Chiral Discrete and Polymeric Uranyl Ion Complexes with (1$R$,3$S$ )-(+)-Camphorate Ligands: Counterion-Dependent Formation of a Hexanuclear Cage

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

Reaction of (1$R$,3$S$)-(+)-camphoric acid (H$_2$cam) with uranyl ions under solvo-hydrothermal conditions and in the presence of bulky countercations gave five chiral complexes of varying dimensionality. [Cu($R,S$-Me$_6$cyclam)][UO$_2$(Hcam)$_2$(HCOO)$_2$] (1) and [Ni($R,S$-Me$_6$cyclam)][UO$_2$(cam)(HCOO)$_2$] (2), in which the formate coligand is formed in situ, involve very similar countercations, but 1 is a discrete, mononuclear complex, whereas 2 crystallizes as a one-dimensional (1D) coordination polymer, and NH-bond donation by the macrocyclic ligand of the countercation complexes is present in both. [Co(en)$_3$][(UO$_2$)$_4$(cam)($R,R$-tart)$_2$(OH)]⋅3H$_2$O (3), in which en is ethylenediamine and H$_4$$R,R$-tart is $R,R$-tartaric acid, contains three enantiomerically pure chiral species, and it displays a two-dimensional (2D) arrangement, with the countercation again involved in NH-bond donation. While [PPh$_4$][UO$_2$(cam)(NO$_3$)] (4) is a 1D polymer, [PPh$_3$Me]$_3$[NH$_4$]$_3$[(UO$_2$)$_6$(cam)$_9$] (5), is a discrete, homochiral and homoleptic hexanuclear cage with $C_3$ point symmetry and a trigonal prismatic arrangement of the uranium atoms. This cage differs from the octanuclear, pseudo-cubic uranyl camphorate species previously described, thus providing an example of modulation of the cage size through variation of the structure-directing counterions. The cage in 5 is closely associated to three PPh$_3$Me$^+$ cations, two of them outside and with their methyl group directed toward the prism basis centre, and one inside the cage cavity. While complex 5 is non-luminescent, complexes 1 and 4 have emission spectra in the solid state typical of equatorially hexacoordinated uranyl complexes. Solid-state photoluminescence quantum yields of 2 and 23% have been measured for complexes 1 and 4, respectively. 2

Domaines: Chimie inorganique; Cristallographie

Pierre Thuéry, Youssef Atoini, Jack Harrowfield. Chiral Discrete and Polymeric Uranyl Ion Complexes with (1$R$,3$S$ )-(+)-Camphorate Ligands: Counterion-Dependent Formation of a Hexanuclear Cage. Inorganic Chemistry, 2018, 58, pp.870-880. ⟨10.1021/acs.inorgchem.8b02992⟩. ⟨cea-01957489⟩