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N1 Atom (n1 + atom)

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Chemistry100%

Selected Abstracts

Coordination Modes of 9-Methyladenine in cis -Platinum(II) Complexes with Dimethyl(phenyl)phosphanes as Ancillary Ligands , Synthesis and Characterization of cis -[PtL2(9-MeAd)2](NO3)2, cis -[PtL2{9-MeAd(,H)}]3(NO3)3, and cis -[L2Pt{9-MeAd(,H)}PtL2](NO3)3

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 1 2003
Bruno Longato
Abstract Treatment of 9-methyladenine (9-MeAd) with cis -[PtL2(NO3)2] (1) (L = PMe2Ph) in a 2:1 molar ratio generated the bis(adduct) cis -[PtL2(9-MeAd)2](NO3)2 (2), which was isolated and fully characterized by multinuclear (1H, 31P, 13C, 195Pt and 15N) NMR analysis, which showed that the two nucleobases are selectively coordinated through the N1 atom. Small amounts of a mono(adduct) cis -[PtL2(S)(9-MeAd)]2+ (3) (S = solvent) and of a diplatinated species cis -[L2Pt(S){9-MeAd(,H)}PtL2]3+ (4) are formed in DMSO solution when 9-MeAd is present in smaller quantities than 1. Complex 3 is platinated at N1, with a solvent molecule representing the fourth ligand around the metal center. Complex 4 contains an adenine molecule deprotonated and platinated at N1,N6,N7, with two cis -L2Pt units bonded to nitrogen atom N1 and to nitrogen atoms N6 and N7, respectively. With increasing relative concentration of the nucleobase, both complexes 3 and 4 progressively convert into the bis(adduct) 2, the only species detectable in solution when the Ad/Pt molar ratio is 2:1. The trinuclear compound cis -[L2Pt{9-MeAd(,H)}]3(NO3)3 (5) (L = PMe2Ph), containing an NH2 -deprotonated nucleobase bridging the metal centers through the N1 and N6 atoms, is quantitatively formed when the dinuclear hydroxo complex cis -[Pt(,-OH)L2]2(NO3)2 (6) reacts with 9-MeAd in CH3CN solution. The isolated complex was fully characterized by multinuclear NMR spectroscopy and mass spectrometry. It appears to be stable in solution in CH3CN and chlorinated solvents, whereas in DMSO it partially converts into a new species, probably the dinuclear analog cis -[PtL2{9-MeAd(,H)}]2(NO3)2, in which the adenine maintains its coordination mode. At equilibrium the trinuclear/dinuclear species molar ratio is 20:1. Through the addition of a stoichiometric amount of nitrate 1 to a DMSO solution of 5 we were able to generate the diplatinated compound 4 in high yield. Complex 4 displays a new coordination mode for the adeninate ion, with N1 bonded to one platinum atom whereas N6 and N7 are chelated to a second one. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source]

Multinuclear magnetic resonance study of the structure and tautomerism of azide and iminophosphorane derivatives of chloropyridazines

MAGNETIC RESONANCE IN CHEMISTRY, Issue 8 2002
Piotr Cmoch
Abstract Some azido- and iminophosphorane derivatives of 3,6-dichloro- and 3,4,5,6-tetrachloropyridazine were synthesized and studied by means of NMR measurements. Based on multinuclear data (chemical shifts, coupling constants) for compounds containing the azide group, no potentially possible tetrazole,azide equilibrium can be observed, even under acidic conditions. An unusual substitution of a chlorine atom (in position 4) of tetrachloropyridazine in the reaction with hydrazine was demonstrated by NMR measurements of two newly synthesized compounds containing azido- and iminophosphorane groups. Using multinuclear magnetic resonance data, the sites of ethylation and protonation of azido- and iminophosphorane derivatives of chloropyridazines were established. In the case of the tetrazolopyridazines, ethylation occurs at the N1, and N2, atoms, whereas for monocyclic compounds it takes place at the N1 and/or N2 atoms of the pyridazine ring. Preferred sites of protonation are the N1, atom of the tetrazole ring and the N1 atom of the pyridazine ring. Moreover, the structures of potassium salts of 6-(3-cyano-1-triazeno)tetrazolo[1,5- b] pyridazine and its amido derivative were established using NMR data, especially 15N NMR chemical shifts. Copyright © 2002 John Wiley & Sons, Ltd. [source]

3-(Ethoxy­carbonyl­di­hydroxy­methyl)-2-oxo-1,2-di­hydro­quinox­aline

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 10 2000
S. Ferfra
The crystal structure of the title compound, ethyl 2,2-di­­hy­droxy-2-(3-oxo-3,4-di­hydro­quinoxalin-2-yl)­acetate, C12H12N2O5, indicates a short intramolecular contact between the N1 atom and a hydroxyl group [2.772,(4),Ĺ]. Two intermolecular hydrogen bonds participate in the molecular packing. [source]

Adsorption of 6-mercaptopurine and 6-mercaptopurine-ribosideon silver colloid: A pH-dependent surface-enhanced Raman spectroscopy and density functional theory study.

BIOPOLYMERS, Issue 6 2005

Abstract Surface-enhanced Raman spectroscopy (SERS) has been applied to characterize the interaction of 6-mercaptopurine-ribose (6MPR), an active drug used in chemotherapy of acute lymphoblastic leukemia, with a model biological substrate at therapeutic concentrations and as function of the pH value. Therefore, a detailed vibrational analysis of crystalline and solvated (6MPR) based on Density Functional Theory (DFT) calculations of the thion and thiol tautomers has been performed. 6MPR adopts the thion tautomeric form in the polycrystalline state. The SERS spectra of 6MPR and 6-mercaptopurine (6MP) recorded on silver colloid provided evidence that the ribose derivative shows different adsorption behavior compared with the free base. Under acidic conditions, the adsorption of 6MPR on the metal surface via the N7 and possibly S atoms was proposed to have a perpendicular orientation, while 6MP is probably adsorbed through the N9 and N3 atoms. Under basic conditions both molecules are adsorbed through the N1 and possibly S atoms, but 6MP has a more tilted orientation on the silver colloidal surface while 6MPR adopts a perpendicular orientation. The reorientation of the 6MPR molecule on the surface starts at pH 8 while in the case of 6MP the reorientation starts around pH 6. Under basic conditions, the presence of the anionic molecular species for both molecules is suggested. The deprotonation of 6MP is completed at pH 8 while the deprotonation of the riboside is finished at pH 10. For low drug concentrations under neutral conditions and for pH values 8 and 9, 6MPR interacts with the substrate through both N7 and N1 atoms, possibly forming two differently adsorbed species, while for 6MP only one species adsorbed via N1 was evidenced. © 2005 Wiley Periodicals, Inc. Biopolymers 78: 298,310, 2005 This article was originally published online as an accepted preprint. The "Published Online" date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com [source]