Morphotropy in alkaline uranyl methacrylate complexes. (5th September 2017) - Klepov, Vladislav V.
Graphical abstract: Five uranyl methacrylates with alkaline cations (Li, Na, Rb, Tl, Cs) have been synthesized. Their crystal structures shares common [UO2 (CH2 C(CH3 )COO)3 ] − complexes, but their arrangement is strongly affected by the nature of the alkaline cations. Non-centrosymmetric compounds with K, NH4, Rb, and Cs cations exhibit SHG properties. Abstract: Five uranyl methacrylate complexes with monovalent cations have been synthesized via isothermal room temperature evaporation. The crystal structures of these compounds, [Li(H2 O)2 ][UO2 (macr)3 ]·2Hmacr (1, macr denotes the methacrylate anion CH2 C(CH3 )COO − ), Na[UO2 (macr)3 ]·H2 O (2 ), Rb[UO2 (macr)3 ] (3 ), Tl[UO2 (macr)3 ] (4 ) and Cs[UO2 (macr)3 ] (5 ), were determined by single crystal X-ray diffraction. In1 –5, the main uranyl-containing structural unit is the [UO2 (macr)3 ] − complex. Variation of the size and nature of the monovalent cations strongly influences the composition and the structure of the compounds. π-interactions between the methacrylate anions, which were previously reported in the crystal structures of [R(H2 O)6 ][UO2 (CH2 C(CH3 )COO)3 ]2 ·8H2 O (R = Mg or Zn), were observed in1 and2 as well, and may play an important structure-directing role. The crystals of3, 4 and5 are lacking inversion centers and should exhibit non-linear optical (NLO) properties as well as the previously reported NH4 [UO2 (macr)3 ] and K[UO2 (macr)3 ] complexes. The second harmonic generation response of tris(methacrylato)uranylates with monovalent cations (except Tl) has been measured by the powder technique and discussed with respect to previously reported data on the acrylate analogs.