Lithium–thallium(i) butyrates binary system: an intermediate salt and liquid crystal from non-mesogenic compounds.

Abstract

The binary system between lithium and thallium(I) butyrates, [xLiC₃H₇CO₂ + (1 − x) TlC₃H₇CO₂], where x = mole fraction, has been carefully analyzed, solving the temperature and enthalpy vs. composition phase diagrams. The formation of an intermediate salt or complex with a composition (2 : 1), an ionic liquid crystal phase and a metastable solid solution has been detected. The complex melts incongruently at T_fus = 494.7 K, with Δ_fusH_m = 7.70 kJ per mol of mixture. Its low temperature crystal structure (monoclinic, P2₁/c) has been solved and refined using X-ray synchrotron radiation and has been found to be bilayered, as is typical from pure metal alkanoates and, as it happens, for other two analogous intermediate salts studied recently by our group. The liquid crystal phase detected is formed from two non-mesogenic pure compounds, appearing in the binary system between 394.1 and 436.6 K and for x = 0.10 up to x = 0.29. Binary phase diagrams are shown to be a powerful tool to detect and predict the formation of liquid crystal phases and mixed crystals.