Protonierung von Purin, Adenin und Guanin NMR.‐Spektren und Strukturen der Mono‐, Di‐ und Tri‐Kationen

Wagner, R.; Philipsborn, W. Von

doi:10.1002/hlca.19710540604

Cited by 31 publications

(7 citation statements)

References 17 publications

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“…Clearly, the results of the gas phase calculations are qualitatively in agreement with the situation in water. In nonaqueous solution formation of AH 2 2+ cations and in superacidic medium (FSO 3 H/SbF 5 /SO 2 ) and at low temperature (252 K) even formation of AH 3 3+ cations, protonated at N1, N3, and N7, has been reported 2 …”

Section: Resultsmentioning

confidence: 96%

Protonation of Platinated Adenine Nucleobases. Gas Phase vs Condensed Phase Picture

et al. 2001

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Protonation of adenine carrying a Pt(II) moiety either at N7, N3, or N1 is possible in solution, but the site of protonation is influenced by the location of the Pt(II) electrophile and to some extent also by the overall charge of the metal entity (+2, +1, 0, -1), hence the other ligands (NH(3), Cl(-), OH(-)) bound to Pt(II). Quantum chemical calculations based on density functional theory (DFT) have been carried out for intrinsic protonation energies of adenine complexes carrying the following Pt(II) species at either of the three ring N atoms: [Pt(NH(3))(3)](2+) (1), trans- [Pt(NH(3))(2)Cl](+) (2a), cis-[Pt(NH(3))(2)Cl](+) (2b), trans-[Pt(NH(3))(2)Cl(2)] (3a), cis-[Pt(NH(3))Cl(2)] (3b), [PtCl(3)](-) (4), trans-[Pt(NH(3))(2)OH](+) (5a), cis-[Pt(NH(3))(2)(OH)](+) (5b), trans-[Pt(NH(3))(OH)(2)] (6a), cis-[Pt(NH(3))(OH)(2)] (6b), and [Pt(OH)(3)](-) (7). The data have been compared with results derived from solution studies (water) and X-ray crystallography, whenever available. The electrostatic effects associated with the charge of the metal entity have the major influence on the calculated intrinsic (gas phase) proton affinities, unlike the condensed phase data. Nevertheless, the relative gas phase trends correlate surprisingly well with condensed phase data; i.e., variation of the pK(a) values measured in solution is consistent with the calculated gas phase protonation energies. In addition to a systematic study of the ring proton affinities, proton transfer processes within the platinated adenine species were often observed when investigating Pt adducts with OH(-) ligands, and they are discussed in more detail. To the best of our knowledge, this is the first study attempting to find a systematic correlation between gas phase and condensed phase data on protonation of metalated nucleobases. The gas phase data provide a very useful complement to the condensed phase and X-ray experiments, showing that the gas phase studies are capable of valuable predictions and contribute to our understanding of the solvent and counterion effects on metal-assisted proton shift processes.

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Section: Resultsmentioning

confidence: 96%

Protonation of Platinated Adenine Nucleobases. Gas Phase vs Condensed Phase Picture

et al. 2001

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“…Under the conditions we used, there was no evidence for significant amount of diprotonation, as has been observed in trifluoroacetic acid. 20 Arguments in support of protonation at other than Nl have been adduced from the fluorescence spectra21 of adenine and its derivatives. Our results are decisive in showing that protonation in solution takes place mainly at N1 but do not exclude lesser amounts of protonation at the other nitrogens.…”

Section: Resultsmentioning

confidence: 99%

Nitrogen-15 nuclear magnetic resonance spectroscopy of some nucleosides and nucleotides

Markowski¹,

Sullivan²,

Roberts³

1977

J. Am. Chem. Soc.

172

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High-resolution nitrogen-15 NMR spectra of six nucleosides and six nucleotides have been obtained at the naturalabundance level by high-resolution NMR spectroscopy. All of the nitrogen resonances have been assigned on the basis of comparison of their chemical shifts and nitrogen-hydrogen coupling constants with those of related compounds. Studies of the effect of protonation on the nitrogen chemical shifts of four of these compounds enabled the site of protonation to be detected directly.

