One- to three-dimensional uranyl–organic assemblies with 3-sulfophthalic and 5-sulfoisophthalic acids

Abstract

Complexes formed by uranyl ions with sulfonate derivatives of phthalic and isophthalic acids under hydrothermal conditions have been investigated. The reaction of uranyl nitrate with 3-sulfophthalic acid (3-SPH3) in the presence of 2,2′-bipyridine (2,2′-bipy) gave the complex [2,2′-bipyH][UO2(3-SP)] (1), which is a one-dimensional coordination polymer in which the three functional groups of 3-SP3− are coordinated. Four complexes were obtained from uranyl nitrate and the lithium salt of 5-sulfoisophthalic acid (5-SIPH2Li). In the presence of additional nickel(II) ions and bipyrimidine (bipym), the complex [Ni2(bipym)3(H2O)4][UO2(5-SIP)(NO3)]2·6H2O (2) is formed, in which uranyl-containing one-dimensional chains result from bridging by 5-SIP3− through its carboxylate groups only. The two compounds obtained in the presence of triethylamine and pyrazine (pyz), [HNEt3][UO2(5-SIP)] (3) and [Hpyz][UO2(5-SIP)]·2.5H2O (4), display both carboxylate and sulfonate coordination, resulting in the formation of two-dimensional assemblies with {44·62} topology. The use of 1,4-diazabicyclo[2.2.2]octane (DABCO) as a base gives the complex [H2DABCO][UO2(5-SIP)(H2O)]2·4H2O (5) which crystallizes as a three-dimensional framework with channels containing the counter-ions. The structure of 5 comprises uranyl–organic layers, in which the 5-SIP3− ligands are stacked in rows held by π-stacking interactions; these layers are connected to one another by uranyl groups orthogonal to those in the layers. The variation of dimensionality in complexes 3–5, which likely arises from structure-directing effects exerted by the counter-ions, is discussed in relation with geometry differences around the ligand coordination sites.