Effect of Sr2+ association on the tautomerization processes of uracil and its dithio- and diseleno-derivatives.
The structures and relative stabilities of the complexes formed by uracil and its thio- and seleno-derivatives with the Sr(2+) cation, in the gas phase, have been analyzed by means of G96LYP density functional theory (DFT) calculations. The attachment of the Sr(2+) cation to the heteroatom at position 4 is preferred systematically. Although the enolic forms of uracil and its derivatives should not be observed in the gas phase, the corresponding Sr(2+) complexes are the most stable. The enhanced stability of these tautomers is two-fold, on the one hand Sr(2+) interacts with two basic sites simultaneously, and on the other hand an aromatization of the six-membered ring takes place upon Sr(2+) association. Sr(2+) attachment also has a clear catalytic effect in the tautomerization processes involving uracil and its derivatives. This catalytic effect increases when oxygen is replaced by sulfur or selenium. The Sr(2+) binding energy with uracil and its derivatives is bigger than the tautomerization barriers connecting the dioxo forms with the corresponding enolic tautomers. Consequently, when associated with Sr(2+), all tautomers are energetically accessible and should all be observed in the gas phase.
Departamento de Química, Módulo 13, Universidad Autónoma de Madrid, Cantoblanco, Campus de Excelencia UAM-CSIC, 28049-Madrid, Spain.
Ane
A
Eizaguirre
Otilia
O
Mó
Manuel
M
Yáñez
Russell J
RJ
Boyd
D002384:Catalysis; D002413:Cations, Divalent / Q000737:chemistry; D015394:Molecular Structure; D018036:Selenium Compounds / Q000737:chemistry*; D013237:Stereoisomerism; D013324:Strontium / Q000737:chemistry*; D013889:Thiouracil / Q000737:chemistry*; D014498:Uracil / Q000737:chemistry*
D002413:Cations, Divalent; D018036:Selenium Compounds; D014498:Uracil; D013889:Thiouracil; D013324:Strontium