Same head, different scaffold: a plethora of structural motifs assembled from silver(i) and ditopic 2,2′-bipyridine ligands

Abstract

The condensation of ethane-1,2-diamine, propane-1,3-diamine, butane-1,4-diamine or hydrazine with two equivalents of 2,2′-bipyridine-6-carbaldehyde in the presence of AgBF₄ leads to the formation of silver(I) complexes of ligands 4–7 which differ in the length of the spacer linking two 2,2′-bipyridine-6-carbaldimine domains (4, two carbon spacers; 5, three carbons; 6, four carbons; 7, no spacer). For the complexes containing ligands 4–7, respectively, single crystal X-ray diffraction confirms the assembly of a [2 + 2] double helicate, a non-helical side-by-side dinuclear complex, an infinite coordination polymer and a cyclic tetramer with a structure that is a hybrid of a grid and cyclic helicate. Face-to-face π-stacking between bpy domains of the ligands plays a dominant role in the assembly of the double helical [Ag₂(4)₂]²⁺, polymeric [Ag₃(6)₂]_n³ⁿ⁺ and cyclic [Ag₄(7)₄]⁴⁺ cations. However, the structure of the [Ag₂(5)₂]²⁺ cation in [Ag₂(5)₂][BF₄]₂·2MeCN exhibits no face-to-face embraces, and the inter-cation packing is controlled by CH⋯N and CH⋯π interactions.