Metal-Mediated Assembly of 1,N6-Ethenoadenine: From Surfaces to DNA Duplexes

Mandal S, Wang C, Prajapati R, Kösters J, Verma S, Chi L, Müller J

Abstract

The design of multinuclear metal complexes requires a match of the ligand-to-metal vectors and the preferred coordination geometries of the metal ions. Only a few ligands are known with a parallel orientation of N→M vectors that brings the metal ions into close proximity. We establish here the adenine derivative 1,N6-ethenoadenine (ϵA) as an ideal bis(monodentate) ligand. Scanning tunneling microscope images of alkylated ϵA on graphite surface clearly indicate that these ligands bind to Ag(I) ions. The molecular structures of [Ag2(1)2](ClO4)2 and [Ag2(2)2](ClO4)2 (1, 9-ethyl-1,N6-ethenoadenine; 2, 9-propyl-1,N6-propylenoadenine) confirm that dinuclear complexes with short Ag⋯Ag distances are formed (3.0256(3) and 2.984(1) Å, respectively). The structural motif can be extended to divalent metal ions, as was shown by determining the molecular structure of [Cu2(1)2(CHO2)2(OH2)2](NO3)2·2H2O with a Cu⋯Cu distance of 3.162(2) Å. Moreover, when introducing the 1,N6-ethenoadenine deoxyribonucleoside into parallel-stranded DNA duplexes, even dinuclear Ag(I)-mediated base pairs are formed, featuring the same transoid orientation of the glycosidic bonds as the model complexes. Hence, 1,N6-ethenoadenine and its derivatives are ideally suited as bis(monodentate) ligands with a parallel alignment of the N→M vectors for the construction of supramolecular metal complexes that require two metal ions at close distance.

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