Application of Protonic Acid-Doped Silica Gels to Electric Double-Layer Capacitors

Silica gels doped with several protonic acids such as HClO₄, H₂SO₄ and H₃PO₄ have been prepared by the sol-gel method and totally solid electric double-layer capacitors have been successfully fabricated using the highly proton-conductive silica gels as an electrolyte and activated carbon powder (ACP) hybridized with the silica gels as a polarizable electrode. It was found that the addition of HClO₄, which had the highest value of acid dissociation constant among these three acids, most effectively increased the proton conductivity of the resultant acid-doped silica gels. Tablets of the HClO₄-doped silica gels exhibited conductivities as high as 10^–5–10^–2 S cm^–1 at room temperature in dry N₂ atmosphere. One of the capacitors fabricated using the protonic acid-doped silica gels had a capacitance of 44 F/(gram of total ACP in the capacitor), which was comparable to those of conventional capacitors using liquid electrolytes.     

New ion exchange membrane derived from sulfochlorated polyether sulfone for electrodialysis desalination of brackish water

The purpose of this work is to study the desalination of brackish water using a new ion exchange membrane, made from sulfochlorated polyethersulfone (Cl‐PES), and crosslinked using aminated polyethersulfone (NH2‐PES) as a crosslinking reagent. This membrane, named ClNH2 membrane, has been obtained by reaction between Cl‐PES with 1.3 SO₂Cl groups per monomer unit and 0.2 equivalent amount of NH2‐PES. ClNH2 membrane has been characterized in terms of contact angle, transport number, intrinsic conductivity, and water uptake (as a function of temperature). Electrodialysis performances of the newly synthetized membranes have been measured using an electrodialysis cell at a laboratory scale and compared to commercial membranes. All the experiments have been performed using synthetic brackish water solutions prepared from sodium chloride salts with different concentrations (varying from 0.5 to 5.0 g/L). The concentration of different water samples obtained has been found to be below the amount recommended by the World Health Organization (WHO) for drinking water.     

Pd(II)/Lewis Acid Catalyzed Intramolecular Oxidative C−H Amination to Construct Carbazoles with Dioxygen

Transition-metal-catalyzed oxidative C−H amination reactions are among the most attractive topics in organic synthesis to construct nitrogen-containing motifs. The challenge is that most of these reactions employed stoichiometric oxidants to achieve satisfied catalytic efficiencies. Herein, we report a Pd(II)/LA-catalyzed (LA: Lewis acid) oxidative C−H amination reaction of 2-acetaminobiphenyls to construct carbazoles by using dioxygen balloon as the sole oxidant source, and the presence of LA sharply improved the catalytic efficiency of Pd(OAc)₂. Remarkably, in certain cases, the deacetylation of the annulation product happened under standard conditions to afford free carbazoles as the final product. The H/D exchange studies confirmed the reversibility of C−H activation and also disclosed multiple C−H activation sites by using −NAc and −NTs as the directing groups. In addition, the palladacycle compound was identified through ¹H NMR characterizations and proved to be the intermediate prior to the carbazole formation.     

Triel Bond Formed by Malondialdehyde and Its Influence on the Intramolecular H-Bond and Proton Transfer

Malondialdehyde (MDA) engages in a triel bond (TrB) with TrX₃ (Tr = B and Al; X = H, F, Cl, and Br) in three modes, in which the hydroxyl O, carbonyl O, and central carbon atoms of MDA act as the electron donors, respectively. A H···X secondary interaction coexists with the TrB in the former two types of complexes. The carbonyl O forms a stronger TrB than the hydroxyl O, and both of them are better electron donors than the central carbon atom. The TrB formed by the hydroxyl O enhances the intramolecular H-bond in MDA and thus promotes proton transfer in MDA-BX₃ (X = Cl and Br) and MDA-AlX₃ (X = halogen), while a weakening H-bond and the inhibition of proton transfer are caused by the TrB formed by the carbonyl O. The TrB formed by the central carbon atom imposes little influence on the H-bond. The BH₂ substitution on the central C-H bond can also realise the proton transfer in the triel-bonded complexes between the hydroxyl O and TrH₃ (Tr = B and Al).     

Effect of a metal ion on intramolecular spin exchange in spin-labeled complexes

The characteristic features of intramolecular spin exchange in 14 complexes of Ag^I, Hg^II, Ni^II, Pd^II, Pt^II, Au^III, and Pt^IV with spin-labeled ligands were studied by ESR spectroscopy. The measured values of the exchange integral ‖J‖ and the differences between the enthalpies of the efficient conformations (ΔH) were compared with the electronic polarization (refraction)R _f of the Ni^II, Pd^II, and Pt^II ions and Klopman's rigidity parameters σ_K, which characterize the total polarazibility of the ions and the degree of covalence of the bond between the metal atom and the donor atom of the ligand, respectively. Delocalization of the electron spin density and the efficiency of spin exchange are determined by the relative contributions of the s, p, and d orbitals, which produce the overlap integral of wave functions, ‖J‖, and by the geometric features of the coordination polyhedron, which affect the mutual orientation of the N−O fragments. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2005–2009, October, 1999.     

