Selective Hydrogenolysis of Glycerol to Propylene Glycol on Supported Pd Catalysts: Promoting Effects of ZnO and Mechanistic Assessment of Active PdZn Alloy Surfaces

Pd catalysts have received increasing attention for selective hydrogenolysis of glycerol to propylene glycol because of their good hydrothermal stability and high selectivity for cleavage of C–O bonds over C–C bonds. Addition of Zn can facilitate glycerol hydrogenolysis to propylene glycol on Pd surface, but the promoting role of Zn, stability of the resulting active PdZn alloys and reaction mechanism remain largely unexplored. Here, we synthesized monoclinic zirconia-supported PdZn (PdZn/m-ZrO₂) catalysts via an incipient wetness impregnation method. Glycerol hydrogenolysis turnover rates (normalized per surface Pd atom measured by H₂ chemisorption) and propylene glycol selectivity on these PdZn/m-ZrO₂ catalysts depended sensitively on their Zn/Pd molar ratios, and Zn leaching from the PdZn alloy phases led to deactivation of PdZn/m-ZrO₂. Such deactivation was efficiently inhibited when physical mixtures of Pd/m-ZrO₂ and ZnO were directly used in glycerol hydrogenolysis, leading to in situ formation of PdZn alloy layers on Pd surfaces with excellent stability and recyclability. Dependence of turnover rates on glycerol and H₂ concentrations, combined with the primary kinetic isotope effects (<i>k</i>_H<i>/k</i>_D = 2.6 at 493 K), reveals the kinetically relevant step of glycerol hydrogenolysis involving the α-C-H cleavage in 2,3-dihydroxypropanoxide intermediate to glyceraldehyde on PdZn alloys and Pd. Measured rate constants show that the transition state of α-C-H cleavage is more stable because of the stronger oxophilicity of Zn on PdZn alloys than on Pd, which thus facilitates α-C-H cleavage of the Zn-bound intermediate by adjacent Pd on PdZn alloys. Such synergy between Zn and Pd sites accounts for the observed superiority of PdZn alloys to Pd in glycerol hydrogenolysis

Total Syntheses of Festuclavine, Pyroclavine, Costaclavine, <i>epi</i>-Costaclavine, Pibocin A, 9‑Deacetoxyfumigaclavine C, Fumigaclavine G, and Dihydrosetoclavine

A new approach for the divergent total synthesis of eight ergot alkaloids is reported. The approach allows the first total syntheses of pyroclavine, pibocin A, 9-deacetoxyfumigaclavine C, and fumigaclavine G and also enables the efficient synthesis of festuclavine, costaclavine, <i>epi</i>-costaclavine, and dihydrosetoclavine. The main feature of the synthesis is the use of an unprecedented Pd-catalyzed intramolecular Larock indole annulation/Tsuji–Trost allylation cascade to assemble the tetracyclic core in one step

Transforming Thermally Activated Delayed Fluorescence to Room-Temperature Phosphorescence through Modulation of the Donor in Charge-Transfer Cocrystals

A cocrystallization strategy is used through incorporation of 1,2,4,5-tetracyanobenzene (TCNB) as an acceptor with halogen-substituent thioxanthone (TX) derivatives as donors. The resulting cocrystals TT-R (R = H, F, Cl, Br, or I) transform the thermally activated delayed fluorescence emission in the TT-H, TT-F, and TT-Cl cocrystals to room-temperature phosphorescence in the TT-Br and TT-I cocrystals. Definite crystal packing structures demonstrate a 1:1 alternative donor–acceptor stacking in the TT-H cocrystal, a 2:1 alternative donor–acceptor stacking in the TT-F and TT-Cl cocrystals, and a separate stacking of donor and acceptor in the TT-Br and TT-I cocrystals. A transformation law can be revealed that with an increase in atomic number from H, F, Cl, Br, to I, the cocrystals show the structural transformation of the number of aggregated TX-R molecules from monomers to dimers and finally to multimers. This work will facilitate an understanding of the effect of halogen substituents on the crystal packing structure and luminescence properties in the cocrystals

Pressure Tuning Dual Fluorescence of 4‑(<i>N</i>,<i>N</i>‑Dimethylamino)benzonitrile

