Room temperature crystallization of trichlorodioxouranate [UO2Cl3(L)] species in molecular assemblies involving aliphatic dicarboxylate linkers

Three uranyl carboxylates (UO2)2Cl6(succ)·4dmaH (1), (UO2)2Cl6(adip)·4dmaH (2) and (UO2)2Cl6(1,4-chdc)·4dmaH (3) have been synthesized from slow evaporation in ambient atmosphere of solutions of aliphatic carboxylic acids and UCl4 in N,N-dimethyformamide (DMF) after a solvothermal treatment (succ = succinate, adip = adipate, 1,4-chdc = 1,4-cyclohexanedicarboxylate, dmaH = monoprotonated dimethylamine). These three compounds possess a similar crystal structure based on the molecular assembly of discrete dinuclear motifs (UO2)2Cl6(L) separated by dimethylammonium cations (coming from the in situ decomposition of DMF). Hexavalent uranium cation is found in seven-fold coordination (pentagonal bipyramid) with the typical double uranyl bond. Three chloride anions and two carboxyl oxygen atoms are located in the equatorial pentagonal plane, resulting in a trichlorodioxouranate ‘UO2Cl3(OC)2’ tecton. The uranyl centers are linked to each other through the ditopic ligand via the two carboxylate arms. The three compounds have been characterized by infrared and luminescence spectroscopies.