A series of silver coordination polymers constructed from flexible bis(benzimidazole) ligands and different carboxylates

In this article, eight new silver coordination polymers constructed from two structurally related ligands, 1,1'-(1,4-butanediyl)bis(2-methylbenzimidazole) (bbmb) and 1,1'-(1,4-butanediyl)bis(2-ethylbenzimedazole) (bbeb), have been synthesized: [Ag(L1)(bbmb)]center dot C2H5OH center dot H2O (1), [Ag(L2)(bbmb)]C2H5OH (2), [Ag(L3)(bbmb)] (3), [Ag-2(L4)(bbmb)(2)]center dot C2H5OH (4), [Ag(L2)(bbeb)]center dot C2H5OH (5), [Ag(L5)(bbeb)]center dot CH3OH (6), [Ag-2(L6)(2)(bbeb)]center dot H2O (7), and [Ag-2(L7)(bbeb)(2)]center dot 4(H2O) (8), where L1 = benzoate anion, L2 = p-methoxybenzoate anion, L3 = 2-amino-benzoate anion, L4 = oxalate anion, L5 = cinnamate ainon, L6 = 3-amino-benzoate anion, and L7 = fumaric anion. In 1-3, 5 and 6, the bidentate N-donor ligands (bbmb and bbeb) in trans conformations bridge neighboring silver centers to form 1D single chain structures. The carboxylate anions are attached on both sides of the chains. Moreover, 1 and 3 are extended into 2D layers, while 2 and 6 are extended into 3D frameworks through pi-pi interactions. In 4, the bbmb ligands bridge adjacent Ag(1) centers to form -Ag-bbmb-Ag- chains, which are further connected by L4 anions to form a 2D layer. The resulting layers are extended into 3D frameworks through strong pi-pi interactions. In 7, the N-donor ligands (bbeb) in trans conformations bridge two silver centers to generate a (Ag-2(bbeb)](2+) unit. The adjacent [Ag-2(bbeb)](2+) units are further connected via the 16 anions to form a 1D ladder chain. Moreover, the structure of compound 7 is extended into a 3D framework through hydrogen bonding and pi-pi interactions. In 8, two Ag(l) cations are bridged by two bbeb ligands in cis conformations to form a [Ag-2(bbeb)(2)](2+) ring, which are further linked by 17 anions to generate a 1D string chain. Furthermore, the hydrogen bonding and pi-pi interactions link L7 anions to form a 2D supramolecular sheet. Additionally, the luminescent properties of these compounds were also studied. (C) 2011 Elsevier Ltd. All rights reserved.