CaL.cif from Investigating the geometrical preferences of a flexible benzimidazolone-based linker in the synthesis of coordination polymers

A series of new group 2 coordination polymers, <b>MgL</b> = {MgL(H₂O)(DMF)_0.75}_∞, <b>CaL</b> = {CaL(DMF)₂}_∞, <b>SrL</b> = {SrL(H₂O)_0.5}_∞ and <b>BaL</b> = {BaL(H₂O)_0.5}_∞, were synthesized using a flexible benzimidazolone diacetic acid linker (<b>L</b>) in which the two carboxylic acid binding sites are connected to a planar core via {–CH₂–} spacers that can freely rotate in solution. In a ‘curiosity-led' diversion from group 2 metals, the first row transition metal salts Mn²⁺, Cu²⁺ and Zn²⁺ were also reacted with <b>L</b> to yield crystals of <b>MnL =</b> {MnL(DMF)(H₂O)_3.33}_∞, <b>Cu₃L₂</b> = {Cu₃L₂(DMF)₂(CHO₂)₂}_∞ and <b>ZnL</b> = {ZnL(DMF)}_∞. Crystal structures were obtained for all seven materials. All structures form as two-dimensional sheets and, with the exception of <b>ZnL,</b> which displays tetrahedrally coordinated metal centres, and <b>Cu₃L_2,</b> which contains square planar coordinated metal centres and Cu paddle wheels, contain six-coordinate metal centres. In each structure, the linker adopts one of two distinct conformations, with the carboxylate groups either <i>cis</i> or <i>trans</i> to each other with respect to the plane of the core. All materials were also characterized by powder X-ray diffraction and thermogravimetric analysis