Synthesis and macrocyclization-induced emission enhancement of benzothiadiazole-based macrocycle

Abstract

We presented an effective and universal strategy for the improvement of luminophore’s solid-state emission, i.e., macrocyclization-induced emission enhancement (MIEE), by linking luminophores through C(sp3) bridges to give a macrocycle. Benzothiadiazole-based macrocycle (BT-LC) has been synthesized by a one-step condensation of the monomer 4,7-bis(2,4-dimethoxyphenyl)−2,1,3-benzothiadiazole (BT-M) with paraformaldehyde, catalyzed by Lewis acid. In comparison with the monomer, macrocycle BT-LC produces much more intense fluorescence in the solid state (ΦPL = 99%) and exhibits better device performance in the application of OLEDs. Single-crystal analysis and theoretical simulations reveal that the monomer can return to the ground state through a minimum energy crossing point (MECPS1/S0), resulting in the decrease of fluorescence efficiency. For the macrocycle, its inherent structural rigidity prohibits this non-radiative relaxation process and promotes the radiative relaxation, therefore emitting intense fluorescence. More significantly, MIEE strategy has good universality that several macrocycles with different luminophores also display emission improvement.

Intramolecular Through-Space Interactions Induced Emission of Pillar[4]arene[1]dicyanobenzene

“…AIE luminogens (AIEgens) that are brightly emissive in the aggregated state, known as the opposite of aggregation-caused quenching effect, generally possess adequate conformational freedom that can dissipate excited state energy in a nonradiative decay manner . Ideally, the RIM mechanism plays a significant role in triggering AIE. − Inspired by the unique AIE-active behaviors of pillararenes, , we investigated the fluorescence properties of P5-2CN in the THF/water mixture by recording their PL spectra with different water fractions ( f w ). The TSCT band at 520 nm remained nearly unchanged when the f w increased from 0 to 50%.…”

Synthesis of a luminescent macrocycle and its crystalline structure-adaptive transformation

“…This is attributed to the spatial separation and the suppression of non-radiation relaxation caused by the macrocyclic topological structure. 11 The fluorescence quantum yields in solution were also tested. In chloroform, the macrocycle ( Φ PL = 12.6%) exhibits higher quantum yields than the monomer ( Φ PL = 7.1%), which is consistent with solid-state luminescence.…”

Macrocyclization-induced phosphorescence enhancement of pyridinium-based macrocycles

“…Herein, we designed and synthesized pyridine/pyridinium-based macrocycles PC and PC 2+ , using our synthetic method for functional biphen[ n ]arenes. 49,50 All these macrocycles exhibited prolonged phosphorescence lifetime and improved quantum efficiencies in comparison with their monomers, thus exhibiting macrocyclization-induced phosphorescence enhancement (MIPE). Single crystal X-ray diffraction analysis and photophysical characterization revealed that this enormous enhancement is because of the restriction of the macrocyclic skeleton for the phosphorescent units which efficiently suppressed the radiative decay of the singlet state and triplet state, and nonradiative decay of the triplet state.…”