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31.
将酞菁锰(MnPc)掺入阳离子表面活性剂双十二烷基二甲基溴化铵(DDAB)的氯仿溶液,并涂布于热解石墨电极表面,待氯仿挥发后即制得MnPc-DDAB薄膜电极。循环伏安实验表明,在KBr溶液中,该薄膜电极有两对还原氧化峰,第一对峰的Epc1=-0.27V,Epa1=0.01V;第二对峰的Epc2=-0.76V,Epa2=-0.62V(vs.SCE)。本文着重探讨了第二对峰的电化学行为,估计了该体系的电荷传递扩散系数Dct和表观非均相电极反应速率常数K0′等电化学参数,并可将该薄膜电极用于催化三氯乙酸的电化学还原。 相似文献
32.
A new salicylic-based open-chain crown ether ligand, 1,10-bis(2′-carboxylphenyl)-1,4,7,10-tetraoxadecane (BCPTD) was synthesized. Solutions of its complex with Tb3+ can emit the intrinsic fluorescence of Tb3+. The fluorescence intensity of the complex in KCl solution was enhanced by the addition of silver(I), leading to a new fluorescence enhancement phenomenon. The spectrofluorimetric determination of traces of silver(I) based on the above phenomenon was carried out. The excitation and emission wavelengths are 298 and 545 nm, respectively. Under optimal conditions, the differential value of fluorescence intensity in the absence and presence of Ag+ was proportional to the concentration of silver(I) in the range 0.5-20 μg ml−1. The method was applied to the determination of silver(I) in a standard ore sample. The analytical performance is investigated in detail by using common aromatic carboxylic acids or synthetic analogues of BCPTD as ligands to replace BCPTD. It was found that Tb-aromatic acid complexes did not result in fluorescence enhancement of Tb3+ in AgCl collosol. The phenomenon was only observed in Tb(III) with BCPTD or its open-chain crown ether analogues solutions.In addition, the enhancement of the fluorescence intensity of terbium(III) in these complexes depends on the extent of formation of the AgCl collosol. 相似文献
33.
Enantioselective transition metal catalysis directed by chiral cations is the amalgamation of chiral cation catalysis and organometallic catalysis. Thus far, three strategies have been revealed: ligand scaffolds incorporated on chiral cations, chiral cations paired with transition metal ‘ate’-type complexes, and ligand scaffolds incorporated on achiral anions. Chiral cation ion-pair catalysis has been successfully applied to alkylation, cycloaddition, dihydroxylation, oxohydroxylation, sulfoxidation, epoxidation and C–H borylation. This development represents an effective approach to promote the cooperation between chiral cations and transition metals, increasing the versatility and capability of both these forms of catalysts. In this review, we present current examples of the three strategies and suggest possible inclusions for the future.Enantioselective transition metal catalysis directed by chiral cations is the amalgamation of chiral cation catalysis and organometallic catalysis. 相似文献
34.
The coordination of silver cation to diphosphene Mes*P=PMes* ( 1 , Mes* = tBu3C6H2) was investigated in detail. The reaction of 1 with Ag[Al(ORF)4] (ORF = OC(CF3)3) in the ratios of 2 : 1, 3 : 2 and 1 : 2 led to the formation of the first cationic silver linked diphosphene complexes 2 — 4 . Complexes 2 and 3 contain two and three diphosphene molecules linked by the linear Ag(I) cation, respectively, and they feature unusual zig‐zag topologies. Complex 4 is a dinuclear silver complex, and each Ag(I) center features a tetrahedral geometry, coordinated by one phosphorus atom of diphosphene 1 and three chloro atoms of two CH2Cl2 molecules. 相似文献
35.
The reduction of microcrystalline C60
fullerene, adhered at a carbon electrode and immersed in aqueous electrolyte, has been studied under various voltammetric conditions. This work reports mainly the voltammetric studies carried out principally in electrolyte containing potassium ions. Comparison of adherence techniques, such as solvent casting and mechanical transfer methods, are made to assess if the type of adhered techniques has any significant influence on the observed electrochemistry. The solvent casting method is found to produce three peaks in the potential for C600/n- redox couple as compared to a single and large peak produced when a mechanical transfer technique is employed. When the reduction potential of microcrystalline C60 in the presence of K+ is compared with other cations, such as Li, Na, Rb and Cs, it is observed that the shift of reduction potential follows the change in the hydration energy in the order Cs>Rb>K>Na>Li. In a mixed electrolyte study of CsCl/KCl, the reduction potential and peak shape of C600/n- redox couple during cyclic voltammetry is observed to change with concentration of the cations and the observed electrochemistry can be attributed to a cation-exchange mechanism. The reduction of C60 is irreversible in aqueous electrolyte containing alkaline cations as the re-oxidation process does not produce any observed electro-activity. Evidence of the formation of a passive coating of K n
C60 fulleride, which does not appear to undergo dissolution is obtained under cyclic voltametric conditions. This coating remains electrochemically active in the presence of tetrabutylammonium ions in acetonitrile. Scan rate, chronocoulometric, and scanning electron microscopic studies provide evidence of the presence of a surface process involving solid–solid transformation. 相似文献
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38.
The magneto-structural correlation between a Mn(ll) ion, coordinated in an octahedral environment, and two nitronyl nitroxide
radical ligands in trans- and cis-metal-radical complexes is investigated by the broken symmetry (BS) approach within density functional theory (DFT).
The dependences of coupling constants J on three structural parameters: (i) bond angle θ (Mn-O-N (nitroxide)); (ii) rotating angle ψ, defined by the nitronyl nitroxide radical plane rotating around the axial Mn-O (nitroxide); (iii) bond distance R (Mn-O (nitroxide)) are directly calculated. Our calculations showed that both trans- and cis-Mn(ll)-radical complexes behave a stronger antiferromagnetic interaction, consistent with experiments. In view of
molecular orbital theory, the direct exchanges, including σ-type and π-type exchanges, are responsible for the magnetic exchange
pathways. There is a preferable linear correlation between the calculated coupling constants J and the overlap integral squares S b between the local magnetic orbitals at the various rotating angle ψ at the fixed bond angle θ and bond distance R, in both trans- and cis-Mn(ll)-radical complexes. 相似文献
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