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1,085 results on '"Lippert, Bernhard"'

16. On the Heterogeneous Nature of Cisplatin‐1‐Methyluracil Complexes: Coexistence of Different Aggregation Modes and Partial Loss of NH3 Ligands as Likely Explanation

Author

Pullen, Sonja, Hegmans, Alexander, Hiller, Wolf G., Platzek, André, Freisinger, Eva, and Lippert, Bernhard

Subjects
Full Paper, Molecular Structure, Water, Full Papers, 1-methyluracil, Ligands, NMR spectroscopy, condensation reactions, Ammonia, Coordination Complexes, Silver Nitrate, platinum, Cisplatin, Uracil, mass spectrometry
Abstract

The conversion of the 1 : 1‐complex of Cisplatin with 1‐methyluracil (1MeUH), cis‐[Pt(NH3)2(1MeU‐N3)Cl] (1 a) to the aqua species cis‐[Pt(NH3)2(1MeU‐N3)(OH2)]+ (1 b), achieved by reaction of 1 a with AgNO3 in water, affords a mixture of compounds, the composition of which strongly depends on sample history. The complexity stems from variations in condensation patterns and partial loss of NH3 ligands. In dilute aqueous solution, 1 a, and dinuclear compounds cis‐[(NH3)2(1MeU‐N3)Pt(μ‐OH)Pt(1MeU‐N3)(NH3)2]+(3) as well as head‐tail cis‐[Pt2(NH3)4(μ‐1MeU‐N3,O4)2]2+ (4) represent the major components. In addition, there are numerous other species present in minor quantities, which differ in metal nuclearity, stoichiometry, stereoisomerism, and Pt oxidation state, as revealed by a combination of 1H NMR and ESI‐MS spectroscopy. Their composition appears not to be the consequence of a unique and repeating coordination pattern of the 1MeU ligand in oligomers but rather the coexistence of distinctly different condensation patterns, which include μ‐OH, μ‐1MeU, and μ‐NH2 bridging and combinations thereof. Consequently, the products obtained should, in total, be defined as a heterogeneous mixture rather than a mixture of oligomers of different sizes. In addition, a N2 complex, [Pt(NH3)(1MeU)(N2)]+ appears to be formed in gas phase during the ESI‐MS experiment. In the presence of Na+ ions, multimers n of 1 a with n=2, 3, 4 are formed that represent analogues of non‐metalated uracil quartets found in tetrastranded RNA., Multiple condensation reactions of mononuclear 1‐methyl uracilato (1MeU) complexes of Cisplatin, and numerous side reactions, lead to a heterogeneous mixture of products, as shown by 1H‐NMR and ESI‐MS

Published
2021

19. Assembly of nucleobases into rings and cages via metal ions

Author

German Research Foundation, Universidad de Zaragoza, Lippert, Bernhard, Sanz Miguel, Pablo J., German Research Foundation, Universidad de Zaragoza, Lippert, Bernhard, and Sanz Miguel, Pablo J.

Abstract

Metal ions are natural counterparts of nucleic acids and crucial in stabilizing many specific structures. While the relevant bulk main group metal ions (Na+, K+, Mg2+) are predominantly important in keeping base pairs in register and/or allowing the formation of particular specific RNA structures, transition metal ions, and specifically the soft ones, display a pronounced affinity for donor atoms of the heterocyclic nucleobases as part of nucleic acids. Their nature in fact provides a large number of different binding patterns, including specific cross-links and/or the formation of cyclic entities and/or cages. This review article summarizes constructs obtained this way, without over-emphasizing their biological relevance. Nevertheless, it can be claimed that in a number of cases model findings have preceded their discoveries in biorelevant events.

Published
2022

20. Beyond sole models for the first steps of Pt-DNA interactions: Fundamental properties of mono(nucleobase) adducts of PtII coordination compounds

Author

TU Dortmund University, Universidad de Zaragoza, Lippert, Bernhard, Sanz Miguel, Pablo J., TU Dortmund University, Universidad de Zaragoza, Lippert, Bernhard, and Sanz Miguel, Pablo J.

