Lithium propanoate and pentanoate were characterized by DSC, single crystal and powder XRD and FTIR and impedance spectroscopies. Lithium propanoate presents a solid-to-solid transition (SII-SI) at T(ss) = (549.1 +/- 0.7) K on first heating that varies on the second and next ones, followed by a fusion at T(f) = (606.1 +/- 0.5) K. For lithium pentanoate, two solid-to-solid transitions (SIII-SII and SII-SI), at T(ss) = (205.5 +/- 0.5) K and T(ss) = (325.2 +/- 0.7) K, respectively, and a melting point at T(f) = (576.5 +/- 0.3) K were found. The crystal structures for both compounds were characterized at 100 and 298 K (and for the lithium propanoate also at 160 K). Single-crystal XRD showed that the SII phase of both compounds has a monoclinic structure with the same symmetry group (P2(1)/c). This is the first time that a single-crystal structure has been reported for any member of the lithium alkanoates series, so far. FTIR and impedance spectroscopies were also carried out to better characterize the solid phases in these compounds.

Lead(II) alkanoates, from hexanoate to dodecanoate, have been analyzed by means of XRD, optical microscopy, DSC, FTIR, and electric spectroscopy. Four different phases have been identified, corresponding to the three thermal transitions measured by DSC:  two of them solid (crystal and “intermediate” phases), and another two fluid (neat phase and isotropic liquid). Powder crystal XRD data indicate that the samples present a bilayered structure. The analysis of the (00l) spacing dependence with temperature in the three ordered phases strongly points to the intermediate phase to be a rotator phase. Optical microscopy and FTIR versus temperature also confirm a structural change from the crystal to the intermediate phase and its solid-state nature. Electrical conductivity maps the thermal transitions of the samples and shows a high ionic conductivity in the intermediate phase, which does not depend much on the carbon chain length. The high conductivity values (3 orders of magnitude higher in comparison with that of the ordered crystal at room temperature) obtained for the intermediate phase gave a further support to the existence of a rotator mesophase in the lead(II) alkanoate series.

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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.

Lead(II) pentanoate was studied by DSC, XRD, and FTIR and solid state CP/MAS-NMR spectroscopies. A transition from the crystal to the intermediate phase, at T(ss) = 328.2 +/- 0.6 K, with delta(ss)H = 8.8 +/- 0.1 kJ x mol(-1), and a melting at T(f) = 355.6 +/- 0.3 K, with delta(f)H = 12.6 +/- 0.1 kJ x mol(-1), were observed on first heating. The thermal and structural behavior of the lead(II) pentanoate shows as a link between those of the shorter and longer members of the previously studied lead(II) alkanoate series. The optical microscopy and FTIR vs temperature studies show structural changes from the crystal to the intermediate phase and its solid state nature. Moreover, X-ray diffraction and C-13 and Pb-207 CP/MAS-NMR studies confirm the rotator nature of the intermediate phase in this compound. Two different glass states, one from the isotropic liquid and another from the rotator phase, were obtained by quenching at high and low rates, respectively. The glass transition temperatures (measured at 5 K x min(-1)) were 322.9 and 275.7K, respectively.