Heteroleptic pyrimidine-2-olate and 4,4′-bipyridine copper(ii) layered metal–organic frameworks with swelling properties

Abstract

One-pot reaction of CuX₂ salts (X = NO₃, Cl, ClO₄, AcO, SO₄/2), 2-Hydroxypyrimidine hydrochloride (2-Hpymo·HCl) and 4,4′-bipyridine (4,4′-bpy), in H₂O : ethanol : ammonia (20 : 10 : 5) solution, leads to isomorphous extended layered materials of type [Cu₃(µ-OH)₂(µ-Cl)₂(µ-2-pymo)(µ-4,4′-bpy)₃]_nX_n·mH₂O (X = NO₃ (1a), Cl (1b), ClO₄ (1c), AcO (1d), SO₄/2 (1e)). The single crystal X-ray crystallographic analysis performed on species 1a exemplifies that it is built by 2D [Cu₃(µ-OH)₂(µ-Cl)₂(µ-2-pymo)(µ-4,4′-bpy)₃]_nⁿ⁺ cationic sheets, which pack in a staggered fashion, with non coordinated NO₃⁻ anions and crystallisation water molecules included in the interlayer voids. XRPD studies performed on the 1a–e species show a swelling response along the crystallographic a axis concomitant to aliphatic alcohol inclusion. Additionally, we have also studied the magnetic properties of 1a, which show that its magnetic behaviour is dominated by the strong antiferromagnetic interactions taking place in the Cu₃(µ-OH)₂(µ-Cl)₂ trinuclear cores.