Azetidine donors are known to improve the quantum yield of rhodamines compared to dimethylamine groups, 9 e.g., compare 38 (F = 0.47; Table ) to 4 (F = 0.34; Table ). Simodification was well tolerated within this scaffold as well, as we found that the diphenylsilyl dye 40 and the chloropropylsilyl dye 41 are brighter than the dimethylsilyl dye 38 (Table ).