Redox history effects accompanying the electrochemical cycling of poly(vinylferrocene)

Cyclic voltammetric studies of poly(vinylferrocene), PVF, in aqueous sodium perchlorate, sodium p-toluenesulfonate, and sodium naphthalenesulfonate solutions revealed unexpected history effects. The films contain redox sites in two local environments. One type of ferrocene site is in a compact, unsolvated environment; it undergoes redox switching in NaClO₄ with only the transfer of counter ions. The other type of ferrocene site is in a more diffuse environment; it undergoes redox switching with the transfer of perchlorate counter ion and water. Only the latter sites can accommodate large anions (toluenesulfonate or naphthalenesulfonate), and therefore undergo redox switching in such media. Upon multiple redox cycling, these large anions get progressively locked into the structure, thereby blocking the diffuse sites. Upon transfer back to NaClO₄ solution, only the compact sites are able to undergo redox switching.Contribution to the 3^rd Baltic Conference on Electrochemistry, Gdask-Sobieszewo, 23–26 April 2003.Dedicated to the memory of Harry B. Mark, Jr. (February 28^th, 1934 – March 3^rd, 2003).     

Stereospecific synthesis and redox properties of ruthenium(II) carbonyl complexes bearing a redox-active 1,8-naphthyridine unit

Two stereoisomers of cis-[Ru(bpy)(pynp)(CO)Cl]PF₆ (bpy = 2,2′-bipyridine, pynp = 2-(2-pyridyl)-1,8-naphthyridine) were selectively prepared. The pyridyl rings of the pynp ligand in [Ru(bpy)(pynp)(CO)Cl]⁺ are situated trans and cis, respectively, to the CO ligand. The corresponding CH₃CN complex ([Ru(bpy)(pynp)(CO)(CH₃CN)]²⁺) was also prepared by replacement reactions of the chlorido ligand in CH₃CN. Using these complexes, ligand-centered redox behavior was studied by electrochemical and spectroelectrochemical techniques. The molecular structures of pynp-containing complexes (two stereoisomers of [Ru(bpy)(pynp)(CO)Cl]PF₆ and [Ru(pynp)₂(CO)Cl]PF₆) were determined by X-ray structure analyses.     

ZIF-67及其衍生物复合材料的制备及其电化学性能研究进展

由于钴基沸石咪唑酯骨架材料(ZIF-67)结构和功能的多样化使其在电化学领域得到了广泛应用。本文概述了ZIF-67的结构特点及性能,总结了ZIF-67及其衍生物的合成方法,着重整理分析了该材料在超级电容器、锂离子电池等方面的应用。最后阐述了ZIF-67及其衍生物的未来发展前景和挑战,为今后的相关研究提供参考。     

Copper coordination complexes of bis(4-(pyridin-2-yl)pyrimidin-2-ylthio)methane with in situ metal redox reactions

Five copper coordination complexes 1–5 with 2-bppm (2-bppm?=?bis(4-(pyridin-2-yl)pyrimidin-2-ylthio)methane) have been prepared and structurally elucidated. Complexes 1 and 2 are both discrete dinuclear [2?+?2] macrocyclic structures, simultaneously formed in one-pot reaction with Cu(NO₃)₂ with in situ reduction of Cu²⁺. Similarly, dinuclear [2?+?2] macrocyclic motifs are found with 3 and 4, which are also obtained by one-pot reaction but with CuCl accompanied by in situ air oxidation of Cu⁺. Compound 5 exhibits a 1-D chain structure with 2-bppm and Cu₂I₂ connected one by one. Luminescence is measured for 2, 4, and 5, all based on d¹⁰-closed shell Cu(I).     

双羟甲基-18-冠-6及其衍生物的合成

报道了双羟甲基-18-冠-6及其正丁基、烯丙基、酯基、羧酸基衍生物的合成。所合成的八种新冠醚化合物的结构已经IR、MS、NMR、元素分析证实。     

Synthesis, spectroscopic characterization, electrochemical behaviour, reactivity and antibacterial activity of some transition metal complexes with 2-(N-salicylideneamino)-3-carboxyethyl-4,5-dimethylthiophene

