A recent study has designed and synthesized four TSCT-based anti-Kasha emissive AIEgenic rotors, revealing unique emission properties in the condensed state.
Bullet Point Summary:
- Four anti-Kasha emissive AIEgenic rotors designed and synthesized
- Dual fluorescence emission and ambient stable triplet emission observed
- Unique emission mechanism of WLE in crystals and unusual AIE property in water
- Intrinsic mechanoresponsive behavior by varying the alkyl chain length
The study, conducted by Barman and Krishnan Iyer, aimed to design and synthesize anti-Kasha emissive AIEgenic rotors and study their emission properties in the condensed state. The researchers designed four rotors, denoted as BT2OxCz (x = 3, 4, 5, and 6), which contained 2,2′-(5-(3-(9H-carbazol-9-yl)alkoxy)-1,3 phenylene)bis (benzothiazole) as an acceptor and carbazole as a donor connected by a series of odd/even alkyl chains.
The results of the study showed that the integrated molecules exhibited dual fluorescence emission in the aggregated state, including locally excited state (LE) and TADF (transitions between 1LE and 3LE), and RTP (3LE*) was also seen together in a single molecular structure. Furthermore, the study revealed ambient stable triplet emission through the use of single-crystal X-ray diffraction (SC-XRD) analysis, which showed two distinct packing motifs, sterically strained “J-aggregation” and geometrically relaxed “H-aggregations.”
Deep quantum mechanical computations by TD-DFT and ESD and numerous experimental studies were performed to understand the underlying mechanistic insights of the involvement of higher-lying excited states and revealed the origin of AIE emission in the condensed state as SOKR. The study also demonstrated the unique emission mechanism of WLE in crystals and unusual AIE property in water via SOKR, including their intrinsic mechanoresponsive behavior by varying the alkyl chain length.
In conclusion, the study designed and synthesized four anti-Kasha emissive AIEgenic rotors, revealing unique emission properties in the condensed state, offering a new concept for further research in this field.
Outcomes:
- The study designed and synthesized four anti-Kasha emissive AIEgenic rotors, denoted as BT2OxCz (x = 3, 4, 5, and 6), containing 2,2′-(5-(3-(9H-carbazol-9-yl)alkoxy)-1,3 phenylene)bis (benzothiazole) as an acceptor and carbazole as a donor connected by alkyl chains.
- The molecules exhibited dual fluorescence emission in the aggregated state and revealed ambient stable triplet emission.
- The study demonstrated the unique emission mechanism of WLE in crystals and unusual AIE properties in water via SOKR, including their intrinsic mechanoresponsive behavior by varying the alkyl chain length.
Aggregation-Induced Delayed Fluorescence and Phosphorescence from Hot Excitons via Suppression of Kasha’s Rule in a Stimuli-Active Molecular Rotor
Barman; Krishnan Iyer
Full-text link: https://doi.org/10.1021/acs.jpcc.2c08479
What this paper is about
Yet, as an exception to this rule, suppression of Kasha’s rule could be accomplished by retardation of ultrafast vibrational relaxation and internal conversion from higher excited states to S 1 when the energy gap between S n and S 1 is quite large.
Kasha emissive AIEgenic rotors have been designed and synthesized, denoted as BT2OxCz, which contains 2,2-bis as an acceptor and carbazole as a donor connected via a series of odd/ even alkyl chains.
The integrated molecules exhibited dual fluorescence emissions in the aggregated state, such as the locally excited state and TADF, while RTP was also seen together in a single molecular structure.
What you can learn
- Thus, the phosphorescence spectrum exhibited as aggregation-induced delayed fluorescence at 430 nm and an additional aggregation-induced phosphorescence peak at >600 nm in 99% f w with the av = 114.61, 91.61, 7.86, and 114.98 s for higher chains containing B2O6Cz, which could be due to high-order intermolecular noncovalent interactions rather than other congeners, triggering intense triplet utilization at the B3LYP/6-31G level.
- DFT and TD-DFT calculations were carried out to compute relaxed potential energy curves as a function of DA for the ground and a few singlet excited states of BT2O3Cz.
- Prior to ESD studies, static TD-DFT calculations were also performed, and the obtained results were found to be consistent with the results of vertical and adiabatic transitions at different spin multiplicities calculated using the Gaussian 16 software.
- However, an exothermic crystalline phase transition was observed at 107C for BT2O3Cz, and this was not found after grinding, depicting the transformation of amorphous material under mechanical stress. These results indicate that intramolecular packing offers more rigid packing than intermolecular interactions, which could contribute to the emission in distinct ML and MC behaviors by restricting the nonradiative transitions.
- Precisely, deep quantum mechanical computations by TD-DFT and ESD and numerous experimental studies were performed to justify the underlying mechanistic insights of the involvement of higher-lying excited states and revealed the origin of AIE emission in the condensed state as SOKR.
- Through this work, a new concept revealing the unique emission mechanism of WLE in crystals and unusual AIE properties in water via SOKR, including their intrinsic mechanoresponsive behavior by varying the alkyl chain length, has been precisely demonstrated.
What is the paper about?
The paper describes the design and synthesis of anti-Kasha emissive AIEgenic rotors, denoted as BT2OxCz, which contain 2,2′-(5-(3-(9H-carbazol-9-yl)alkoxy)-1,3 phenylene)bis (benzothiazole) as an acceptor and carbazole as a donor connected via a series of odd/even alkyl chains. These rotors exhibit dual fluorescence emission in the aggregated state, such as the locally excited state and TADF, and also show aggregation-induced delayed fluorescence and phosphorescence.
What are the two distinct packing motifs revealed by the SC-XRD analysis?
The two distinct packing motifs are “sterically strained J-aggregation” and “geometrically relaxed H-aggregations”.
What is the mechanism of AIE emission in the condensed state as explained in the paper?
The mechanism of AIE emission in the condensed state is explained as “Suppression of Kasha’s Rule” (SOKR) in the paper.
What did the DFT and TD-DFT calculations reveal about the rotors?
The DFT and TD-DFT calculations revealed the relaxed potential energy curves as a function of DA for the ground and singlet excited states of BT2O3Cz. The calculations also showed consistent results with the Gaussian 16 software for vertical and adiabatic transitions at different spin multiplicities.
What is the concept demonstrated in this work?
The concept demonstrated in this work is the unique emission mechanism of WLE in crystals and unusual AIE properties in water via SOKR, including their intrinsic mechanoresponsive behavior by varying the alkyl chain length.
