THERMOGRAVIMETRIC AND CALORIMETRIC INVESTIGATION OF ACETONITRILE-SOLVATED ZN(II) AND CU(II) COMPLEXES STABILIZED BY NON-COORDINATING ANIONS.

Abstract

 The thermal stability and decomposition behavior of acetonitrile-solvated Zn(II) and Cu(II) complexes stabilized by non-coordinating anions have been systematically investigated using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Complexes of the type [M(MeCN)₆]₂X (M = Zn(II), Cu(II); X = PF₆⁻, BF₄⁻, OTf⁻) were synthesized and subjected to controlled heating under inert atmosphere. The TGA profiles revealed multistep decomposition processes, beginning with the gradual release of coordinated acetonitrile ligands, followed by structural rearrangements and eventual formation of metal oxides as final residues. DSC traces provided complementary information, showing distinct endothermic events associated with ligand loss and exothermic peaks correlated with lattice collapse or secondary decomposition. Zn(II) complexes exhibited higher thermal stability and more well-defined decomposition steps compared to Cu(II) analogues, which displayed broader transitions due to Jahn–Teller distortions and partial anion involvement. The choice of counter anion strongly influenced thermal profiles, with PF₆⁻ and BF₄⁻ providing greater stabilization than OTf⁻. These findings highlight the crucial interplay between ligand solvation, metal electronic configuration, and anion effects in determining the thermal behavior of acetonitrile-coordinated complexes, offering valuable insights for their application in catalysis and materials design.