Kiev 01033, Ukraine, LCC Toulouse, 205, Route de Narbonne, 31077 Toulouse Cedex 4, France, Institute of Organic Chemistry, Murmanskaya Str. 4, 253660, Ukraine, and Institut für Anorganische Chemie, Universität Leipzig, Linnéstraβe 3, D-04103 Leipzig, Germany

Cryst. Growth Des., 2009, 9 (6), pp 2895–2905

DOI: 10.1021/cg9002109

http://pubs.acs.org/doi/pdf/10.1021/cg9002109