Complexes of Copper with a Flexible Bis-benzimidazole Ligand

The flexible bidentate ligand 1,3-bis(benzimidazol-2-yl)propane, L3, and its N-methylated derivative L4, form complexes with CUI and CUII. The X-ray crystal structure of [Cu(L4)(MeCN)] (PF6) (1) shows a trigonal coordination of the CuI with the eight-membered chelate ring adopting a half-chair conformation. With CuII in EtOH, L3 forms dimeric [(L3)Cu(μ-EtO)2Cu(L3)](ClO4)2 · 2EtOH (2) whose X-ray crystal structure shows CuII in a distorted square-planar environment with one bidentate ligand and two bridging ethoxides. The chelate ring now has a boat-chair conformation which forms a hydrophobic pocket around the metal.