COMPUTATIONAL STUDY OF THE N-H DISSOCIATION IN N,N'-ETHYLENEBIS(4-AMINOPENT-3-EN-2-ONE) AND OF ITS INTERACTION WITH METAL ATOMS

 

JOSÉ R. B. GOMES*, MARIA D. M. C. RIBEIRO DA SILVA, MANUEL A. V. RIBEIRO DA SILVA

 

Centro de Investigação em Química, Departamento de Química da Faculdade de Ciências do Porto, R. Campo Alegre, 687, P-4169-007 Porto, Portugal

e-mail address: [email protected]

 

Condensation products of acetylacetone and related b-diketones with amines and diamines have induced a strong research due to their increased ability to coordinate metal ions. These metal complexes with uncyclic tetradentate N₂O₂-ligands are applied, among others, as second order non-linear optical materials, spin-crossovers, catalysts of asymmetric oxidations, flame retardants and photostabilizers. Thus, these important applications are accompanied with investigation of their molecular and electronic structures as well as with their reactivity. Thermodynamic parameters such as, metal-ligand bond energies, enthalpies of formation, etc., for this kind of compounds are still unknown.

The present communication is devoted to the study of the thermodynamic properties of transition metal complexes with N,N’-ethylenebis(4-aminopent-3-en-2-one), H₂ACACEN. One important property that is calculated is the N-H bond dissociation enthalpy, BDE, in the ligand since this parameter is required to obtain the strength of the metal-ligand bonds, c.f. reaction (1).

 

M + H₂ACACEN → MACACEN + 2 H                    (1)

 

Reaction (1) is also used to estimate the enthalpy of formation in the gas-phase of the metal complex based on the calculated enthalpy of reaction (1) and the experimental enthalpies of formation of all species except MACACEN. The enthalpy of reaction (1) and the N-H BDEs were computed by accurate density functional theory calculations at the B3LYP/6-311+G(2d,2p)//B3LYP/6-31G(d) level of theory. This approach was successfully used in recent studies^1,2. It consists of enthalpies computed from the energies coming from full-optimization at the B3LYP/6-311+G(2d,2p) level and incorporating corrections for T = 298.15 K computed by the B3LYP/6-31G(d) approach.

 

The authors are grateful to Fundação para a Ciência e a Tecnologia, FCT, Lisbon, for financial support. JRBG thanks also FCT, for his post-doctoral (SFRH/BPD/11582/2002) research grant.

 

REFERENCES

1.     Gomes J. R. B., Ribeiro da Silva M. D. M. C., Ribeiro da Silva M. A. V.: J. Phys. Chem. A 108, 2119 (2004).

2.     Ribeiro da Silva M. D. M. C., Gomes J. R. B., Gonçalves, J. M., Sousa E. A., Pandey S., Acree Jr. W. E.: J. Org. Chem. 69, 2785 (2004).