Crystal structure and phase behavior of the tolyl glycerol ethers. From the conglomerate former to the chirality-driven nanogelator

Abstract

According to differential scanning calorimetry data ortho-, meta-, and para-tolyl glycerol ethers 1–3 form thermodynamically most stable crystal phases during solution crystallization. For all members of the series the crystal phases formed during melt crystallization have different thermodynamic characteristics from those of the stable ones. Binary melting diagrams were constructed for the stable solid phases; on this basis it was found that 1 is prone to spontaneous resolution, and 2 and 3 form stable solid racemic compounds, the Gibbs energy of formation for which are found to be −2.70 and −2.43 kJ mol⁻¹. Solution grown single crystals of 1–3 were investigated by an X-ray diffraction method. The principal supramolecular crystal formative motifs were revealed: 1D columns for 1 and scal-2, 2D bilayers having developed a 2D system of intermolecular hydrogen bonds (IMHB) for rac-2 and rac-3, and 2D bilayer having 1D spiral IMHB organization for scal-3. The possible reasons preventing the solid racemic compound formation in the case of 1, and the spontaneous resolution manifestation in the cases of 2 and 3 are disclosed. It was demonstrated that, from the whole family of tolyl glycerol ethers, only scal-3 samples are capable of supramolecular gels formation. This property is connected with the peculiarities of the scalemic 3 crystal packing.