Abstract
The solid-state structures of the Na+, Li+, and NH4+ salts of the 4,5-di-hydroxy-benzene-1,3-di-sulfonate (tiron) dianion are reported, namely disodium 4,5-di-hydroxy-benzene-1,3-di-sulfonate, 2Na+·C6H4O8S22-, μ-4,5-di-hydroxy-benzene-1,3-di-sulfonato-bis-[aqua-lithium(I)] hemihydrate, [Li2(C6H4O8S2)(H2O)2]·0.5H2O, and di-ammonium 4,5-di-hydroxy-benzene-1,3-di-sulfonate monohydrate, 2NH4+·C6H4O8S22-·H2O. Inter-molecular inter-actions vary with the size of the cation, and the asymmetric unit cell, and the macromolecular features are also affected. The sodium in Na2(tiron) is coordinated in a distorted octa-hedral environment through the sulfonate oxygen and hydroxyl oxygen donors on tiron, as well as an inter-stitial water mol-ecule. Lithium, with its smaller ionic radius, is coordinated in a distorted tetra-hedral environment by sulfonic and phenolic O atoms, as well as water in Li2(tiron). The surrounding tiron anions coordinating to sodium or lithium in Na2(tiron) and Li2(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, (NH4)2(tiron) exhibits extensive hydrogen-bonding arrays between NH4+ and the surrounding tiron anions and inter-stitial water mol-ecules. This series of structures may be valuable for understanding charge transfer in a putative solid-state fuel cell utilizing tiron.