Synthesis, characterization and thermal behavior of solid state of some mefenamate of trivalent lanthanides (La, Ce, Pr and Nd)

Abstract

Solid-state Ln(Mef) 3 compounds, where Ln stands for some trivalent lanthanides (La, Ce, Pr and Nd) and Mef is the mefenamate (C 15 H 14 NO 2-) ligand, were synthesized. The characterization and thermal and spectroscopic study of the compounds were performed using elemental analysis, complexometry, image analysis by field emission gun, simultaneous thermogravimetry and differential scanning calorimetry coupled to Fourier transform infrared spectroscopy, X-ray diffractometry, near-infrared and mid-infrared spectroscopy. All the analyses showed that the compounds were obtained in the anhydrous state. The thermoanalytical results showed that the stability and thermal behavior were markedly influenced by the atmosphere used. Moreover, the curves show that the thermal decomposition takes place in two or three steps, with the formation of lanthanide oxide (La 2 O 3 , CeO 2 , Pr 6 O 11 and Nd 2 O 3), as the final residue. Furthermore, the theoretical and experimental spectroscopic data suggested the possible modes of coordination of the ligand with the metals. The DR spectra provided information about the ligand absorption bands and the f-f transitions of Nd 3? and Pr 3? ions.

Thermal behavior, spectroscopic studies and free radical scavenging potential of some mefenamate trivalent lanthanides (Sm, Eu, Gd, Tb and Dy)

“…5). The assignments and discussion of the H-Mef and the Na-Mef bands are consistent with literature [11]. The Gd(Mef) 3 assignment was found to be representative (see Table S3).…”

“…These curves also show that the first two mass losses occur through a fast process that corresponds to exothermic peaks, which themselves are attributed to oxidation of the organic matter and/or of the gaseous products that evolve during the thermal decomposition, with the formation of carbonaceous residue and/or a derivative of carbonate. Tests using a hydrochloric acid solution on samples heated up to the temperatures at which these intermediates form (as indicated by the corresponding TG-DSC curves), confirmed the evolution of CO 2 and the presence of the carbonaceous residue in all cases, with the exception of terbium, for which only carbonaceous residue was observed [11]. The last step is slow and the TG curves exhibited different mass losses, depending on the amount of carbonate derivative and carbonized material formed in the previous steps and no thermal event associated with this mass loss is observed on the DSC curve, probably because endothermic events (carbonate derivative decomposition) and exothermic event (oxidation of carbonized waste) occur simultaneously.…”

“…Mefenamic acid (C 15 The lanthanide (Sm to Dy) mefenamates were prepared following the same procedure described in the literature [11].…”

“…Analysis of the spectra shows that the main gaseous products released in air atmosphere were CO 2 , CO, 2,3-dimethyl-Nphenylaniline and NH 3 [11]. Already in nitrogen atmosphere only CO 2 and 2,3-dimethyl-N-phenylaniline were identified.…”

“…Terbium compounds produced by carproxen have also exhibited strong energy transfer between the ligand and the metal, which leads to a substantial luminescent property [10]. The f-block metals associated with NSAID are important because they exhibit different properties, including pharmacological activity (free radical scavenging ability) and technological characteristics (magnetism, conductivity, luminescence and electroluminescence) [2,11].…”