The intramolecular charge-transfer (ICT) emission band in the dual fluorescence of the 4-(<i>N</i>,<i>N</i>-dimethylamino)­benzonitrile (DMABN) molecular crystal exhibits increase in response to compression up to 10 GPa. On the basis of Raman and angle-dispersive X-ray diffraction (ADXRD) experiments combining with computational studies, the mechanism of this phenomenon could be assigned to the change of the intramolecular geometrical conformation, especially for the decrease of the dihedral angle between the dimethylamino (NMe₂) and phenyl moieties. Meanwhile the reduction of excited-state energies and the HOMO–LUMO band gap leads to the redshifts of photoluminescence (PL) spectra and the absorption edge, respectively. Competing with the aggregation caused quenching (ACQ) effect, the planarity of molecular conformation and the slight rotation of the NMe₂ group under high pressure both could enhance the ICT process, which will contribute to the revelation of the ICT mechanism and designs of new piezochromic luminescent materials

Dopant-Induced Modification of Active Site Structure and Surface Bonding Mode for High-Performance Nanocatalysts: CO Oxidation on Capping-free (110)-oriented CeO₂:Ln (Ln = La–Lu) Nanowires

Active center engineering at atomic level is a grand challenge for catalyst design and optimization in many industrial catalytic processes. Exploring new strategies to delicately tailor the structures of active centers and bonding modes of surface reactive intermediates for nanocatalysts is crucial to high-efficiency nanocatalysis that bridges heterogeneous and homogeneous catalysis. Here we demonstrate a robust approach to tune the CO oxidation activity over CeO₂ nanowires (NWs) through the modulation of the local structure and surface state around Ln_Ce′ defect centers by doping other lanthanides (Ln), based on the continuous variation of the ionic radius of lanthanide dopants caused by the lanthanide contraction. Homogeneously doped (110)-oriented CeO₂:Ln NWs with no residual capping agents were synthesized by controlling the redox chemistry of Ce­(III)/Ce­(IV) in a mild hydrothermal process. The CO oxidation reactivity over CeO₂:Ln NWs was dependent on the Ln dopants, and the reactivity reached the maximum in turnover rates over Nd-doped samples. On the basis of the results obtained from combined experimentations and density functional theory simulations, the decisive factors of the modulation effect along the lanthanide dopant series were deduced as surface oxygen release capability and the bonding configuration of the surface adsorbed species (i.e., carbonates and bicarbonates) formed during catalytic process, which resulted in the existence of an optimal doping effect from the lanthanide with moderate ionic radius

Enhancing the Electroluminescent Efficiency of Acridine-Based Donor–Acceptor Materials: Quasi-Equivalent Hybridized Local and Charge-Transfer State

Excited-state properties (characteristics and composition) play a crucial role in luminescence properties of the new-generation organic light-emitting materials. As a special excited species, the hybridized local and charge-transfer (HLCT) state is composed of locally excited (LE) state and charge-transfer (CT) state, which can harvest simultaneous high photoluminescence (PL) efficiency and high exciton utilization in organic light-emitting diodes. In this work, we designed and synthesized three donor (D)–acceptor (A) compounds with different donor units and a typical electron-deficient unit acridine as the acceptor unit to investigate the different hybridization statuses among them. As is revealed by the molecular design, the three compounds precisely show the different hybridization statuses: LE-dominated hybridization (CZP-1AC), quasi-equivalent HLCT (qHLCT, TPA-1AC), and CT-dominated hybridization (PTZ-1AC). As a result, TPA-1AC exhibits the highest PL efficiency and multifold device performance, meriting from the most effective suppression of nonradiative processes that originated from a qHLCT state due to the strong interstate coupling and the small energy gap between LE and CT states. This work not only provides a comprehensive insight into the hybridization formation and a fine modulation in HLCT state composition but also provides a valuable strategy to design new-generation, low-cost, high-performance organic electroluminescence materials based on lowly emissive chromophores of D or A

Specificity of the polyclonal antiserum mBicc1p for Bicc1.

