Latest ArticlesTwo n-butoxy-encapsulated dendritic thermally activated delayed fluorescent (TADF) emitters (namely O-D1 and O-D2) with the first-/second-generation carbazoledendrons are designed and synthesized via CN coupling between carbazoledendrons and 2,4,6-tris(4-bromophenyl)-1,3,5-triazine core. It is found that, compared with the commonly-used tert-butyl groups, the use of n-butoxy encapsulation groups can lead to smallersinglet-triplet energy gap for the dendrimers, producing stronger TADF effect together with faster reverse intersystem crossing process. Solution-processed TADF organic light-emitting diodes (OLEDs) utilizingalkoxy-encapsulated dendrimers O-D1 and O-D2 as emitters exhibitstate-of-the-art device efficiency withthe maximum external quantum efficiency up to 16.8% and 20.6%, respectively, which are ~1.6 and ~2.0 times that of the tert-butyl-encapsulated counterparts. These results suggest that alkoxy encapsulation of the carbazole-based TADF dendrimers can be a promising approach for developing highly efficient emitters for solution-processed OLEDs.
Multiple hydrogen bonds containing nucleophilic phosphines derived from dipeptide dual-reagents catalyzed asymmetric Michael addition reactions between indene esters and activated olefins in high yields and good to excellent enantioselectivities under mild reaction conditions. The success of current highly selective reactions should provide inspiration for expansion to other reactions and would open up new paradigms for the synthesis of indanone derivatives bearing chiral quaternary carbon centers.
A simultaneous C2-H arylation and C8-H alkylation of naphthalene ring has been achieved by palladium-catalyzed cascade reaction of N-(2-halophenyl)-2-(naphthalen-1-yl)acrylamides with aryl iodides, which provides an efficient method for synthesizing various aryl-substituted spirocyclic oxindoles. The protocol enables three CC bonds formation via an intramolecular Heck reaction and sequentially regioselective CH bond activation.
Pincer complexes are widely used in organometallic and coordination chemistry. The role of antimony as a central donor atom in pincer ligands has been extensively explored in recent years. Although phenylenediamine derived PXP (X = B, Al, C, Si, Ge, Sn, N) type ligands exhibit diverse reactivity, analogues species based on antimony have been reported less frequently. Herein, we report a new PSbP complex and evaluate its reactivity. These species will broaden the family of phenylenediamine derived pincer complexes.
In many reactions involving selenosulfonate or thiosulfonate, the sulfone group often leaves in form of benzenesulfinic acid or sodium benzenesulfinate. A one-pot two-step reaction of selenosulfonate with isocyanides and allyl alcohol under aqueous conditions to afford selenocarbamates and allyl sulfone compounds is reported. The sulfinic acid as the first-step side product is converted to the allyl sulfone compound by water promoted reaction with allyl alcohol. Water acts as both an oxygen source of selenocarbamates and as a promoter to drive the second step reaction. The reactions have the advantages of mild conditions, green, environment-friendly, and high atomic economy.
The effect of cucurbit[7]uril (CB[7]) on fluorescence properties and biocompatibility of the bis-viologen biphenyl molecule (BPV22+) was investigated by using 1H NMR spectroscopy, fluorescence emission titration, and in vitro cytotoxicity experiments. CB[7] can be combined with BPV22+ in a stoichiometric ratio of 1:1 and 2:1. After the formation of host-guest complex, the fluorescence emission intensity of BPV22+ increased significantly, and the emission spectrum blue shifted. Meanwhile, the host-guest complexes showed better biocompatibility than BPV22+ in cell cytotoxicity studies. Results of this paper lay a foundation for the development of host-guest type of fluorescent probes, biological imaging and so forth.