Mn(II), Fe(II), Co(II), Ni(II), Cu(II) and Zn(II) complexes with a potentially tridentate Schiff base, formed by condensation of 2-amino-3-carboxyethyl-4,5-dimethylthiophene with salicylaldehyde were synthesized and characterized on the basis of elemental analyses, molar conductance values, magnetic susceptibility measurements, UV-vis, IR, EPR and NMR spectral data, wherever possible and applicable. Spectral studies reveal that the free ligand exists in a bifunctionally hydrogen bonded manner and coordinates to the metal ion in a tridentate fashion through the deprotonated phenolate oxygen, azomethine nitrogen and ester carbonyl group. On the basis of electronic spectral data and magnetic susceptibility measurements, suitable geometry has been proposed for each complex. The EPR spectral data of the Cu(II) complex showed that the metal-ligand bonds have considerable covalent character. The Ni(II) complex has undergone facile transesterification reaction when refluxed in methanol for a lengthy period. X-ray diffraction studies of Cu(II) complex showed that the complex has an orthorhombic crystal lattice. In view of the biological activity of thiophene derivatives, the ligand and the complexes were subjected to antibacterial screening. It has been observed that the antibacterial activity of the ligand increased on chelation with metal ion.     

Examining the binding mechanism of 3,4-dihydro-3-(2-oxo-2-phenylethylidene)-quinoxalin-2(1H)-one and its fragments to Cu2+

The structure and stoichiometries of the complexes that could be formed between Cu²⁺ and 3,4-dihydro-3-(2-oxo-2-phenylethylidene)-quinoxalin-2(1H)-one (1) were investigated by various spectral techniques such as IR, fluorescence, UV–vis and electron paramagnetic resonance. The results suggest that initially 3?:?1 and 2?:?1 (1/Cu²⁺) complexes are formed at low Cu²⁺ concentration and upon adding more Cu²⁺, 1?:?1 (preferred) and 1?:?2 complexes are generated. Since 1 possesses two possible binding sites, further exploration was done by testing the binding ability of Cu²⁺ to fragments of 1, namely β-enaminoketone derivatives (2–3) and quinoxaline-2-one (4), and by executing calculations of thermodynamic parameters of the reaction between 1 and Cu²⁺ in ethanol, optimized geometries of the possible complexes, and estimation of stability constants at various stoichiometries. Consequently, a step-by-step binding mechanism is suggested for formation of various complexes between 1 and Cu²⁺.     

Synthesis of a novel macrocyclic dinuclear iron(III) complex and its electrochemical behaviour on an ultramicrodisc platinum electrode

A new macrocyclic dinuclear iron(III) complex, prepared by condensing 2,6-diformylpyridine N-oxide with 1,3-diaminopropane in the presence of FeCl2·4H2O, and formulated as Fe2LCl6C2H5OH·6H2O, was characterized by its elemental analyses, by i.r., Mo¨ssbauer and e.p.r. spectra, and was investigated electrochemically. The results show that two iron ions are situated in the same chemical environment in the compound and that the electrode reaction can be considered as a double electron-transfer process. The diffusion coefficient is 2.16×10–6 cm2 s–1 and E° –0.169 V (versus s.c.e.) and = 0.37. The average electron transfer rate constant ko is 2.8×10–3 cm s–1.     

Distribution coefficient and redox behaviour of uranium in Authie Bay (northern France)

Some mechanistic aspects associated with uranium release/immobilization and sedimentation in Authie Bay are presented in the present work. For this purpose, U contents in estuarine oxic waters, porewaters and sediment solids are determined. These analytical data allow us to appraise the partitioning of this metal between the liquid phase and the particulate matter/sedimentary material by calculating its distribution coefficient. Our findings further reveal that the distribution coefficient varies significantly with depth probably in response to the microbial activities in these sediments. This is confirmed by our studies on the geochemical behaviour of Fe and Mn in Authie Bay sediments. Finally, studies on the thermodynamic characteristics of sedimentary U in Authie Bay are undertaken in order to select possible U water–mineral equilibria that could involve in this environment, and to help define conditions of sedimentary U bioreduction.     

Synthesis and electrochemical studies of organometallic cobalt(III) complexes with substituted benzonitrile chromophores: NMR spectroscopic data as a probe on the second-order non-linear optical properties

The family of organometallic Co(III) benzonitrile derivatives of general formula [CoCp(dppe)(p-NCR)][PF₆]₂ (R = C₆H₄NMe₂, C₆H₄NH₂, C₆H₄OMe, C₆H₄C₆H₅, C₆H₅, C₆H₄C₆H₄NO₂, and C₆H₄NO₂) have been synthesized. Spectroscopic and electrochemical data were analyzed in order to evaluate the extent of electronic coupling between the organometallic fragment and the nitrile ligands. An attempt of correlation between NMR spectroscopic data and the second-order non-linear optical properties is presented, based on this work and available published data for related η⁵-monocyclopentadienyliron, ruthenium and nickel complexes.     

