Analytical HPLC was used to quantify the E and Z isomer ratio after irradiation with light of 505 nm and 400 nm, respectively, to determine the photostationary state distribution (PSD). In the case of 7, the PSD after irradiating with  = 505 nm is a Z:E-ratio of 82:18. Irradiation with  = 400 nm leads to a Z:E-ratio of 29:71.