Crown Ethers and Their Alkali Metal Ion Complexes as Assembler Groups in Uranyl–Organic Coordination Polymers with cis -1,3-, cis -1,2-, and trans -1,2-Cyclohexanedicarboxylates

Pierre Thuéry (1) , Youssef Atoini (2) , Jack Harrowfield (2)

1 LCMCE - Laboratoire de Chimie Moléculaire et de Catalyse pour l'Energie (ex LCCEF)
2 ISIS - Institut de Science et d'ingénierie supramoléculaires

Alkali metal cations (Na$^+$, K$^+$) and crown ether molecules (12C4, 15C5, 18C6) were used as additional reactants during the hydrothermal synthesis of uranyl ion complexes with cis/trans-1,3-, cis-1,2- and trans-1,2-cyclohexanedicarboxylic acids ($c/t$-1,3-chdcH$_2$, c-1,2-chdcH$_2$, and t-1,2-chdcH$_2$, respectively, the latter as racemic or pure (1R,2R) enantiomer). Oxalate anions generated in situ are present in all the six complexes isolated and crystallographically characterized, [(UO$_2$)$_2$(c-1,3-chdc)$_2$(C$_2$O$_4$)][UO$_2$(H$_2$O)$_5$]·(12C4)·2H$_2$O (1), [(UO$_2$)$_4$Na$_2$(c-1,2-chdc)$_2$(C$_2$O$_4$)$_3$(15C5)$_2$] (2), [(UO$_2$)$_4$K$_2$(c-1,2-chdc)$_2$(C$_2$O$_4$)$_3$(18C6)$_{1.5}$(H$_2$O)$_{1.5}$] (3), [(UO$_2$)$_{12}$K$_5$(R-t-1,2-chdc)$_4$(C$_2$O$_4$)$_{10}$(18C6)$_5$(OH)(H$_2$O)$_3$]·4H$_2$O (4), [(UO$_2$)$_{12}$K$_5$(rac-t-1,2-chdc)$_4$(C$_2$O$_4$)${10}$(18C6)$_5$(OH)(H$_2$O)$_3$]·4H$_2$O (5), and [(UO$_2$)$_8$K$_4$(rac-t-1,2-chdc)$_4$(C$_2$O$_4$)$_6$(18C6)$_3$(H$_2$O)$_2$] (6). In complex 1, the [UO$_2$(H$_2$O)$_5$]$_2$+ counterions link the ladderlike uranyl-containing one-dimensional polymers and the uncomplexed crown ether molecules through hydrogen bonds. In all the other complexes, two-dimensional uranyl/chdc/oxalate subunits are formed, with topologies depending on the stoichiometry, in which the 1,2-chdc$^{2–}$ ligands are bound to three uranium atoms, one of them chelated by the two carboxylate groups, and the oxalate ligands are bis-chelating. In complex 2, the Na(15C5)$^+$ cations are bound to one layer through double Na-carboxylate or Na-oxo cis-bonding and they are thus mere decorating groups. In contrast, the quasi-planar K(18C6)$^+$ groups in 3–6, partially affected by disorder, are generally trans-coordinated to two uranyl oxo groups pertaining to different layers, thus uniting the latter into a three-dimensional framework.

Domaines: Chimie organique; Cristallographie

Pierre Thuéry, Youssef Atoini, Jack Harrowfield. Crown Ethers and Their Alkali Metal Ion Complexes as Assembler Groups in Uranyl–Organic Coordination Polymers with cis -1,3-, cis -1,2-, and trans -1,2-Cyclohexanedicarboxylates. Crystal Growth & Design, In press, 18 (5), pp.3167-3177. ⟨10.1021/acs.cgd.8b00266⟩. ⟨cea-01759418⟩