The Structure of <i>m</i>-Xylylenediguanidinium Sulfate:  A Putative Molecular Tweezer Ligand for Anion Chelation

While solution <sup>1</sup>H and <sup>13</sup>C NMR spectra of the sulfate salt of <i>m</i>-xylylenediguanidinium dication <b>2</b> indicate a symmetrical conformation for the cation, a single-crystal X-ray structural determination of <b>2</b> reveals that this dication does not offer symmetrical tweezer-like coordination toward sulfate in the solid state (consistent with solid phase <sup>13</sup>C NMR spectra) but rather assembles into a complex three-dimensional H-bonded network in which the two guanidinium arms adopt different conformations, and all guanidinium N−H units plus one C−H unit of each CH<sub>2</sub> group are involved in H-bonds to sulfate.