Graham Smith, U. Wermuth
Oct 21, 2017
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Journal
Zeitschrift für Kristallographie - Crystalline Materials
Abstract
Abstract The crystal structures of the 1:1 proton-transfer compounds of (4-aminophenyl)arsonic acid (p-arsanilic acid) with the strong organic acids, 2,4,6-trinitrophenol (picric acid), 3,5-dinitrosalicylic acid, (3-carboxy-4-hydroxy)benzenesulfonic acid (5-sulfosalicylic acid) and toluene-4-sulfonic acid have been determined at 200 K and their hydrogen–bonding patterns examined. The compounds are, respectively, anhydrous 4-arsonoanilinium 2,4,6-trinitrophenolate (1), the hydrate 4-arsonoanilinium 2-carboxy-4,6-dinitrophenolate monohydrate (2), the hydrate 4-arsonoanilinium (3-carboxy-4-hydroxy)benzenesulfonate monohydrate (3) and the partial solvate 4-arsonoanilinium toluene-4-sulfonate 0.8 hydrate (4). The asymmetric unit of 2, a phenolate, comprises two independent but conformationally similar cation-anion pairs and two water molecules of solvation, and in all compounds, extensive inter-species hydrogen–bonding interactions involving arsono O–H···O and anilinium N–H···O hydrogen–bonds generate three-dimensional supramolecular structures. In the cases of 1 and 2, the acceptors include phenolate and nitro O-atom acceptors, with 3 and 4, additionally, sulfonate O-atom acceptors, and with the hydrates 2–4, the water molecules of solvation. A feature of the hydrogen–bonding in 3 is the presence of primary chains extending along (010) through centrosymmetric cyclic R22(8) motifs together with conjoined cyclic R34(12) motifs, which include the water molecule of solvation. The primary hydrogen–bonding in the substructure of 4 involves homomolecular cation–cation arsono O–H···O interactions forming columns down the crystallographic four-fold axis of the unit cell.