Syntheses and crystal structures of CuIIBiIII, CuIIBaIICuII, [CuIIPbII]2 and cocrystallized (UVIO2)2.4CuII complexes: structural diversity of the coordination compounds derived from N,N′-ethylenebis(3-ethoxysalicylaldiimine)

Abstract

Syntheses, characterization and structures of heterodinuclear compound [Cu^IIL¹Bi^III(NO₃)₃] (1), sandwich type heterotrinuclear compound [(Cu^IIL¹)₂Ba^II(NO₃)₂]·0.2H₂O (2), heterotetranuclear compound [{Cu^IIL¹Pb^II(µ-NO₃)(NO₃)}₂] (3) and heterohexanuclear [2 × 1 + 1 × 4] cocrystal [(U^VIO₂)₂(µ-H₂O)₂(NO₃)₄]·4[Cu^IIL¹⊂(H₂O)] (4) are described in this investigation (H₂L¹ = N,N′-ethylenebis(3-ethoxysalicylaldiimine)). Compounds 1 and 4 crystallize in orthorhombic P2₁2₁2₁ and triclinic Pī systems, respectively, while the space group of compounds 2 and 3 is monoclinic P2₁/c. The structure of 1 consists of a diphenoxo-bridged Cu^IIBi^III dinuclear core containing three chelating nitrates and a 10-coordinate bismuth(III) centre. The dinuclear cores are self-assembled to two dimensions through intermolecular nitrate oxygen⋯copper(II) semicoordination and weak C–H⋯O hydrogen bonds. Compound 2 is a double-decker Cu^IIBa^IICu^II system in which a barium(II) ion is sandwiched between two mononuclear [Cu^IIL¹] moieties. The barium(II) centre is 11-coordinate, four phenoxo and four ethoxy oxygen atoms and one chelating and one monodentate nitrate ions. Compound 3 is a tetranuclear system (dimer of two dinuclear moieties) in which one nitrate is chelating, while the second nitrate behaves as both a chelating and bridging ligand. The lead(II) centre is 9-coordinate in this compound. Compound 4 is a [2 × 1 + 1 × 4] cocrystal of one diaqua-bridged diuranyl(VI) moiety, containing two chelating nitrates and 8-coordinated hexagonal bipyramidal uranium(VI) centres and four inclusion species [Cu^IIL¹⊂(H₂O)]. The governing factor for the self-assembled cocrystallization in 4 are the C–H⋯·π and C–H⋯O hydrogen bonds. The compounds reported in this investigation and other heteronuclear systems derived from N,N′-ethylenebis(3-ethoxysalicylaldiimine) indicate that this ligand system is an important example which gives rise to structurally diverse heteronuclear compounds. In addition to the structural diversity, the structural resemblance of bismuth(III) with lanthanides(III) and utilization of noncovalent interactions to form self-assembly and cocrystals are the major outcomes of the present investigations.