(1:1) solution in order to determine the isomer composition in the corresponding photostationary states (pss) by UV/Vis spectroscopy. Although the rhodanine 1 absorptions largely exceed the PAT 2 absorption in the 1:1 mixture, noticeable photoisomerization of PAT 2 took place when irradiating with wavelengths of 350 nm -490 nm (for full analysis of different irradiation conditions and resulting isomer mixtures see the Supporting Information).