Synthesis and properties of new crystalline poly(arylene ether)s containing pendant benzoyl groups

Poly(arylene ether)s ( 3 ) containing pendant benzoyl groups were prepared by the aromatic substitution reaction of 2,5-difluoro-4-benzoylbenzophenone (2) with hydroquinone ( 1a ) and methylhydroquinone ( 1b ) in the presence of potassium carbonate in N,N-dimethylacetamide. The polycondensation proceeded smoothly at 165°C and produced poly(arylene ether)s with inherent viscosities up to 0.8 dL/g. The polymer ( 3b ) derived from methylhydroquinone was quite soluble in common organic solvents and could be processed into uniform films from solutions. On the other hand, the polymer ( 3a ) derived from hydroquinone was only soluble in pentafluorophenol and methanesulfonic acid and had a high crystallinity. These polymers showed 10% weight losses at around 420 and 490°C in nitrogen. Polymer 3b also showed good tensile strength and tensile moduli. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 605–611, 1997     

双极绿色磷光主体材料1-甲基-3-[4-(9-咔唑基)苯基]-4-苯基喹啉-2(1H)-酮的合成与性能研究

设计并合成了一种基于喹诺酮衍生物的双极绿色磷光主体材料1-甲基-3-[4-(9-咔唑基)苯基]-4-苯基喹啉-2(1 H)-酮.计算发现,化合物的HOMO轨道的电子云位于咔唑基团,LUMO轨道的电子云位于喹诺酮基团,是一种良好的双极材料.化合物的磷光发射峰为515 nm(2.41 eV),符合绿色磷光主体材料的基本要求(>2.4 eV).热失重和差热分析结果表明,该化合物具有较高的热稳定性,分解温度和玻璃化转变温度分别为312℃和105℃.研究结果表明:该新型化合物是一种潜在的具有双极特性的绿色磷光主体材料.     

Synthesis and properties of (E)-1,2-difluoroethylene derivatives: improvement of the ultraviolet light stability

The synthesis and properties of (E)-α,β-difluorostilbene derivatives were studied. In particular, we investigated three suppression methods of (E)–(Z) isomerisation by shortening the molecular conjugation length, which included the introduction of a fluorine atom into the ortho or para position of the benzene ring or the replacement of the benzene ring with a cyclohexane ring. The relationship between the molecular structure of liquid crystals and the level of isomerisation by ultraviolet (UV) light was discussed.     

Acid-base and metal ion binding properties of guanylyl(3'-->5')guanosine (GpG-) and 2'-deoxyguanylyl(3'-->5')-2'-deoxyguanosine [d(GpG)-] in aqueous solution

The acidity constants of guanylyl(3'-->5')guanosine (GpG(-)) and 2'-deoxyguanylyl(3'-->5')-2'-deoxyguanosine [d(GpG)(-)] for the deprotonation of their (N1)H sites were measured by potentiometric pH titrations in aqueous solution (25 degrees C; I = 0.1 M, NaNO(3)). The same method was used for the determination of the stability constants of the 1:1 complexes formed between Mg(2+), Ni(2+), or Cd(2+) (= M(2+)) and (GG-H)(2-), and in the case of Mg(2+) also of (GG-2H)(3-), where GG(-) = GpG(-) or d(GpG)(-). The stability constants of the M(GG)(+) complexes were estimated. The acidity constants of the H(dGuo)(+) and dGuo species (dGuo = 2'-deoxyguanosine) and the stability constants of the corresponding M(dGuo)(2+) and M(dGuo-H)(+) complexes were also measured. Comparison of these and related data allows the conclusion that N7 of the 5'G unit in GG(-) is somewhat more basic than the one in the 3'G moiety; the same holds for the (N1)(-) sites. On the basis of comparisons with the stability constants measured for the dGuo complexes, it is concluded that M(2+) binding of the GG dinucleoside monophosphates occurs predominantly in a mono-site fashion, meaning that macrochelate formation is not very pronounced. Indeed, it was a surprise to find that the stabilities of the complexes of dGuo or (dGuo-H)(-) and the corresponding ones derived from GG(-) are so similar. Consequently, it is suggested that in the M(GG)(+) and M(GG-H) complexes the metal ion is mainly located at N7 of the 5'G unit since this is the more basic site allowing also an outer-sphere interaction with the C6 carbonyl oxygen and because this coordination mode is also favorable for an electrostatic interaction with the negatively charged phosphodiester bridge. It is further suggested that Mg(2+) binding (which is rather weak compared to that of Ni(2+) and Cd(2+)) occurs mainly in an outer-sphere mode, and on the basis of the so-called Stability Ruler it is concluded that the binding properties of Zn(2+) to the GG species are similar to those of Ni(2+) and Cd(2+).     

