Complexes of Uranyl Ions with Aromatic Di‐ and Tetracarboxylates Involving [Ni(bipy)n]2+ (n = 2, 3) Counterions

Abstract

Four di‐ and tetracarboxylate ligands based on aromatic platforms have been used to synthesize four uranyl ion complexes under solvo‐hydrothermal conditions and in the presence of nickel(II) cations and 2,2′‐bipyridine (bipy). The four complexes [Ni(bipy)3][(UO2)2(bdc)3]·4H2O (1, bdc2– = 1,3‐benzenedicarboxylate), [Ni(bipy)3][(UO2)2(ndc)3]·DMF·5H2O (2, ndc2– = 2,6‐naphthalenedicarboxylate), [UO2(ntcma)(H2O)2]·2H2O (3, ntcma2– = 1,4,5,8‐naphthalenetetracarboxylate‐1,8‐monoanhydride), and [UO2Ni(hfdp)(bipy)2(H2O)]·H2O (4, hfdp4– = 4,4′‐(1,1,1,3,3,3‐hexafluoroisopropylidene)diphthalate) crystallize as two‐dimensional assemblies. While separated [Ni(bipy)3]2+ counterions are present in 1 and 2, the Ni(bipy)22+ groups in 4 are bound to carboxylate donors and are decorating species on the polymeric network, while nickel(II) is absent in the neutral complex 3. The networks in 1–3 have the {63} hcb topology and that in 4 the {4.82} fes one. Apart from Coulombic interactions in 1 and 2, OH···O and CH···O hydrogen bonds are prominent interactions in the lattices, as shown by Hirshfeld surface analysis. Uranyl emission spectra in 1 and 4, in spite of almost complete quenching in the former, are in agreement with those measured in other polycarboxylate complexes with six and five equatorial donors, respectively.