Recyclable N-Heterocyclic Carbene Porous Coordination Polymers with Two Distinct Metal Sites for Transformation of CO2 to Cyclic Carbonates.

Single-component catalysts with integrated multiple reactive centers could work in concert to achieve enhanced activity tailored for specific catalytic reactions, but they remain underdeveloped. Herein, we report the construction of heterogeneous bimetallic porous coordination polymers (PCPs) containing both porphyrin and N-heterocyclic carbene (NHC) metal sites via the coordinative assembly of the NHC functionalities. Three heterobimetallic PCPs (TIPP-Zn-Pd, TIPP-Cu-Pd and TIPP-Ni-Pd) have been prepared to verify this facile synthetic strategy for the first time. In order to establish a cooperative action toward the catalytic CO2 cycloaddition with epoxides, an additional tetraalkylammonium bromide functionality has also been incorporated into these polymeric structures through the N-substituent of the NHC moieties. The resulting heterogeneous bimetallic catalyst TIPP-Zn-Pd exhibits the best catalytic performance in CO2 cycloaddition with styrene oxide (SO) under solvent-free conditions at atmospheric pressure and is applicable to a wide range of epoxides. More importantly, TIPP-Zn-Pd works smoothly and is recyclable in the absence of a cocatalyst under 1.0 MPa of CO2 at 60 °C. This indicates that TIPP-Zn-Pd is quite competitive with the reported heterogeneous catalysts, which typically require a high reaction temperature above 100 °C under cocatalyst-free conditions. Thus, this work provides a new approach to design heterogeneous bimetallic PCP catalysts for high-performance CO2 fixation under mild reaction conditions.

Postsynthetic Modification of Half-Sandwich Ruthenium Complexes by Mechanochemical Synthesis.

A mild and environmentally friendly method to synthesize half-sandwich ruthenium complexes through the Wittig reaction between an aldehyde-tagged half-sandwich ruthenium complex and phosphorus ylide mechanochemically is reported herein. The mechanochemical synthesis of valuable half-sandwich ruthenium complexes resulted in a fast reaction, good yield with simple workup, and the avoidance of harsh reaction conditions and organic solvents. The synthesized half-sandwich ruthenium complexes exhibited high catalytic activity for transfer hydrogenation of ketones using 2-propanol as the hydrogen source and solvent. Density functional theory was carried out to propose a mechanism for the transfer hydrogenation process. The modeling suggests the importance of the labile p-cymene ligand in modulating the reactivity of the catalyst.

Lipoprotein A, combined with alanine aminotransferase and aspartate aminotransferase, contributes to predicting the occurrence of NASH: a cross-sectional study.

BACKGROUND: Nonalcoholic steatohepatitis (NASH) progresses from simple nonalcoholic fatty liver (NAFL) and has a poor prognosis. Abnormal lipid metabolism is closely related to the occurrence and development of nonalcoholic fatty liver disease (NAFLD). This study aimed to study the relationships between serum lipid metabolites and NASH, and to improve the early diagnosis of NASH. METHODS: This study included 86 NAFLD patients (23 NASH and 63 NAFL), and 81 unaffected individuals as controls from West China Hospital between October 2018 and May 2019. With lipid metabolites as the focus of the study, the differences in lipid metabolites were compared between the control group, NAFL patients, and NASH patients. Logistic regression analysis was used to examine the risk factors of NASH. Finally, receiver operating characteristic curve (ROC curve) was used to analyze the efficacy of the metabolites in NASH prediction. RESULTS: The levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), and lipoprotein A (LPA) increased with the severity of NAFLD. In NAFLD patients, LPA (OR:1.61; 95%CI: 1.03-2.52) was a potential risk factor for NASH, and ROC analysis showed that the combination of LPA, ALT, and AST had a greater predictive efficiency for NASH. CONCLUSIONS: Abnormal apolipoprotein/lipoprotein is closely related to lipid metabolism disorder in patients with NAFLD. In NAFL, the combination of LPA, ALT, and AST contributes to predicting the occurrence of NASH. LPA may be a potential biomarker and therapeutic target for diagnosing and treating NASH.

A ruthenium bisoxazoline complex as a photoredox catalyst for nitro compound reduction under visible light.

An unreported ruthenium(ii) complex containing bisoxazoline ligands has been synthesized and characterized. To test the catalytic ability of the ruthenium complex, the synthesis of anilines from nitro compounds in the presence of a mild reducing agent sodium borohydride and visible light has been developed. Mechanistic studies involving the experiment and DFT calculations suggest that the reaction could involve a radical pathway with the assistance of a photoredox catalyst.

