catena-Poly[[disilver(I)(Ag-Ag)-bis[mu-1,1'-(butane-1,4-diyl)diimidazole-kappa2N(3):N3']] bis(perchlorate)]: a double helix stabilized by ligand-unsupported argentophilic interactions.

The title compound, {[Ag(2)(C(10)H(14)N(4))(2)](ClO(4))(2)}(n), is a one-dimensional coordination polymer formed by Ag(I) atoms linearly bridged by 1,1'-(butane-1,4-diyl)diimidazole molecules. The chains have a helical arrangement and pairs of chains are held together by the rarely reported ligand-unsupported Ag-Ag interaction [2.966 (1) A], which results in a double-helix structure. The double helix contains twisted 24-membered metallomacrocycles, which are composed of four Ag atoms and two ligands. The Ag atoms lie on twofold axes.