A three-component co-crystal and a mono crystal isolated from the same crystallisation of a copper(II) carboxylate

Abstract

The vagaries of recrystallisation are highlighted in this contribution which describes the full characterisation of crystals isolated from the recrystallisation of [Cu₂L₄(EtOH)₂] from a 1 : 2 mixture of DMSO and CHCl₃ (v/v); L is 4-nitrobenzoate. Slow evaporation over four weeks yielded blue-green crystals of 1 that were shown to be a rare example of a three-component co-crystal comprising [CuL₂(OH₂)(DMSO)]₂, [CuL₂(OH₂)₂(DMSO)] and [CuL₂(OH₂)(DMSO)₂] in the ratio 1 : 2 : 2. After crystals of 1 were removed from the solution, blue crystals of 2 were isolated after another week had elapsed. These proved to be [CuL₂(OH₂)(DMSO)₂] and to be the trans-DMSO isomer of one of the components of 1. The supramolecular aggregation in each crystal structure features ten-membered {…HOH…OCOCuOCO} synthons whereby the hydrogen atoms of a water molecule link two carbonyl-O atoms of another complex molecule. In 1, these synthons lead to an isolated six-copper aggregate, and in 2, these lead to supramolecular chains. IR and thermal analysis (TGA and DSC) data are also presented. Crystal data for (1): triclinic, P-1, a = 13.9035(4), b = 15.5305(4), c = 15.7069(4) Å, α = 80.062(2), β = 83.174(2), γ = 70.109(2)°, V = 3134.75(15)ų, Z = 2, R = 0.036. Crystal data for (2): monoclinic, C2/c, a = 30.0180(16), b = 5.8440(3), c = 14.2639(8) Å, β = 114.669(7)°, V = 2273.9(2) ų, Z = 4, R = 0.027.