Thermal and Structural Study of the Crystal Phases and Mesophases in the Lithium and Thallium(I) Propanoates and Pentanoates Binary Systems: Formation of Mixed Salts and Stabilization of the Ionic Liquid Crystal Phase

Abstract

The temperature and enthalpy vs composition phase diagrams of the binary systems [xC(2)H(5)CO(2)Li + (1 - x)C(2)H(5)CO(2)Tl], and [x(n-C(4)H(9)CO(2)Li) + (1 - x)n-C(4)H(9)CO(2)Tl], where x is the mole fraction, were determined by DSC. Both binary systems display the formation of one 2:1 mixed salt each (at x = 0.667) that appear as a peritectic (incongruent melting) at T(fus) = 512.0 K, and T(fus) = 461.1 K, with Delta(fus)H(m) = 13.76 and 8.08 kJ.mol(-1) for Li-Tl (I) propanoates, and n-pentanoate mixed salts, respectively. The thermotropic liquid crystal of the thallium(I) n-pentanoate transforms into a more stable liquid-crystal phase, which appears in the phase diagram between 380 and 488 K and for x = 0 up to x = 0.56. The crystal structure of thallium(I) propanoate and of the two mixed salts were obtained via X-ray synchrotron radiation diffraction measurements. These compounds present a bilayered structure similar to the two pure lithium salts previously found by our group.

Thermotropic Ionic Liquid Crystals

“…It has been observed that due to a smectic anisotropic molecular arrangement, electric current conductivity along the cation-anion layers is larger by four orders of magnitude than that in the perpendicular direction. Tl pentanoate ( A , M m+ = Tl + , (Z − ) = -COO − , Scheme 17) exhibits a smectic mesophase in a range of 180–214 °C, which could be stabilized by the addition of Li pentanoate [105]. Long-chain Eu alkanoates ( A , (Z − ) = -COO − , n = 6–9, Scheme 17) display lamellar structures, where Eu ionic layers are separated by perpendicularly oriented alkanoate chains arranged in a hexagonal packing [106].…”

Tetrahalidocuprates(ii)—structure and EPR spectroscopy. Part 1: Tetrabromidocuprates(ii)

“…[34][35][36] Reports on tetrahalidometalate-based ILCs and their transformation into inorganic materials are, however, relatively rare. [30][31][32][33][37][38][39][40][41][42][43][44][45][46][47] This is somewhat surprising because metal containing ILs and ILCs may open the door towards a new valuable branch of IL research, which derives its importance from the additional properties such as colour, geometry, or magnetism, which are brought about the material by the metal ion.…”

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

“…Actually, the systems between lithium and thallium(I) propionates and pentanoates have been recently analyzed in depth by our group. 18 Pure lithium and thallium(I) butyrates have been studied separately by different calorimetric techniques, such as adiabatic calorimetry, 19,20 DSC, 21,22 and TG. 23,24 However, the crystal structure of alkanoates belonging to the respective series were solved in the last 2 years, for example LiC4, 25 LiC3 and LiC5, 26 anhydrous LiC2 and hydrates, 27 or TlC3.…”