Salt formation is an approach to improve the physicochemical properties of the solid forms of an active pharmaceutical ingredient. As the anticonvulsant drug Lamotrigine presents low water solubility, a set of its salts with four different counterions has been obtained, and the influence of the counterion on the salt properties has been investigated. Lamotrigine salts have been obtained from succinic acid, fumaric acid, DL-tartaric acid, and saccharin. Powder samples of each salt have been characterized by infrared spectroscopy, powder X-ray diffraction, and thermal methods. Single crystal structures of four of these salts have been solved from single crystal X-ray diffraction data. The salts crystallized in P2 1 /c and P2 1 /n space groups, being isostructural dicarboxylic acid salts of lamotrigine. Crystal structures of these salts are built up by hydrogen bond interactions of type NThe water solubility of these salts has been determined and appears directly related to the solubility of the precursor acid. The isostructural nature of the studied salts allows connection of their properties with those of the counterion involved. The importance of the counterion solubility on the final solubility of the salts is rationalized considering their crystal structures.

The search for materials capable of storing small molecular species is experiencing a shift from solids with permanent porosity towards organic materials capable of the uptake and release of lowmolecular-weight guests. We demonstrate that a solid mixture of the pharmaceutical compound lamotrigine with a range of saturated and unsaturated 1,4-butanedicarboxylic acids, when in combination with a third molecule, can result in the formation of a family of isostructural materials involving a structurally persistent binary-host framework based on a hydrogen-bonded molecular salt of lamotrigine and the acid. A systematic study, based on mechanochemical screening, has revealed a remarkable robustness to subtle changes in the chemical functionality of the acid in that at least 12 different acids can be used in combination with lamotrigine to generate isostructural binary-host frameworks. Such robust isostructurality results in the important attribute that the shape, size and surface chemistry of the inclusion cavities can be fine-tuned by systematic variation of the substituents on the dicarboxylic acid.

Isostructurality in three-component crystals achieved by the combination of persistent hydrogen bonding motifs and solvent inclusion3

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Liquid-assisted grinding and solvent crystallizations have been undertaken to prepare salts and cocrystals of the modified nucleobase 9-ethyladenine with several carboxylic acids. The new solid forms have been characterized by X-ray powder and single crystal diffraction, attenuated total reflectance Fourier transformed infrared spectroscopy and thermal methods. From single crystal structures we have observed that the length of the alkylic chain in the carboxylic acid prevents from a canonical self-assembly for the longest coformer. Moreover, density functional theory (DFT) calculations combined with

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Page s 253SHELXL97 program. Samples had significantly different colors, depending on the growth atmosphere (Ar+O 2 : yellow or orange) and post-grown treatment (Ar and vacuum: almost colorless; air: bright orange). The analysis of the color and crystal composition of La 3 (Ga x Ta 1-x ) Ga 5 O y allowed to divide their into four groups: colorless (y~14), orange (y~13.95-13.97), yellow (y~13.92-13.93), and colorless (y~13.90). These results are agreed with transmission spectroscopy («Specord-M40», wave range 11000-50000 cm -1 ): the yellow crystals with the oxygen vacancies () have the band 28500 cm -1 . The low-grade band 20800 cm -1 is present at colored crystals and absent at colorless ones (the like result has been wrote in [1]). At that the study of their chromaticity diagrams showed the different shade for the samples of the like visual color. The orange and colorless (the last group) Y54°-crystals, Y54° cut and the orange, yellow and colorless (the first group) Z-crystals, Z cut have the microhardness value ~13.8, ~12.2 GPa and ~12.6, ~10.4 and ~9.7Gpa, respectively. It was found that the temperature maximum of the yellow plate (Z-crystal, Z-cut) dielectric loss tangent has an effusive relaxation maximum in the temperature range 300-550 о С. The topography by Shultz method (reflection 50.0) of the yellow plate (Z-crystal, Z-cut) with the refined composition La 3 (Ga 0.58 Ta 0.42 )Ga 5 (O 13.92 0.08 ) shown absence of blocks. According to the rocking curves (the scheme of a doublecrystal X-ray diffractometer: Si (400) monochromator, (n, -n)) of the same sample, the half-width of the Bragg 50.0 and 40.0 peaks (value β exp ) are ~22′′ in contrast to the Z-crystalLGT, Y cut [2], in which β exp~6 ′′. So, a series of properties of LGT can be associated with the atmosphere of growth and post-grown treatment (the composition of crystals and their color), the growth and cut directions (the microhardness and structural perfection). Moreover langatate crystals are more appropriate for the high temperature applications compared with langasite ones. [1] O.A.Buzanov et al., Crystallography Reports, 52(4) 2007,691-696. [2] D.V.Roshchupkin et al.

The process of molecular recognition in inclusion compounds is governed by the intermolecular interactions which occur between the various host and guest molecules making up the resultant crystalline assembly. We have studied the diol host, 2,2'-bis (hydroxydiphenylmethyl-1,1'-binaphthyl(H), which crystallised in three different polymorphic structures and formed a series of inclusion compounds with pyridine(P), morpholine(M) and benzene(B). Different stoichiometries were obtained by manipulating the proportions of the guests and the crystallisation temperatures. Four of these inclusion compounds, H.3P, H.2P.M, H.2P.B and H.P.M.B, are isomorphous and the guests are located at fixed sites in the crystal structure. Their thermal analysis results were explained in terms of the host guest interactions. The three polymorphs of the host compound show strong structural similarities as depicted by their Hirshfeld surface fingerprint plots, which exhibit dominant H H interactions. The conformation of the host molecule remains essentially constant, and is governed by an intramolecular O-H O hydrogen bond in the polymorphs of the apohost and in all the nine inclusion compounds analysed.