Nitroxides occupy a privileged position among plausible metal-free magnetic resonance imaging (MRI) contrast agents (CAs) due to their inherently low-toxicity profiles; nevertheless, their translational development has been hindered by a lack of appropriate contrast sensitivity. Nanostructured materials with high nitroxide densities, where each individual nitroxide within a macromolecular construct contributes to the image contrast, could address this limitation, but the synthesis of such materials remains challenging. Here, we report a modular and scalable synthetic
Near-infrared (NIR) organic solid-state lasers play an essential role in applications ranging from laser communication to infrared night vision, but progress in this area is restricted by the lack of effective excited-state gain processes. Herein, we originally proposed and demonstrated the cascaded occurrence of excited-state intramolecular proton transfer for constructing the completely new energy-level systems.Cascading by the first ultrafast proton transfer of < 430 fs and the subsequent irreversible second proton transfer of ca. 1.6 ps,the stepwise proton transfer process favors the true six-level photophysical cycle,w hichs upports efficient population inversion and thus NIR single-mode lasing at 854 nm. This work realizes longest wavelength beyond 850 nm of organic single-crystal lasing to date and originally exploits the cascaded excited-state molecular proton transfer energy-level systems for organic solid-state lasers.
Excited state intramolecular proton transfer (ESIPT) molecules are considered to be natural born laser materials because of their intrinsic four-level system. Organic lasers based on ESIPT materials, especially recently developed micro/nanolasers, have been drawing great attention in the past few decades due to their unique photophysical properties, such as ultralow threshold and high-quality value, as well as near-infrared (NIR) and wavelength tunable emission. These photophysical properties facilitate their widespread applications in lasing communication, ultrasensitive sensing, biological imaging, data storage and on-chip optical circuits. In this Review, first, the ESIPT process is introduced concisely. Second, recent advances of ESIPT-based organic lasers in solution, film and crystal states are reviewed. Finally, the current challenges and future development of ESIPT-based organic lasers are presented.
A photoredox-mediated direct cross-dehydrogenative coupling reaction to accomplish α-aminoalkylation of N-heteroarenes is reported. This mild reaction has a broad substrate scope, offers the first general method for synthesis of aminoalkylated N-heteroarenes without the need for substrate prefunctionalization, and is scalable to the gram level. Furthermore, the reaction was found to be applicable to other hydrogen donors besides amines (i.e., ethers, an aldehyde, a formamide, p-xylene, and alkanes), thus enabling the preparation of N-heteroarenes bearing various types of substituents.
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