The crystal structures of trimesic acid, its hydrates and complexes. II. Trimesic acid monohydrate–2/9 picric acid and trimesic acid 5/6 hydrate

The crystal structures of trimesic acid monohydrate 2 picric acid [TMA. H20.~-PA, triclinic, a = 18.269 (8), b = 8.852 (5), e = 3.642 (4) A, a = 90.43 (8), fl = 92.59 (6), y = 99.56 (5) °, P | , Z = 2] and trimesic acid hydrate [TMA.SH20, triclinic, a = 16.640 (1), b = 18.548 (1), e = 9.512 (1) A, a = 95.81 (1), fl = 91.06 (4), y = 94.35 (1) °, P1, Z = 12] were determined by standard four-circle diffractomcter techniques (Mo Ka', 2840 and 6768 non-zero reflections respectively). In TMA. H20.~PA there are hydrogen-bonded layers of-composition TMA .H20 in the (i i 1) planes; these layers are pierced by channels along [001] containing the picric acid molecules. Diffuse X-ray scattering by these crystals suggests that the enclathrated pictic acid molecules have only a short-range coherence with the TMA .HzO layers. TMA.5H2 O contains very similar layers of TMA. HzO in the (100) planes; the five such layers in the [I00] repeat are offset such that the channel takes on a zigzag shape in order to accommodate zigzag ribbons of TMA molecules (two per cell), hydrogen bonded through the carboxyl groups in the 1and 3-positions. The enclathrated TMA molecules are strictly ordered with respect to the TMA. H20 framework.