The characterization, thermal stability and thermal decomposition of some lighter trivalent lanthanide p-aminobenzoates, Ln(C 7 H 6 NO 2) 3 •H 2 O (Ln = La, Ce, Pr, Nd, Sm), as well as the thermal behavior and spectroscopic study of p-aminobenzoic acid C 7 H 7 NO 2 and its sodium salt were investigated. The following methods were utilized: simultaneous thermogravimetry and differential thermal analysis (TG-DTA) in dynamic dry air and nitrogen atmospheres; differential scanning calorimetry (DSC); middle (MIR) and near (NIR) infrared region spectroscopy; evolved gas analysis (EGA); elemental analysis; complexometry; X-ray diffraction (XRD); and diffuse reflectance spectroscopy (DR) in the ultraviolet and visible regions. All the compounds were obtained monohydrated and the thermal decomposition occurred in two, three or four steps in an air atmosphere, and three or four steps in N 2 atmosphere. In both atmospheres (air and N 2) the final residues were CeO 2 , Pr 6 O 11 , Ln 2 O 3 (Ln = La, Nd, Sm). The results also provided information concerning the coordination mode and thermal behavior, as well as the identification of the gaseous products which evolved during the thermal decomposition of these compounds. The DR and NIR spectra provided information about the ligand absorption bands and the f-f transitions of the Nd 3+ , Pr 3+ and Sm 3+ ions.

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Natural products produced by plants are one of the most investigated natural sources, which substantially contributed to the development of the natural products field. Even though these compounds are widely explored, the literature still lacks comprehensive investigations aiming to explore the evolution of secondary metabolites produced by plants, especially if classical methodologies are employed. The development of sensitive hyphenated techniques and computational tools for data processing has enabled the study of large datasets, being valuable assets for chemosystematic studies. Here, we describe a strategy for chemotaxonomic investigations using the Malpighiaceae botanical family as a model. Our workflow was based on MS/MS untargeted metabolomics, spectral searches, and recently described in silico classification tools, which were mapped into the latest molecular phylogeny accepted for this family. The metabolomic analysis revealed that different ionization modes and extraction protocols significantly impacted the chemical profiles, influencing the chemotaxonomic results. Spectral searches within public databases revealed several clades or genera-specific molecular families, being potential chemical markers for these taxa, while the in silico classification tools were able to expand the Malpighiaceae chemical space. The classes putatively annotated were used for ancestral character reconstructions, which recovered several classes of metabolites as homoplasies (i.e., non-exclusive) or synapomorphies (i.e., exclusive) for all sampled clades and genera. Our workflow combines several approaches to perform a comprehensive evolutionary chemical study. We expect it to be used on further chemotaxonomic investigations to expand chemical knowledge and reveal biological insights for compounds classes in different biological groups.

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.