Coordination-driven self-assembly vs dynamic covalent chemistry: versatile methods for the synthesis of molecular metallarectangles.

Supramolecular coordination assemblies have a range of potential applications in chemical and biological sciences. Herein, simple modular methods for the synthesis of metallarectangles are described. The desired tetranuclear metallarectangles were synthesized by using coordination-driven self-assembly of half-sandwich rhodium-based organometallic clip units and organic ligands. The reaction of such an organometallic clip with 4-formylpyridine provided a dinuclear molecular tweezer with pendant aldehyde groups, and subsequent [4 + 4] condensation reactions with diamines provides another route to the target metallarectangles in good yields. The same assemblies can also be easily isolated in one-pot procedures by mixing the organometallic clip, diamines and 4-formylpyridine.

[Identification and preparation of a glycol-protein fraction AN from tea extracts and its in vivo and in vitro anti-hyperglycosemia activity].

The present study compared active ingredients of tea from different sources to select tea type and the fraction of tea extracts for the highest anti-hyperglycemic activity, and to verify anti-hyperglycemic activity of the selected tea extract. Tea extracts were separated and enriched by molecular weight using ultra-filtration technology. The extracts were first screened by α-glucosidase inhibition assay, followed by using a rat inverted intestine sac system to measure the effect on glucose transport. Both alloxan-induced diabetic rat model and high-fat diet combined with streptozotocin-induced rat diabetes mellitus model were used to study the effects of active components on blood glucose, body weight, insulin resistance. The experimental results showed that the different kinds of tea extracts had different inhibitory effects on α-glucosidase, and the inhibitory effect of tea extract E on α-glucosidase was stronger. The effects of different components of tea extract E also varied greatly, of which Fraction AN protein had stronger inhibitory effect on α-glucosidase than other fragments, and Fraction AN protein had a strong inhibitory effect on glucose transport, reduced blood sugar and normalized insulin secretion in diabetic rats. The results suggest that a glycol-protein fraction(AN) from the extracts might be responsible for the anti-hyperglycemic activity of tea polysaccharides. The AN glycol-protein fraction has strong inhibitory effects on both α-glucosidase activity and glucose transport by the small intestine. It also reduced blood glucose level and normalized insulin secretion in diabetic rats, and has a protective effect on diabetic rats.

Half-sandwich cycloruthenated complexes from aryloxazolines: synthesis, structures, and catalytic activities.

Seven half-sandwich cycloruthenated complexes [Ru(p-cymene)LCl] (2a-2g) (L = 2-phenyl-2-oxazoline (2a), 2-p-tolyl-4,5-dihydrooxazole (2b), 4,4-dimethyl-2-phenyl-2-oxazoline (2c), 2-(4-chlorophenyl)-4,5-dihydrooxazole (2d), 2-(4-bromophenyl)-4,5-dihydrooxazole (2e), 2-(4-fluorophenyl)-4,5-dihydrooxazole (2f) and 2-(4-nitrophenyl)-4,5-dihydrooxazole (2g)) were synthesized and characterized. All half-sandwich cycloruthenated complexes were fully characterized by (1)H and (13)C NMR spectra, elemental analyses and infrared spectroscopy. The molecular structures of 2a, 2d and 2e were confirmed by single-crystal X-ray diffraction methods. These half-sandwich cycloruthenated complexes were employed in nitroarene reduction using sodium borohydride (NaBH4) as a reducing agent in ethanol at room temperature. The catalytic results indicate that half-sandwich cycloruthenated complexes show promising catalytic activity in nitroarene reduction with a broad substrate and varied functional group compatibility.

Crystal structure of 3,3'-diisopropyl-1,1'-(pyridine-2,6-di-yl)bis-[1H-imidazole-2(3H)-thione].

In the title compound, C17H21N5S2, the dihedral angles between the central pyridine ring and its pendant imidazole rings are 29.40 (9) and 40.77 (9)°; the pendant rings are twisted in an opposite sense with respect to the central ring. In each case, the S atom is approximately anti to the N atom of the pyridine ring. For both substituents, the H atom attached to the central C atom of the isopropyl group is approximately syn to the S atom in the attached ring. In the crystal, mol-ecules are linked by weak C-H⋯S inter-actions, generating C(5) chains propagating along [001].

Six Zn(II) and Cd(II) coordination polymers assembled from a similar binuclear building unit: tunable structures and luminescence properties.

