Dimerization of metallated nucleobase pairs via hydrogen-bond formation: open metallated base quartets of mixed adenine-N-3, guanine-N-7 complexes of trans-(H3N)(2)Pt-II with two different guanine-guanine pairing schemes

摘要

Reactions of trans-[Pt(NH3)(2)(tmade-N-3)X](n+) (tmade = N-6',N-6',N-9-trimethyladenine, X = Cl, n = 1; X = H2O, n = 2) with other nucleobases [9-ethylguanine (Hegua), 9-methyladenine (made) or l-methylcytosine (mcyt)] have been studied in solution (D2O) applying H-1 NMR spectroscopy. Mixed nucleobase complex formation has been observed in all cases. The complex trans-[Pt(NH3)(2)(tmade-N-3)(Hegua-N-7)][ClO4](2) 1a and its hemideprotonated form trans-[{Pt(NH3)(2)(tmade-N-3)(Hegua-N-7)}.{Pt(NH3)(2)(tmade-N-3)(egua-N-7) }][ClO4](2)[NO3].1.6H(2)O 2 have been isolated in crystalline form and characterized by X-ray crystallography. In both cases mononuclear cations are associated via two (la) and three (2) hydrogen bonds between the guanine nucleobases. In la association is via N-3 and the amino group N-2, whereas in 2 a neutral Hegua and a deprotonated egua are joined via three hydrogen bonds involving O-6 N-1 and N-2 sites. [References: 46]