Extended structures sustained by hydrogen bonding and π–π interactions: Synthesis and characterization of Cd(II) complexes with bis(benzimidazolyl) ligands

Two new Cd(II) complexes, {[Cd(C4BIm)Cl2] · DMF}n (1) and [Cd(HC4BIm)Cl3] · 3H2O (2) (C4BIm = 1,4-bis(benzimidazolyl)butane and HC4BIm = mono-protonated 1,4-bis(benzimidazolyl)butane), have been prepared and characterized spectroscopically and crystallographically. In both complexes, the Cd(II) atom exhibits distorted tetrahedral coordination geometry with CdN2Cl2 and CdNCl3 in 1 and 2, respectively. Complex 1 adopts a racemic structure built up from P- and M-helical [Cd(C4BIm)Cl2]n chains, which are alternately linked into two-dimensional network by N–H⋯Cl hydrogen bonds and further stabilized by the intermolecular π⋯π stacking. In complexes 2, the HC4BIm is monodentate, coordinating to Cd(II) ion via the unprotonated benzimidazolyl nitrogen donor to form mononuclear [Cd(HC4BIm)Cl3]. The mononuclear units are linked by N–H⋯Cl hydrogen bonds to form one-dimensional planar belts, which interact via intermolecular π⋯π stacking to result in three-dimensional framework.