Rh-Catalyzed C–H Amidation of 2-Arylbenzo[d]thiazoles: An Approach to Single Organic Molecule White Light Emitters in the Solid State

Achieving White-Light Emission Using Organic Persistent Room Temperature Phosphorescence

Artificial lighting currently consumes approximately one-fifth of global electricity production. Organic emitters with white persistent RTP have potential for applications in energy-efficient lighting technologies, due to their ability to harvest both singlet and triplet excitons. Compared to heavy metal phosphorescent materials, they have significant advantages in cost, processability, and reduced toxicity. Phosphorescence efficiency can be improved by introducing heteroatoms, heavy atoms, or by incorporating luminophores within a rigid matrix. White-light emission can be achieved by tuning the ratio of fluorescence to phosphorescence intensity or by pure phosphorescence with a broad emission spectrum. This review summarizes recent advances in the design of purely organic RTP materials with white-light emission, describing single-component and host-guest systems. White phosphorescent carbon dots and representative applications of white-light RTP materials are also introduced.

Mn(III)-Mediated Radical Addition/Cyclization of Isocyanides with Aryl Boronic Acids/Diarylphosphine Oxides: Access to 11-Functionalized Dibenzodiazepines

A Mn(III)-mediated radical addition/cyclization reaction of isocyanides with aryl boronic acids/diarylphosphine oxides has been developed. A series of 11-arylated/-phosphorylated dibenzodiazepines were efficiently constructed in moderate to excellent yields under mild reaction conditions via imidoyl radical process. The present protocol offers novel access to functionalized seven-membered N-heterocycles.

Cobalt(II)-Catalyzed C-H and N-H Functionalization of 1-Arylpyrazolidinones with Dioxazolones as Bifunctional Synthons

Dioxazolone has been attractive as an important synthon for a direct C-H amidation through a nitrene intermediate or Curtius rearrangement to form the isocyanate. However, the combination of two reaction models of dioxazolone has not been reported. Herein, a cobalt-catalyzed C-H and N-H functionalization of 1-arylpyrazolidinones with dioxazolones was developed. The dioxazolones acted as an amidated and carboxamidated reagent. Three C-N bonds were formed in a "one-pot" manner, which promoted the requirement of synthetic diversity.

Ru(II)-Catalyzed Regioselective C-N Bond Formation on Benzothiazoles Employing Acyl Azide as an Amidating Agent

A Ru(II)-catalyzed regioselective direct ortho-amidation of 2-aryl benzo[d]thiazoles employing acyl azides as a nitrogen source has been accomplished. This approach utilizes the efficiency of benzothiazole as a directing group and the role of acyl azide as an effective amidating agent toward C-N bond formation, thereby evading the general Curtius rearrangement. The protocol highlights significant functional group tolerance, single-step, and external oxidant-free conditions, with the release of only innocuous molecular nitrogen as the byproduct. The reaction mechanism and the intermediates associated with this selective Ru-catalyzed reaction have been investigated using ESI-MS. The protocol also aided in the construction of ortho-amidated β-carbolines, unveiling another class of fluorescent molecules.

Structural Features of a Family of Coumarin-Enamine Fluorescent Chemodosimeters for Ion Pairs

A family of coumarin-enamine chemodosimeters is evaluated for their potential use as fluorescent molecular probes for multiple analytes [cadmium(II), cobalt(II), copper(II), iron(II), nickel(II), lead(II), and zinc(II)], as their chloride and acetate salts. These fluorophores displayed excellent optical spectroscopic modulation when exposed to ion pairs with different Lewis acidic and basic properties in dimethyl sulfoxide (DMSO). The chemodosimeters were designed to undergo excited-state intramolecular proton transfer (ESIPT), which leads to significant Stokes shifts (ca. 225 nm) and lower-energy fluorescence emission (ca. 575 nm). A more basic anion, e.g., acetate, inhibited the ESIPT mechanism by deprotonation of the enol, producing a binding pocket (N^O^- chelate) that can coordinate to an appropriate metal ion. Coordination of the metal ions enhances the fluorescent intensity via the chelation-enhanced fluorescence emission mechanism. Subjecting the spectroscopic data to linear discriminant analysis provided insights into the source of these systems' markedly different behavior toward ion pairs, despite the subtle structural differences in the organic framework. These compounds are examples of versatile, low-molecular-weight, dual-channel fluorescent sensors for ion-pair recognition. This study paves the way for using these probes as practical components of a sensing array for different metal ions and their respective anions.

