Coumarin salen-based zinc complex for solvent-free ring opening polymerization of ε-caprolactone

A new zinc complex based on a tetradentate N,N,O,O-type coumarin salen ligand (H₂L) was prepared and characterized by elemental analysis, thermogravimetric analysis (TGA), and FT-IR, UV–vis and ¹H NMR spectroscopy. The complex [Zn(L)(H₂O)]·H₂O was active in the ring opening polymerization (ROP) of ε-caprolactone under solvent-free conditions, producing polycaprolactone (PCL) with a molecular weight up to 17,700 g mol^?1 and a narrow molecular weight distribution. ¹H NMR analysis showed that the PCL obtained was mainly linear, having hydroxymethylene groups in the chain ends. Differential scanning calorimetry (DSC) showed that the polymer had high crystallinity (61%) and that TGA had a decomposition temperature above 300 °C.     

Sensitive detection of thyroid stimulating hormone by inkjet printed microchip with a double signal amplification strategy

In this paper, we reported a sensitive electrochemical immunosensor coupling protein A/G@magnetic beads and an ALP-based enzymatic-electrochemical reaction on the inkjet printing microchips for the determination of thyroid stimulating hormone.     

G-quadruplex-assisted enzyme strand recycling for amplified label-free fluorescent detection of UO22+

A G-quadruplex-assisted enzyme strand recycling strategy was developed for amplified label-free fluorescent detection of uranyl ion (UO₂²⁺).     

Novel method for the synthesis of dinucleoside-(N3′ → P5′)-phosphoramidothioates

A new approach for the synthesis of dinucleoside-(N3′ → P5′)-phosphoramidothioates based on the Atherton–Todd reaction has been developed using nucleoside H-thiophosphonates and 3′-amino-2′,3′-dideoxynucleosides with an unprotected 5′-hydroxyl group. A mixture of P-diastereomers of dinucleosides was separated by column chromatography into fast migrating and slow migrating isomers. Based on single crystal X-ray diffraction analysis, the absolute configuration at the phosphorus atom in the slow eluting diastereomer of the dinucleoside-(N3′ → P5′)-phosphoramidothioate G_NPSG_NHTr was assigned as Rp.     

Synthesis,spectroscopic, structural and thermal characterizations of [(C7H6NO4)2TeBr6·4H2O]

Tellurium (IV) complexes with pyridine-2,6-dicarboxylate ligand were synthesized by slow evaporation from aqueous solutions yielding a new compound: [(C₇H₆NO₄)₂TeBr₆·4H₂O]. The structure of this compound was solved and refined by single-crystal X-ray diffraction. The compound is centrosymmetric P2₁/c (N°: 14) with the parameters a = 8.875(5) Å, b = 15.174(5) Å, c = 10.199(5) Å, β = 94.271° (5) and Z = 2. The structure consists of isolated H₂O, isolated [TeBr₆]^2? octahedral anions and (pyridine-2,6-dicarboxylate) [C₇H₆NO₄]⁺ cations. The stability of the structure was ensured by ionic and hydrogen bonding contacts (N–H?Br and O–H?Br) and Van-Der Walls interaction. The thermal decomposition of the compound was studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The FTIR and Raman spectroscopy at different temperatures confirm the existence of vibrational modes that correspond to the organic, inorganic and water molecular groups. Additionally, the UV–Vis diffuse reflectance spectrum was recorded in order to investigate the band gap nature. The measurements show that this compound exhibits a semiconducting behavior with an optical band gap of 2.66 eV.     

A photocleavable low molecular weight hydrogel for light-triggered drug delivery

A photocleavable low-molecular-weight hydrogelator (LMWG) was synthesized based on coumarin derivative.~1H NMR and UV spectroscopy study suggested that the gelator had good gelling ability, and the driving force for the gelation were hydrogen bonding and π-π stacking. This molecular hydrogel exhibited satisfied photocleavage at C-N bond in 7-amino coumarin with the light irradiation (365 nm,77.5 mW/cm~2). The promising photo-triggered drug release of antineoplastics cytarabine hydrochloride has been obtained, due to the photocleavage motived gel-sol transition.     