Six Zn(ii) and Cd(ii) coordination polymers were constructed by treating a 2-substituted 8-hydroxyquinolinate ligand containing a pyridyl group with zinc or cadmium salts, and characterized by a variety of techniques. Interestingly, based on a similar binuclear Zn(ii) or Cd(ii) building unit, the supramolecular structures of the six coordination polymers () exhibit an unprecedented structural diversification due to the different choices of metal salts. and represent a novel 2D framework containing 1D infinite right- and left-handed helical chains. and are 2D coordination frameworks based on binuclear Cd(ii) building units. For and , the L ligands can bridge binuclear building units forming a 1D infinite chain. Interestingly, the adjacent Cd2O2 planes of the 1D chain in are in parallel with each other, while the dihedral angle between the two Zn2O2 planes in is 83.43°. Photoluminescence properties revealed that the six coordination polymers exhibit redshifted emission maximum compared with the free ligand HL, which can be ascribed to an increased conformational rigidity and the fabrication of coplanar binuclear building units M2L2 in . Coordination polymers also display distinct fluorescence lifetimes and quantum yields because of their different metal centers and supramolecular structures.

Synthesis and characterization of bisoxazolines- and pybox-copper(II) complexes and their application in the coupling of α-carbonyls with functionalized amines.

Binuclear complexes [{(DMOX)CuCl}2(µ-Cl)2] (1), mononuclear complexes [(DMOX)CuBr2] (2) (DMOX = 4,5-dihydro-2-(4,5-dihydro-4,4-dimethyloxazol-2-yl)-4,4-dimethyloxazole) and the pybox Cu(II) complex [(Dm-Pybox)CuBr2] (3) (Dm-Pybox = 2,6-bis[4',4'-dimethyloxazolin-2'-yl]pyridine) were obtained by reactions of CuX2 (X = Cl, Br) with DMOX and Dm-Pybox ligands, respectively. The molecular structures of 1, 2 and 3 have been determined by single-crystal X-ray diffraction analyses. The complexes 2 and 3 are efficient in catalyzing α-amination of ketones and esters through α-bromo carbonyl intermediate. The procedures are environmentally benign methods using molecular oxygen as an oxidant with water as the only byproduct.

Half-sandwich Ir-based neutral organometallic macrocycles containing pyridine-4-thiolato ligands.

Neutral organometallic cyclic tri- and tetra-nuclear half-sandwich iridium complexes and , connected with pyridine-4-thiolato ligands, were synthesized and characterized by X-ray crystallography.

Stepwise formation of organometallic macrocycles, prisms and boxes from Ir, Rh and Ru-based half-sandwich units.

Over the past decade, supramolecular compounds with organometallic Ir, Rh, Ru based half-sandwich complexes have received considerable attention as materials with a variety of potential applications. The major emphasis of this tutorial review lies on the self-assembly of such organometallic half-sandwich molecular rectangles, prisms and cages with half-sandwich corners and two different rigid bifunctional ligands using an approach of stepwise construction. Synthetic methods and the structural and functional properties of the target complexes are discussed in detail.

Helicobacter pylori infection in the gastric mucosa of patients with HIV/AIDS in different clinical stages / 南方医科大学学报

<p><b>OBJECTIVE</b>To analyze Helicobacter pylori infection in the gastric mucosa of patients with HIV/AIDS in different clinical stages.</p><p><b>METHODS</b>This study involved 170 patients with HIV/AIDS and 34 HIV-negative patients. All the patients underwent upper endoscopy and antral gastric biopsy to determine the status of Helicobacter pylori infection using aniline red staining and rapid urease test. The patients with HIV/AIDS were stratified based on CD4(+)T lymphocyte counts and clinical setting into asymptomatic HIV infection (A1, A2) group, symptomatic HIV infection (B1, B2) group and AIDS (A3, B3, C1-3) group.</p><p><b>RESULTS</b>The prevalence of Helicobacter pylori infection in HIV/AIDS patients was 16.5% (28/170), and in the 3 groups classified, the infection rates were 23.4% (11/47), 14.0% (8/57), and 13.6% (9/66), respectively; the infection rate was 47.1% (16/34) in the control group. Helicobacter pylori infection rate in the gastric mucosa of the patients with HIV/AIDS in different clinical stages was significantly lower than that of the control group (P<0.05); the infection rates in symptomatic HIV-infected (B1, B2) group and AIDS (A3, B3, C1-3) group were significantly lower than that in asymptomatic HIV-infected (A1, A2) group (P<0.05).</p><p><b>CONCLUSION</b>The low Helicobacter pylori infection rate in HIV/AIDS patients may result from severe immunodeficiency in the gastric mucosa.</p>

Syntheses and structures of half-sandwich iridium(III) and rhodium(III) complexes with organochalcogen (S, Se) ligands bearing N-methylimidazole and their use as catalysts for norbornene polymerization.

