Análise computacional da hidrólise de ésteres de fosfato: estudo eletrônico e estrutural de espécies intermediárias e do potencial de catálise heterogênea de matrizes organolantanídicas

Abstract

Phosphate esters are an important group of chemical compounds. They are naturally found and intrinsically related to life since are involved in genetic and energy storage. However, there is a concern about the use of anthropogenic phosphate esters emerges due to their persistence, toxicity especially to the nervous system and exponential rise of its uses. In this work phosphate esters with linear carbonic chain (methyl, ethyl, and propyl), were simulated in neutral and anionic forms using MP2, B3LYP, and M06-2X as methodology. Results point out that MP2 is the best methodology, since it was energetically more accurate compared to DFT. For conformational results, all methodologies give similar results. After the oxygen deprotonation, a structural and electronic rearrangement took place, pushing deprotonated oxygen away from each other, compensated by the approximation of oxygen esters (and consequently carbonic chains). Results of Monomethyl phosphate (MMP) indicate that the anomeric effect (hyperconjugation) has a great influence on species stability. Conformational analysis of neutral MMP allowed identifying maximum and minimum energy points, including second-order saddles points. Many pathways for reactions are possible with these configurations. The molecular description was performed characterizing atomic interaction and distance. This analysis involved many tools, such as topological or orbitals (Molecular or Natural) composition. No significant participation of P-d electrons was founded. Since phosphate ester hydrolysis occurs in water medium and this reaction could be catalyzed by metals, especially lanthanides. A polymeric base of polymethacrylate (maximum of 10 monomers) was simulated in neutral and anionic forms, with and without solvation, and linearly of consecutive constructed. These simulations indicated a consistent behavior regarding the chain size. Furthermore, high-charged chains tend to elongate more than lower ones. Concerning the lanthanide coordination to reference monomers, the use of semiempirical software generates results compatible with the literature. The coordination seems to tend to an ideal number (9), where distances metal-ligand stabilizes. When the monomer is not able to supply the metal with ligands sites to reach the previously number, water molecules complete the coordination sphere.