Synthesis and antiviral bioactivity of novel chalcone derivatives containing purine moiety

A series of novel chalcone derivatives containing purine group was synthesized and evaluated for their antiviral activities against cucumber mosaic virus and tobacco mosaic virus. Compound 3o exhibited remarkable antiviral activities and strong combining capacity to tobacco mosaic virus coat protein.     

Ultrafine molybdenum carbide nanoparticles supported on nitrogen doped carbon nanosheets for hydrogen evolution reaction

Nitrogen doped carbon nanosheets supported molybdenum carbides nanoparticles (Mo_xC/NCS) have been synthesized by tuning the mass ratio of melamine and ammonia molybdate. The Mo₂C/NCS-10 exhibits superior electrocatalytic performance and stability for HER, which was attributed to N-doped carbon nanosheets, small particle size, mesoporous structure, and large electrochemical active surface area.     

Nodupetide,a potent insecticide and antimicrobial from Nodulisporium sp. associated with Riptortus pedestris

Nodupetide (1), a new cyclodepsipeptide unique in its incorporation of a 3-hydroxy-4-methylhexanoic acid (HMHA) derived motif, was discovered from Nodulisporium sp. IFB-A163, a fungus residing in the insect (Riptortus pedestris) gut. The nodupetide structure was elucidated by its MS/MS and 2D NMR spectra, and its absolute configuration by the X-ray crystallography and modified Marfey’s method. Nodupetide is insecticidal against rice brown planthopper (Nilaparvata lugens) with an LD₅₀ value of 70 ng/larva, and inhibitory towards the drug-resistant human pathogenic bacterium Pseudomonas aeruginosa with its MIC value (5.0 μM) comparable to that (3.2 μM) of ciprofloxacin, a prescribed antibacterial agent co-assayed equally.     

Novel dual inhibitors against FP-2 and PfDHFR as potential antimalarial agents: Design,synthesis and biological evaluation

A series of novel 2,4-diaminopyrimidine-modified compounds was designed and synthesized. Compound 14 showed micromolar dual inhibitory effect on both FP-2 and PfDHFR, and potential inhibition to the proliferation of P. falciparum 3D7 strain and chloroquine-resistant P. falciparum Dd2 strain.     

Enantioselective synthesis of new oxazolidinylthiazolidines as enzyme inhibitors

The synthesis of new oxazolidinylthiazolidines bicycles, oxygen analogues of bisthiazolidines, also known as metallo-β-lactamase inhibitors is described. The reaction of β-aminoalcohols and 2,5-dihydroxy-1,4-dithiane led to oxazolidinylthiazolidines and/or dithioazabicycles as the main products. The distribution pattern depends mainly on the aminoalcohol substituents. In a one-pot reaction, four new bonds are formed in good yields and with high atom efficiency. When the oxazolidinylthiazolidines are formed, two stereogenic centres are generated with high enantiospecificity. The reaction mechanism is discussed based on crystallographic data and interconversion studies. Two oxazolidinylthiazolidines were evaluated as inhibitors of the potent lactamase NDM-1 and compound 4f displayed competitive inhibition with K_i = 1.6 ± 0.6 μM.     

Synthesis and antimicrobial activities of novel quinazolin-4(3H)-one derivatives containing a 1,2,4-triazolo[3,4-b][1,3,4]thiadiazole moiety

A series of novel quinazolin-4(3H)-one derivatives (6a–6y) containing a 1,2,4-triazolo[3,4-b][1,3,4]thiadiazole moiety were designed and synthesized, and their structures were fully characterized by ¹H NMR, ¹³C NMR, HRMS and IR spectra. Among them, the structure of compound 6u was unambiguously confirmed via single crystal X-ray diffraction analysis. The obtained bioassay results showed that compounds 6h, 6k, 6l and 6y had the EC₅₀ (half-maximal effective concentration) values of 34.8, 28.2, 41.5 and 42.5 μg/mL against the phytopathogenic bacterium Xanthomonas oryzae pv. oryzae (Xoo), respectively, which were significantly better than commercial bactericide Bismerthiazol (EC₅₀ = 95.8 μg/mL). Additionally, compounds 6a and 6b exhibited the strong inhibition activity against the pathogen Xanthomonas axonopodis pv. citri (Xac).     

