Solid-state reaction among [CoCl4]2−, [CuCl4]2− and [CuCl4(H2O)]2− ions through transmetalation and liquid-assisted grinding

Abstract

Transmetalation plays a very important role in the study of functional MOFs, but it is rarely used in metal–organic salts (MOSs). In this paper, four kinds of MOSs were synthesized by using the tetradentate ligand N,N′-bis (pyridin-4-ylmethyl) ethane-1,2-diamine and MCl₂ (M = Zn, Co, Cu), labelled as [H₄L]⁴⁺·2[CoCl₄]²⁻·2H₂O (1), [H₄L]⁴⁺·2[ZnCl₄]²⁻·2H₂O (2), [H₄L]⁴⁺·[CuCl₄]²⁻·2Cl⁻ (3), and [H₄L]⁴⁺·2[CuCl₄(H₂O)]²⁻ (4). Salt 3 was obtained by the metal-ion exchange of salt 1, and salt 4 was successfully synthesized by liquid-assisted grinding (LAG) of salt 3 and CuCl₂·2H₂O, which was a stoichiometric ratio-controlled transformation that occurred with the change in the geometry of copper(II) anions from [CuCl₄]²⁻ and [CuCl₄(H₂O)]²⁻. The reaction process was monitored dynamically by atomic absorption spectroscopy (AAS), fluorescence spectroscopy, and powder X-ray diffraction (PXRD). This suggested that transmetalation combined with LAG was an alternative method to obtain MOSs for different metal ions.