Twofold rigidity activates ultralong organic high-temperature phosphorescence.

A strategy is pioneered for achieving high-temperature phosphorescence using planar rigid molecules as guests and rigid polymers as host matrix. The planar rigid configuration can resist the thermal vibration of the guest at high temperatures, and the rigidity of the matrix further enhances the high-temperature resistance of the guest. The doped materials exhibit an afterglow of 40 s at 293 K, 20 s at 373 K, 6 s at 413 K, and a 1 s afterglow at 433 K. The experimental results indicate that as the rotational ability of the groups connected to the guests gradually increases, the high-temperature phosphorescence performance of the doped materials gradually decreases. In addition, utilizing the property of doped materials that can emit phosphorescence at high temperatures and in high smoke, the attempt is made to use organic phosphorescence materials to identify rescue workers and trapped personnel in fires.

Cyclodextrin Polymer-Loaded Micro-Ceramic Balls for Solid-Phase Extraction of Triazole Pesticides from Water.

A citric acid cross-linked ß-cyclodextrin (ß-CD) polymer was synthesized and loaded on micro-ceramic balls to fabricate the solid-phase adsorbents (P-MCB) for adsorption and extraction of triazole pesticides from water. The stability of ß-CD polymer and P-MCB was investigated in solutions with different pH values at different temperatures. The adsorption properties and the influence of kinetics, sorbent amount, pesticide concentration, and temperature on the adsorption capacity were evaluated. The results showed P-MCB had favorable adsorption of 15.98 mg/g flutriafol in 3.5 h. The equilibrium data followed the Freundlich equation, and the adsorption of flutriafol and diniconazole followed the second-order kinetics. The recovery rate of P-MCB for triazole pesticides in water was satisfactory, and the recovery rate was still 80.1%, even at the 10th cycle. The P-MCB had good stability, with a degradation rate of 0.2% ± 0.08 within 10 days, which could ensure extraction and recycling.

Transition-metal-free four-component reaction of nitriles and disulfides/diselenides.

One-pot synthesis of structurally diverse sulfurized/selenated 4-aminopyrimidines has been reported via t-BuOK/K2S2O8-promoted four-component reaction of mixed nitriles and disulfides/diselenides. Mechanistic studies indicate that the reaction proceeds through radical and ionic pathways, and an alkenyl sulfide serves as a key intermediate.

Microparticles of Sericin-Dextran Conjugate for Improving the Solubility of Antiviral Drug.

A novel sericin-dextran conjugate (SDC) and self-assembled microparticles has been prepared for improving solubility of atazanavir. Microparticles of SDC were assembled by the reprecipitation method. The size and morphology of SDC microparticles could be adjusted by the concentration and solvents. Low concentration was conducive to the preparation of microspheres. Heterogeneous microspheres could be prepared in ethanol with the range of 85-390 nm, and hollow mesoporous microspheres in propanol with an average particle size of 2.5-22 µm. The aqueous solubility of atazanavir was improved to 2.22 mg/mL in buffer solutions at pH 2.0 and 1.65 mg/mL at pH 7.4 by SDC microspheres. In vitro release of atazanavir from hollow microspheres of SDC exhibited a slower release, had the lowest linear cumulative release in basic buffer (pH 8.0), and the most rapid double exponential diphase kinetic cumulative release in acid buffer (pH 2.0).

Solid-State Luminescence Stimulus-Responsive Property and Doped RTP Emission of Novel 7a,8,10,11-Tetrahydro-9H- pyrido[2',1':2,3][1,3]oxazino[6,5,4-ij]isoquinoline Derivative.

A novel 7a,8,10,11-tetrahydro-9H-pyrido[2',1':2,3][1,3]-oxazino[6,5,4-ij]isoquinoline derivative (POIQ) is accidentally obtained from an isoquinoline derivative and iodine in dimethyl sulfoxide, which is demonstrated to undergo a mechanism of demethylation and thus intramolecular nucleophilic substitution. POIQ with twisted molecular conformation and loose stacking arrangement shows multifunctional optical properties including dual-state emission, mechanochromic, and solid-state acidochromic activities. Furthermore, an organic room temperature phosphorescence (RTP) doped system with green afterglow of 2 s is constructed using POIQ as the guest and easily available phenyl benzoate as the host, in which the host molecules assist in the transfer of the triplet excitons of the guest molecules. Rewritable optical recording media and information encryption are also realized based on multifunctional optical properties of this compound. This work provides inspiration for the development of N,O-containing fused-ring compounds with fluorescence/RTP properties.

Palladium-Catalyzed Ring-Opening Reaction of Cyclopropenones with Vinyl Epoxides.

We report herein the Pd-catalyzed selective ring-opening reaction of cyclopropenones with vinyl epoxides. By using a commercially available Pd2(dba)3·CHCl3-BINAP catalyst, a wide range of conjugated alkadienyl carboxylates could be accessed in good yield and excellent regioselectivity. The new application of zwitterionic π-allyl palladium intermediates has been demonstrated in organic synthesis.