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“…Starting Compounds. 9-MeA and deuterated 9-MeA (ND 2 , C(8)D) were prepared as previously described. 9-MeGH, 9-EtGH, and 1-EtTH were purchased from Chemogen, Konstanz, Germany, and used without further purification.…”

Section: Methodsmentioning

confidence: 99%

Bis(purine) Complexes oftrans-a₂Pt^II: Preparation and X-ray Structures of Bis(9-methyladenine) and Mixed 9-Methyladenine, 9-Methylguanine Complexes and Chemistry Relevant to Metal-Modified Nucleobase Triples and Quartets

et al. 1996

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Mononuclear bis(purine) complexes of trans-a 2 Pt II , trans-[(NH 3 ) 2 Pt(9-MeA-N7) (9-MeGH-N7)](NO 3 ) 2 ‚H 2 O (1b) and trans-[(NH 3 ) 2 Pt(9-MeA-N7) 2 ](ClO 4 ) 2 ‚H 2 O (3c), have been prepared and their structures determined by X-ray crystallography. 1b: Space group P1, a ) 7.245 (5) Å, b ) 7.715(6) Å, c ) 10.907(8) Å, R ) 82.36(6)°, ) 86.62(6)°, γ ) 70.15(6)°, V ) 568.3(7) Å 3 , Z ) 1. 3c: Space group P2 1 /c, a ) 8.312(2) Å, b ) 15.386(3) Å, c ) 12.365(2) Å, ) 94.83(3)°, V ) 1575.72(55) Å, Z ) 2. The cation of 3c is centrosymmetric. In the cation of 1b, the two purines adopt a head-head orientation with an intramolecular H bond of 2.94(3) Å between the exocyclic amino group of 9-MeA and the exocyclic carbonyl group of 9-MeGH. Di-and trinuclear derivatives of 1b and 3c have been synthesized and/or studied in solution. They include compounds of types Cl (4), GH (5a), T (5b)) with • representing trans-a 2 Pt II entities (a ) NH 3 or CH 3 NH 2 ). The fact that Pt-(A-N1) and Pt-(A-N7) vectors are at right angles and the nucleobases essentially coplanar in many cases leads to intramolecular H bonding involving NH 2 (6) of 9-MeA and exocyclic groups of the other nucleobases. The chemical shifts of the NH 2 protons of 9-MeA in DMSO-d 6 or DMF-d 7 permit a differentiation between the various possibilities (no H bonding, single H bond, 2 H bonds, 1 Pt or 2 Pt coordinated to 9-MeA). As far as intermolecular H bonding is concerned, the neutral 9-MeGH ligand in 1b forms a Watson-Crick pair with 1-MeC but a 9-MeGH ≡ 9-MeG pair at pH 8. The potential usefulness of the complexes prepared with regard to the formation of two-dimensional sheet structures and molecular squares built up of purine nucleobase and trans-a 2 Pt II entities is briefly discussed, as are aspects of the stabilization of triplex nucleic acid structures by metal ions.(4) Under special circumstances, even tetrahedral metal coordination can allow a coplanar arrangement of two nucleobases; cf.: Fusch, E. C.; Lippert, B.

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Protonierung von Purin, Adenin und Guanin NMR.‐Spektren und Strukturen der Mono‐, Di‐ und Tri‐Kationen

Cited by 31 publications

References 17 publications

Protonation of Platinated Adenine Nucleobases. Gas Phase vs Condensed Phase Picture

Protonation of Platinated Adenine Nucleobases. Gas Phase vs Condensed Phase Picture

Nitrogen-15 nuclear magnetic resonance spectroscopy of some nucleosides and nucleotides

Bis(purine) Complexes oftrans-a₂Pt^II: Preparation and X-ray Structures of Bis(9-methyladenine) and Mixed 9-Methyladenine, 9-Methylguanine Complexes and Chemistry Relevant to Metal-Modified Nucleobase Triples and Quartets

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Protonierung von Purin, Adenin und Guanin NMR.‐Spektren und Strukturen der Mono‐, Di‐ und Tri‐Kationen

Cited by 31 publications

References 17 publications

Protonation of Platinated Adenine Nucleobases. Gas Phase vs Condensed Phase Picture

Protonation of Platinated Adenine Nucleobases. Gas Phase vs Condensed Phase Picture

Nitrogen-15 nuclear magnetic resonance spectroscopy of some nucleosides and nucleotides

Bis(purine) Complexes oftrans-a2PtII: Preparation and X-ray Structures of Bis(9-methyladenine) and Mixed 9-Methyladenine, 9-Methylguanine Complexes and Chemistry Relevant to Metal-Modified Nucleobase Triples and Quartets

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Bis(purine) Complexes oftrans-a₂Pt^II: Preparation and X-ray Structures of Bis(9-methyladenine) and Mixed 9-Methyladenine, 9-Methylguanine Complexes and Chemistry Relevant to Metal-Modified Nucleobase Triples and Quartets