Crystal structures of sodium-, lithium-, and ammonium 4,5-di­hydroxy­benzene-1,3-di­sulfonate (tiron) hydrates

The solid-state structures of the Na(+), Li(+), and NH(4) (+) salts of the 4,5-di­hydroxy­benzene-1,3-di­sulfonate (tiron) dianion are reported, namely disodium 4,5-di­hydroxy­benzene-1,3-di­sulfonate, 2Na(+)·C(6)H(4)O(8)S(2) (2−), μ-4,5-di­hydroxy­benzene-1,3-di­sulfonato-bis­[aqua­lithium(I)] hemihydrate, [Li(2)(C(6)H(4)O(8)S(2))(H(2)O)(2)]·0.5H(2)O, and di­ammonium 4,5-di­hydroxy­benzene-1,3-di­sulfonate monohydrate, 2NH(4) (+)·C(6)H(4)O(8)S(2) (2−)·H(2)O. Inter­molecular inter­actions vary with the size of the cation, and the asymmetric unit cell, and the macromolecular features are also affected. The sodium in Na(2)(tiron) is coordinated in a distorted octa­hedral environment through the sulfonate oxygen and hydroxyl oxygen donors on tiron, as well as an inter­stitial water mol­ecule. Lithium, with its smaller ionic radius, is coordinated in a distorted tetra­hedral environment by sulfonic and phenolic O atoms, as well as water in Li(2)(tiron). The surrounding tiron anions coordinating to sodium or lithium in Na(2)(tiron) and Li(2)(tiron), respectively, result in a three-dimensional network held together by the coordinate bonds to the alkali metal cations. The formation of such a three-dimensional network for tiron salts is relatively rare and has not been observed with monovalent cations. Finally, (NH(4))(2)(tiron) exhibits extensive hydrogen-bonding arrays between NH(4) (+) and the surrounding tiron anions and inter­stitial water mol­ecules. This series of structures may be valuable for understanding charge transfer in a putative solid-state fuel cell utilizing tiron.