Single-Molecule White-Light-Emitting Starburst Donor-Acceptor Triphenylamine Derivatives and Their Application as Ratiometric Luminescent Molecular Thermometers

White-light emission (WLE) from a single molecule is a highly desirable alternative to a complex mixture of complementary colour emitters, which suffers from poor stability and reproducibility for potential use in organic electronic devices and lighting applications. We report single-molecule WLE both in solution and thin films by judiciously controlled π-electron delocalisation between the triarylamine subchromophoric units. Triphenylamine (TPA) forms the central core, and the phenyl rings are substituted with the electron-deficient acceptor 3-ethylrhodanine (Rh) and electron-rich donors triphenylamine or carbazole. The enforced biphenyl configuration of the TPA core and the other donors renders the π-conjugation across the entire chromophore poor, thus the individual subchromophoric units retain their individual emission characteristics, which cover all three primary colour emissions, that is, red, green and blue (RGB). TPA-Rh units exhibit broad fluorescence in the green-red region originating from the local excited (LE) state and intramolecular charge transfer state (ICT), strongly influenced by the solvent, water, and temperature. Different fluorescence parameters, including spectral maxima, ratiometric changes in ICT emission at the expense of blue emission from terminal donor units, and changes in lifetime, have a linear relationship with temperature between 180-330 K, thus the molecules can function as a multiparameter luminescent molecular thermometer. A temperature coefficient of 0.19 K^-1 in ratiometric fluorescence changes along with a spectral shift of 0.3 nm K^-1 and their workability over the wide temperature makes these molecules promising materials for potential applications. At lower temperatures, individual subchromophoric properties subside because of the reduced dihedral angle of biphenyl, and fluorescence from the whole molecule becomes dominant.

Mechanically induced single-molecule white-light emission of excited-state intramolecular proton transfer (ESIPT) materials

Described herein is the first example of mechanically induced single-molecule white-light emission based on excited-state intramolecular proton transfer (ESIPT) materials. The mechanism of mechanochromism is clearly disclosed by powder and single crystal X-ray diffraction (XRD) data, infrared spectroscopy, and fluorescence up-conversion measurement, etc. 2-(2'-Hydroxyphenyl)oxazole (6b) with a herringbone packing motif exhibits a predominant keto-form emission, giving off yellowish-green fluorescence. Mechanical grinding transforms the herringbone packing motif into a brickwork packing motif, decreases the intermolecular distances, which results in an enhanced intermolecular charge-transfer interaction, and therefore changes the ESIPT dynamics, leading to an enhanced enol-form emission and white fluorescence. Herringbone-packing 6b is thermodynamically more stable than brickwork-packing 6b. Thus, the latter can convert to the former by solvent fuming or thermal annealing.

Recent Advances in the Synthesis and Applications of 2-Arylbenzothiazoles

This review firstly covers the applications of 2-arylbenzothiazoles as amyloid imaging agents, antitumor agents, and organic luminescent materials. Then we review the recent advances in the synthesis of 2-arylbenzothiazole derivatives. On the one hand, we introduce the approaches for construction of the 2-arylbenzothiazole core, including the following categories: (i) classic condensation of 2-aminothiophenols, (ii) direct arylation of benzothiazoles, (iii) intramolecular cyclization of thiobenzanilides, and (iv) tandem cyclization of anilines/ nitroarenes­ with elemental sulfur or sulfides. On the other hand, the transition-metal-catalyzed direct C–H functionalizations of 2-aryl­benzothiazoles are also involved in this review.

1 Introduction

2 Applications of 2-Arylbenzothiazoles

3 Construction of the 2-Arylbenzothiazole Core

4 Synthesis 2-Arylbenzothiazoles via Direct C–H Functionalization

5 Conclusion

Copper-catalyzed ortho-C(sp2)-H amination of benzamides and picolinamides with alkylamines using oxygen as a green oxidant

A versatile Cu-catalyzed direct ortho-C(sp2)-H amination of benzamides and picolinamides with alkylamines has been achieved. This method employs cheap and eco-friendly copper as a catalyst and oxygen as an oxidant, and also has the advantages of straightforward steps and excellent functional group compatibility. Further application of our approach was demonstrated by the synthesis of TCMDC-125116, SPHINX, and SRPIN340.

Single-Molecular White-Light Emitters and Their Potential WOLED Applications

White organic light-emitting diodes (WOLEDs) are superior to traditional incandescent light bulbs and compact fluorescent lamps in terms of their merits in ensuring pure white-light emission, low-energy consumption, large-area thin-film fabrication, etc. Unfortunately, WOLEDs based on multilayered or multicomponent (red, green, and blue (RGB)) emissive layers can suffer from some remarkable disadvantages, such as intricate device fabrication and voltage-dependent emission color, etc. Single molecules, which can emit white light, can be used to replace multiple emitters, leading to a simplified fabrication process, stable and reproducible WOLEDs. Recently, the performance of WOLEDs by using single molecules is catching up with that of the state-of-the-art devices fabricated by multicomponent emitters. Therefore, an increasing attention has been paid on single white-light-emitting materials for efficient WOLEDs. In this review, different mechanisms of white-light emission from a single molecule and the performance of single-molecule-based WOLEDs are collected and expounded, hoping to light up the interesting subject on single-molecule white-light-emitting materials, which have great potential as white-light emitters for illumination and lighting applications in the world.

A removable directing group-assisted Rh(iii)-catalyzed direct C–H bond activation/annulation cascade to synthesize highly fused isoquinolines

A removable directing group-assisted Rh(iii)-catalyzed direct C–H bond activation/annulation cascade was developed to synthesize highly fused isoquinolines with good to excellent yields and a good functional group tolerance.

White light emission in water through admixtures of donor–π–acceptor siblings: experiment and simulation

White light emission through binary admixtures of push–pull stilbenes.