Effect of intramolecular hydrogen bond in unsaturated dicarboxylic acid molecules on the formation of cobalt(II) and nickel(II) carboxylates

Resumo

The energies of formation of intramolecular hydrogen bonds (IHB) in unsaturated dicarboxylic acid molecules in aqueous solutions were calculated by the DFT method (B3LYP hybrid functional, 6-31G** basis set) using the GAMESS software, Version 1, May 2013 (R1). The medium effect was taken into account in terms of the Polarized Continuum Model (PCM). In the case of allylmalonic, itaconic, and maleic acids, fairly weak IHB with an energy of 5.8–13.9 kJ/mol were found to form. The enthalpies of formation of acid and normal cobalt and nickel salts of carboxylic acids in aqueous solutions were calculated by the semiempirical PM3 method using the HyperChem 8.0.8 software (Hypercube Inc.). The results indicate that in aqueous solutions, the formation of cobalt and nickel acid salts of allylmalonic, itaconic, and cis,cis-muconic acids is energetically more favorable than the formation of normal carboxylates, which is consistent with experimental data.