Coordination Polymers of Flexible Bis(benzimidazole) Ligand: Halogen Bridging and Metal···Arene Interactions

2011-12-07T00:00:00Z (GMT) by Suman Samai Kumar Biradha
A new organic ligand, namely 1,4-bis[2-(1-methylbenzimidazol-2-ylmethyl)]benzene (<b>L</b>), was synthesized, and its crystal structure has been determined. The ability of <b>L</b> to form coordination polymers was explored with various metal salts under different conditions. Six complexes of <b>L</b>[Cu<sub>2</sub>(<b>L</b>)I<sub>2</sub>], <b>1</b>; [Cu<sub>2</sub>(<b>L</b>)I<sub>2</sub>], <b>2</b>; [Cd<sub>3</sub>(<b>L</b>)Cl<sub>6</sub>·2DMF], <b>3</b>; [Cu(<b>L</b>)Cl<sub>2</sub>], <b>4</b>; [Zn(<b>L</b>)I<sub>2</sub>·MeOH], <b>5</b>; and [Cd(<b>L</b>)(NO<sub>3</sub>)<sub>2</sub>·H<sub>2</sub>O]·2THF, <b>6</b>have been synthesized by the reaction of <b>L</b> with the corresponding metal salts at room temperature, either by direct mixing or by a layering technique. Single crystal X-ray analyses revealed that complexes <b>1</b> and <b>2</b> are isomers of each other and that both contain Cu<sub>2</sub>I<sub>2</sub> building units. The crystal structure of <b>1</b> contains a discrete unit that contains a strong Cu(I)···arene interaction, whereas, in <b>2</b>, the Cu<sub>2</sub>I<sub>2</sub> units act as a linear linker and form a one-dimensional zigzag chain. Complex <b>3</b> exhibits a two-dimensional layer in which the 1D polymeric chains of halide bridged Cd(II) ions are linked by the organic ligand <b>L</b>. The crystal structures of <b>4</b> and <b>5</b> contain a 1D zigzag chain and a discrete hydrogen bonded dimer, respectively. The crystal structure of complex <b>6</b> contains nitrate as a counterion and forms an interesting one-dimensional helical chain containing cavities that are occupied by THF molecules. In these crystal structures, the ligand <b>L</b> is found to exhibit four different conformations. The Cambridge Structural Database was used to rationalize the results obtained here and to provide some insight into the metal coordination geometries, the halide bridging of metal centers, as well as metal···arene interactions.