Inside Cover: From Reactivity and Regioselectivity to Stereoselectivity: An Odyssey of Designing PIP Amine and Related Directing Groups for C—H Activation (Chin. J. Chem. 7/2019)

The inside cover picture shows the journey of developing PIP amine directing group for C—H activation, from controlling the reactivity and diastereoselectivity to enantioselectivity. In the presence of Pd or base metal catalysts, PIP amine enabled the activation of inert C—H bonds to form diverse C—C and C—heteroatom bonds. Its tuneable structure has triggered the design of chiral auxiliaries for diastereoselective C—H activation. More recently, enantioselective activation of unbiased methylene C—H bonds has been achieved by cooperative effects between PIP amine and axial chiral ligands. More details are discussed in the article by Shi et al. on page 647–656.

     

Flow Injection Chemiluminescence for the Determination of Estriol via a Noncompetitive Enzyme Immunoassay

A novel approach to the detection of estriol using a flow injection system coupled to enhanced chemiluminescent immunoassay was developed based on noncompetitive immunoassay formats. A conjugated estriol-ovalbumin immobilized immunoaffinity column was inserted into the flow system to trap the unbound horseradish peroxidase (HRP)-labeled antibody after an off-line incubation of estriol and HRP-labeled anti-estriol antibody. The trapped enzyme conjugate was detected by the injection of chemiluminescent substrates to produce enhanced chemiluminescence. The linear range for the determination of estriol is 10.0 to 400 ng · mL⁻¹ with a correlation coefficient of 0.996 and a detection limit of 5.0 ng · mL⁻¹. The total time for sampling and chemiluminescent detection of one sample is 400 seconds after 30 min of pre-incubation. The results for pregnancy serum samples obtained by this method are in good agreement with those obtained using ELISA.     

Synthesis and Structure of MnCl2(HDpyF) (HDpyF = N,N′‐di(2‐pyridyl)formamidine): New Crystallographic Disorder and Bonding Mode of the HDpyF Ligand

The reaction of N,N′‐di(2‐pyridyl)formamidine (HDpyF) with MnCl₂‐4H₂O afforded the complex MnCl₂(HDpyF), which was characterized by X‐ray crystallography. The HDpyF ligand chelates to the Mn(II) center through the first and the third nitrogen atoms to form a six‐membered ring, leaving the second and the fourth nitrogen atoms uncoordinated. The HDpyF ligand is crystallographically disordered such that two different molecules can be solved. The neutral HDpyF ligand adopts the new s‐cis‐syn‐s‐trans conformation.     

Neue Kupferkomplexe mit Phosphaalkenliganden. Molekülstruktur von [Cu{P(Mes*)C(NMe2)2}2]BF4 (Mes* = 2,4,6‐tBu3C6H2)

New Copper Complexes Containing Phosphaalkene Ligands. Molecular Structure of [Cu{P(Mes*)C(NMe₂)₂}₂]BF₄ (Mes* = 2,4,6‐tBu₃C₆H₂) Reaction of equimolar amounts of the inversely polarized phosphaalkene tBuP=C(NMe₂)₂ ( 1a ) and copper(I) bromide or copper(I) iodide, respectively, affords complexes [Cu₃X₃{μ‐P(tBu)C(NMe₂)₂}₃] ( 2 ) (X =Br) and ( 3 ) (X = I) as the formal result of the cyclotrimerization of a 1:1‐adduct. Treatment of 1a with [Cu(L)Cl] (L = PiPr₃; SbiPr₃) leads to the formation of compounds [CuCl(L){P(tBu)C(NMe₂)₂}] ( 4a ) (L = PiPr₃) and ( 4b ) (L = SbiPr₃), respectively. Reaction of [(MeCN)₄Cu]BF₄ with two equivalents of PhP=C(NMe₂)₂ ( 1b ) yields complex [Cu{P(Ph)C(NMe₂)₂}₂]BF₄ ( 5b ). Similarly, compounds [Cu{P(Aryl)C(NMe₂)₂}₂]BF₄ ( 5c (Aryl = Mes and 5d (Aryl = Mes*)) are obtained from ArylP=C(NMe₂)₂ ( 1c : Aryl = Mes; 1d : Mes*) and [(MeCN)₄Cu]BF₄ in the presence of SbiPr₃. Complexes 2 , 3 , 4a , 4b , and 5b‐5d are characterized by means of elemental analyses and spectroscopy (¹H‐, ¹³C{¹H}‐, ³¹P{¹H}‐NMR). The molecular structure of 5d is determined by X‐ray diffraction analysis.     

