Synthesis and structure of novel 6-(pyrazol-1-yl)-4-methyl-1H-pyrazolo[3,4-b]pyridin-3-ol derivatives

New 6-(pyrazol-1-yl)pyrazolo[3,4-b]pyridin-3-ol compounds were synthesized by cyclization reaction from 2,6-dichloro-4-methylnicotinonitrile. Their derivatives exist as the 3-hydroxy tautomer. The structure of the compound 1a of one of the resulting compounds was studied in detail by X-ray diffraction.     

高效液相色谱法测定强化食品中维生素C的含量

建立了强化食品(饮料、奶粉、含乳饮料、大米、果泥及果冻)中维生素C含量的高效液相色谱检测方法。优化了样品处理方法,在水浴控温和避光条件下处理样品,避免维生素C被氧化。选用Tech Mate C18–ST(250 mm×4.6 mm,5μm)反相色谱柱,以0.05 mol/L磷酸二氢钾缓冲溶液(p H 3)为流动相,流量为1.0m L/min,检测器为光电二极管阵列检测器,检测波长为266 nm。线性范围为0.2~100μg/m L,相关系数为0.999 6,果泥中维生素C的定量限为20 mg/kg,其它为100 mg/kg,加标回收率为82.2%~107%,测定结果的相对标准偏差为1.23%~6.86%(n=8)。该方法简单快速,其灵敏度、准确度和精密度均能满足强化食品中维生素C的检测要求。     

A Dual‐Ligand Porous Coordination Polymer Chemiresistor with Modulated Conductivity and Porosity

Single‐ligand‐based electronically conductive porous coordination polymers/metal–organic frameworks (EC‐PCPs/MOFs) fail to meet the requirements of numerous electronic applications owing to their limited tunability in terms of both conductivity and topology. In this study, a new 2D π‐conjugated EC‐MOF containing copper units with mixed trigonal ligands was developed: Cu₃(HHTP)(THQ) (HHTP=2,3,6,7,10,11‐hexahydrotriphenylene, THQ=tetrahydroxy‐1,4‐quinone). The modulated conductivity (σ≈2.53×10^?5 S cm^?1 with an activation energy of 0.30 eV) and high porosity (ca. 441.2 m² g^?1) of the Cu₃(HHTP)(THQ) semiconductive nanowires provided an appropriate resistance baseline and highly accessible areas for the development of an excellent chemiresistive gas sensor.     

Enantiomeric Discrimination by Surface‐Enhanced Raman Scattering–Chiral Anisotropy of Chiral Nanostructured Gold Films

A surface‐enhanced Raman scattering‐chiral anisotropy (SERS‐ChA) effect is reported that combines chiral discrimination and surface Raman scattering enhancement on chiral nanostructured Au films (CNAFs) equipped in the normal Raman scattering Spectrometer. The CNAFs provided remarkably higher enhancement factors of Raman scattering (EFs) for particular enantiomers, and the SERS intensity was proportional to the enantiomeric excesses (ee) values. Except for molecules with mesomeric species, all of the tested enantiomers exhibited high SERS‐ChA asymmetry factors (g), ranging between 1.34 and 1.99 regardless of polarities, sizes, chromophores, concentrations and ee. The effect might be attributed to selective resonance coupling between the induced electric and magnetic dipoles associated with enantiomers and chiral plasmonic modes of CNAFs.     

High‐Tc Enantiomeric Ferroelectrics Based on Homochiral Dabco‐derivatives (Dabco=1,4‐Diazabicyclo[2.2.2]octane)

1,4‐Diazabicyclo[2.2.2]octane (dabco) and its derivatives have been extensively utilized as building units of excellent molecular ferroelectrics for decades. However, the homochiral dabco‐based ferroelectric remains a blank. Herein, by adding a methyl (Me) group accompanied by the introduction of homochirality to the [H₂dabco]²⁺ in the non‐ferroelectric [H₂dabco][TFSA]₂ (TFSA=bis(trifluoromethylsulfonyl)ammonium), we successfully designed enantiomeric ferroelectrics [R and S‐2‐Me‐H₂dabco][TFSA]₂. The two enantiomers show two sequential phase transitions with transition temperature (T_c) as high as 405.8 K and 415.8 K, which is outstanding in both dabco‐based ferroelectrics and homochiral ferroelectrics. To our knowledge, [R and S‐2‐Me‐H₂dabco][TFSA]₂ are the first examples of dabco‐based homochiral ferroelectrics. This finding opens an avenue to construct dabco‐based homochiral ferroelectrics and will inspire the exploration of more eminent enantiomeric molecular ferroelectrics.     

Aligning retention time shifts in HPLC three‐dimensional spectra by icoshift approach combined with data arrangement methods and the release of a graphical user interface

High‐performance liquid chromatography coupled with photodiode array detection has been extensively applied in many fields and the peaks among the analyzed samples can be shifted due to the variations of instrumental and experimental conditions. In multivariate analysis, retention time alignment is an important pretreatment step. Hence, the shifted peaks in high‐performance liquid chromatography coupled with photodiode array detection three‐dimensional spectra should be aligned for further analysis. Being motivated by this purpose, the interval correlated shifting method combined with the proposed data arrangement methods are recommended and employed on high‐performance liquid chromatography coupled with photodiode array detection data as a demonstration. We validate the alignment performance of the proposed method through comparison the consistency of the retention time before and after alignment. The obtained results demonstrated that the proposed method is capable of successful aligning the employed data. Additionally, the interval correlated shifting method combined with the data arrangement modes is implemented in an easy‐to‐use graphical user interface environment and so can be operated easily by users not familiar with programming languages.     

Three New Isoprenylated 2‐Arylbenzofurans from Artocarpus petelotii

Three new isoprenylated 2‐arylbenzofurans, artopetelins A–C ( 1 – 3 ), were isolated as minor constituents from the EtOH extract of the root barks of Artocarpus petelotii Gagnep . Their structures were elucidated by spectroscopic methods, including HR‐EI‐MS and 2D‐NMR techniques.     

Three Octacyanometallate‐Based LnIII–MV (Ln = La,Ce; M = Mo,W) Bimetallic Assemblies with a One‐Dimensional Rope‐Ladder Chain Structure

Three octacyanometallate‐based hetero‐bimetallic complexes, [Ln(H₂O)₄(CH₃CN)₂][M(CN)₈] · CH₃CN [Ln = La, M = Mo( 1 ), W( 2 ); Ln = Ce, M = W( 3 )], were synthesized and characterized structurally. Single‐crystal X‐ray analysis reveals that 1 – 3 are isomorphous and consist of infinite one‐dimensional (1D) 3,3 rope‐ladder chains, in which the 12‐membered puckered square Ln₂M₂(CN)₄ is the basic building unit. The 1D chains are further linked through interchain hydrogen bonds, resulting in a three‐dimensional (3D) supramolecular network.     

Improved free space optical communications performance by using time diversity

A laser beam propagating through turbulence experiences random amplitude and phase fluctuations, which can severely degrade the performance of free space optical communication systems. It this letter, time diversity is demonstrated as a technique which can decrease turbulence influence. Statistically, laser propagation along an atmospheric path is uncorrelated with an earlier-time path for a time interval greater than the atmospheric turbulence correlation time. To estimate time diversity system performance, a 2.2-km optical link is set up for comparing the fade probability of a system using time diversity with a system not using time diversity. The experimental results obtained under different turbulence conditions are shown which are in good agreement with the theory.