Efficient Cu(OTf)2-catalyzed and microwave-assisted rapid synthesis of 3,4-fused chromenopyridinones under neat conditions

An efficient, solvent-free, environmentally benign, Cu(OTf)₂-catalyzed and microwave-assisted fast synthesis of a fascinating class of a number of angularly fused chromenopyridinones having a carboxylate group at C-2 position on the pyridine ring via a one-pot [3+3] annulation reaction of several aminocoumarins/cyclic β-enaminones with different kinds of γ-aryl/styryl/heteroaryl-substituted-β,γ-unsaturated α-ketoesters as Michael acceptors under open atmosphere. This eco-friendly method delivers good to excellent yields of pyridine-fused-heterocycles within (15–40 min) without using any traditional oxidants and allows several important functionalities. Furthermore, by this method, stereoselective synthesis of trans-7,8-diaryl-8.9-dihydrochromeno[4,3-b]cyclopenta[e]pyridine-6,10-diones were obtained in an excellent diastereoselective manner (dr ≤ 99:1).     

A nitroxide diradical containing a ferrocen-1,1′-diyl-substituted 1,3-diazetidine-2,4-diimine coupler

An Aza-Wittig reaction of 1,1′-bis(triphenylphosphoranylidenamino)-ferrocene with 3-isocyanato-2,2,5,5-tetramethyl-2,5-dihydro-1H-pyrrol-1-oxyl and subsequent intramolecular [2+2]-cycloaddition of the bis(carbodiimide) intermediate was used for the synthesis of a 1,3-diazetidine-2,4-diimine moiety bearing two radical groups and bridging the cyclopentadienyl (Cp) rings. According to single-crystal X-ray data, the planar 2,4-diimino-1,3-diazetidine moiety adopts a perpendicular orientation with respect to the eclipsed Cp rings. One of the radical groups lies almost within the plane of the four-membered 1,3-diazetidine ring, while the other has a conformationally preferred orientation with dihedral angles ±62.3°. The two Cp rings are constricted by the 1,3-diazetidine-2,4-diimine moiety so that the angle between their planes is 11.0°. The synthesized diradical contains ferrocene and nitroxide redox signaling units that can be oxidized step-by-step at E_1/2 = 0.26 and 0.48 V (vs Fc/Fc⁺), respectively. Electron spin resonance spectroscopy revealed a moderate exchange interaction (|J| ～ a_N) between the two nitroxide radical moieties and the following values of zero-field splitting parameters: ∣D∣ = 3.5 mT and E/D = 0 were obtained. These data were in agreement with density functional theory calculations. The newly developed approach to multispin systems may be interesting for the construction of weakly coupled rigid polyradicals for quantum technologies, the molecular design of magnets, and the creation of ferrocene-based electron-paramagnetic-resonance–active chemical sensors.     

Forced proximity of nitroxide groups in pincer compounds with a xanthene spacer

We designed bisnitroxide compounds where the radical sites are located close to each other in a molecule. Two new pincer-type bisnitroxide compounds have been synthesized, involving xanthene-4,5-diyl as a spacer and tert-butyl phenyl nitroxides as arms. From the X-ray crystal structure analysis, the shortest intramolecular interatomic N?O and O?O distances respectively are 5.074(6) and 5.258(6) Å for the m,m′-derivative and 3.624(3) and 3.771(3) Å for the p,p′-derivative. The N?O distance in the latter satisfies the empirical criterion for possible dimerization/degradation reaction accompanied by dia-/paramagnetic transition. However, the magnetic study clarified paramagnetic behavior in all the temperature range. According to a singlet-triplet model, antiferromagnetic couplings were characterized with 2J/k_B = ?7.71(2) and ?8.83(4) K for the m,m′ and p,p′-derivatives, respectively. The present result suggests that a more flexible spacer is required for realization of possible dia-/paramagnetic transition.     

