Stoichiometry mechanosynthesis and interconversion of metal salts containing [CuCl3(H2O)]- and [Cu2Cl8]4-

Solid-state grinding plays a very important role in the study of the dynamics changes of reaction, especially as a means of selectively preparing specific stoichiometric crystalline supramolecular complexes or cocrystals. Using the tetradentate ligand, (1R, 2R)-N,N′-bis(pyridin-4-ylmethyl)cyclohexane-1,2-diamine (L), two copper (II) chloride salts, [H4L]4+•[CuCl3(H2O)]-•3Cl- (1) and [H4L]4+•[Cu2Cl8]4-•H2O (2) are produced via 1:1 and 1:2 stoichiometric controlled synthesis, in two step process by grinding together the reactants with a mortar and pestle. By adding the appropriate amount of the corresponding components, the reversible transformation of two salts occurs. The reversible reaction progress between salt 1 and 2 was dynamically monitored by fluorescence spectra, powder X-ray diffraction and Raman spectra. Quantum-Mechanical (QM) calculations specific for crystalline solid phases give some insights on the relative stabilities of the two salts showing plausible driving forces of the reversible transformation.