A Unique Helicate Comprised of Four Cytosine Nucleobases and Four Metal Entities (Pt-II, Pt-II, Au-III, Au-I). Implications for the Interactions of Linearly Coordinated Metal Ions with Nucleotide Duplexes

作者：Fusch Gerhard; Zangrando Ennio^*; Randaccio Lucio; Lippert Bernhard

来源：Zeitschrift fur Anorganische und Allgemeine Chemie, 2013, 639(8-9): 1674-1679.

DOI：10.1002/zaac.201300038

• Metal helicate
• 1-Methylcytosine
• Platinum
• Gold
• N-chirality

Reaction of trans-[Pt(CH3NH2)(2)(1-MeC-N3)(2)]X-2 (1-MeC = 1-methylcytosine; X = NO3- or ClO4-) with Na[AuCl4] in strongly alkaline aqueous solution yields an asymmetrical double helicate containing two central Pt-II as well as Au-III and Au-I atoms, four 1-methylcytosinato bridges (1-MeC--N3,N4), two terminal methylamine and two bridging methylamido ligands, [Au2Pt2(CH3NH2)(2)(CH3NH)(2)(1-MeC-)(4)]Cl-2 center dot 2H(2)O (2). The four 1-MeC- ligands, which are pairwise oriented in head-head fashion, are deprotonated at their N4 positions and cross-linked by the gold ions. While one of the gold ions, Au-I, adopts a linear coordination arrangement, the second, Au-III, is square-planar and completes its coordination arrangement through two methylamido ligands, which behave as bridging species between Au-III and Pt. As a consequence of deprotonation of the original methylamine ligands, the nitrogen atoms of the CH3NH- bridges have become chiral. The four heavy metals form a diamond-shaped plane, with an intramolecular Au-III center dot center dot center dot Au-I distance of 3.053(4) angstrom. On the basis of the structure of cation 2 a new model is proposed how linear transition metal ions (M) might interact with (natural or artificial) nucleobases (L) within a double helix to produce compact M4L4 adducts.

• 出版日期2013-7