Use of 3-(2'-formyl-l'-chlorovinyl)coumarin in the syntheses of pyrazol, salicylaldazine and pyrimidine derivatives

3-(Pyrazol-5'-yl)coumarin (3) was prepared from condensation of 3-(2'-formyl-1'-chlorovinyl)-coumarin (1) with hydrazine hydrate at room temperature, followed by cyclization with base. Salicylaldazine was prepared from methoxylation of 1 to give acetal 7, followed by condensation of 7 with hydrazine hydrate at 80℃. Treatment of acetal 7 with thiourea yielded the corresponding 4-substituted-2-thioxo-2H-pyrimidine [ 3, 4-b]-coumarin (12).     

Computational assessment of the electronic structure of 1-azacyclohexa-2,3,5-triene (3 delta 2-1H-pyridine) and its benzo derivative (3 delta 2-1H-quinoline) as well as generation and interception of 1-methyl-3 delta 2-1H-quinoline

Treatment of a solution of 3-bromo-1-methyl-1,2-dihydroquinoline (9) and [18]crown-6 in furan or styrene with KOtBu followed by hydrolysis afforded a mixture of 1-methyl-1,2-dihydroquinoline (10) and 1-methyl-2-quinolone (11). If the reaction was performed in [D(8)]THF and the mixture was immediately analysed by NMR spectroscopy, 2-tert-butoxy-1-methyl-1,2-dihydroquinoline (17) was shown to be the precursor of 10 and 11. The structure of 17 is evidence for the title cycloallene 7, which arises from 9 by beta elimination of hydrogen bromide and is trapped by KOtBu to give 17 so fast that cycloadditions of 7 with furan or styrene cannot compete. Since this reactivity is unusual compared to the large majority of the known six-membered cyclic allenes, we performed quantum-chemical calculations on 8, which is the parent compound of 7, and the corresponding isopyridine 6 to assess the electronic nature of these species. The ground state of 6 was no longer an allene (6 a) but the zwitterion 6 b. In the case of 8, the allene structure 8 a is more stable than the zwitterionic form 8 b by only approximately 1 kcal mol(-1). These results suggest a high reactivity of 6 and 8 towards nucleophiles and explains the behaviour of 7. In addition to the ground states, the low-lying excited states of 6 and 8 were considered, which are represented by the diradicals 6 c and 8 c and, as singlets, lie above 6 b and 8 a by 19.1-24.8 and 14.4-17.7 kcal mol(-1), respectively.     

On the structural and spectroscopic properties of the thienyl chalcone derivative: 3-(5-Bromo-2-thienyl)-1-(4-nitrophenyl)-prop-2-en-1-one

In this study, we investigate the structural and spectroscopic properties of the thienyl chalcone derivative 3-(5-Bromo-2-thienyl)-1-(4-nitrophenyl)-prop-2-en-1-one, C₁₃H₈BrNO₃S, using nuclear magnetic resonance (¹H and ¹³C NMR), UV–vis and Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy at room conditions combined with density functional theory (DFT) and time-dependent DFT (TD-DFT) augmented with B3LYP/6-311G(d,p) and CAM-B3LYP/6-311G(d,p) basis sets, yielding valuable information on the molecular conformational preferences, vibrational assignments, optical properties and electronic transitions. The vibrational mode assignments of the most stable conformer of C₁₃H₈BrNO₃S are discussed based on potential energy distribution (PED) analysis and establishing a comparison with a similar chemical structure. The temperature dependence on the Raman spectra of the C₁₃H₈BrNO₃S shows a reversible phase transition in the range 443–443 K pointed out by the discontinuity in the dω/dT of bands in the external and internal modes region. The UV–vis spectrum of the C₁₃H₈BrNO₃S indicates a semiconductor behavior with an optical band gap of 2.6 eV, corresponding to the predicted value of 3.42 eV assigned as the electronic transition from the highest occupied molecular orbital (HOMO) to the lowest unoccupied molecular orbital (LUMO). TD-DFT calculations reveal that the electron donor and acceptor group substitution on the 1-phenyl-3-(thiophen-2-yl)prop-2-en-1-one affects its absorption and nonlinear activity.