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(H<sub>2</sub>O)(DMF)<sub>0.75</sub>}<sub>∞</sub>, <b>CaL</b> = {CaL(DMF)<sub>2</sub>}<sub>∞</sub>, <b>SrL</b> = {SrL(H<sub>2</sub>O)<sub>0.5</sub>}<sub>∞</sub> and <b>BaL</b> = {BaL(H<sub>2</sub>O)<sub>0.5</sub>}<sub>∞</sub>, 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 {–CH<sub>2</sub>–} spacers that can freely rotate in solution. In a ‘curiosity-led' diversion from group 2 metals, the first row transition metal salts Mn<sup>2+</sup>, Cu<sup>2+</sup> and Zn<sup>2+</sup> were also reacted with <b>L</b> to yield crystals of <b>MnL =</b> {MnL(DMF)(H<sub>2</sub>O)<sub>3.33</sub>}<sub>∞</sub>, <b>Cu<sub>3</sub>L<sub>2</sub></b> = {Cu<sub>3</sub>L<sub>2</sub>(DMF)<sub>2</sub>(CHO<sub>2</sub>)<sub>2</sub>}<sub>∞</sub> and <b>ZnL</b> = {ZnL(DMF)}<sub>∞</sub>. 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>Cu<sub>3</sub>L<sub>2,</sub></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.