Reactant-Mediated Diversity in Uranyl Phosphonates

Four organically templated uranyl phosphonates, [C₄N₂H₁₂][UO₂F(PO₃CH₃)]₂ (UPNO-1), [C₄N₂H₁₂][UO₂(PO₃CH₃)(PO₂(OH)CH₃)]₂ (UPNO-2), [C₄N₂H₁₂][(U₂O₄F₃)(UO₂F(H₂O))(PO₃C₆H₅)₂]·2H₂O (UPNO-3), and [C₄N₂H₁₂]₂[(UO₂)₅(PO₃CH₂C₆H₅)₆(PO₂(OH)CH₂C₆H₅)₂] (UPNO-4) have been synthesized under hydrothermal conditions. UPNO-1 contains doubly protonated piperazine templates, [C₄N₂H₁₂]²⁺, residing between [UO₂F(PO₃CH₃)]^1- anionic layers. Distinct hydrophobic and hydrophilic regions are present between [UO₂(PO₃CH₃)(PO₂(OH)CH₃)]^1- layers in UPNO-2. The template is found in the hydrophilic interlayer space only, completely segregated from the methyl groups of the uranyl methylphosphonate layer, which protrude into the hydrophobic interlayer space. UPNO-3 contains [(U₂O₄F₃)(UO₂F(H₂O))(PO₃C₆H₅)₂]^2- layers separated by both piperazine templates, [C₄N₂H₁₂]²⁺, and phosphonate phenyl groups, which exist in the same interlayer region. In UPNO-4 the region between [(UO₂)₅(PO₃CH₂C₆H₅)₆(PO₂(OH)CH₂C₆H₅)₂]^4- layers is completely hydrophobic as a result of the large number of benzyl groups occupying the interlayer space. The template is found in voids within each layer. The structures of these compounds are dependent upon the reactant concentrations. Crystal data for the compounds are as follows:  UPNO-1, a = 6.9288(3) Å, b = 8.1174(4) Å, c = 14.8505(9) Å, β = 91.7173(19)°, monoclinic P2₁/n (no. 14), Z = 2; for UPNO-2, a = 10.0682(4) Å, b = 8.9121(3) Å, c = 12.9631(7) Å, β = 90.4901(15)°, monoclinic P2₁/a (no. 14), Z = 2; for UPNO-3, a = 6.7796(1), b = 17.2821(4) Å, c = 24.6754(6) Å, orthorhombic Pbcm (no. 57), Z = 4; and for UPNO-4, a = 11.4732(2) Å, b = 14.9097(2) Å, c = 15.4480(3) Å, α = 64.2307(6)°, β = 70.2105(7)°, γ = 84.136(1)°, triclinic P1̄ (no. 2), Z = 2.