[Ni(cyclam)] 2+ and [Ni(R,S-Me6cyclam)] 2+ as Linkers or Counterions In Uranyl–Organic Species with cis-and trans-1,2-Cyclohexanedicarboxylate Ligands

Pierre Thuéry (1) , 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

The macrocyclic species [Ni(cyclam)] 2+ and [Ni(R,S-Me6cyclam)] 2+ were used as additional cations in the solvo-hydrothermal synthesis of five uranyl ion complexes with cis-or trans-1,2-cyclohexanedicarboxylic acids (c-1,2-chdcH2 and t-1,2-chdcH2). In the complex [UO2(c-chdc)2Ni(cyclam)(H2O)] (1), dimeric uranyl dicarboxylate subunits are assembled into a two-dimensional (2D) network through axial coordination of Ni II to carboxylate groups. Although they involve different isomers, the complexes [(UO2)2(c-chdc)2(c-chdcH)2Ni(cyclam)] (2) and [(UO2)2(t-chdc)2(t-chdcH)2Ni(cyclam)] (3) are very similar, both containing uranyl-based one dimensional (1D) subunits which are assembled into 2D networks by bridging [Ni(cyclam)] 2+ groups. The orientation of the uncoordinated carboxylic group is different in 2 and 3, the layers in 2 being hydrogen bonded to each other through carboxylic acid dimer formation. Using the pure (1R,2R) enantiomer of t-1,2-chdcH2 gives the complex [Ni(cyclam)][(UO2)5(R-t-chdc)3(R-t-chdcH)(O)2(CH3COO)] (4), in which pentanuclear uranyl subunits are assembled into 1D chains by dicarboxylic/ate ligands in the usual bis(equatorial) chair conformation, another ligand in the divergent bis(axial) conformation uniting these chains into a 2D assembly; the [Ni(cyclam)] 2+ ions are simple counterions and are stacked in parallel fashion between the layers. [Ni(R,S-Me6cyclam)][Ni(R,S-Me6cyclam)(H2O)2][(UO2)2(t-chdc)2(O)]2 (5), in which the (1R,2R) enantiomer used has undergone racemization, contains discrete bis(µ3-oxo)-centered tetranuclear uranyl complexes, organized into columns and layers by extensive hydrogen bonding to the counterions. The discoidal shape, available axial coordination sites and hydrogen bond donor potential of these macrocyclic Ni II complexes make them efficient assembling agents in uranyl–organic coordination polymers. As often observed in the presence of d-block metal cations, uranyl luminescence is either completely or partially quenched in complexes 1 and 3, respectively.

Domaines: Chimie de coordination; Cristallographie

Pierre Thuéry, Jack Harrowfield. [Ni(cyclam)] 2+ and [Ni(R,S-Me6cyclam)] 2+ as Linkers or Counterions In Uranyl–Organic Species with cis-and trans-1,2-Cyclohexanedicarboxylate Ligands. Crystal Growth & Design, 2018, 18, pp.5512-5520. ⟨10.1021/acs.cgd.8b00834⟩. ⟨cea-01855343⟩