A novel rotator glass in lead(II) pentanoate: calorimetric and spectroscopic study

Abstract

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 Tss = 328.2 ± 0.6 K, with ΔssH = 8.8 ± 0.1 kJ·mol−1, and a melting at Tf = 355.6 ± 0.3 K, with ΔfH = 12.6 ± 0.1 kJ·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·min−1) were 322.9 and 275.7K, respectively.