A zwitterion of 1,5‐bis­(2‐hydroxy­benzamido)‐3‐aza­pentane: a two‐dimensional hydrogen‐bonding network involving dimers

The title compound, 2‐{N‐[2‐(2‐hydroxy­benzamido)ethyl­ammonio­ethyl]amino­carbon­yl}phenolate, C₁₈H₂₁N₃O₄, crystallizes in a zwitterionic form as a result of inter­molecular proton transfer and possesses a negatively charged phenolate group and a protonated amino group. The 2‐hydroxy­benzamide and 2‐(amino­carbonyl)­phenolate moieties attached to the two ends of the C—C—N—C—C backbone adopt a cis conformation in relation to this backbone. All N‐ and O‐bound H atoms are involved in hydrogen‐bond formation; the zwitterions are first linked into head‐to‐tail dimers, which are further organized into a two‐dimensional network parallel to the crystallographic bc plane.     

A Novel Dinuclear Nickel(II) Complex with Three Bridges of Cl–, OAc– and (‐OCH2CH2O‐) Group of N,N, N′, N′‐Tetrakis(2‐benzimidazolyl methyl‐1, 4‐di‐ethylene amino) Glycol Ether

The novel dinuclear Ni²⁺ complex [Ni₂(μ‐Cl)(μ‐OAc) (EGTB)]·Cl·ClO₄·2CH₃OH, where EGTB is N, N, N′, N′‐tetrakis (2‐benzimidazolyl methyl‐1, 4‐di‐ethylene amino)glycol ether, crystallizes in the orthorhombic space group Pnma with a = 15.272(2), b = 14.768(2), c = 22.486(3) Å, V = 5071.4(12) ų, Z = 4, D_calc = 1.414 g cm^?3, and is bridged by triply bridging agents of a chloride ion, an acetate and an intra‐ligand (‐OCH₂CH₂O‐) group. The nickel coordination geometry is that of a slightly distorted octahedron with a NiN₃O₂Cl arrangement of the ligand donor atoms. The Ni–Cl distance is 2.361(2) Å, and two Ni–O distances are 1.996(5) and 2.279(6) Å. The three Ni–N distances are 2.033(7), 2.060(6), and 2.166(6) Å with the Ni–N bond trans to an ether oxygen the shortest, the Ni–N bond trans to an acetate oxygen the middle and the Ni–N bond trans to Cl the longest.     

Preparation and Properties of Nickel and Iron Oxides obtained by Calcination of Layered Double Hydroxides

A constant pH precipitation method has been applied to obtain solids with Ni/Fe molar ratios of 2/1, 3/2, 1/1, 2/3, and 1/2. In all cases, a phase with the hydrotalcite‐like structure is obtained, containing Ni^II and Fe^III in the brucite‐like layers and carbonate in the interlayer, and, for samples with a Ni/Fe molar ratio lower than 2/1, amorphous hydrated iron oxides, undetected by X‐ray diffraction, are also formed. The solids have been characterized by element chemical analysis, powder X‐ray diffraction, differential thermal analysis, thermogravimetric and differential thermogravimetric analysis, FT‐IR spectroscopy, temperature‐programmed reduction and assessment of specific surface area by nitrogen adsorption at ?196 °C. In all cases reduction leads to zero‐valent state for the metals, reduced nickel particles probably favouring reduction of Fe^III species; the specific surface area increases with the iron content, probably due to the amorphous nature of the hydrated iron oxides formed. Calcination at 1200 °C in air leads to well crystallized solids, formed by NiFe₂O₄ spinel and, additionally, rocksalt‐type NiO for Ni/Fe ratios larger than 1/2. In this way, solids with tailored compositions of these two phases can be prepared.     