Abstract

A major feature of mono(nucleobase) complexes of PtII containing one or more aqua ligands is their ability to engage in intermolecular condensation reactions leading to multinuclear species with bridging nucleobases, bridging hydroxido or amido ligands. Their chemistry appears to be more versatile with isolated model nucleobases than is the case when relevant PtII species interact with nucleic acids. Special emphasis of this review article is on compounds obtained with pyrimidine model nucleobases (1-methylcytosine, 1-metylthymine, 1-methyluracil) and their cyclic condensation products. Aspects of chirality of mononuclear as well as head–tail dinuclear species will be discussed.

Published
2022

22. On the Heterogeneous Nature of Cisplatin‐1‐Methyluracil Complexes: Coexistence of Different Aggregation Modes and Partial Loss of NH 3 Ligands as Likely Explanation

Author

Pullen, Sonja, Hegmans, Alexander, Hiller, Wolf G, Platzek, André, Freisinger, Eva, Lippert, Bernhard, University of Zurich, Pullen, Sonja, Freisinger, Eva, and Lippert, Bernhard

Subjects
10120 Department of Chemistry, 540 Chemistry, 1600 General Chemistry, General Chemistry
Published
2021
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24. Modelling Platinum-DNA Interactions

Author

Lippert, Bernhard, Frommer, Gudrun, Renn, Oliver, Krizanovic, Olga, Dieter, Iris, Krumm, Michael, Trotscher, Gabriele, Pesch, Ferdinand, Schwarz, Frank, Menzer, Stephan, Hillgeris, Edda C., and Howell, Stephen B., editor

Published
1991
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29. Tetrakis- and tris(1-methyluracil) complexes of [Pt.sup.II]: formation and properties of a carbon-bonded nucleobase species as well as of heteronuclear derivatives

Author

Holland, Lars, Wei-Zheng Shen, Micklitz, Wolfgang, and Lippert, Bernhard

Subjects
Platinum compounds -- Research, Platinum compounds -- Chemical properties, Coordination compounds -- Research, Coordination compounds -- Chemical properties, Chemistry
Abstract

Linkage isomerism is found in a [Pt.sup.II] complex with the model nucleobase 1-methyluracil (1-MeUH). The basic properties of tetrakis- and tris(1-methyluracil) complexes of [Pt.sup.II] are analyzed, concentrating on their acid-base properties and their affinity for additional metal ions.

Published
2007

32. Pyrazine as a building block for molecular architectures with Pt(super II)

Author

Willermann, Michael, Mulcahy, Clodagh, Sigel, Roland K.O., Miguel, Pablo J. Sanz, Cerda, Marta Morell, Freisinger, Eva, Roitzsch, Michael, and Lippert, Bernhard

Subjects
Pyridazine -- Chemical properties, Pyridazine -- Structure, Platinum compounds -- Chemical properties, Platinum compounds -- Structure, Nuclear magnetic resonance spectroscopy -- Usage, Chemistry
Abstract

A series of pyrazine (pz) complexes containing cis-(NH3)(sub 2)Pt(super II), (tmeda)Pt(super II), and trans-(NH3)(sub 2)Pt(super II) entities are synthesized and characterized by X-ray crystallography and/or (super 1)H NMR spectroscopy. The formation of the cyclic tetramer [Pt(super II)](sub 4) complex conforms to expectations of the molecular library approach, which predicts a molecular box when two ditopic building blocks with 90 degree and 180 degree angles, respectively, are combined.

