The photoisomerization was carried out on a 1.0 cm path length quartz cell placed on a foursided cuvette holder (Cuvette Holder with Four Light Ports, CVH100 Thorlabs). Unless otherwise specified, the concentration of the samples was 40 μM. The kinetics of the photoisomerization process were measured by following the absorption spectrum during irradiation by selected LEDs, placed perpendicular to the absorbance measurement. To reach the PSS of the E→Z isomerization, the E-stereoisomer was illuminated within the ππ* band using an M375L4.1540 mW LED (LED Power Output 1540 mW, 2% power used) with a central wavelength of 375 nm and a bandwidth (FWHM) of 9 nm. For the reverse transformation, Z→E isomerization, the compound was excited within the nπ* band using an M300L4.32 mW LED (LED Power Output: 47 mW, full power used) with a central wavelength of 300 nm and a bandwidth (FWHM) of 20 nm. The thermal return process between Z and E isomers was analyzed by measuring the changes of the maximum absorbance wavelength at 25 and 40 °C, respectively.