Complexes of three transition-metal (TM) cations, Ni(II), Cu(II) and Zn(II), with four different ligands, namely, the tetradentate bis(acetylacetone)ethylenediamine, H2acacen, and bis(salicylidene)ethylenediimine, H2salen, ligands and the bidentate glycine, Hgly, and 8-hydroxyquinoline, Hox, ligands have been studied by means of the density functional theory based B3LYP method and considering all-electron basis sets. The enthalpies of deprotonation and of bond dissociation, at T=298.15 K, of the ligands were calculated and the values are found to be in very good agreement with available experimental data. The calculations were further extended to the standard molar enthalpies of formation in the gas-phase, T = 298.15 K, for the metal complexes by using pertinent working reactions and previously determined experimental enthalpies of formation for key species. Very good agreement was obtained and new values are estimated for the TM(gly)2 and Zn(acacen) complexes. In the cases of the Ni(gly)2 and Cu(gly)2 compounds, new values are suggested.
Keywords: Density functional theory, Enthalpy of formation, Enthalpy of bond dissociation, Thermochemistry, Metal complex, Schiff base, Gas-phase acidity, Amino acid, Thermochemistry of TM(II) Complexes, DFT Calculations, transition-metal (TM), bidentate glycine, light-emitting materials, transition metals, Metal complexes, antibacterial, antimalarial, antineoplasic properties, hydroformilation, epoxidation, enthalpies of sublimation, reaction-solution calorimeter, isotenoscopic method, sublimation bulb technique, mass-loss Knudsen effusion apparatus, thermochemical cycles, gas-phase enthalpies, computational organometallic chemistry, medium-sized metal complexes, H2acacen, M(acacen), H2salen, M(salen), Hox, M(ox)2, Hgly, M(gly)2, heterocycle aromatic, gas-phase electron diffraction, intrinsic structure, bidentate ligands, quasi-planar conformation, enthalpy of deprotonation, gaseous-phase glycine, (α)-leucine, L-(α)-isoleucine, L-(α)-phenylglycine, L-(α)-phenylalanine, metal-aminoacid complexes
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