DNA-induced circularly polarized luminescence of helicene racemates

Supergelation via Weak Interactions: An Efficient Method for the Fabrication of Hydrophobic Circularly Polarized Luminescent Materials

The hydroxylated derivative of stearic acid, 12-hydroxy stearic acid (12-HSA), is derived from castor oil and possesses a unique chemical structure that renders it noteworthy in the field of cosmetics and medicine. Being derived from renewable sources, it aligns with the growing demand for sustainable and eco-friendly material. While the gelation properties of 12-HSA are known, its chiroptical properties remain unexplored. Herein, a host-guest approach is adopted for the induction of optical activity in achiral chromophores using 12-HSA as a chiral template. The induction of optical activity from the host gelator to the guest chromophores resulted in the generation of circularly polarized luminescence (CPL) from hybrid nanocomposites. This strategy was effective in generation of chiral luminescence in non-polar chromophores, a class of molecules unexplored in CPL. The use of red- and blue-emitting chromophores led to the fabrication of chiral light-emitting materials in the respective spectral range. The structural attributes of the gelator imparted hydrophobic character to the co-assembled nanostructures. The robustness of the nanocomposites helped derive self-standing chiral luminescent soft materials of desired sizes and shapes. The readily available raw materials and ease of operation make this an effective approach for the fabrication of CPL active materials for diverse applications.

Construction and Circularly Polarized Luminescence of Thiophene-Based Multiple Helicenes

Thiophene-based monohelicene (TS[7]H), triple helicenes (TT[7]H), and hexapole helicenes (TH[7]H) were synthesized via oxidative photocyclization and cascade Suzuki/intramolecular cyclization as the crucial steps. The enantiomers of TS[7]H, TT[7]H-2, and TH[7]H exhibited circularly polarized luminescence (CPL), and the luminescence dissymmetry factors (glum) gradually increased from -5.1 × 10-4 to -2.0 × 10-3 with an increase in multiplicity from TS[7]H to TH[7]H. In addition, TS[7]H, TT[7]H, and TH[7]H displayed a second-level long afterglow at 77 K.

Boron- and Oxygen-Doped π-Extended Helical Nanographene with Circularly Polarised Thermally Activated Delayed Fluorescence

Helical nanographenes have garnered substantial attention owing to their finely adjustable optical and semiconducting properties. The strategic integration of both helicity and heteroatoms into the nanographene structure, facilitated by a boron-oxygen-based multiple resonance (MR) thermally activated delayed fluorescence (TADF), elevates its photophysical and chiroptical features. This signifies the introduction of an elegant category of helical nanographene that combines optical (TADF) and chiroptical (CPL) features. In this direction, we report the synthesis, optical, and chiroptical properties of boron, oxygen-doped Π-extended helical nanographene. The π-extension induces distortion in the DOBNA-incorporated nanographene, endowing a pair of helicenes, (P)-B2NG, and (M)-B2NG exhibiting circularly polarized luminescence with glum of -2.3×10-3 and +2.5×10-3, respectively. B2NG exhibited MR-TADF with a lifetime below 5 μs, and a reasonably high fluorescence quantum yield (50 %). Our molecular design enriches the optical and chiroptical properties of nanographenes and opens up new opportunities in multidisciplinary fields.