Previous sections highlight the importance of working in a transparent region to optimise for photon flux in the reaction medium. Running reactions as a suspension, though manageable in terms of hardware, significantly reduces light penetration and makes it difficult to quantify light scattering, thus increasing the risk of irreproducibility. For a reductive deiodination reaction, Nguyen et al. reported 750% scaling of the reaction whilst simultaneously decreasing fac-Ir(ppy)3 catalyst loading by 2,000% and HE equivalents from 2.0 to 1.1 equivalents without a significant loss in reaction efficiency. Whilst attributed to serendipity, this is likely due to the presence of fac-Ir(ppy)3 catalyst and HE in solid forms in the reaction. On the smaller scale, the catalyst concentration in the reaction corresponded to 2.5 mM whilst it was only 0.38 mmol/L on the larger scale. Considering the measured solubility of 0.41 mmol/L for Ir(ppy)3 in acetonitrile, the authors conducted the larger scale reaction under fully transparent conditions, promoting higher light penetration. Therefore, in our study, experimental solubility results reported by Jesperson et al. were used to decide the upper limit for fac-Ir(ppy)3 (Table , ESI) in case algorithm suggested values were above the solubility limit. values for HE were predicted using COSMOtherm for the 107 solvents remaining from the original list. The software requires a reference list for solvents based on experimental measurements. Measuring solubility can be done via a solvent drying method, which works well with volatile solvents. For this reason, measuring concentrations with benchtop 1 H NMR with mesitylene as an internal standard was also used for solubility measurements. Both approaches led to similar results, confirming the validity of either approach for the generation of solubility data (Table , ESI). COSMOtherm solubility prediction accuracies were compared using 9, 18 and 35 references. Whilst prediction accuracy improved with more experimentally measured references, predicted values using COSMOtherm were used as a qualitative guide to select the solvents to be verified experimentally. Using 40 mmol/L reaction concentration as a criterion and based on the measured solubility values, 20 solvents were selected to be used in the final solvent candidates list for optimisation. For certain solvents, solubility limit was used as the upper bound in running the reaction to achieve a clear solution.