Multiple Metal Binding to the 9-Methyladenine Model Nucleobase Involving N1, N6, and N7: Discrete Di- and Trinuclear Species with Different Combinations of Monofunctional Pd-II and Pt-II Entities

作者：Mihaly Timea; Anorbe Marta Garijo; Alberti Francisca M; Sanz Miguel Pablo J; Lippert Bernhard

来源：Inorganic Chemistry, 2012, 51(19): 10437-10446.

DOI：10.1021/ic301681f

Several di- and trinuclear metal complexes consisting of the model nucleobase 9-methyladenine (9-MeA) or its mono-deprotonated form (9-MeA(-)) and monofunctional (dien)Pd-II, (dien)Pt-II, (NH3)(3)Pt-II, or (trpy)Pd-II in different combinations have been prepared and/or studied in solution by NMR spectroscopy: [{Pd(dien)}(3)(9-MeA(-)-N1,N6,N7)]-Cl-3.5(PF6)(1.5)center dot 3H(2)O (1), [(dien)Pd(N1-9-MeA-N7)Pt(NH3)(3)](ClO4)(4)center dot 9.33H(2)O (2), [(dien)Pt-(N1-9-MeA-N7)Pt(NH3)(3)](ClO4)(4)center dot H2O (3), and [{(trpy)Pd}(2)(N1,N6-9-MeA(-)-N7)Pt(NH3)(3)](ClO4)(5)center dot 3H(2)O (4). A migration product of 3, [(dien)Pt(N6-9-MeA(-)-N7)Pt(NH3)(3)](3+) (3a), has been identified in solution. Unlike Pt-adenine bonds, Pd-adenine bonds are substantially labile, and consequently all Pd-containing complexes discussed here (1, 2, 4) exist in aqueous solution in equilibria of slowly interconverting species, which give rise to individual resonances in the H-1 NMR spectra. For example, 1 exists in an equilibrium of five adenine-containing species when dissolved in D2O, 2 undergoes dissociation to [Pt(NH3)(3)(9-MeA-N7)](2+) or forms the migration product [(dien)Pd(N6-9-MeA(-)-N7)Pt(NH3)(3)](3+) (2a), depending on pD, and 4 loses both (trpy)Pd-II entities as the pD is increased. In no case is Pd binding to N3 of the adenine ring observed. A comparison of the solid-state structures of the two trinuclear complexes 1 and 4 reveals distinct differences between the Pd atoms bonded to N1 and N6 in that these are substantially out of the nucleobase plane in 1, by ca. 0.6 angstrom and -1.0 angstrom, respectively, whereas they are coplanar with the 9-MeA(-) plane in 4. These out-of-plane movements of the two (dien)Pd-II units in 1 are not accompanied by changes in hybridization states of the N1 and N6 atoms.

• 出版日期2012-10-1