Supramolecular Architectures Based on Metal–Cytosine Systems

Abstract

Five new compounds of cytosine with first‐row transition metals, (H2Cyt)2[CoCl4]·2(HCyt) (1), [CoBr2(HCyt)2] (2), [ZnCl2(HCyt)2] (3), [CuCl2(HCyt)2] (4), and [CuBr2(HCyt)2] (5) (in which HCyt = cytosine, H2Cyt = cytosinium cation), are reported. In 1, the protonation of one of the cytosine molecules facilitates base pairing with the neutral cytosine, instead of the expected coordination to the metal center. In all other compounds, neutral cytosine molecules are coordinated to the MII centers through N3 positions, forming monomeric entities. The supramolecular crystal structure of 1 is sustained by the base‐pairing interactions between the 1H,3H‐cytosinium cation and the neutral 1H‐cytosine molecule through their Watson–Crick and sugar edges, giving rise to zig‐zag supramolecular ribbons, in which neutral and cationic cytosine molecules alternate. In the isostructural compounds 2 and 3, only one of the cytosine molecules establishes base pairing through sugar‐edge‐forming supramolecular dimers, and the 3D cohesiveness is achieved by means of noncomplementary hydrogen bonding, involving the sugar edge of the other cytosine with the amino group and the bromide anions of the adjacent dimer. Compounds 4 and 5 show similar supramolecular arrangements, with cytosine molecules self‐assembling along the sugar edge into 1D chains.