May 03, 2022
16:00
Louvain-La-Neuve
Auditoire LAVO51 Place L. Pasteur
Fine-tuning photochromic properties of N-Salicylideneaniline derivatives using cocrystal engineering
Pour l’obtention du grade de Docteur en sciences
N-Salicylideneaniline (also called anil) is a compound which exhibits photochromism (reversible color change induced by light) in the solid-state. Such a feature is quite rare and requires in-deep studies to fully understand it, especially because it can be quite useful in many industrial applications such as secured inks (for banknotes for instance), screens or even optical data storage.
Within this thesis, N-Salicylideneaniline and many of its derivatives (called the “anils”) were studied in the scope of crystal engineering in order to establish a structure-property relationship and to improve its properties.
More specifically, cocrystals were researched and studied using small organic molecules (such as carboxylic acids, amides, amines, benzene halides) as coformers. This resulted in the identification of about 100 cocrystals through the use of X-ray powder diffraction (XRPD), single crystal X-ray diffraction (SC-XRD), diffuse reflectance spectroscopy (DRS), thermal analysis such as thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) along with a few other methods such as Raman spectroscopy. The amount of collected data allowed to show a correlation between the number of intermolecular interactions involving the “moving moiety” of the anils and the presence of photochromism.
We also present here a new approach of the Diffuse Reflectance Spectroscopy data treatment, which allows a better classification of the photochromic properties and also allowed the discovery of “weakly” photochromic compounds. These results encourage a revision of the old-empirical “dihedral angle rule” especially because a link between the intensity of photochromism and the torsion angle has been observed in this work.
In the last part, we focused on cocrystals containing 2 different anils (instead of one anil and one coformer) and this allowed to observe the existence of a complex multi-phases binary diagram in the case of N-Salicylideneaniline/ N-Salicylidene-4-fluoroaniline solid-solution. Also, intermediate photochromic intensity values and kinetical parameters could be observed for the first time compared to parent anils alone, achieving a step towards control and fine-tuning of photochromic properties of anils.
Jury members :
- Prof. Tom Leyssens (UCLouvain), supervisor
- Prof. Sophie Demoustier (UCLouvain), chairperson
- Prof. Yaroslav Filinchuk (UCLouvain), secretary
- Prof. Johan Wouters (UNamur)
- Prof. Benoit Champagne (UNamur)
- Dr. Koen Robeyns (UCLouvain)
Pay attention :
The public defense of Gabriel Mercier scheduled for Tuesday 03 May at 4:00 p.m will also take place in the form of a video conference