Metal–ligand binding energies in copper (II) and nickel (II) complexes with tetradentate N2O2 Schiff base ligands

• Published in: Inorganica Chimica Acta Vol. 535; p. 120845
• Main Authors: Silva, Ana L.R., Oliveira, Paula C.F.C., Gonçalves, Jorge M., Morais, Victor M.F., Ribeiro da Silva, Maria D.M.C.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 24.05.2022; Elsevier Science Ltd
• Subjects: Coordination compounds; Copper; Dissociation enthalpies; Enthalpy; Formation enthalpies; Imines; Ligands; N,N'-bis(salicylaldehydo)propylenediimine; N,N'-bis(salicylaldehydo)tetramethylene-diimine; Nickel; Nickel(II) and copper(II) complexes with Schiff-bases; Quantum chemistry; Sublimation; Sublimation enthalpies; Transition metal compounds; Dissociation enthalpies; Formation enthalpies; Nickel(II) and copper(II) complexes with Schiff-bases; N,N'-bis(salicylaldehydo)tetramethylene-diimine; Sublimation enthalpies; N,N'-bis(salicylaldehydo)propylenediimine
• ISSN: 0020-1693; 1873-3255
• DOI: 10.1016/j.ica.2022.120845

[Display omitted] •Energy values for the binding of copper and nickel complexes were estimated.•Dissociation enthalpy of the metal–ligand bond comparison is Ni − L > Cu − L > Zn − L.•Flexibility structure vs methylene groups chain are expressed by energetic results.•The computational estimates are in quite good agreement with the experimental results. This work constitutes a new contribution for understanding the relationship between the metal–ligand bonding and, indirectly, the inherent reactivity of metallic complexes with tetradentate N2O2 Schiff base ligands, being reported the energetic characterization of two transition metal complexes – (N,N'́-bis(salicylaldehydo)tetramethylenediiminate)nickel(II) and (N,N'-bis(salicylaldehydo)propylenediiminate)copper(II). The standard molar enthalpies of formation of these complexes were determined by solution-reaction calorimetry measurements. Their standard molar enthalpies of sublimation, at T = 298.15 K, were obtained by an effusion method. From these studies, the gas-phase enthalpies of formation of Ni(II) and Cu(II) complexes, at T = 298.15 K, were derived. Differences between the metal–ligand and mean hydrogen-ligand bond dissociation enthalpies were derived and discussed in structural terms, in comparison with identical parameters for complexes of the same metals with analogous tetradentate Schiff bases. High-level quantum chemical calculations have also been conducted, complementing the results obtained experimentally.