Study of the first nucleation steps of thin films by XPS inelastic peak shape analysis

The initial steps in the formation of thin films have been investigated by analysis of the peak shape (both inelastic background and elastic contributions) of X‐ray photoelectron spectra. Surface coverage and averaged height of the deposited particles have been estimated for several overlayers (nanometre range) after successive deposition cycles. This study has permitted the assessment of the type of nucleation and growth mechanisms of the films. The experiments have been carried out in situ in the preparation chamber of an XPS spectrometer. To check the performance of the method, several materials (i.e. cerium oxide, vanadium oxide and cadmium sulfide) have been deposited on different substrates using a variety of preparation procedures (i.e. thermal evaporation, ion beam assisted deposition and plasma enhanced chemical vapour deposition). It is shown that the first deposited nuclei of the films are usually formed by three‐dimensional particles whose heights and degree of surface coverage depend on the chemical characteristics of the growing thin film and substrate materials, as well as the deposition procedure. It is concluded that XPS peak shape analysis can be satisfactorily used as a general method to characterize morphologically the first nanometric moieties that nucleate a thin film. Copyright © 2006 John Wiley & Sons, Ltd.     

A novel high-performance fourier transform ion cyclotron resonance cell for improved biopolymer characterization

A new trapped ion cell design for use with Fourier transform ion cyclotron resonance mass spectrometry is described. The design employs 15 cylindrical ring electrodes to generate trapping potential wells and 32 separately assignable rod electrodes for excitation and detection. The rod electrodes are positioned internal to the ring electrodes and provide excitation fields that are thereby linearized along the magnetic field over the entire trapped ion volume. The new design also affords flexibility in the shaping of the trapping field using the 15 ring electrodes. Many different trapping well shapes can be generated by applying different voltages to the individual ring electrodes, ranging from quadratic to linearly ramped along the magnetic field axis, to a shape that is nearly flat over the entire trap volume, but rises very steeply near the ends of the trap. This feature should be useful for trapping larger ion populations and extension of the useful range of ion manipulation and dissociation experiments since the number of stages of ion manipulation or dissociation is limited in practice by the initial trapped ion population size. Predicted trapping well shapes for two different ring electrode configurations are presented, and these and several other possible configurations are discussed, as are the predicted excitation fields based on the use of rod electrodes internal to the trapping ring electrodes. Initial results are presented from an implementation of the design using a 3.5 T superconducting magnet. It was found that ions can be successfully trapped and detected with this cell design and that selected ion accumulation can be performed with the utilization of four rods for quadrupolar excitation. The initial results presented here illustrate the feasibility of this cell design and demonstrate differences in observed performance based upon different trapping well shapes.     

Development of a new reaction system for the synthesis of highly optically active alpha,gamma-substituted gamma-butyrolactones

A highly useful method for the synthesis of optically active alpha,gamma-substituted gamma-butyrolactones has been developed. The SmI(2)-induced reductive coupling of chiral 2-alkyl acrylates derived from isosorbide with ketones in the presence of (1S)-(-)-2,10-camphorsultam as a proton source give the chiral alpha,gamma-substituted gamma-butyrolactones in good yields and high enantiomeric purities (up to >99% ee for trans and 75% ee for cis). The reaction system has been investigated with various ketones, and it is demonstrated that this system is very effective for trans-alpha,gamma-substituted gamma-butyrolactones. Both the chiral auxiliary and the hindered proton source in this system are necessary for the observed excellent ee values of the products. The absolute configuration of the trans products is assigned on the basis of the X-ray crystal structure.