The low-temperature triclinic crystal structure of silver 3-sulfo-benzoic acid

Poly[(μ₄-3-carboxybenzenesulfonato)silver(I)], Ag(O₃SC₆H₄CO₂H) or [Ag(C₇H₅O₅S)] , 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 ) has been determined at 100 K. In contrast to the reported room temperature monoclinic structure, in which the nearly equivalent carboxyl-ate 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 .