Anhydrous praseodymium salts in the ionic liquid [bmpyr][Tf2N]:: Structural and optical properties of [bmpyr]4[PrI6][Tf2N] and [bmyr]2[Pr(Tf2N)5]

Purposely designed ionic liquids can be excellent solvents for spectroscopic studies of rare earth compounds. Absorption and emission spectra of anhydrous PrI3 and Pr(Tf2N)(3) in the ionic liquid 1,1-n-butyl-methylpyrrolidinium bis(trifluoromethanesulfonyl)amide, [bmpyr][Tf2N], at room temperature are presented together with the emission spectra of solid [bmpyr](2)[Pr(Tf2N)(5)] and [bmpyr](4)[PrI6][Tf2N]. After excitation into the 3p(1) level, remarkable luminescence not only from the D-1(2) level but also from the P-3(0) and even from the P-3(1) level is observed. Amazingly in the case of the solid compounds and even more astonishing for a solution of Pr(Tf2N)3 in [bmpyr] [Tf2N] the strongest luminescence transitions start from the (3)p(0) level. From a solution of PrI3 in [bmpyr][Tf2N] single crystals of [bmpyr](4)[PrI6][Tf2N] were grown. The compound crystallizes in the space group P4(3)2(1)2 with a = b = 1464.8(2) pin and c = 2846.9(5) pm at 298(2) K and a = b = 1454.52(7) pm and c = 2852.4(2) pin at 170(2) K, respectively. The structure is characterized by [PrI6] octahedra winding along the 43 screw parallel to the crystallographic c axis. Above each octahedral face one 1-butyl-1-methyl-pyrrolidinium cation is tangentially located. The bis(trifluoromethylsulfonyl)amide anions fill the remaining space. From a solution of Pr(Tf2N)3 in [bmpyr][Tf2N] the compound [bmpyr](2)[Pr(Tf2N)(5)] is obtained which crystallizes triclinic, space group P (1) over bar, with a = 12.3217(13) pm, b = 12.4275(14) pm, c = 22.6422(24) pm, alpha = 94.440(9)degrees, beta = 102.630(8)degrees, and gamma = 105.791(9)degrees. Here the main structural feature is the separation of the hydrophobic [Pr(Tf2N)(5)](2-) and hydrophilic bmypr(+) parts in the structure.