Trinuclear {Sr[UO2L3](2).H2O)(4)} and pentanuclear {Sr[UO2L3](4)}(2-) uranyl monocarboxylate complexes (L-acetate or n-butyrate ion)

Crystals of two acetate complexes, Cs-2{Sr[UO2L3](4)} (1) and [Sr(H2O)(6)][UO2L3](2){Sr(H2O)(4)[UO2L3](2)}(2) (2), and one n-butyrate complex, {Sr.H2O)(4)[UO2L3](2)}center dot 2H(2)O (3), of uranium(VI), where L is a corresponding monocarboxylate ion, were studied by means of FTIR spectroscopy and single crystal X-ray analysis. The structure of 1 contains pentanuclear anionic complexes, {Sr[UO2L3](4)}(2-), bonded in a three dimensional framework by electrostatic interactions with Cs+ cations. The structure of 2, in addition to 'typical' uranyl triacetate complexes of [UO2L3](-) and (Sr.H2O)(6)](2+) cations, contains neutral trinuclear complexes, {Sr(H2O)(4)[UO2L3](2)}. The structure of 3 with n-butyrate ions consists of neutral complexes of {Sr.H2O)(4)[UO2L3](2)} and molecules of crystallized water. Analysis of intermolecular interactions in 2 and 3 by means of two independent approaches (molecular Voronoi-Dirichlet polyhedra and molecular Hirshfeld surfaces) revealed that discrete complex groups are connected with one another mostly due to H/O hydrogen bonds and H/H dispersion interactions. A dynamic balance among mono- and poly-nuclear complexes in aqueous solutions containing R2+ and.UO2L3]-ions is proposed. The effect of the alkyl chain and the nature of the R2+ cation on the balance is discussed.