Incorporation of Mn(II) and Fe(II) into Uranyl Carboxyphosphonates

Five heterobimetallic U(VI)/M(II) (M = Mn, Fe) carboxyphosphonates have been synthesized under mild hydrothermal conditions by reacting UO3, triethyl phosphonoacetate, with either Mn(II) or Fe(II) acetate. The manganese reactions yield Mn2[(UO2)6(PO3CH2CO2)3O3(OH)(H2O)2]·16H2O (MnUPAA-1) and [Mn(H2O)6][Mn(H2O)5Mn2(UO2)5(PO3CH2CO2)6(H2O)]·5.75H2O (MnUPAA-2). The addition of boric acid, which lowers the crystallization temperature, allows for the production of a third product, [Mn(H2O)4]2(UO2)3(PO3CH2CO2)2O2 (MnUPAA-3). The iron-containing reactions yield [Fe(H2O)6][UO2(PO3CH2CO2)]2·8H2O (FeUPAA-1) and [Fe(H2O)6][UO2(PO3CH2CO2)H2O]2·4H2O (FeUPAA-2). Four of these five compounds crystallize in low-symmetry space groups; whereas MnUPAA-1 crystallizes in the cubic space group Im3̅ and possesses a remarkably complex open-framework structure containing both UO7 pentagonal bipyramids and UO8 hexagonal bipyramids. MnUPAA-3 adopts a one-dimensional uranium oxide topology that contains both UO6 tetragonal bipyramids and UO7 pentagonal bipyramids. The remaining three compounds solely contain UO7 pentagonal bipyramids.本研究通过温和水热条件下的反应，使三氧化铀（UO₃）与膦酰乙酸三乙酯（triethyl phosphonoacetate）分别与乙酸锰(II)或乙酸铁(II)作用，成功合成了5种异双金属U(VI)/M(II)（M=Mn、Fe）羧基膦酸酯（carboxyphosphonates）化合物。锰系反应体系可生成Mn₂[(UO₂)₆(PO₃CH₂CO₂)₃O₃(OH)(H₂O)₂]·16H₂O（记为MnUPAA-1）与[Mn(H₂O)₆][Mn(H₂O)₅Mn₂(UO₂)₅(PO₃CH₂CO₂)₆(H₂O)]·5.75H₂O（记为MnUPAA-2）；通过添加可降低结晶温度的硼酸，可得到第三种产物[Mn(H₂O)₄]₂(UO₂)₃(PO₃CH₂CO₂)₂O₂（记为MnUPAA-3）。铁系反应体系则生成[Fe(H₂O)₆][UO₂(PO₃CH₂CO₂)]₂·8H₂O（记为FeUPAA-1）与[Fe(H₂O)₆][UO₂(PO₃CH₂CO₂)H₂O]₂·4H₂O（记为FeUPAA-2）。5种化合物中有4种结晶于低对称空间群；其中MnUPAA-1结晶于立方空间群Im3̅，其拥有极为复杂的开放骨架结构，同时包含UO₇五角双锥（UO₇ pentagonal bipyramids）与UO₈六方双锥（UO₈ hexagonal bipyramids）两种铀配位构型。MnUPAA-3则呈现出同时包含UO₆四方双锥（UO₆ tetragonal bipyramids）与UO₇五角双锥的一维铀氧化物拓扑结构。其余3种化合物仅含有UO₇五角双锥配位构型。