Excited-State Intramolecular Proton Transfer Parent Core Engineering for Six-Level System Lasing Toward 900 nm.

Organic molecules which can undergo excited-state intramolecular proton transfer (ESIPT) process have been considered as ideal gain materials for near-infrared organic lasers owing to their effective four-level systems. However, extending lasing wavelength beyond 800 nm with present ESIPT-active gain materials is still in challenge. Herein, we established a molecular design strategy that operates via extending the π-conjugated system of the ESIPT parent core to enhance the cascaded double ESIPT process and thus to achieve the red-shifted six-level system lasing.

Thermally Activated Delayed Fluorescent Gain Materials: Harvesting Triplet Excitons for Lasing.

Thermally activated delayed fluorescent (TADF) materials have attracted increasing attention because of their ability to harvest triplet excitons via a reverse intersystem crossing process. TADF gain materials that can recycle triplet excitons for stimulated emission are considered for solving the triplet accumulation problem in electrically pumped organic solid-state lasers (OSSLs). In this mini review, recent progress in TADF gain materials is summarized, and design principles are extracted from existing reports.

Target-Directed Design, Synthesis, Antiviral Activity, and SARs of 9-Substituted Phenanthroindolizidine Alkaloid Derivatives.

On the basis of our previous studies on the antiviral mechanism against tobacco mosaic virus (TMV) and structure-activity relationship of phenanthroindolizidine alkaloids, a series of 9-substituted tylophorine derivatives targeting TMV RNA were designed, synthesized, and assessed for their anti-TMV activities. The bioassay results indicated that most of these compounds showed good anti-TMV activities, and some of them displayed higher activity than that of commercial ribavirin. Especially, the anti-TMV activities of compound , , and are 2-3 times higher than that of commercial ribavirin, according to EC values.

Cascaded Excited-State Intramolecular Proton Transfer Towards Near-Infrared Organic Lasers Beyond 850 nm.

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.

Triply Loaded Nitroxide Brush-Arm Star Polymers Enable Metal-Free Millimetric Tumor Detection by Magnetic Resonance Imaging.

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 approach to nitroxide-based brush-arm star polymer (BASP) organic radical CAs (ORCAs) with high nitroxide loadings.

Photoredox-Mediated Direct Cross-Dehydrogenative Coupling of Heteroarenes and Amines.

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.

C(sp)-H Azidation Reaction: A Protocol for Preparation of Aminals.

We report a protocol for the synthesis of N, N- and N, O-aminals via direct azidation of sp C-H bonds of substrates with an α-nitrogen or α-oxygen atom. A broad range of tetrahydroisoquinolines, tetrahydro-β-carbolines, and cyclic benzyl ethers gave high yields under mild conditions. The protocol could be carried out on a gram scale without a decrease in the yield, and the aminal products could be readily transformed into complex aminals.

Merging Photoredox with Brønsted Acid Catalysis: The Cross-Dehydrogenative C-O Coupling for sp C-H Bond Peroxidation.

A photoredox and Brønsted acid synergistically catalyzed cross-dehydrogenative C-O coupling reaction is developed in which isochroman peroxyacetals are formed through sp C-H bond peroxidation. The reported method is characterized by its extremely mild reaction conditions, excellent yields, and broad substrate scope. An oxocarbenium ion p-chlorobenzenesulfonate was speculated to be the reactive intermediate.

Direct and Oxidant-Free Electron-Deficient Arylation of N-Acyl-Protected Tetrahydroisoquinolines.

A direct α-C-H electron-deficient arylation reaction of N-acyl protected tetrahydroisoquinolines is developed via visible light photoredox catalysis. The reaction was performed under mild conditions without any extra oxidant and could also proceed smoothly when sunlight was used as the light source. The protecting group on the tetrahydroisoquinolines could be removed easily.

Direct C-H Allylation of N-Acyl/Sulfonyl Tetrahydroisoquinolines and Analogues.

A highly efficient direct C-H allylation reaction at the α position of N-acyl/sulfonyl tetrahydroisoquinolines under mild conditions was developed. The reaction was also suitable for allylation of other protected nitrogen-containing heterocycles. Several interesting transformations of the products into valuable synthetic intermediates are featured with the successful total synthesis of (±)-crispine A.