The effects of 1-and 3-positions substitutions on the photophysical properties of perylene and its application in thiol fluorescent probes

A series of perylene derivatives bearing electron-donating group (amino) and electron-withdrawing group (nitro, maleimide) at the 1- and 3-position have been synthesized. Interestingly, 3-monosubstituted perylenes shown different photophysical properties compared with 1-monosubstituted perylenes. 3-nitroperylene ( 3-NO ) attained 80.62% photoluminescence quantum yield ( Φ PL ${\text{Φ}}_{\text{PL}}$ ) in toluene which is higher than 3-aminoperylene ( 3-NH , Φ PL ${\text{Φ}}_{\text{PL}}$  = 71.70%) and 1-aminoperylene (1-NH, Φ PL ${\text{Φ}}_{\text{PL}}$  = 48.04%), but for 1-nitroperylene ( 1-NO ), no fluorescence in any solvent were observed. The calculated ground-state geometries of 3-monosubstituted perylenes actually correspond to nearly planar structures, but the molecules substituted at the 1-position all have a twisted structure. Among them, 3-NO had a great π-conjugated system, resulting in the allowed ππ∗ fluorescence. In contrast, the twisting structure of 1-NO enhanced nonradiative decay pathways, coupled with the electron-withdrawing effect of the nitro group, which can explain the non-luminescence of 1-NO . Furthermore, the moleculars with maleimide group were used as “off-on” fluorescent probes and successfully used for imaging biothiols in living H1299 lung cancer cells. The fluorescence of probe 2 (substitutes at 3-position of perylene) afforded a 188-fold intensity increase after reaction with thiol which is much higher than (65-fold) probe 1 (substitutes at 1-position) because of the better π-conjugated structure. We envision that the investigation on the effects of substitute at 1-and 3-positions of perylene may be helpful for a rational design and application of highly fluorescent molecule base on perylene.