Solvation of uranyl-CMPO complexes in dry vs. humid forms of the [BMI][PF6] ionic liquid. A molecular dynamics study.
The solvation of the [UO(2)(NO(3))(CMPO)](+) and [UO(2)(NO(3))(2)(CMPO)(2)] complexes (CMPO = octyl(phenyl)-N,N-diisobutylmethylcarbamoyl phosphine oxide) is investigated by molecular dynamics in the "dry" and "humid" forms of a room temperature ionic liquid (IL) based on the 1-butyl-3-methylimidazolium (BMI(+)) cation and the hexafluorophosphate (PF(6)(-)) anion. The simulations reveal the importance of the solvent anions in "dry" conditions and of water molecules in the "humid" solvent. For the [UO(2)(NO(3))(CMPO)](+) complex, the monodentate vs. bidentate coordination modes of CMPO are compared, and the first solvation shell of uranyl is completed by 1-3 PF(6)(-) anions in the dry IL and by 2-3 water molecules in the humid IL, leading to a total coordination number close to 5. The energy analysis shows that interactions with the IL stabilize the [UO(2)(NO(3))(bi)(CMPO)(mono)](+) form (with bidentate nitrate and monodentate CMPO) in the dry IL and the [UO(2)(NO(3))(mono)(CMPO)(mono)](+) form (with monodentate nitrate and CMPO) in the humid IL. The extracted compound characterized by EXAFS is thus proposed to be the [UO(2)(NO(3))(mono)(CMPO)(mono)(H(2)O)(3)](+) species. Furthermore we compare the [UO(2)(NO(3))(2)(CMPO)(2)] complex in its associated and dissociated forms ([UO(2)(NO(3))(mono)(CMPO)(mono)](+) + CMPO + NO(3)(-)) and discuss the results in the context of uranyl extraction by CMPO to ionic liquids.
Laboratoire MSM, UMR CNRS 7177, Institut de Chimie, 4 rue B. Pascal, 67 000 Strasbourg, France.
Alain
A
Chaumont
Georges
G
Wipff
D002219:Carbamates / Q000737:chemistry*; D007093:Imidazoles / Q000737:chemistry*; D007477:Ions / Q000737:chemistry; D008956:Models, Chemical; D015394:Molecular Structure; D010720:Phosphines / Q000737:chemistry*; D012997:Solvents / Q000737:chemistry; D014501:Uranium / Q000737:chemistry*; D017974:Uranium Compounds / Q000737:chemistry*
C412621:1-butyl-3-methylimidazolium hexafluorophosphate; D002219:Carbamates; D007093:Imidazoles; D007477:Ions; D010720:Phosphines; D012997:Solvents; D017974:Uranium Compounds; C509724:uranyl-octyl(phenyl)-N,N-diisobutylmethylcarbamoyl phosphine oxide; D014501:Uranium