Highly Twisted Thermally Activated Delayed Fluorescence (TADF) Molecules and Their Applications in Organic Light-Emitting Diodes (OLEDs)

Thermally activated delayed fluorescence (TADF) materials have attracted great potential in the field of organic light-emitting diodes (OLEDs). Among thousands of TADF materials, highly twisted TADF emitters have become a hotspot in recent years. Compared with traditional TADF materials, highly twisted TADF emitters tend to show multi-channel charge-transfer characters and form rigid molecular structures. This is advantageous for TADF materials, as non-radiative decay processes can be suppressed to facilitate efficient exciton utilization. Accordingly, OLEDs with excellent device performances have also been reported. In this Review, we have summarized recent progress in highly twisted TADF materials and related devices, and give an overview of the molecular design strategies, photophysical studies, and the performances of OLED devices. In addition, the challenges and perspectives of highly twisted TADF molecules and the related OLEDs are also discussed.     

Structure characterization and possible biogenesis of three new families of nortriterpenoids: schisanartane, schiartane, and 18-norschiartane

Four new, highly oxygenated nortriterpenoids with unique schisanartane skeletons, micrandilactones D-G (1-4), have been isolated from the leaves and stems of Schisandra micrantha, and their structures have been elucidated on the basis of extensive spectral studies. The postulated biogenetic sequences of sixteen highly oxygenated nortriterpenoids and bisnortriterpenoids with new skeletons from three Schisandra species are discussed and have been compared from a chemotaxonomic standpoint.     

Investigation of glyme additives to metalorganic ink systems

Journal of Sol-Gel Science and Technology - Printing of metal oxides at low temperatures is highly challenging, and highly reactive metalorganic inks have been investigated to achieve the target...     

Structure, function and therapeutic potential of omega conopeptides: Novel blockers of neuronal calcium channels

Recent molecular cloning strategies have revealed that the diversity of voltage-sensitive calcium channels (VSCC) in the nervous system is much larger than indicated by electrophysiological studies. Elucidation of the physiological functions of these novel classes of VSCC requires pharmacological tools such as the blockers which were highly useful in characterizing the L-type VSCC in skeletal, smooth and cardiac muscle. Omega conopeptides found in the venom of fish-eating marine snails are proving to be highly selective blockers of neuronal VSCC. Several omega conopeptides have been isolated from a variety ofConus, characterized and synthesized. Biochemical, electrophysiological and morphological studies with these synthetic conopeptides have shown that novel types of VSCC are located in discrete regions of the brain and control the release of neurotransmitters in a highly selective manner, hitherto unsuspected. Pharmacological studies in animal models of cerebral ischemia have shown that omega conopeptides which selectively block N-type VSCC are highly effective in preventing brain damage caused by the loss of oxygen supply to the brain during the ischemia episode. This article is dedicated to Professor CNR Rao, eminent scientist, scholar and educator, on the occasion of his sixtieth birthday     

Polymer-supported monodentate phosphite ligands for asymmetric hydrogenation

Several new polymer-supported monophosphite ligands have been developed and the rhodium complexes were shown to be highly efficient, highly enantioselective and easily separable catalysts for asymmetric hydrogenation of itaconates, enamides, α-dehydroamino acid derivatives and β-dehydroamino acid derivatives.     

Scope of palladium-catalyzed alkylative ring opening

We have explored the scope of the palladium-catalyzed nucleophilic ring opening methodology. New highly selective and highly active catalysts have been found for the ring opening of oxabenzonorbornadienes. Employing these catalysts, the addition of various alkyl nucleophiles to oxabenzonorbornadiene has been achieved. In addition, reaction of diethylzinc with [3.2.1] oxabicyclic alkenes has been accomplished to yield ring-opened products as well as functionalized alkene addition products.     

Sterically Controlled C−H Olefination of Heteroarenes

The regioselective functionalization of heteroarenes is a highly attractive synthetic target due to the prevalence of multiply substituted heteroarenes in nature and bioactive compounds. Some substitution patterns remain challenging: While highly efficient methods for the C2-selective olefination of 3-substituted five-membered heteroarenes have been reported, analogous methods to access the 5-olefinated products have remained limited by poor regioselectivities and/or the requirement to use an excess of the valuable heteroarene starting material. Herein we report a sterically controlled C−H olefination using heteroarenes as the limiting reagent. The method enables the highly C5-selective olefination of a wide range of heteroarenes and is shown to be useful in the context of late-stage functionalization.     