新型L-羟脯氨酸聚合物键合手性固定相的制备及对手性化合物的拆分

以单分散亲水性交联聚甲基丙烯酸环氧丙酯-甲基丙烯酸乙二醇双酯(PGMA/EDMA)树脂为载体,制备新型L-羟脯氨酸聚合物键合高效手性配体交换固定相。该固定相在配体交换分离模式下,以0.2mol/LNaAc和0.1mmol/LCu(Ac)2水溶液(pH5.2)为流动相,柱温为30℃～50℃,对衍生和非衍生的D,L-氨基酸和α-羟基酸等9种手性化合物进行了高效液相色谱拆分。详细考察了流动相pH值、温度、流速和进样量对手性分离的影响,选择了合适的色谱分离条件。结果表明,所拆分的9种手性化合物,有5种手性化合物能得到基线分离,最好的分离因子α=2.32。     

Electrochemical insights into the mechanisms of proton reduction by [Fe2(CO)6{micro-SCH2N(R)CH2S}] complexes related to the [2Fe](H) subsite of [FeFe]hydrogenase

Electrochemical investigations on a structural analogue of the [2Fe](H) subsite of [FeFe]H(2)ases, namely, [Fe(2)(CO)(6){micro-SCH(2)N(CH(2)CH(2)- OCH(3))CH(2)S}] (1), were conducted in MeCN/NBu(4)PF(6) in the presence of HBF(4)/Et(2)O or HOTs. Two different catalytic proton reduction processes operate, depending on the strength and the concentration of the acid used. The first process, which takes place around -1.2 V for both HBF(4)/Et(2)O and HOTs, is limited by the slow release of H(2) from the product of the {2 H(+)/2 e} pathway, 1-2H. The second catalytic process, which occurs at higher acid concentrations, takes place at different potentials depending on the acid present. We propose that this second mechanism is initiated by protonation of 1-2H when HBF(4)/Et(2)O is used, whereas the reduction of 1-2H is the initial step in the presence of the weaker acid HOTs. The potential of the second process, which occurs around -1.4 V (reduction potential of 1-3H(+)) or around -1.6 V (the reduction potential of 1-2H) is thus dependent on the strength of the available proton source.     

Excited State Intramolecular Proton Transfer in Methyl and Methoxy Substituted Salicylic Acid

The excited state intramolecular proton transfer (ESIPT) processes in 3‐methylsalicyclic acid (3‐MeSA) and 3‐methoxysalicyclic acid (3‐MeOSA) have been investigated in cyclohexane medium by emission spectroscopic techniques. The ESIPT process was characterized in 3‐MeSA from the large Stokes fluorescent band (455 nm), but it was suppressed by 3‐MeOSA in cyclohexane. The ESIPT process was found to be accelerated both in 3‐MeSA and 3‐MeOSA in the presence of a hydrogen bond accepting agent, triethylamine (TEA). Further, theoretical calculations were carried out at the ground and excited states to complement the experimental evidences.     

Magnetic molecular wheels and grids - the need for novel concepts in “zero-dimensional” magnetism

Supramolecular chemistry has allowed the production, by self-assembly, of inorganic complexes with a [N × N] square matrix-like configuration of N² metal centers. Interest in these systems is driven by the potential applications in information technology suggested by such a “two-dimensional” (2D), addressable arrangement of metal ions. From the magnetic perspective [N × N] grids constitute molecular model systems for magnets with extended interactions on a square lattice, which have gained enormous attention in the context of high-temperature superconductors. Numerous [2 × 2] grids as well as a few [3 × 3] grids with magnetic metal ions such as Cu(II), Ni(II), Co(II), Fe(II), and Mn(II) have been created. Magnetic studies unraveled a remarkable variety in their magnetic properties, which will be reviewed in this work with emphasis on the underlying physical concepts. An intriguing issue is the connection of [2 × 2] and [3 × 3] grids with “one-dimensional” (1D) rings, as experimentally realized in the molecular wheels. For a [2 × 2] square of spin centers the distinction between a 2D grid and a 1D ring is semantic, but also a [3 × 3] grid retains 1D character: it is best viewed as an octanuclear ring with an additional ion “doped” into its center. Challenging familiar concepts from conventional magnets, the current picture of elementary excitations in antiferromagnetic rings will be discussed, as a prerequisite to understand the complex [3 × 3] grids.