<p>(A) The mBicc1-GST antigen was subjected to western blot analysis with the antibodies shown. The anti-Bicc1 (mBicc1p) and anti-GST antibodies, but not the preimmune serum (Pre-IM), recognized the mBicc1-GST antigen of the expected size (43 kD). (B) Schematic representation of the <i>Bicc1</i>-pCMV-Tag4 expression vector constructed by inserting the full-length ORF of <i>Bicc1</i> into Flag-tagged pCMV-Tag4. (C) <i>Bicc1</i>-pCMV-Tag4-transfected HEK293 cell lysates were subjected to western blot analysis with the antibodies shown. The anti-Bicc1 (mBicc1p) and anti-GST antibodies but not the Pre-IM recognized the <i>Bicc1</i>-pCMV-Tag4 protein of the expected size (∼110 kD). (D) Western analysis of duplicated protein lysates from wildtype, <i>Bicc1</i>-silenced (IMCD^shC4C), and <i>Bicc1</i>-overexpressed IMCD cells (IMCD^Bicc1) were blotted with the mBicc1p antibody. Compared to the wildtype control, the immunoreactivity was significantly increased in <i>Bicc1</i>-overexpressed IMCD cells and was almost not detected in the <i>Bicc1</i>-silenced cells. (E) Normalized quantitative analysis of the densitometry values of the western analyses. Compared to wildtype IMCD and <i>Bicc1</i>-silenced IMCD (IMCD^shC4C) cells, <i>Bicc1</i>-overexpressed IMCD (IMCD^Bicc1) cells showed significantly increased Bicc1 expression (*P<0.05). (F) Immunohistochemistry (IHC) staining of Bicc1 protein in the kidneys of E18.5 <i>Bicc1</i>^−/− and its wildtype littermates. Positive staining (arrows) were showed in the wildtype kidney (a), while no obvious positive staining was seen in the E18.5 <i>Bicc1</i>^−/− kidney (b). (a'–b') Corresponding areas of a–b were stained by Bicc1p IHC without counterstaining. Data presented are representative of two to three independently replicated experiments. “cy” = renal cysts. Bars: 25 µm in F.</p

Bicc1 expression in renal nephrons.

<p>Double immunofluorescence staining with mBicc1p and nephronic markers (LTL, THG, and AQP2) in paraffin-embedded sections of adult wildtype mouse kidneys (n≥5). (A) The Pre-IM was used as a negative staining control. (B) Bicc1 (red) was co-expressed with LTL (green) in the epithelial cells of the renal proximal tubules; (C) Bicc1 (red) was also co-expressed with THG (green) in the epithelial cells of the Henle's thick ascending limbs; (D) With mBicc1p staining (red), Bicc1 was highly expressed in the renal proximal tubules (top arrow) and weakly expressed in the collecting ducts (lower arrow). mBicc1p co-staining with the anti-AQP2 antibody (green) showed weakly co-expression of Bicc1 and AQP2 in the epithelial cells of the collecting ducts (middle arrow). Bar: 30 µm in A–D.</p

Loss of PC1 downregulates Bicc1 expression <i>in vitro</i>.

<p>(A) qPCR analysis of cultured cell lines with or without <i>Pkd1</i>, <i>Pkd2</i>, or <i>Pkhd1</i> showed no change in the <i>Pkd2</i> or <i>Pkhd1</i> mRNA expression, while <i>Bicc1</i> was significantly downregulated in the cells lacking <i>Pkd1</i> compared to the wildtype control (*P<0.05) (n = 3). (B) Western blot analysis of protein lysates from null-<i>Pkd2</i> cells (E8) and <i>Pkd2</i>-heterozygous cells (D3) using the mBicc1p antibody suggested that PC2 loss did not affect Bicc1 expression. (C) Similar western blots for null-<i>Pkhd1</i> cells (M10H2) and <i>Pkhd1</i>-wildtype cells (W10B2) showed that loss of <i>Pkhd1</i> also did not affect Bicc1 expression. (D) Western blot analysis for the null-<i>Pkd1</i> cells and their wildtype littermate cells showed that loss of <i>Pkd1</i> markedly downregulated the Bicc1 protein expression. (E) Normalized quantitative analysis of the densitometry values of the western analyses. Compared to null-<i>Pkd2</i> or -<i>Pkhd1</i> cells, only the null-<i>Pkd1</i> cells showed significantly reduced Bicc1 expression (*P<0.05). (F) With the wildtype littermate cell control, western blot analyses for the null-<i>Pkd1</i> pool cells and their PC1-CT transfected cells showed that the restoration of PC1 COOH-terminus markedly rescued the downregulation level of Bicc1 expression in the null-<i>Pkd1</i> cells. (G) Normalized quantitative analysis of the densitometry values of the western analyses. Compared to the null-<i>Pkd1</i> cells, the cells with PC1-CT transfection can partially restored Bicc1 expression in the null-<i>Pkd1</i> cells (*P<0.05). Data presented are representative of two to three independently replicated experiments.</p

Growth of Semiconducting Single-Walled Carbon Nanotubes by Using Ceria as Catalyst Supports

The growth of semiconducting single-walled carbon nanotubes (s-SWNTs) on flat substrates is essential for the application of SWNTs in electronic and optoelectronic devices. We developed a flexible strategy to selectively grow s-SWNTs on silicon substrates using a ceria-supported iron or cobalt catalysts. Ceria, which stores active oxygen, plays a crucial role in the selective growth process by inhibiting the formation of metallic SWNTs via oxidation. The so-produced ultralong s-SWNT arrays are immediately ready for building field effect transistors