Highlighting of Properties of Thermochromy and Photochromy in Salicylideneamines

This research aimed to understand the effects induced by PP, PQ and QQ complexes on the geometry, thermodynamic stability and vibration frequencies of salicylideneamines. It planned to determine the interactions within them. It envisaged identifying the impact of the solvent during the creation of these dimers by analyzing variations in electronic energies and associated dipole moments. To do this, the study utilized exploited DFT combined with sets of basis functions such as those of Pople and the HF method to optimize the geometries of P or Q monomers and PP, PQ or QQ dimers. The results obtained were employed for the calculations of NBO and QTAIM in the case of isopropyl amine N-(2,3-dihydroxybenzylidene) structures. For the last objective, SPSS Statistics v27 software was used to compare variations in energies or electronic moments during transitions from monomers to dimers. This methodological approach made it possible to prove that the electronic transitions σ → σ* and π → π* improve the equilibrium of the P and Q monomers. Their “dimeric” associations are steadied by those of the Lp → σ* and Lp → π* type with the heteroatoms of the PP, PQ and QQ complexes. These phenomena are obtained thanks to the hydrogen bonds established between the latter and the hydrogen favourable to these interactions. The observed “thermochromic” and photochromic trends can be explained by the stability of the PQ. The presence of the thermodynamically disadvantaged Q tautomer is also justified. The nature and polarity of the solvents don’t significantly influence these latter results.