2021 Fiscal Year Research-status Report
Extended Pyrazinacenes as a New Class of Near-Infrared Emissive Materials for Potential Bioimaging Applications
| Project/Area Number |
21K05044
|
|---|
| Research Institution | Shibaura Institute of Technology |
|---|
Principal Investigator |
RICHARDS GARY 芝浦工業大学, 工学部, 准教授 (00708620)
|
|---|
| Co-Investigator(Kenkyū-buntansha) |
堀 顕子 芝浦工業大学, 工学部, 教授 (90433713)
|
|---|
| Project Period (FY) |
2021-04-01 – 2024-03-31
|
| Keywords | Pyrazinacenes / Azaacenes / Near Infrared Emitters / Fluorescence / REDOX / Near infrared absorption |
|---|
| Outline of Annual Research Achievements |
A family of new pyrazinacenes has been synthesised. These include a dodecaazahexacene which shows deep-red fluorescence with high photoluminescence quantum yield and was published in our account article (Acc. Chem. Res). We have also prepared redox-active octaazatetracenes and decaazapentacenes appended with electron-donor triphenylamine groups that show a dramatic shift in absorption from the visible to near-infrared (NIR) region upon simple oxidation of the central dihydropyrazine ring. These results have been presented at national and international conferences. We have also prepared a water-soluble tetradecaazaheptacene that shows highly efficient NIR photoluminescence. In aqueous solution, fluorescence is quenched due to chromophore aggregation, but addition of the surfactant cetyltrimethylammonium bromide (CTAB) results in de-aggregation and a consequent fluorescence switch-on effect. Our initial results indicate that NIR fluorescence (peaking at 730 nm) in aqueous solution with high photoluminescence quantum yield (PLQY > 20%) can be achieved and we expect this to improve with optimization. Work is now underway to assess the performance of this material as a new type of NIR fluorescent probe for bioimaging applications.
|
| Current Status of Research Progress |
Current Status of Research Progress
1: Research has progressed more than it was originally planned.
Reason
In addition to preparing the water-soluble tetradecaazaheptacene outlined in the research proposal, we have also established that smaller molecules consisting of four or five fused pyrazines can also show NIR-active absorption behaviour when appended with electon-donor triphenylamine groups. These compounds show a dramatic shift in absorption from the visible (abs max around 586 nm) to the NIR region (around 1050 nm) upon simple oxidation of the central dihydropyrazine ring. This unexpected result will no doubt be of interest in redox sensing and switching applications. Our newly-prepared water-soluble tetradecaazapentacene exhibits highly efficient NIR fluorescence (PLQY = 20%, 728 nm emission) once de-aggregated by addition of CTAB.
|
| Strategy for Future Research Activity |
For the REDOX active octaazatetracene and decaazapentacene, electrochemical experiments are underway to probe their REDOX behaviours. In collaboration with researchers at NIMS, we continue to investigate the water-soluble tetradecaazaheptacene, particularly with respect to potential bioimaging applications. Work is being done to establish cytotoxicity levels as well as appropriate conditions to maintain de-aggregation of the compound in aqueous conditions (CTAB is known to be cytotoxic). We continue with synthesis of new derivatives, as detailed in the research proposal, including the preparation of pyrazinacenes appended with both electron-donor and acceptor groups.
Write up and publication of available results is also underway.
|
| Causes of Carryover |
One international and one national conference were online due to COVID-19
|