P/N-Heteroleptic Cu(I)-Photosensitizer-Catalyzed [3 + 2] Regiospecific Annulation of Aminocyclopropanes and Functionalized Alkynes.

We report here a regiospecific [3 + 2] annulation between aminocyclopropanes and various functionalized alkynes enabled by a P/N-heteroleptic Cu(I) photosensitizer under photoredox catalysis conditions. Thus, a divergent construction of 3-aminocyclopentene derivatives including methylsulfonyl-, arylsulfonyl-, chloro-, ester-, and trifluoromethyl-functionalized aminocyclopentenes could be achieved with advantages of high regioselectivity, broad substrate compatibility, and mild and environmentally benign reaction conditions.

Construction of Heterobiaryl Skeletons through Pd-Catalyzed Cross-Coupling of Nitroarenes and Heterocyclic Arylborononate Esters with a Sterically Demanding NHC Ligand.

The palladium-catalyzed Suzuki-Miyaura cross-couplings of nitroarenes and heteroarylboronate esters has been developed. A number of heterobiaryl compounds containing pyridine, pyrimidine, quinoline, furan, thiophene, and pyrazole were prepared using [Pd(cinnamyl)Cl]2/2-aryl-5-(2,4,6-triisopropylphenyl)-2,3-imidazolylidene[1,5-a]pyridines as the catalysts in good to excellent yields. The synthetic practicality of this approach is demonstrated through the synthesis of druglike molecules.

Guest-activated quaternary ammonium salt hosts emit room temperature phosphorescence.

A novel doped system based on quaternary ammonium salts as hosts was established. Interestingly, it is the guest-activated hosts that emit room temperature phosphorescence, rather than the host-assisted guests in traditional doped systems.

Unexpected synthesis, delayed emission and solid-state acidochromism of novel 2,7-naphthyridine derivatives obtained from 2-(3,5-diaryl-4H-pyran-4-ylidene)malononitrile.

Two novel 2,7-naphthyridine derivatives are unexpectedly synthesized by the reaction of 2-(3,5-diaryl-4H-pyran-4-ylidene)malononitrile and benzylamine, and are achieved through different ring-closing mechanisms. These two derivatives with twisted molecular conformations display phosphorescence, thermally activated delayed fluorescence, and high contrast solid-state acidochromism due to special chemical structures.

Metal Ions as the Third Component Coordinate with the Guest to Stereoscopically Enhance the Phosphorescence Properties of Doped Materials.

The construction of multicomponent doped systems is an important direction for the development of phosphorescence materials. Herein, benzophenone is selected as the host, phenylquinoline isomers are designed as guests, and seven metal ions are selected as the third component (Al3+, Cu+/2+, Zn2+, Ga3+, Ag+, Cd2+, and In3+) to construct the three-component doped system. Ag+ and Cd2+ can considerably increase the emission intensity up to 38 times, and the highest phosphorescence quantum efficiency reaches 70%. Al3+, Ga3+, and In3+ can prolong the emission wavelength, and the phosphorescence wavelength can be red-shifted up to 60 nm. Cu2+, Ga3+, and In3+ can extend the phosphorescence lifetime by a maximum of 3.6 times. A series of experiments demonstrated that the coordination of metals and guests is the key to improve the phosphorescence properties. This work presents a simple and effective strategy to enhance the phosphorescence properties of doped materials.

Reactivity Umpolung of the C═N Bond in Quinoxaline Scaffold Enabling Direct Nucleophilic Attack of Alkyl Grignard Reagents at the N-Terminus.

The reactivity umpolung of the C═N bond in the quinoxaline scaffold has been successfully realized for the first time by introduction of a formyl or an acyl group adjacent to the C-position of the C═N moiety. The reversed reactivity of the C═N bond thus enabled direct nucleophilic attack of alkyl Grignard reagents at the N-terminus rather than the C-terminus, thereby providing an unprecedented and efficient method for the synthesis of quinoxalin-2(1H)-one derivatives involving a tandem N-alkylation/C─C bond cleavage process.

An (NH4)2S2O8-promoted cross-coupling of thiols/diselenides and sulfoxides for the synthesis of unsymmetrical disulfides/selenosulfides.

An (NH4)2S2O8-promoted cross-coupling of thiols/diselenides and sulfoxides to construct unsymmetrical disulfides/selenosulfides is disclosed. Control experiments demonstrate that (NH4)2S2O8 acts as an acid and an oxidant, while both ionic and radical routes are involved in the reaction. The KIE experiments reveal that C-H bond cleavage of sulfoxides was involved in the turnover-limiting step.

Construction of Mechanofluorochromic and Aggregation-Induced Emission Materials Based on 4-Substituted Isoquinoline Derivatives.