Published
2006

33. Intrinsic acid-base properties of purine derivatives in aqueous solution and comparison of the acidifying effects of platinum(II) coordinated to N1 or N7: acidifying effects are reciprocal and the proton 'outruns' divalent metal ions

Author

Griesser, Rolf, Kampf, Gunnar, Kapinos, Larisa E., Komeda, Seiji, Lippert, Bernhard, Reedijk, Jan, and Sigel, Helmut

Subjects
Chemistry, Inorganic -- Research, Acids, Solution (Chemistry) -- Composition, Complex compounds, Coordination compounds, Metal ions, Platinum compounds, Ligands, Chemistry
Abstract

Research has been conducted on platinum(II) coordination compounds. The effect of these compounds on the acid-base properties of such purine ligands as 9-ethylguanine has ben quantitatively evaluated, and the details are reported.

Published
2003

39. Association patterns of platinated purine nucleobases in metal-modified pairs and triples

Author

Roitzsch, Michael, Rother, Irene B., Willermann, Michael, Erxleben, Andrea, Costisella, Burkhard, and Lippert, Bernhard

Subjects
Chemistry, Inorganic -- Research, Platinum, Nucleotides, Coordination compounds, Hydrogen bonding, Purines, Chemistry
Abstract

Research has been conducted on purine nucleobases. The study of the metal-modifed base pair and metal-modified base triplet containing purine bases is presented.

Published
2002

40. Loss of Hoogsteen pairing ability upon N1 adenine platinum binding

Author

Schmidt, Kathrin S., Reedijk, Jan, Weisz, Klaus, Janke, Eline M. Basilio, Sponer, Judit E., Sponer, Jiri, and Lippert, Bernhard

Subjects
Chemistry, Inorganic -- Research, Platinum -- Physiological aspects, Chloroform -- Physiological aspects, Solution (Chemistry) -- Physiological aspects, Coordination compounds -- Physiological aspects, Chlorofluorocarbons -- Physiological aspects, Hydrogen bonding -- Physiological aspects, Chemistry
Abstract

Research has been conducted on the chloroform- and Freon-soluble thymine, adenine complexes. The H bonding interactions of the chloroform-soluble platinum complex have been investigated and the results are discussed.

Published
2002

41. Detection and measurement of noncoincidence between the principal axes of the g-matrix and zero-field splitting tensor using multifrequency powder EPR spectroscopy: application to cis-[(NH (sub)3) (sub)2 Pt(1-MeU) (sub)2 Cu(H (sub)2 O) (sub)2](SO (sub)4).4.5H (sub)2 O (1-MeU= monoanion of 1-methyluracil)

Author

Collison, David, Goodgame, David M. L., Hitchman, Michael A., Lippert, Bernhard, Mabbs, Frank E., and McInnes, Eric J. L.

Subjects
Chemistry, Inorganic -- Research, Anions -- Physiological aspects, Copper -- Physiological aspects, Sulfur -- Physiological aspects, Oxygen -- Physiological aspects, Nitrogen -- Physiological aspects, Hydrogen -- Physiological aspects, Platinum -- Physiological aspects, Monomers -- Physiological aspects, Chemistry
Abstract

Research has been conducted on the noncoisidence between the g-matrix principle axes and metal hyperfine matrix in the monomeric metal complexes. This noncoisidence has been detected and measured via the use of the multifrequency powder EPR spectra and the spectrum simulation and the details are reported.

Published
2002

45. How nucleobases rotate when bonded to a metal ion: detailed view from an ab initio qantum chemical study of a cytosine complex of trans-a (sub)2 Pt (super)II

Author

Sponer, Judit E., Glahe, Frank, Leszczynski, Jerzy, Lippert, Bernhard, and Sponer, Jiri

Subjects
Chemistry, Physical and theoretical -- Research, Metal ions -- Physiological aspects, Quantum chemistry -- Research, Cytosine -- Physiological aspects, Platinum -- Physiological aspects, Chemicals, plastics and rubber industries
Published
2001

46. Protonation of platinated adenine nucleobases. Gas phase vs condensed phase picture

Author

Sponer, Judit E., Leszczynski, Jerzy, Glahe, Frank, Lippert, Bernhard, and Sponer, Jiri

Subjects
Chemistry, Inorganic -- Research, Platinum -- Physiological aspects, Nitrogen -- Physiological aspects, Oxygen -- Physiological aspects, Hydrogen -- Physiological aspects, Density functionals -- Usage, Chemistry
Abstract

Research has been conducted on the intrinsic protonation energies of adenine complexes. The use of the density functional theory in performing quantum chemical calculations for these complexes carrying Pt(II) species at the ring N atoms is described.

