ORIGINAL PAPER Three Dimensional Network Polymeric Structure of (4,4 0 -bipyridinium)[CdBr 4 ] n : Supramolecular Motifs and Crystal Supramolecularity Rawhi Al-Far Æ Basem Fares Ali Received: 15 April 2007 / Accepted: 5 November 2007 / Published online: 28 November 2007 Ó Springer Science+Business Media, LLC 2007 Abstract A single crystal structure determination of the complex (4,4 0 -bipyridinium)[CdBr 4 ] n , [henceforth (I)], has been carried out. It crystallizes in the monoclinic space group C2/c, with the following cell parameters: a = 16.119(3) A ˚ , b = 13.206(3) A ˚ , c = 7.2601(15) A ˚ , b = 115.62°, V = 1393.5(6) A ˚ 3 , with Z = 4 formula units. The polymeric anion forms an infinite zig-zag chain of edge-sharing octahedra along c, with a distorted octa- hedral stereochemistry around Cd. There are N–HÁÁÁBr [Br2ÁÁÁN1 of 3.386(13) A ˚ and Br1ÁÁÁN1 of 3.363(13) A ˚ ] and C–HÁÁÁBr [Br2ÁÁÁC5 of 3.552(16) A ˚ ] hydrogen bonding interactions, tying the CdBr chains to the cations to form 2D-network. The resulting 2D-networks are further linked by arylÁÁÁaryl (pÁÁÁp) interactions within the cationic chains leading to a 3D-network. Keywords Crystal structure Á Polymeric [CdBr 4 ] n Á BrÁÁÁH–C and BrÁÁÁH–N interactions Á ArylÁÁÁaryl (pÁÁÁp) interactions Introduction Research in the field of organic–inorganic hybrid com- pounds is of great interest. This is because of their special magnetic, [1] electronic [2] and optoelectronic properties [3]. Cadmium(II) complexes, in particular, have demonstrated both chemical and structural diversity [4–9], mainly due to their capability to adopt different modes depending on size, as well as electrostatic and covalent bonding forces [10]. One-, two- and three- dimensional infinite supramolecular coordination assem- blies of Cd(II) have been the subject of great interest due to their potential applications in catalysis, [11] optical properties, [12, 13] clathration, [14, 15] etc. In such supramolecular entities, the influence of the features of the organic ligands has been observed to control the structural diversity and stereochemistry of the metal centers [16]. The packing interactions that govern the crystal organization are expected to affect the packing and then the specific properties of such solids. For example, 4,4 0 -bipyridine (bpy) and similar ligands, have been utilised through their two nitrogen atoms as neutral linkers to generate and stabilize many open 1-, 2- and 3- D coordination polymers to form supramolecular coor- dination assemblies [17]. On the other hand, the protonated 4,4 0 -bipyridine [bpyH 2 ] 2+ cation has been utilised in the preparation of in many crystalline salts of the type (bpyH 2 )[MX 4 ] where N–HÁÁÁX hydrogen bond synthons have been exploited in the formation of these salts [18]. One of the structural motifs observed contains the layer cross-linked polymeric [MX 4 ] n anions (M = Mn, Cd, Pb) [18]. From which, the series (bpyH 2 )[MCl 4 ] n ; M = Mn and Cd [18] and (bpyH 2 )[MnBr 4 ] n [18] represent an isostructural com- pounds. Herein, we report the isostructural Cd(II) polymeric complex, (bpyH 2 )[CdBr 4 ] n , where the proton- ated ligand [bpyH 2 ] 2+ is not involved in coordination, but in extensive N–HÁÁÁBr and C–HÁÁÁBr hydrogen bonding and pÁÁÁp interactions, affording a 3-D network structure. R. Al-Far Faculty of Science and Information Technology, Al-Balqa’a Applied University, Salt, Jordan B. F. Ali (&) Department of Chemistry, Al al-Bayt University, Mafraq 25113, Jordan e-mail: bfali@aabu.edu.jo 123 J Chem Crystallogr (2008) 38:289–293 DOI 10.1007/s10870-007-9298-2