3D-supermolecular structure and electronic absorption of uranyl β-diketone [UO2(tfa)2(L)] (L = H2O, OHCH2CH3) complex

Uranyl β-diketone complex UO2(tfa)2·H2O (3) (tfa = deprotonated 4,4,4,-trifluoro-1-(2-furyl)-1,3-butanedione) has been successfully prepared by reacting UO2(OAc)2·2H2O (OAc = O2CMe) with two equivalents of 4,4,4,-trifluoro-1-(2-furyl)-1,3-butanedione (H-tfa: 1) in ethanol. Complex 3 was characterized by elemental analysis and FT-IR. Dissolving 3 in ethanol gave during several days single crystals of [UO2(tfa)2(OHCH2CH3)] (4), wherein one ethanol molecule replaces aqua ligand. The solid-state structure of 4 was determined by a single X-ray analysis. Crystal data of C18H14F6O9U: a = 13.7163(7), b = 20.7528(10), c = 7.4664(4) Å, β = 90.818(4)°, space group P2(1)/c, Z = 4 and dcalc = 2.270 mg/m3. Complex 4 adopted a distorted pentagonal bipyramidal geometry. The coordinated oxygen atoms of tfa (deprotonated-1) ligands are occupying equatorial positions, while the oxygen atoms of UO22+ are still in the axial positions. The formation of the π–π interactions together with hydrogen bonded result in the set up a 3D-supramolecular architecture. The electronic absorption of 3 is reported and discussed.

► The reaction of UO22+ ion with 4,4,4,-trifluoro-1-(2-furyl)-1,3-butanedione yielded a mononuclear [UO2(tfa)2(H2O)] (3) complex.
► The electronic absorption for 3 shows LMCT (384 nm (<10)), wherein the U(VI) center is only capable to function as acceptor site.
► Dissolving 3 in ethanol gave a single crystals of 3D-supramilecular polymer of [UO2(tfa)2(HOCH2CH3)]n (4).