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101.
铝酸钠溶液的紫外吸收峰 总被引:4,自引:0,他引:4
分别用量子化学MNDO和DV-X_α方法计算了二聚铝酸离子[Al_2O(OH)_6]~(2-)和Al(OH)_4~-。结果表明前者旋转势垒很低, 只有10.08 kJ·mol~(-1), 最稳定平衡构型为C_s。用X_α过渡态理论计算获得这两个离子紫外吸收峰的理论值分别为266.6 nm和234.4 nm, 与实验值270.0 nm和230.0 nm相当接近。因此可以认为, 紫外吸收峰270.0 nm和230.0 nm分别为[Al_2O(OH)_6]~(2-)和Al(OH)_4~-离子的最高占有轨道电子向最低空轨道跃迁时产生的吸收峰。计算结果支持铝酸钠溶液中存在二聚铝酸离子的观点。 相似文献
102.
桥联双(甲巯咪唑)化合物的合成和配位性能 总被引:3,自引:0,他引:3
研究了桥联双(甲巯咪唑)化合物(Ⅰ_a—Ⅳ_a、Ⅰ_b)的合成和配位性能。UV谱显示Ⅰ_a—Ⅳ_a与UO_2~(2+)离子(硬酸)配位,溶液中形成3:1的配合物。Ⅰ_b与Hg~(2+)、Au~(3+)离子(软酸)配位形成2:1的配合物,用CNDO/2方法计算了各配体分子中原子净电荷密度和HOMO、LUMO能量。 相似文献
103.
Feth MP Bolm C Hildebrand JP Köhler M Beckmann O Bauer M Ramamonjisoa R Bertagnolli H 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(6):1348-1359
XANES and EXAFS spectroscopic studies at the Mn-K- and Br-K-edge of reaction products of (S,S)-(+)-N,N'-bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexanediaminomanganese(III) chloride ([(salen)Mn(III)Cl], 1) and (S,S)-(+)-N,N'-bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexanediaminomanganese(III) bromide ([(salen)Mn(III)Br], 2) with 4-phenylpyridine N-oxide (4-PPNO) and 3-chloroperoxybenzoic acid (MCPBA) are reported. The reaction of the Mn(III) complexes with two equivalents of 4-PPNO leads to a hexacoordinated compound, in which the manganese atom is octahedrally coordinated by four oxygen/nitrogen atoms of the salen ligand at an average distance of approximately 1.90 A and two additional, axially bonded oxygen atoms of the 4-PPNO at 2.25 A. The oxidation state of this complex was determined as approximately +IV by a comparative study of Mn(III) and Mn(V) reference compounds. The green intermediate obtained in reactions of MCPBA and solutions of 1 or 2 in acetonitrile was investigated with XANES, EXAFS, UV/Vis, and Raman spectroscopy, and an increase of the coordination number of the manganese atoms from 4 to 5 and the complete abstraction of the halide was observed. A formal oxidation state of IV was deduced from the relative position of the pre-edge 1s-->3d feature of the X-ray absorption spectrum of the complex. The broad UV/Vis band of this complex in acetonitrile with lambda(max)=648 nm was consistent with a radical cation structure, in which a MCPBA molecule was bound to the Mn(IV) central atom. An oxomanganese(V) or a dimeric manganese(IV) species was not detected. 相似文献
104.
Marek Daszkiewicz Zbigniew Staszak Adam Pietraszko Wiesława Bronowska Maria Cieślak-Golonka 《Structural chemistry》2006,17(6):599-608
Two polymeric complexes: catena(μ-CrO4-O,O′)[Co(HIm)3H2O] (1) and catena(μ-CrO4-O,O′)[Co0.43Ni0.57(HIm)3H2O] (2) (where HIm=imidazole) with a cis-bridging coordination mode of the CrO4
2− anion have been synthesized and characterized by X-ray and spectroscopic methods. These crystals were isolated from nine
systems of varying reagent molar ratios and three excluding anions: Cl−, NO3
− and SO4
2− exclusively as mer [M(HIm)3O3]-type isomers. The unit cell of these isostructural complexes (monoclinic crystal system P21
/n) contains two independent helixes, left- and right handed, stabilized by intrahelical and interhelical hydrogen bonding and
π–π interaction between pairs of the imidazole rings from neighbouring helixes. The Raman spectra at 77 K of 1 and 2 deconvoluted into lorentzian components revealed the block-type polymeric structure of the complexes. Moreover, the solution
studies at millimolar concentrations of 1 and 2 indicated their complete decomposition in water. Four K electronic spectral analysis of the crystals (band deconvolution
into gaussian components) enhanced with the data obtained in the polarized light allowed for assignment of the bands to the
respective d–d transition (D4h symmetry). It was found that the metallic centres are independently absorbing species, which supports the suggestion of a
block-type structure of the polymers. The respective crystal field parameters for Co and Ni were calculated. 相似文献
105.