Systematic trends in (0 0 1) surface ab initio calculations of ABO3 perovskites

By means of the hybrid exchange–correlation functionals, as it is implemented in the CRYSTAL computer code, ab initio calculations for main ABO₃ perovskite (0 0 1) surfaces, namely SrTiO₃, BaTiO₃, PbTiO₃, CaTiO₃, SrZrO₃, BaZrO₃, PbZrO₃ and CaZrO₃, were performed. For ABO₃ perovskite (0 0 1) surfaces, with a few exceptions, all atoms of the upper surface layer relax inward, all atoms of the second surface layer relax outward, and all third layer atoms, again, inward. The relaxation of (0 0 1) surface metal atoms for ABO₃ perovskite upper two surface layers for both AO and BO₂-terminations, in most cases, are considerably larger than that of oxygen atoms, what leads to a considerable rumpling of the outermost plane. The ABO₃ perovskite (0 0 1) surface energies always are smaller than the (0 1 1) and especially (1 1 1) surface energies. The ABO₃ perovskite AO and BO₂-terminated (0 0 1) surface band gaps always are reduced with respect to the bulk values. The B–O chemical bond population in ABO₃ perovskite bulk always are smaller than near the (0 0 1) and especially (0 1 1) surfaces.     

Anionic polymerization initiated by lithium amides for preparing high molecular weight polyacrylonitrile

Lithium amides have been proved to be effective anionic initiators for the anionic polymerization of acrylonitrile to get high molecular weight polyacrylonitrile in this study. Polyacrylonitrile with weightaverage molecular weight ranging from 1.02 × 10~6 g/mol to 1.23 ×10~6 g/mol (M_w/M_n= 1.9-2.2) could be prepared utilizing lithium amides derived from diisopropylamine, diethylamine, hexamethyldisilazane,dicyclohexylamine, and 2,2,6,6-tetramethylpiperidine as initiators. The polymerization of acrylonitrile proceeded in a homogeneous manner in N,N-di methyl for mamide and insignificant contribution of side reactions was confirmed.     

Simultaneous determination of bisphenols,benzophenones and parabens in human urine by using UHPLC-TQMS

An analytical method for the simultaneous determination of six bisphenols, five benzophenones and seven parabens by using ultra-high performance liquid chromatography coupled with triple quadrupole mass spectrometry was developed and applied for human urine sample analysis.     

Facile synthesis of α, β-unsaturated esters through a one-pot copper-catalyzed aerobic oxidation-Wittig reaction

An efficient one-pot synthesis of α, β-unsaturated esters through the aerobic oxidation – Wittig tandem reaction of alcohols and phosphorous ylide is developed. This new method operates under mild reaction conditions, and uses CuI/TEMPO (TEMPO = 2,2,6,6-tetramethylpiperidine-N-oxyl) as co-catalyst and air (O₂) as the oxidant. It tolerates a wide range of functionalized benzylic alcohol and aliphatic alcohols.     

Synthesis,spectroscopy, electrochemistry and in situ spectroelectrochemistry of partly halogenated coumarin phthalonitrile and corresponding metal-free,cobalt and zinc phthalocyanines

In this study, the preparation of novel 7-hydroxy-3-(2-chloro-4-fluorophenyl)coumarin (1), the ligand, 7-(3,4-dicyanophenoxy)-3-(2-chloro-4-fluorophenyl)coumarin (2), metal-free phthalocyanine 3 and metallophthalocyanine complexes 4 and 5 (MPcs, M = Co, Zn), β-substituted with 7-oxo-3-(2-chloro-4-fluorophenyl)coumarin functional group was achieved. By the reaction of 7-hydroxy-3-(2-chloro-4-fluorophenyl)coumarin (1) with 1,2-dicyano-4-nitrobenzen in dry DMF as the solvent in the presence of K₂CO₃ as the base, the 7-(3,4-dicyanophenoxy)-3-(2-chloro-4-fluorophenyl)coumarin (2) was synthesized. Compound 2 reacted with Co(CH₃COO)₂·4H₂O in 2-N,N-dimethylaminoethanol to furnish a novel coumarin containing cobalt(II) phthalocyanine 4. The cyclotetramerization of 2 with Zn(CH₃COO)₂·2H₂O in 2-N,N-dimethylaminoethanol gave the novel coumarin containing Zn(II)phthalocyanine 5; while tetramerization without any metal salts in 2-N,N-dimethylaminoethanol gave the metal-free phthalocyanine 3. The structures of obtained compounds were confirmed by elemental analysis, UV–Vis, IR, MALDI-TOF mass and ¹H NMR spectra. The cyclic and differential pulse voltammetry, and in situ spectroelectrochemistry of 7-oxo-3-(2-chloro-4-fuorophenyl)coumarin substituted phthalocyanines 3, 4 and 5 allowed us to identify metal- and phthalocyanine ring-based redox processes of the complexes.