Sagarika Bhattacharya

Crystal structures of discrete, one-dimensional and cocrystalline copper(II)–uranyl(VI) systems: the influence of the reactant ratio in the competition between hydrogen bonds and coordinate bonds

This paper presents the syntheses and crystal structures of four copper(II)–uranyl(VI) compounds [{CuIILOEt–en}2·{(UVIO2)(NO3)2(H2O)2}] (1), [CuII(MeCN)LOEt–pn(UVIO2)(NO3)2] (2), [(UVIO2)2(μ-H2O)2(NO3)4]∙4[CuIILOEt–py(H2O)]∙2MeCN (3) and {[CuIILOMe–en(UVIO2)(NO3)]2[(UVIO2)2(μ-HO)2(NO3)4]}n (4), where H2LOEt–en, H2LOEt–pn, H2LOEt–py and H2LOMe–en are 3-ethoxysalicylaldehyde-diamine (H2LOEt) or 3-methoxysalicylaldehyde-diamine (H2LOMe) ligands in which the diamine functionality are ethylenediamine, 1,3-diaminopropane, 2,3-diaminopyridine and ethylenediamine, respectively. Compound 1 is a [1 × 2 + 1 × 1] trinuclear cocrystal containing two mononuclear [CuIILOEt–en] and one mononuclear [(UVIO2)(NO3)2(H2O)2] moiety; two coordinated water molecules interact with two O4 compartments by forming hydrogen bonds. Compound 2 is a dinuclear system in which two phenoxo oxygen atoms coordinate with the uranium(VI) centre. Compound 3 is a [2 × 1 + 1 × 4] hexanuclear cocrystal of four mononuclear [CuIILOEt–py(H2O)] units and one dinuclear [(UVIO2)2(μ-H2O)2(NO3)4] moiety; O–H⋯O and C–H⋯O interactions interlink the five units here. In 4, there are two dinuclear [CuIILOMe–en(UVIO2)(NO3)]+ cations and one dinuclear [(UVIO2)2(μ-HO)2(NO3)4]2− anion, which are self-assembled to generate a one-dimensional topology. Interesting structural aspects including the weak interaction directed self-assemblies and most importantly, the competition between hydrogen bond and coordinate bond formation and the influence of the reactant ratio in governing that competition are discussed. The diffuse reflectance or solution transmission spectra (for the d–d band) of 1–4 and the corresponding mononuclear copper(II) precursors are also described.

Bis(nitrate)diaquauranyl(VI) synthon to generate [1 x 2+1 x 1] and [1 x 1+1 x 1] co-crystalized 3d center dot center dot center dot 5f self-assemblies

The syntheses, characterization and crystal structures of four copper(II)/nickel(II)⋯uranyl(VI) self-assemblies of composition [{NiIIL1}2·{(UVIO2)(NO3)2(H2O)2}] (1), [{CuIIL2}2·{(UVIO2)(NO3)2(H2O)2}]·0.68H2O (2), [{NiIIL2}2·{(UVIO2)(NO3)2(H2O)2}] (3) and [{CuIIL3}·{(UVIO2)(NO3)2(H2O)2}]n (4) are described in this investigation (H2L1, H2L2 and H2L3 are the Schiff base ligands obtained on condensing 3-ethoxysalicylaldehyde with ethylenediamine, o-phenylenediamine and trans-1,2-diaminocyclohexane, respectively). Compounds 1 and 4 crystallized in the monoclinic P21/n and C2/c space groups, respectively, while compounds 2 and 3 crystallized in the triclinic space group P. Two water molecules of the [(UVIO2)(NO3)2(H2O)2] moiety in 1–4, have a linear H2O–U–OH2 arrangement. Each of these two water molecules in 1–3 interacts with the O(phenoxo)2O(ethoxy)2 compartment of a mononuclear copper(II) or nickel(II) moiety due to the formation of bifurcated hydrogen bonds between each of the two water hydrogen atoms and a pair of one phenoxo and one ethoxy oxygen atoms resulting in the interlinking of the two mononuclear 3d units by the [(UVIO2)(NO3)2(H2O)2] synthon and therefore these three compounds may be considered as supramolecular dimers. Compounds 1–3 are also two component [1 × 2 + 1 × 1] co-crystals consisting of two mononuclear copper(II) or nickel(II) units and one [(UVIO2)(NO3)2(H2O)2] moiety. On the other hand, in 4, two water molecules, from two different [(UVIO2)(NO3)2(H2O)2] moieties, interact with one O(phenoxo)2O(ethoxy)2 compartment resulting in the formation of a self-assembled one-dimensional topology. Again, since one mononuclear copper(II) unit and one [(UVIO2)(NO3)2(H2O)2] moiety exist in a single crystal in 4, this compound is a two component [1 × 1 + 1 × 1] co-crystal. The outcomes of the present study utilize [(UVIO2)(NO3)2(H2O)2] synthon to derive 3d⋯5f co-crystals, provide the first observation of the interaction of two water molecules with one O(phenoxo)2O(ethoxy)2 compartment, demonstrate the formation of supramolecular dimers and show the first example of a one-dimensional self-assembly resulting from water⋯O4 compartment hydrogen bonds, and the first example of [1 × 2 + 1 × 1] co-crystals in 3-ethoxysalicylaldehyde-diamine ligand system.