Abstract :
[en] To meet the challenge of the ever-increasing energy consumption producing greenhouse gases and other atmospheric pollutants, the development of solar energy solutions has been widely investigated over the past decades. Molecular Solar Thermal systems (MOST) are molecules that undergo light-induced isomerization into high-energy metastable isomers which can be used to store solar energy in closed and carbon neutral cycles [1]. Azobenzenes have emerged as promising MOST candidates, but key parameters need to be optimized through different strategies for their versatile synthesis. One of the most important parameters to improve is the half-life time of the metastable isomers, which is directly related to the activation barrier of thermal back-isomerization [1]. Kinetic studies of the thermal back-isomerization of MOST systems are usually carried out by UV-Visible measurements, but this technique has certain limitations such as the need for non-overlapping absorption bands. The main objective of this work is thus to develop a method for the rapid determination of these kinetic parameters, and in this regard, mass spectrometry offers a considerable potential. On the one hand, liquid chromatography coupled to mass spectrometry allows to determine the kinetic parameters in solution by monitoring the evolution of the photoisomer distribution over time at different temperatures [2]. On the other hand, ion mobility spectrometry can be used to measure the distribution of photoisomers resulting from collision-induced back-isomerization using a Waters Synapt G2-Si. To determine the activation energies in the case of collisional activation, we use a method recently proposed by Donor et al. to calibrate the Synapt G2-Si in terms of internal energy [3]. The calibration is performed using reference values obtained in gas phase by direct thermal activation in an original tandem ion mobility instrument at ULyon [4].
References
1. A. Lennartson, A. Roffey; Tetrahedron Lett., 56, 1457-1465 (2015)
2. B. Tassignon; Master thesis, UMons (2020)
3. M. Donor, A.Mroz; Chem. Sci., 10, 4097-4106 (2019)
4. A. Simon, F. Chirot; Rev. Sci. Instrum., 86, 094101 (2015)
