In this study, we synthesised new halochromic fluoranthene derivatives and found that although the same chromophore skeleton was used, changing the position of the auxochromes afforded contrasting halochromic properties under basic conditions. Notably, 9- Table . Photophysical properties of the hydroxy-dibenzofluoranthenes 2 and 3 in CH2Cl2. a a) Both absorption and emission spectra were recorded in solution at room temperature at c = 5.0 × 10 -5 M. b) Each hydroxy-dibenzofluoranthene (anionic form) was studied in the presence of DBU (for 2a-c: 1.0 eq.; 3a: 30 eq.; 3b: 100 eq.; 3c: 40 eq.) c) Quinine sulfate was used as reference dye (𝜆 ex = 366 nm, 𝛷 = 55%). 14