The Low-Temperature Triclinic Crystal Structure of Silver 3-Sulfo-benzoic Acid.

Poly[(μ4-3-carboxybenzenesulfonato)silver(I)], Ag(O3SC6H4CO2H) or [Ag(C7H5O5S)]n, has been found to undergo a reversible phase transition from monoclinic to triclinic between 160 and 150 K. The low-temperature triclinic structure (space group P\overline{1}) has been determined at 100 K. In contrast to the reported room temperature monoclinic structure, in which the nearly equivalent carboxylate C—O distances indicate that the acidic hydrogen is randomly distributed between the O atoms, at 100 K the C—O (protonated) and C=O (unprotonated) bonds are clearly resolved, resulting in the reduction in symmetry from C2/c to P\overline{1}.