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

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+)<middle dot>2[CoCl4](2-)<middle dot>2H(2)O (1), [H4L](4+)<middle dot>2[ZnCl4](2-)<middle dot>2H(2)O (2), [H4L](4+)<middle dot>[CuCl4](2-)<middle dot>2Cl(-) (3), and [H4L](4+)<middle dot>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<middle dot>2H(2)O, 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.