The organochalcogen ligands derived from 3-methyl-imidazole-2-thione/selone groups, Mbit, Mbis, Ebit and Ebis [Mbit = 1,1'-methylenebis(3-methyl-imidazole-2-thione); Mbis = 1,1'-methylenebis(3-methyl-imidazole-2-selone), Ebit = 1,1'-(1,2-ethanediyl)bis(3-methyl-imidazole-2-thione), Ebis = 1,1'-(1,2-ethanediyl)bis(3-methyl-imidazole-2-selone)] have been synthesized and characterized. Reactions of [Cp*Ir(micro-Cl)Cl]2 and [Cp*Rh(micro-Cl)Cl]2 (Cp* = eta5-pentamethylcyclopentadienyl) with Mbit, Mbis, Ebit and Ebis result in the formation of the complexes [Cp*Ir(Mbit)Cl]Cl 1a x Cl), [Cp*Ir(Mbis)Cl]Cl (3a x Cl), [Cp*Ir(Ebit)Cl]Cl (1b x Cl), [Cp*Ir(Ebis)Cl]Cl (2a x Cl), [Cp*Rh(Mbit)Cl]Cl (2b x Cl), Cp*Rh(Mbis)Cl][Cp*RhCl(3)] (3b x[Cp*RhCl(3)]), [Cp*Rh(Ebit)Cl]Cl (4a x Cl) and [Cp*Rh(Ebis)Cl]Cl (4b x Cl), respectively. All compounds have been characterized by elemental analysis, NMR and IR spectra. The molecular structures of 1b, 2b, 3a, 3b and 4a have been determined by X-ray crystallography. After activation with methylaluminoxane (MAO), the iridium complexes exhibit moderate activities for the vinyl polymerization of norbornene.

Template-controlled topochemical photodimerization based on "organometallic macrocycles" through single-crystal to single-crystal transformation.

Organometallic macrocycles and undergo [2+2] photochemical cycloaddition to form and in quantitative yield, accompanied by a single-crystal to single-crystal transformation.

[The feasibility exploration of cultured newborn rat ventricular myocyte taking the place of acutely enzymatic isolated myocardium for study in electrophysiology of pacemaker current].

OBJECTIVE: To investigate the feasibility of cultured rat ventricular myocytes taking the place of acutely enzymatic isolated myocardia for study in the pacemaker current electrophysiology. METHODS: By using patch-clamp technique, the whole-cell pacemaker currents were recorded to study the difference of pacemaker current electrophysiology between neonatal rat ventricular myocytes isolated acutely and maintained in cell culture. RESULTS: The cell membrane capacitances (Cm) were significantly decreased in myocardia even upon short term of cell culture. The Cm of myocardia cultured 1-3 day were (43 +/- 3) pF, with decreased 23% compared to acute enzymatic isolated cells C(56+/-7) pF, P<0. 013. It seemed like the Cm increased slightly upon cell cultured time, but no significant difference appearing among various culture stages (P > 0. 05) . No significant difference of pacemaker current electrophysiological character, such as reverse potential, current density, active threshold and V0.5, was detected from different cell group (P>0. 05). CONCLUSION: The cultured myocardium can take place of acute enzymatic isolated myocardium used to study in pacemaker current. The cells cultured no more than one week may be more suitable to this kind of electrophysiological experiment.

Association of serum leptin and insulin resistance with nonalcoholic fatty liver disease / 南方医科大学学报

<p><b>OBJECTIVE</b>To investigate the relationship among serum leptin, homeostasis model assessment of insulin resistance (HOMA-IR), body mass index (BMI) and dyslipidema in patients with nonalcoholic fatty liver disease (NAFLD).</p><p><b>METHODS</b>Eighty-two patients with NAFLD were divided into mild, moderate and severe NAFLD groups according histological examination results of the liver. Twenty healthy volunteers were chosen as the normal control (NC) group. Fasting insulin, glucose, leptin and lipid levels were measured in the 82 patients with NAFLD and the BMI calculated. IR index of the patients was calculated according to the HOMA method.</p><p><b>RESULTS</b>Leptin, HOMA-IR index, BMI and dyslipidemia showed significant differences between NAFLD and NC groups (P<0.05 or 0.01). Leptin and HOMA-IR index increased with the exacerbation of NAFLD, both of which were positively correlated with the severity of NAFLD.</p><p><b>CONCLUSION</b>Increased leptin level, HOMA-IR, BMI and dyslipidemia can be important risk factors of NAFLD, and serum leptin level and HOMA-IR are positively correlated with the severity of NAFLD.</p>