Thermal behavior, spectroscopic study and evolved gas analysis (EGA) during pyrolysis of picolinic acid, sodium picolinate and its light trivalent lanthanide complexes in solid state

Abstract

Synthesis, characterization, and thermal behavior of light trivalent lanthanide picolinate (La-Gd, except Pm) as well as the thermal behavior of picolinic acid and its sodium salt were investigated employing elemental analysis, complexometry, differential scanning calorimetry (DSC), simultaneous thermogravimetry and differential scanning calorimetry (TG-DSC), infrared spectroscopy (FTIR), X-ray power diffractometry, and evolved gas analysis (EGA) for TG-DSC coupled to FTIR. All the synthesized compounds were obtained in the anhydrous state and the thermal decomposition in dynamic dry air atmosphere occured in a single step or two consecutive steps with formation of the respective oxides, CeO 2 , Pr 6 O 11 and Ln 2 O 3 (Ln = La, Nd to Gd). In dynamic dry nitrogen atmosphere the thermal decomposition occured in two or three consecutive steps and mass loss was observed up to 1000 • C. The EGA data allowed the identification of gaseous products evolved during pyrolysis and oxidative decomposition. The results of density functional theory (DFT) and FTIR also provided information on the ligand's denticity.

Novel solid-state compounds of heavy rare-earth (III) picolinates. A pyrolytic study using: TG-DSC-IR, HSM-MS and GC-MS

“…The understanding of the thermal and pyrolytic decomposition of heavy picolinates is essential in the event that these compounds are made into functional materials which may operate in unknown thermal environments. This work extends on our previous studies on light trivalent lanthanide picolinates [20] and reports the synthesis of heavy trivalent lanthanide (Tb to Lu) and yttrium (III) picolinates. The investigation and characterisation of these novel compounds were carried out using a range of thermoanalytical, chromatographic, spectrometric and spectroscopic techniques.…”

“…Spectroscopic studies of some light-lanthanides have suggested that picolinate complex binds through the nitrogen in the pyridine ring and with the carboxylate group [20]. The same mode of coordination is observed for the dysprosium [21] and terbium [19] complexes that bind monodentatively with the carboxylate group.…”

“…Picolinic acid (C6H6NO2, 99.5%) was obtained from Sigma and was used without further purification. Aqueous solutions of heavy lanthanide (Tb to Lu and Y) chlorides were prepared from the corresponding metal oxides (Aldrich ≥ 99%), by treatment with concentrated hydrochloric acid (Merck, 37%), following the previously described procedure [20].…”

“…Following the procedure established to the light lanthanide picolinates [20], any precipitate was observed to heavy series (all of them have high aqueous solubility). Other synthetic routes were tried without success which may explain why some of these compounds are unreported.…”

A study on enhancing the quantum yield and antimicrobial activity of Pr(iii) by varying the coordination environment

“…The exothermic peak around 420 C indicates the bond formation when the oxidation of the organic moiety occurs. The temperature difference between the TGA-DTG and differential scanning calorimetry (DSC) incidence can be explained using reports in the literature [69][70][71] which reveal that the oxidizing atmosphere accelerates the thermal decomposition. Excluding this there is no other clear result obtained from the DTA curve.…”