Thermochemical studies on copper(II) and nickel(II) complexes of the Schiff base derived from 2-(2-aminophenyl)benzimidazole and salicylaldehyde

Microcalorimetric measurements were made on copper(II) and nickel(II) complexes of the Schiff base (L) derived from 2-(2-aminophenyl)benzimidazole and salicylaldehyde. The complexes were of the general type MX₂L₂ with M = Cu or Ni, and X = Cl, Br, NO₃ or ClO₄. The enthalpies of decomposition of the solid complexes to solid products, MX₂ and L, were derived. Despite showing some variation depending on the anion, the average binding enthalpy of the ligand to nickel was 47.5 ± 7.3 kJ mol⁻¹, greater than that to copper, 16.8 ± 3.5 kJ mol⁻¹ by 30.7 ± 8.1 kJ mol⁻¹.