Tetrametallic [2 × 1 + 1 × 2], octametallic double-decker–triple-decker [5 × 1 + 3 × 1], hexametallic quadruple-decker and dimetallic-based one-dimensional complexes of copper(ii) and s block metal ions derived from N,N′-ethylenebis(3-ethoxysalicylaldimine)

Abstract

In the present investigation, various copper(II)–alkali/alkaline earth metal ion heteronuclear complexes derived from N,N′-ethylenebis(3-ethoxysalicylaldimine) (H₂L) have been studied. The syntheses, characterization and crystal structures of three [2 × 1 + 1 × 2] cocrystals [{Cu^IILLi^I(H₂O)₂}{Cu^IIL}₂](ClO₄) (1), [{Cu^IILNa^I(H₂O)₂}{Cu^IIL}₂](dicyanamide) (2) and [{Cu^IILMg^II(H₂O)₃}{Cu^IIL}₂](NO₃)₂·H₂O (3), one [3 × 1 + 5 × 1] double-decker–triple-decker cocrystal [{(Cu^IIL)₂K^I}(ClO₄)]·[{(Cu^IIL)₃K^I₂(μ-ClO₄)}(ClO₄)] (4), one dinuclear Cu^IIK^I-based one-dimensional polymer [Cu^IILK^I(μ-PF₆)]_n (5) and one hexametallic quadruple-decker compound [{(Cu^IIL)₂Rb^I(μ-H₂O)}₂](BPh₄)₂·2CH₃COCH₃ (6) are reported. Compounds 1, 2, 3 and 6 crystallize in the triclinic crystal system (space group P), while the crystal systems of 4 and 5 are monoclinic (space group C2/c) and orthorhombic (space group P2₁2₁2₁), respectively. The cocrystallization in 1–3 takes place through the encapsulation of coordinated water molecules into the O₄ compartment of two mononuclear [Cu^IIL] moieties; both the coordinated water molecules are involved in the case of 1 and 2, while 2 of the 3 coordinated water molecules are involved for 3. In 4, the potassium(I) centre in the double-decker moiety is sandwiched in between two mononuclear [Cu^IIL] moieties, while each of the two potassium(I) centres in the triple-decker moiety are sandwiched in between a pair of two [Cu^IIL] moieties. The two potassium(I) centres in the triple-decker moiety are bridged by a perchlorate anion. In 5, two cis fluorine atoms from the hexafluorophosphate anion bridge the potassium(I) centres of the neighbouring dinuclear Cu^IIK^I units to build up a one-dimensional polymer. The quadruple-decker hexanuclear [{(Cu^IIL)₂Rb^I(μ-H₂O)}₂]²⁺ dication in 6 can be considered to consist of two trinuclear double-decker [(Cu^IIL)₂Rb^I]⁺ moieties, interlinked by two bridging water molecules. Structural resemblance between the structures formed with Li^I, Na^I and Mg^II and those with 3d metal ions, the anion dependence of the topology of the copper(II)–potassium(I) complexes, cocrystallization in the presence of the potentially bridging dicyanamide anion, the first report of a one-dimensional polymer derived from H₂L and an interesting example of a quadruple-decker complex, are the major outcomes of the present investigation. All in all, structural diversity in the H₂L ligand system has been further enriched by some interesting structures in the present investigation.