We have identified and characterized the existence of two new polymorphic forms (orthorhombic needles and monoclinic plates) of 3-aminobenzenesulfonic acid, one of which was a previously unrecognized polymorphic form. The circumstances and events indicate that Form I may be considered a disappearing crystal form. The production of Form III was a serendipitous occurrence in an attempt to use the strategy of tailor-made additives to reobtain Form I; although unsuccessful, it has once more shown the need to explore as much of the chemical potential surface as possible even in a system as seemingly simple as this one.

Key indicatorsSingle-crystal X-ray study T = 120 K Mean (C-C) = 0.003 Å R factor = 0.036 wR factor = 0.081 Data-to-parameter ratio = 8.4For details of how these key indicators were automatically derived from the article, see

Of the four known polymorphs of [S,S]-ethambutol dihydrochloride, two transform in an enantiotropic single-crystal-to-single-crystal phase transformation from Form II to Form I on heating. The crystal structures of these two forms have been solved and compared. Because the other two forms are metastable and are only obtained from the melt, single-crystal data could not be obtained on them. However, all four forms have been characterized, and their relative thermodynamic relationships have been investigated by variable-temperature solid-state 13 C NMR, variable-temperature powder X-ray diffraction studies, differential scanning calorimetry, and optical microscopy.

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The title compound, [CoCl(C(12)H(8)N(2))(2)(H(2)O)]Cl.[CoCl(2)(C(12)H(8)N(2))(2)].6H(2)O, is the first example of a new 1:1 cocrystal of the octahedral [CoCl(2)(phen)(2)] and [CoCl(phen)(2)(H(2)O)](+).Cl(-) complexes (phen is 1,10-phenanthroline). The latter form heterochiral dimers held by strong pi-pi stacking interactions via their phenathroline ligands, which confirms that pi stacking is an important and reliable synthon in supramolecular design. In addition, the crystal structure is networked by H(2)O...H(2)O, H(2)O...Cl(-) and H(2)O...Cl hydrogen bonds, which interconnect the different units of the cobalt complexes.