Síntese, caracterização e estudo da aplicabilidade dos complexos entre ligantes carboxílicos e lantanídeos (La, Eu, Tb e Dy) como traçadores

Abstract

A novel series of promising tracers for application in petrochemistry were rationally planned, synthesized and investigated. These new compounds are coordination compounds with some ligands such aspoli and dicarboxylic acids (hydrosoluble ones, as carboxylates, DTPA and PDH derivatives) with lanthanides (La, Eu, Tb e Dy) and their corresponding ethyl esters (liposoluble ones, the analogous ethyl esters, PDL). Four ever known thia-,-dicarboxylic acids (3-thia-pentanodioic (PDH-1); 4-thia-heptanodioic (PDH-2); 3,7-dithia-nonadioic (PDH-3) and 3,6-dithia-octanodioic (PDH-4) acids were synthesized in good yields(through the reaction with from sodium sulfide, or ethane-1,2-dithiolate, or propane-1,3-dithiolate and the corresponding -chloro-substituted acids). The complexation reactions with La, Eu, Tb e Dy were investigatedand sixteen novel complexes were obtained: PDH-1-La-Eu-Tb-Dy; PDH-2-La-Eu-Tb-Dy; PDH-3-La-Eu-Tb-Dy and PDH-4-La-Eu-Tb-Dy. The corresponding diethyl esters (PDL-1, PDL-2, PDL-1 and PDL-4)were also prepared by classical esterification reaction, but the complexation with lanthanides did not occur. Others four complexes (DTPA-La-Eu-Tb-Dy) were also synthesized (in good yields) starting fromdiethylenetriaminepentaacetic acid (DTPA). In fact, he lanthanide complexes can be further analyzed by neutron ativation analysis. The isotopically marked derivatives with 35-S - PDH-1-S, PDH-2-S, PDL-1-S and PDL-S for radiochemical analysis had their synthesis just started through classical nuclear reactions. All synthesized ligands and coordination compounds were characterized by Infrared spectrometry (IR), elemental analysis (CHN), powder x-ray, thermal analysis and mass spectrometry with electronspray ionization (ESI-MS). The analysis of the IR spectra, of the TG and x-ray data confirmed the complexation occurrence and the elemental analysis suggests the obtaining of complexes with general formulas Ln3(Lig)5 and Ln3(Lig)2,correspondingly for PDH-Ln and DTPA-Ln complexes. These kinds of lanthanides-ligands ratios were also determined by ESI-MS through the molecular ion analysis and the study of the fragmentation mechanisms.In order to evaluate the lipophilicity and the hydrophilicity, the logarithm of the octanol/water partition coefficient (log P) for the thiadicarboxylic derivatives PDH and PDL were measured through shake-flask,Flow Injection Analysis (FIA) and Thin Layer Chromatography (TLC). It was observed a straight correlation between the chromatographic parameter values obtained by TLC (Rm) and the log P values given by shakeflask for PDH, DTPA and PDL while none correlation Rm x Log P was observed in the cases of the complexes between the same DTPA-Ln e PDH-Ln. Although, good correlations were obtained for the log Pvalues measured by FIA and the values by shake-flask such as for the acids, as the esters, as the complexes. These data show the possible great applicability of FIA systems for log P determination for any kind ofcompound. After the obtaining of this lipophilicity data in octanol/water from DTPA-Ln and PDH-Ln, the actual partition coefficient in a petroleum/water system (log P) was evaluated by FIA methodology which is faster, easier and more reproductible and the measured values around 10-3 showed that this novel compounds can really be studied as hydrosoluble petrochemical tracers. In a preliminary evaluation in a bench test DTPA-Dy did not show itself suitable as tracer due to its adsorption in the rocks, but DTPA-Eu did not suffer any kindof absorption and it can be really a suitable new kind of petrochemical tracer.