To understand the influence of solvent in a PEnT mechanism, the popular E/Z isomerisation of alkenes was chosen as a representative reaction. Four of the aforementioned 4CzIPN were investigated in the E/Z isomerisation of stilbene across all four solvents (Figure ). The E and Z isomers of stilbene have ET of 2.2 and 2.5 eV, respectively, determined from the absorption spectra in ethyl iodide. Therefore, to maximise the yield of the Z-isomer, simplistically the PC should have an ET within the range of 2.2-2.5 eV. This allows the PC to chemoselectively transfer energy to the E alkene, converting it to the Z isomer without also sensitizing the Z isomer back to the E isomer.