A Highly Stereoselective and Flexible Strategy for the Convergent Synthesis of Long‐Chain Polydeoxypropionates: Application towards the Synthesis of the Glycolipid Membrane Components Hydroxyphthioceranic and Phthioceranic Acid

A highly stereocontrolled and flexible access to biologically relevant polydeoxypropionates in optically pure form has been developed. Taking advantage of our previously established strategy for the asymmetric and stereodivergent synthesis of trideoxypropionate building blocks, we have now been able to assemble large polydeoxypropionate chains with defined configuration in a highly convergent manner. Central steps of this approach include two Suzuki–Miyaura cross‐coupling reactions with subsequent highly diastereoselective hydrogenations to join three advanced synthetic intermediates in excellent yield and with full stereochemical control. We have applied this strategy successfully towards the asymmetric synthesis of glycolipid membrane components phthioceranic acid and hydroxyphthioceranic acid, the latter of which was synthesized on a half‐gram scale.     

Formation of the intermediate-spin iron(III) porphyrin complexes with (dxz, dyz)3(dxy)1(dz2)1 electron configuration

On the basis of the difference in meso-13C chemical shifts, we have concluded that the intermediate-spin iron(III) complexes with highly ruffled and highly saddled porphyrins have different electron configurations. While the latter has a conventional (dxy)2(dxz, dyz)2(dz2)1, the former adopts a novel (dxz, dyz)3(dxy)1(dz2)1.     

Li＋交换的几种分子筛的氮氩分离性能

采用水溶液离子交换法制备了高Li＋交换度的4A、13X和LSX分子筛,并在25 ℃下测定了它们的静态吸附等温线和动态穿透曲线.研究发现,高Li＋离子交换度的4A、13X和LSX分子筛都具有较大的氮吸附容量和较高的氮氩分离选择性,说明高Li＋离子交换度的4A、13X和LSX分子筛是较好的氮氩分离吸附剂.从动态穿透曲线结果来看,所研究的三种分子筛都有一个最优的吸附分离压力,在本文研究的压力范围内,这个最优压力在0.6 MPa附近.对比高锂交换度的三种分子筛,以高锂交换度的LSX分子筛的氮氩吸附分离性能最好.     

Synthesis of Prolinal Dithioacetals as Catalysts for the Highly Stereoselective Michael Addition of Ketones and Aldehydes to beta-Nitrostyrenes

Catalytic highly enantioselective (up to >99% ee) and diastereoselective (up to 99% de) direct Michael addition of ketones and aldehydes to β-nitrostyrenes have been achieved with readily accessible and highly tunable prolinal dithioacetal catalysts.     

Sterically Controlled C−H Olefination of Heteroarenes

The regioselective functionalization of heteroarenes is a highly attractive synthetic target due to the prevalence of multiply substituted heteroarenes in nature and bioactive compounds. Some substitution patterns remain challenging: While highly efficient methods for the C2‐selective olefination of 3‐substituted five‐membered heteroarenes have been reported, analogous methods to access the 5‐olefinated products have remained limited by poor regioselectivities and/or the requirement to use an excess of the valuable heteroarene starting material. Herein we report a sterically controlled C?H olefination using heteroarenes as the limiting reagent. The method enables the highly C5‐selective olefination of a wide range of heteroarenes and is shown to be useful in the context of late‐stage functionalization.     

Squaraines as fluoro-chromogenic probes for thiol-containing compounds and their application to the detection of biorelevant thiols

A highly selective colorimetric chemodosimeter for thiol-containing compounds in aqueous solutions is reported. The design protocol makes use of a highly specific reaction between thiols and the electrophilic four-membered ring of highly colored, fluorescent squaraine backbones. At neutral pH selective decoloration and total emission quenching was found due to the rupture of the highly delocalized squaraine framework upon selective nucleophilic addition of thiol-containing derivatives. The squaraine derivatives have been successfully applied to the determination of low-molecular mass aminothiols in human plasma. The method utters the high potential applicability of the chemodosimeter approach in the search for new or improved chromogenic selective or specific probes for target guests.     

