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

Abstract

(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 1-and 3-positions. The enclathrated TMA molecules are strictly ordered with respect to the TMA. H20 framework. Introduction ExperimentalWe report here the crystal structures of two hydrates of trimesic acid (TMA) that were uncovered during a survey of TMA compounds. The two structures are similar, both being based on a planar framework of hydrogen-bonded TMA and water molecules, with the planar arrays stacked so as to form channels containing guest molecules. In one structure, with empirical formula TMA.]H20, the channels are occupied by additional TMA molecules in an ordered array; in the other, TMA.H20.~-PA (PA = picric acid), the PA molecules occupy the channels in a disordered fashion. Both structures are somewhat unusual. TMA.~H20 contains 12 molecules of TMA and 10 water molecules per unit cell, in space group P1; in the picric acid complex, the chain of PA molecules has a different periodicity from the host framework, leading to additional, diffuse layer lines. Accordingly, we report the structure solutions and refinements in some detail. TMA.H20.2pA was obtained by recrystallization of 25 ml of an aqueous solution containing a total of 4.3 mmol of TMA plus PA. When the TMA:PA ratio in these solutions was 3:1, the predominant product was orthorhombic crystals of TMA.~4PA, together with some straw-colored triclinic needles of TMA.H20.2pA; when the ratio was 1"2, the latter crystals predominated. The composition of these triclinic needles did not appear to vary with the composition of the parent solution, since identical diffraction photographs were obtained from different preparations.Unit-cell dimensions for both crystals were measured from back-reflection Weissenberg photographs about all three axes, with Cu Ka radiation. The density of TMA.]HzO was measured by suspension in tolueneC2H4Br 2 solution, and that of TMA.H20.~PA by suspension in a CCl4-toluene solution. Crystal data are collected in Table 1. Chemical analyses of both compounds were carried out by Galbraith Laboratories. Crystals of TMA.H20.~PA give a diffraction pattern consisting of two components: (1) the Bragg (sharp) reflections that characterize the unit cell described in Table 1 and (2) a series of diffuse reflections which we ascribe to the PA molecules being ar- Table 1 ranged without long-range order but with a considerable degree of short-range order (Fig...

The crystal structures of trimesic acid, its hydrates and complexes. IV. Trimesic acid–dimethyl sulphoxide

“…The geometry of the TMA molecule is essentially identical to that found in an earlier work (Herbstein & Marsh, 1977). Detailed discussion is not given because of the lower accuracy of the present results.…”

“…Firstly, no carboxylic acid dimers are formed, which is unusual among the carboxylic acids (Leiserowitz, 1976). Secondly, the four atoms of the hydrogenbonded group C=O... and TMA.SH20 (Herbstein & Marsh, 1977). A more detailed discussion of the hydrogen-bond dimensions has been given in the preceding paper.…”

“…TMA. HzO.2pA and TMA.~H20 (Herbstein & Marsh, 1977)] has disappeared because the O atom of the DMSO is an essential part of the channel wall while the rest of the DMSO molecule forms the contents of the channel.…”

“…Trimesic acid (TMA) molecules can form hydrogen bonds mutually, as in rt-TMA (Duchamp & Marsh, 1969), or both mutually and with other molecules, as in TMA.H20.~PA (PA = picric acid), TMA.~6H20 (Herbstein & Marsh, 1977) and TMA.H20.dioxane (Herbstein & Kapon, 1978). Among the many molecular complexes formed by TMA is TMA.…”

The crystal structures of trimesic acid, its hydrates and complexes. V. L-(or DL-)Histidinium trimesate–1/3-acetone

“…~ picric acid and TMA.~H20 (Herbstein & Marsh, 1977), TMA.H20.1,4-dioxane and TMA. Me2SO (Herbstein, Kapon & Wasserman, 1978).…”