Periodic Reporting for period 1 - ARCHIMEDES (Approaching 20% emission efficiency in the NIR-II region with radical chromophores)
Período documentado: 2023-09-01 hasta 2026-02-28
The applications of light-based technologies in modern society cannot be underestimated. Some well-known examples of these include organic light-emitting diodes, fluorescent sensors, organic photovoltaics and fluorescence imaging. Emissive radicals have recently appeared as promising and entirely new building blocks for these technologies. This breakthrough is due to the fact that their electron spins at the lowest excited state and ground state are both doublets and the transition from the lowest excited state to the ground state is not hindered by being a spin-forbidden reaction which allows for higher operational efficiencies. Additionally, compared with both classical fluorescence microscopy and infrared imaging methods (750-900 nm), imaging in the second near-infrared window (NIR-II, 1000-1700 nm) allows for both deeper tissue penetration and a higher signal-to-noise ratio. The applicability of NIR-II emitters can be bolstered through combination with circularly polarized luminescence (CPL, the differential emission of left and right polarized light). The overarching goal of this project is to uncover a strategy to create radicals which at the same time: (a) strongly emit light in the NIR-II region; (b) are stable under ambient conditions; (c) strongly absorb light; (d) display large circularly polarized luminescence. The primary objective of ARCHIMEDES is to deliver breakthrough organic materials possessing large fluorescence quantum yields and stable radical structures in the integrated fields of molecular design, chromophore synthesis and fluorescence imaging of living cells. The realization of ARCHIMEDES will be based on both expanding the chemical space of stable, emissive C-centered radicals and on heretofore nonexisting emissive nitroxide radicals. The synergistic effects of increased brightness of NIR-II dyes and the higher sensitivity and resolution offered by CPL fluorophores will provide quality fluorescence imaging on a previously unthinkable level.
Our work was focused on several directions including: (1) the development of new type of radicals; (2) discovery of dyes emitting in near-infrared; (3) development of strongly emissive helicenes; (4) expansion of the chemical space of triarylmethyl radicals. Consequently, many projects have started in parallel. In one of them double helicenes possessing two boron-nitrogen bonds were designed and synthesized. The synthetic methodology is easy and equally importantly it is compatible with diverse substrates. Final double helicene has strong fluorescence in blue-green region and it emits circularly polarized light.
The heretofore unknown polymethine dyes were designed and synthesized by combining electron-rich indolizine with merocyanine scaffold. The synthetic protocol is short and easy and it potentially can be adopted to various needs. Both lipophilic and water-soluble dyes can be prepared using this methodology. New dyes emit blue and green light and optical brightness is around 50,000. We found that some of these dyes display context-dependent localization to mitochondria and RNA-rich nucleoli of the living cells, which is rare and interesting for molecular biologists.
Electrochemical method for transformation of substrates into emissive radical was developed. This new strategy affords cleaner radicals which at the same time are easier to purify. This combination of advantages has a potential to deliver larger amounts of emissive radicals if needed. At the same time due to the regulated voltage which can be applied it can allow the preparation of radicals which do not exist yet.
The most electron-rich heterocycles were bridged with triarylmethyl radical scaffold in an attempt to bathochromically shift the emission. Synthesis was successful and new methodologies were developed. Absorption was shifted to 800 nm but emission was achieved only in a few cases.
The heretofore unknown polymethine dyes were designed and synthesized by combining electron-rich indolizine with merocyanine scaffold. The synthetic protocol is short and easy and it potentially can be adopted to various needs. Both lipophilic and water-soluble dyes can be prepared using this methodology. New dyes emit blue and green light and optical brightness is around 50,000. We found that some of these dyes display context-dependent localization to mitochondria and RNA-rich nucleoli of the living cells, which is rare and interesting for molecular biologists.
Electrochemical method for transformation of substrates into emissive radical was developed. This new strategy affords cleaner radicals which at the same time are easier to purify. This combination of advantages has a potential to deliver larger amounts of emissive radicals if needed. At the same time due to the regulated voltage which can be applied it can allow the preparation of radicals which do not exist yet.
The most electron-rich heterocycles were bridged with triarylmethyl radical scaffold in an attempt to bathochromically shift the emission. Synthesis was successful and new methodologies were developed. Absorption was shifted to 800 nm but emission was achieved only in a few cases.
1. Development of the novel electrochemical method leading to emissive radicals. The use of chemical oxidants generates side-products and results in low content of actual radical species in the products. In contrast the new electrochemical methodology generates cleaner reaction mixtures and products with higher radical content. It can also enable the access to heretofore unachievable radicals via modulation of an applied voltage. Further research is however necessary to prove the large applicability of this method and the scale-up.
2. Discovery of entirely new types of strongly emissive dyes from merocyanine and cyanine families. Large brightness combined with easy preparation and intriguing bioimaging makes these dyes promising in various future applications. In particular since methodology relies on tandem reaction of two easily available building blocks one can imagine almost endless modification of their structure which should lead to dyes possessing bathochromically shifted emission, and better solubility. Crucially these dyes possess reactive sites which potentially can be used for further functionalization. The future uptake of these dyes requires further development focused on reaching the above mentioned goals.
2. Discovery of entirely new types of strongly emissive dyes from merocyanine and cyanine families. Large brightness combined with easy preparation and intriguing bioimaging makes these dyes promising in various future applications. In particular since methodology relies on tandem reaction of two easily available building blocks one can imagine almost endless modification of their structure which should lead to dyes possessing bathochromically shifted emission, and better solubility. Crucially these dyes possess reactive sites which potentially can be used for further functionalization. The future uptake of these dyes requires further development focused on reaching the above mentioned goals.