Novel visible-light-driven photocatalyst of NiO/Cd/g-C3N4 for enhanced degradation of methylene blue
《Arabian Journal of Chemistry》2020,13(6):5810-5820
Novel NiO/Cd/g-C3N4 photocatalysts were synthesized using a green and straightforward microwave-assisted method and characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), the Brunauer–Emmett–Teller (BET) method, transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and ultraviolet–visible spectroscopy (UV–Vis). The ternary NiO/Cd/g-C3N4 nanocomposites were evaluated for the degradation of methylene blue (MB) at room temperature under the visible light irradiation. Experimental results revealed that the weight percent of cadmium had a remarkable effect on the photodegradation efficiency. The NiO/Cd/g-C3N4 (0.1%) sample exhibited superior activity in the degradation reaction. The activity of this nanocomposite was about 4.5 and 3.25 fold higher than those of the pure g-C3N4 and NiO/g-C3N4 samples in the degradation of MB, respectively. The enhanced photocatalytic activity was attributed to the low energy gap, increased absorption capacity of the visible light, and efficient suppression of the recombination of photogenerated electron-hole pairs. A detailed photocatalytic mechanism over the nanocomposite of NiO/Cd/g-C3N4 (0.1%) was proposed with superoxide radical anion O2– as the main reactive species. The stability of the nanocomposite was confirmed after four consecutive runs as well. 相似文献
106.
V. A. Mamedov A. A. Kalinin V. V. Yanilkin N. V. Nastapova V. I. Morozov A. A. Balandina A. T. Gubaidullin O. G. Isaikina A. V. Chernova Sh. K. Latypov I. A. Litvinov 《Russian Chemical Bulletin》2007,56(10):2060-2073
The oxidative dehydrocyclization of the 3-(indolizin-2′-yl)-2-oxoquinoxaline monopodand performed either electrochemically
or under the action of molecular iodine affords new redox-active heterocyclophane consisting of the redox-switchable biindolizine
fragment combined with the polyether-bridged π-deficient quinoxaline systems. The single-crystal X-ray diffraction study showed
that the trioxaundecane chain of heterocyclophane adopts an extended conformation, and one of the phenyl substituents of the
molecule closes the pseudocavity formed by the spacer from one of the sides. The cyclic voltammetric study of heterocyclophane
in MeCN and DMF showed the three-step oxidation of the indolizine fragments accompanied by the single-electron transfer in
each step. The first and third steps are reversible, and the second step is irreversible. The oxidation at potentials of the
first peak gives rise to stable radical cations detected by the ESR method (g = 2.0024, a
2N = 0.26 mT).
Dedicated to Professor E. A. Berdnikov on the occasion of his 70th birthday.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1991–2003, October, 2007. 相似文献
107.
V. V. Avdin A. A. Lymar A. V. Batist E. A. Nikitin M. Yu. Belkanova V. A. Potemkin 《Journal of Structural Chemistry》2007,48(4):747-752
Oxyhydrate gels have a hydrophilic surface, due to which they undergo destruction and secondary polymerization in aqueous media. Prolonged storage in aqueous solution gives rise to regions with selfsimilar helical ordering in gels. Structuring of this kind is also observed when synthesis is conducted under conditions that provide low gelation rates. Electromagnetic UV and visible radiation is another means to change the gel structure; it makes the oligomer species pass into the excited state, due to which one of the directions of structuring becomes dominant. This work summarizes the results of computer simulation of gel agglomerates. For oxyhydrate systems, helical ordering was found to be one of the local energy minima. The units of a macrohelix can lie at various angles relative to one another, and they can change, after absorption of energy, the helix pitch and the order of elements in the helix. 相似文献
108.
We synthesized the new photosensitive oligomer containing a chalcone moiety in the main chain by end-capping reaction of diepoxide compound with methacrylic acid. The chalcone-epoxy oligomeric compound was synthesized with 4,4′-dihydroxychalcone and epichlorohydrin. Investigation of the photosensitivity of the newly synthesized chalcone oligomer was carried out by using UV-Vis absorption and infrared spectroscopies under UV exposure. We observed the photodimerization behavior under UV irradiation. At the same time, we could also observe the photopolymerization of the compound with a trace amount of dimethoxyphenyl acetophenone. Thermal properties of UV-cured dimethacrylate compounds were also studied. 相似文献
109.
Harald Stueger Markus Braunwarth Gottfried Fuerpass Judith Baumgartner Robert Saf 《Monatshefte für Chemie / Chemical Monthly》2006,137(5):595-603
Summary. The previously unknown ruthenio disilanes Rp–Si2Me4–C6H4X (Rp = η5-C5H5Ru(CO)2; X = H, Br, –CHO, CH=C(CN)2) were synthesized from ClSi2Me4C6H4X (X = H, Br) and Rp− using conventional chemical methods. Trends in the UV/Vis absorption spectra indicate strong electronic coupling within the
Rp–Si–Si–Caryl fragment and, therefore, closely resemble the ones observed for the corresponding iron complexes. The four compounds however,
were shown to be less sensitive towards UV irradiation. The crystal structure of Rp–Si2Me4–C6H4CH=C(CN)2 was determined by X-ray diffraction and exhibits an all-trans-array of the Ru–Si–Si–Caryl moiety, what is a basic requirement for optimal through-bond interaction. 相似文献
110.
本文通过酶活性测定,荧光光谱和紫外光谱研究了外加Cu2+与烟草多酚氧化酶(简称PPO)的相互作用。结果表明,微量铜的加入能增加酶的活性,[Cu2+]/[PPO]为0.20左右时酶活性最大,[Cu2+]/[PPO]为0.91时,Cu2+开始表现出对PPO活性的抑制;Cu2+对PPO内源荧光的猝灭机制属于形成络合物所引起的静态猝灭,猝灭常数Ksv为8.0375×103L·mol-1;Cu2+的加入使PPO蛋白质分子构象发生变化,α-螺旋含量增加,多肽链及Trp和Tyr残基的芳杂环进一步向分子内收缩,疏水基团之间的疏水作用增强。 相似文献