Published
2001

48. Self-assembly of palladium(II) and platinum(II) complexes of 2-hydroxypyrimidine to novel metallacalix[4]arenes. Receptor properties through multiple H-bonding interactions

Author

Navarro, Jorge A.R., Freisinger, Eva, Lippert, Bernhard, Kirk, Martin L., Vasconcellos, L.C.G., and Franco, D.W.

Subjects
Hydrogen bonding -- Research, Platinum -- Research, Platinum -- Chemical properties, Palladium -- Research, Palladium -- Chemical properties, Chemistry
Abstract

The direct synthesis of metallacalix[4]arenes by a self-assembly process is possible by making use of a combination of 120 degrees and 90 degrees bond angles provided by the Hpymo ligand and enM (M = Pd(super II), Pt(super II)) metal entities respectively. Interactions with positively charged species are possible despite the positive charge of these metallacalix[4]arenes.

Published
2000

49. Isomeric equilibria in aqueous solution involving aromatic ring stacking in the sexternary complexes formed by the quaternary cis-(NH3)(sub 2)Pt(2'-deoxyguanosine-N7)(dGMP-N7) complex and the binary Cu(2,2'-bipyridine)(super 2+) or Cu(1,10-phenanthroline)(super 2+) complexes (dGMP(super 2-) = 2'-deoxyguanosine 5'-monophosphate)

Author

Luth, Marc Sven, Song, Bin, Lippert, Bernhard, Seigl, Helmut, and Totti, Federico

Subjects
Heterocyclic aromatic compounds -- Research, Heterocyclic aromatic compounds -- Chemical properties, Nucleic acids -- Research, Nucleic acids -- Chemical properties, Copper compounds -- Research, Copper compounds -- Chemical properties, Chemistry
Abstract

The stabilities of sexternary complexes are determined by potentiometric pH titrations in aqueous solution at 25 degrees C and I = 0.1 M (NaNO3) and are formed by the binding of the binary Cu(Arm)(super 2+) complexes, where Arm = 2,2'-bipyridine (Bpy) or 1,10-phenanthrolone (Phen), to the -PO(sub 3)(super 2-) group present in the quaternary cis-(NH3)(sub 2)Pt(dGuo)(dGMP) complex. The result demonstrates that in aqueous solution purine residues of nucleotides or nucleic acids that carry a metal ion at N7 can still undergo stacking interactions with other suitable aromatic ring systems.

Published
2000

50. From simple trans-[a(sub 2)Pt(2-hydroxypyrimidine)(sub 2)](super 2+) (a = NH3, CH3NH2) complexes to structures of higher complexity. Molecular recognition of 2-aminopyrimidine by hydrogen bond formation and reactivity toward additional metal ions

Author

Navarro, Jorge A.R., Freisinger, Eva, Lippert, Bernhard, and Scott, Brian L.

Subjects
Ammonia -- Research, Ammonia -- Chemical properties, Metal ions -- Research, Metal ions -- Chemical properties, Metal ions -- Magnetic properties, Hydrogen bonding -- Research, Hydrogen bonding -- Chemical properties, Chemistry
Abstract

Compounds of type trans-[a(sub 2)Pt(2-hydroxypyrimidine)(sub 2)]-X2 (1) (a = NH3, CH3NH2; X = NO3, ClO4) are used as building blocks for more complex structures. The interaction of the trans-[a(sub 2)Pt(Hpymo-N(super 1))(sub 2)](super 2+) complexes with additional metal ions leads to the formation of polymeric structures after coordination of the new metal to the basic N3 donor atoms of the pyrimidine ring.

Published
2000

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