Stereoselective one-pot synthesis of highly differently substituted thiochromans

A highly stereoselective one-pot procedure to anti-configured thiochromans is described. This reaction functions at room temperature in the presence of catalytic amounts of trifluoroacetic acid. The transformation gives a selective but optional access to highly substituted thiochromans, which have been not attainable until now.     

Adsorption properties versus oxidation states of rutile TiO2(110)

Using density functional theory we have studied the adsorption properties of different atoms and molecules deposited on a stoichiometric, reduced, and oxidized rutile TiO(2)(110) surface. Depending on the oxidation state of the surface, electrons can flow from or to the substrate and, therefore, negatively or positively charged species are expected. In particular, we have found that a charge transfer process from or to the surface always occurs for highly electronegative or highly electropositive species, respectively. For atoms or molecules with intermediate electron affinity, the direction of the charge flow depends on the oxidation state of the rutile surface and on the adsorption site. Generally, the charging effect leads to more stable complexes. However, the increase in the binding energy of the adsorbates is highly dependent on the electronic states of the surface prior to the adsorption event. In this work we have analyzed in details these mechanisms and we have also established a direct correlation between the enhanced binding energy of the adsorbates and the induced gap states.     

Facile synthesis and application of highly luminescent CdTe quantum dots with an electrogenerated precursor

An electrogenerated precursor has been developed for green synthesis of highly luminescent aqueous CdTe quantum dots (QDs) with unique quantum yield and strong electrogenerated luminescence, which can access cellular targets via specific binding and have potential application as biolabels in highly sensitive biosensing and cell imaging.     

Freeze fracture direct imaging of a viscous surfactant mesophase

Freeze fracture direct imaging (FFDI) has been used to image microstructures present in a highly viscous four-component mesophase containing water, isooctane, AOT [bis(2-ethylhexyl) sodium sulfosuccinate], and lecithin. As water is added to a fixed amount of a ternary solution of isooctane and the two surfactants, the microstructure evolves from a water-in-oil microemulsion, to a highly viscous columnar hexagonal, and then to multilamellar vesicles. Each of these microstructures is imaged directly. Previous small-angle neutron scattering measurements have identified the lamellar phase, but the FFDI technique demonstrates that these are onionlike curved multilamellar structures rather than planar bilayers. Freeze fracture direct imaging expands the range of cryo-transmission microscopy to highly viscous, high-organic-content systems that typically have been difficult to visualize.     

Organocatalytic highly enantioselective nitroaldol reaction of alpha-ketophosphonates and nitromethane

[reaction: see text] The first organocatalytic highly enantioselective nitroaldol reaction of alpha-ketophosphonates and nitromethane has been realized by using cupreine (2) or 9-O-benzylcupreine (3) as the catalyst. Both catalysts are highly reactive and highly enantioselective. alpha-Hydroxy-beta-nitrophosphonates have been synthesized in good yields and excellent enantioselectivities (>or=90% ee) at a low catalyst loading (5 mol %). These nitroaldol products may be reduced to the biologically significant beta-amino-alpha-hydroxyphosphonates with complete retention of the stereochemistry.     

Ultrasensitive detection of potassium ions based on target induced DNA conformational switch enhanced fluorescence polarization

We have developed a simple, highly sensitive and selective fluorescence polarization assay for the detection of potassium ions based on target induced DNA conformational switch from hairpin to G-quadruplex enhanced fluorescence polarization. The assay was applied in the detection of low nM concentrations of potassium ions and was highly selective over other cations.     

Diversity oriented and chemoenzymatic synthesis of densely functionalized pyrrolidines through a highly diastereoselective Ugi multicomponent reaction

A highly diastereoselective Ugi reaction involving a chiral cyclic imine, two enantiomerically pure isocyanides and various carboxylic acids was employed for the synthesis of polyfunctionalized pyrrolidines. Both chiral substrates have been efficiently prepared by chemoenzymatic methodologies from readily available achiral substrates. This highly convergent approach can find an application in the fragment-based drug discovery process.