Theoretical investigations on N-salicylideneaniline derivatives : effects of mono- and di-N-substitutions on the phenylamino group

Details

Supervisors

Champagne, Benoit

Faculty

Ecole polytechnique de Louvain

Degree label

Master de spécialisation en nanotechnologie

Abstract

The reaction of condensation leading to the synthesis of N-salicylideneaniline derivatives is the target of this Master thesis and it has been investigated by using a broad range of quantum chemistry methods. N-salicylideneanilines are molecular switches, known for their photo- and thermochromisms. The objective of this work was to start from a well-studied compound, (E)-2-methoxy-6-(pyridine-3-yliminomethyl) phenol, and to consider isomers that differ by the number (1 or 2) and positions of the N atoms of the “pyridine” ring. First, the energies of the condensation reaction to get the enol forms have been evaluated at the reference CCSD level of approximation, showing that the process is energetically favorable. Lower-level approximations have been assessed so that, within density functional theory, the double hybrid B2PLYP exchange-correlation functional appears as a reliable method. Then comes the ωB97X-D, which has the advantage to be computationally much cheaper. A detailed analysis of the “energies” of reaction (ΔE0, ΔH0, and ΔG0) has shown that the electronic contributions are the driving forces to these quantities. Then, calculations performed at the MP2 level reveal that the most exothermic (ΔH0 < 0) and exergonic (ΔG0 < 0) condensations occur for the anils with a single N substitution. Then come the condensations with two nitrogen atoms, with at least one in position 3 (like in the reference compound). At the same level, it appears that for all N-salicylideneaniline derivatives except one the enol form is more stable (on the basis of ΔE0 values) than the keto one and that further studies should be devoted to explain this observation.