Smart strategies that can decrease the side effect and enhance the therapeutic efficacy of chemotherapy are in urgent need to meet the special demands of cancer therapy. Herein, two water-soluble macrocyclic hosts, i. e., a carboxylated leaning tower[6]arene (CLT6) and a carboxylated [2]biphenyl-extended pillar[6]arene (CBpP6), are used to load chemotherapy drug oxaliplatin (OxPt) by forming inclusion complexes (OxPt⊂CLT6 and OxPt⊂CBpP6) through host-guest interactions. Interestingly, OxPt can be released from the macrocyclic cavities of these drug delivery systems (DDSs) via the competitive binding effect of spermine (SPM) because of the stronger binding abilities of CLT6/CBpP6 toward SPM as compared with OxPt, leading to enhanced cytotoxicity on SPM-overexpressed cancer cells, such as breast cancer MCF-7 cells. Moreover, compared to free OxPt, due to the low concentration of SPM in normal cells, OxPt⊂CLT6 and OxPt⊂CBpP6 demonstrated a decreased cytotoxicity on liver L02 cells, which is beneficial for reducing the side effect of anticancer drug during chemotherapy. Such a strategy might be extended to other antitumor drugs and water-soluble macrocycles with suitable cavity sizes to achieve controllable drug delivery and enhanced anticancer ability in supramolecular chemotherapy.
The design and synthesis of a phenoxazine-based metal-organic tetrahedron (Zn4L4) as biomimetic lectin for selectively recognition of glucosamine (GlcN) was reported. Different from the free phenoxazine-based ligand (L), Zn4L4 displayed the highest fluorescent intensity enhancement efficiency toward GlcN over other related natural mono- and disaccharides. Fluorescence titration demonstrated a 1:1 stoichiometric host-guest complex was formed with an association constant about 4.03×104 L/mol. 1H NMR spectroscopic studies confirmed this selectivity resulted from the multiple hydrogen bonding interactions formed between GlcN and Zn4L4. The present results suggested that rational arrangement of recognition sites in the confined space of metal-organic cage is crucial for the selectivity toward target guests.
Three new emitters, namely 10, 10'-(quinoline-2, 8-diyl)bis(10H-phenoxazine) (Fene), 10, 10'-(quinoline-2, 8-diyl)bis(10H-phenothiazine) (Fens) and 10, 10'-(quinoline-2, 8-diyl)bis(9, 9-dimethyl-9, 10-dihydroacridine) (Yad), featuring quinoline as a new electron acceptor have been designed and conveniently synthesized. These emitters possessed small singlet–triplet splitting energy (ΔEst) and twisted structures, which not only endowed them show thermally activated delayed fluorescence (TADF) properties but also afforded a remarkable aggregation-induced emission (AIE) feature. Moreover, they also showed aggregation-induced delayed fluorescence (AIDF) property and good photoluminescence (PL) property, which are the ideal emitters for non-doped organic light-emitting diodes (OLEDs). Furthermore, high-performance non-doped OLEDs based on Fene, Fens and Yad were achieved, and excellent maximum external quantum efficiencies (EQEmax) of 14.9%, 13.1% and 17.4%, respectively, were obtained. It was also found that all devices exhibited relatively low turn-on voltages ranging from 3.0 V to 3.2 V probably due to their twisted conformation and the AIDF properties. These results demonstrated the quinoline-based emitters could have a promising application in non-doped OLEDs.
Metal-free heteroatoms dual-doped carbon has been recognized as one of the most promising Pt/C-substitutes for oxygen reduction reaction (ORR). Herein, we optimize the preparation process by doping order of metal-free heteroatoms to obtain the best electrocatalytic performance through three types of dual-doped carbon, including XC-N (first X doping then N doping), NC-X (first N doping then X doping) and NXC (N and X doping) (X = P, S and F). XC-N has more defect than the other two indicated by Raman spectra. X-ray photoelectron spectrom (XPS) measurements indicate that N and X have been dual-doped into the carbon matrix with different doping contents and modes. Electrocatalytic results, including the potential of ORR peak (Ep), the half-wave potential, the diffusion-limiting current density mainly follows the order of XC-N > NC-X > NXC. Furthermore, the synergistic effect of second atom doping are also compared with the single doped carbon (NC, PC, SC and FC). The differences in electronegativity and atomic radius of these metal-free heteroatoms can affect the defect degree, the doping content and mode of heteroatoms on carbon matrix, induce polarization effect and space effect to affect O2 adsorption and product desorption, ultimately to the ORR electrocatalytic performance.
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