Although many organic mechanofluorochromic (MFC) materials have been reported, the design strategy and formation mechanism are still unclear, and thus some of their discoveries are based on chance or a result of blind screening of some compounds. Herein, we show a strategy for constructing MFC materials from a multisubstituted isoquinoline compound with excellent crystallinity. The introduction of bromine atom at 4-position realizes the morphological change from crystalline state to amorphous state under the stimulation of external pressure, but it is not enough to generate MFC phenomenon. Similarly, although naphthalene, benzofuran, and benzothiophene endow the resultant isoquinolines with twisted molecular conformations and aggregation-induced emission (AIE) activities, no obvious solid-state emission color changes are observed. However, the introduction of 2-benzylidenemalononitrile and (E)-2-cyano-3-phenylacrylate leads not only to the AIE activities of IQ-M and IQ-A, but also to their outstanding and reversible MFC properties. The MFC activities of these two derivatives are demonstrated to come from more twisted molecular conformations, larger deformation spaces, and stronger intramolecular charge transfer compared with the other isoquinolines. This work offers important reference value for the construction of MFC and AIE materials from traditional fluorophores.

Selenium atoms induce organic doped systems to produce pure phosphorescence emission.

A host-guest system is constructed using a guest containing two selenium atoms. The selenium atoms can increase the spin-orbit coupling constant and the conjugation degree, thereby increasing the emission wavelength, and making the materials show only phosphorescence emission.

Guest-host doped strategy for constructing ultralong-lifetime near-infrared organic phosphorescence materials for bioimaging.

Organic near-infrared room temperature phosphorescence materials have unparalleled advantages in bioimaging due to their excellent penetrability. However, limited by the energy gap law, the near-infrared phosphorescence materials (>650 nm) are very rare, moreover, the phosphorescence lifetimes of these materials are very short. In this work, we have obtained organic room temperature phosphorescence materials with long wavelengths (600/657-681/732 nm) and long lifetimes (102-324 ms) for the first time through the guest-host doped strategy. The guest molecule has sufficient conjugation to reduce the lowest triplet energy level and the host assists the guest in exciton transfer and inhibits the non-radiative transition of guest excitons. These materials exhibit good tissue penetration in bioimaging. Thanks to the characteristic of long lifetime and long wavelength emissive phosphorescence materials, the tumor imaging in living mice with a signal to background ratio value as high as 43 is successfully realized. This work provides a practical solution for the construction of organic phosphorescence materials with both long wavelengths and long lifetimes.

Cascade Ring-Opening Dual Halogenation of Cyclopropenones with Saturated Oxygen Heterocycles.

Represented is a CuX2- or I2-promoted ring-opening dual halogenation of cyclopropenones with saturated oxygen heterocycles, providing an efficient method for the synthesis of 3-haloacrylates. The ring-opening reaction enables the construction of two C-X (X = Cl, Br, or I) bonds and a C-O bond as well as the cleavage of two C-O bonds and a C-C bond in a single step. This protocol is highly atom economical, has an excellent substrate scope, and exhibits the ability for gram-scale reaction.

α-Selective C(sp3)-H Thio/Selenocyanation of Ketones with Elemental Chalcogen.

A facile method is disclosed for the synthesis of α-thio/selenocyanato ketones through regioselective C-H thio/selenocyanation of ketones. The advantages include the use of easily available starting materials, high efficiency, simple operation, and easy scale-up. Control experiments provide evidence that the reaction proceeded via a radical way, while kinetic isotope effect experiments reveal that the cleavage of the C-H bond serves as the rate-limiting step.

Palladium-catalyzed coupling reaction of 2-iodobiphenyls with alkenyl bromides for the construction of 9-(diorganomethylidene)fluorenes.

An atom economical protocol for the construction of 9-(diorganomethylidene)fluorenes through palladium-catalyzed coupling reactions of 2-iodobiphenyls with alkenyl bromides has been reported. The reaction proceeds through the C-H activation/oxidative addition/reduction elimination/intramolecular Heck coupling reaction to afford a series of 9-(diorganomethylidene)fluorenes with good yields. Control experiments demonstrate that a five-membered palladacycle acts as a key intermediate and ß-H elimination serves as the rate-limiting step.

Influence of Guest/Host Morphology on Room Temperature Phosphorescence Properties of Pure Organic Doped Systems.

Guest/host phosphorescence materials have attracted much attention; traditionally, researchers have focused on the influence of the electronic properties and energy levels of the molecules on the phosphorescence activities. However, the effects of the morphology on the phosphorescence properties are ignored. Herein, three isoquinoline guests with different aliphatic rings and three hosts are selected to construct guest/host materials. Experimental results confirm that the guests are dispersed in the host in the form of clusters. More importantly, the morphologies of the guest/host directly affect the phosphorescence properties. In these systems, the guests have strong intermolecular interactions, which are beneficial to stabilize the triplet excitons; meanwhile, the hosts should have weak intermolecular interactions with easily changed morphology to accept the guest clusters, which synergistically ensure that the doped materials have excellent RTP properties. This is the first work focusing on the effect of molecular morphology on the phosphorescence characteristics of guest/host systems.