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1.
The spectroelectrochemical behaviour of non-aqueous solutions containing (Chl a·H2O)2 and (Chl a·2 H2O)n, used as models for P 700 and P 680, respectively, is reported. The potential associated with the electron-transfer processes and the kind of electrode reactions in the presence of substances (benzylviologen and dichlorophenolindophenol) used as a specific acceptor for photosystems I and II were studied. To carry out the measurements, a thin-layer spectroelectrochemical cell with a platinum optically transparent electrode was used.  相似文献   

2.
The Raman spectra of chlorophyll a (Chl) forms in aqueous poly(vinyl alcohol) (PVA) and in dimethyl sulfoxide (DMSO)—water mixtures were recorded at 457.9 nm excitation and their structures were characterized by comparison with the spectra of the following well-known chlorophyll forms: (1) monomers (Chl)1 in the polar solvents of group (A), i.e., diethyl ether, tetrahydrofuran, acetone, N,N-dimethylformamide and DMSO, of which the oxygen atom is expected to coordinate to the central magnesium atom; (2) monomers (Chl)1 in the polar solvents of group (B), i.e., methanol, ethanol, 1-propanol, 2-propanol and 1-butanol, which are supposed to form a hydrogen-bond to the C9=O group in addition to the coordination-bond to the Mg atom; (3) dehydrated aggregates (Chl)n in dry non-polar solvents, i.e., carbon tetrachloride, n-hexane and n-octane; and (4) hydrated aggregates (Chl·2H2O)n in wet non-polar solvents, i.e., n-hexane and n-octane. The frequency of the C9 = O stretching Raman line of each of the above chlorophyll forms was: (1) 1702—1680 cm−1; (2) 1673—1668 cm−1; (3) around 1655 cm−1; (4) around 1645 cm−1. The frequency proved to be a marker of intermolecular interaction of the Chl molecules. The spectral patterns in the 1650—700 cm−1 region of (1), (2) and (3) were similar. However, the relative intensities of Raman lines of (4), which was ascribed to a one-dimensional, regular stacking of the Chl macrocycles, were quite different from those of (1)—(3).The chlorophyll form in PVA aqueous solution was identified as (Chl·2H2O)n by spectral comparison. The chlorophyll forms present in the DMSO—water mixtures were highly dependent on the DMSO content. It is suggested that (Chl)1 having hydrogen-bonded H2O should be present in 10% DMSO solution, and that a new chlorophyll form (Chl·DMSO)n having (a) a stoichiometric intermolecular interaction with DMSO and (b) a regular stacking of the chlorophyll macrocycles, should be predominant in 50% DMSO aqueous solution.  相似文献   

3.
Five Mn(II) complexes of bis(thiosemicarbazones) which are represented as [Mn(H2Ac4Ph)Cl2] (1), [Mn(Ac4Ph)H2O] (2), [Mn(H2Ac4Cy)Cl2]·H2O (3), [Mn(H2Ac4Et)Cl2]·3H2O (4) and [Mn(H2Ac4Et)(OAc)2]·3H2O (5) have been synthesized and characterized by elemental analyses, electronic, infrared and EPR spectral techniques. In all the complexes except [Mn(Ac4Ph)H2O], the ligands act as pentadentate neutral molecules and coordinate to Mn(II) ion through two thione sulfur atoms, two azomethine nitrogens and the pyridine nitrogen, suggesting a heptacoordination. While in compound [Mn(Ac4Ph)H2O], the dianionic ligand is coordinated to the metal suggesting six coordination in this case. Magnetic studies indicate the high spin state of Mn(II). Conductivity measurements reveal their non-electrolyte nature. EPR studies indicate five g values for [Mn(Ac4Ph)H2O] showing zero field splitting.  相似文献   

4.
2-Fold interpenetrating 3D framework for selective adsorption of CO2 over CH4 and fluorescence detection of Fe3+ ions and nitroaromatic compounds through fluorescence quenching.  相似文献   

5.
It is shown that the photophysical properties of chlorophyll a (Chl) depend on the nature and relative amounts of 2-methyl-1,4-naphthoquinone (MNQ) and nicotinamide adenine dinucleotide phosphate (NADP). Photoinduced charge separation occurs in aqueous ethanol solutions of Chl (1 × 10?5 M) and NADP (5 × 10?6–5 × 10?4 M), resulting in the dynamic quenching of Chl fluorescence. Coordination interaction between Chl and NADP is established at an NADP concentration of ≥5 × 10?4 M. The nonlinear Stern-Volmer dependence in this range is due to the input from static quenching. It is shown that the quenching of Chl fluorescence in an MNQ solution at Chl and MNQ concentrations of 1 × 10?5 M and 6.7 × 10?5–1 × 10?4 M, respectively, is described by a linear dependence in the Stern-Volmer coordinates; no complex formation is observed for Chl and MNQ under these conditions, and electron transfer is of the dynamic type. Static or mixed-type energy transfer from MNQ to Chl dominates at elevated MNQ concentrations.  相似文献   

6.
A new inorganic–organic hybrid framework coordination polymer, Cd3(BDC)0.5(BTC)2(DMF)(H2O)·3DMF·H3O·H2O 1, in which two carboxylate ligands, 1,4-benzenedicarboxylic acid (H2BDC) and 1,3,5-benzenetricarboxylic acid (H3BTC), coordinate with cadmium ions, has been synthesized under mild conditions and its structure solved by single-crystal X-ray diffraction (XRD) analysis. Polymer 1 crystallizes in the monoclinic system, space group P21/c (No. 14) with a=15.750(3) Å, b=14.501(3) Å, c=19.363(4) Å, β=113.67(3)°, V=4050.4(14) Å3, Z=4, R1=0.0374 and wR2=0.1148. Its structure revealed that the nine vertices of the secondary building units are linked by benzene rings from both H3BTC and H2BDC ligands to form a 3D network with 10×10 Å channels along [001] direction. Complex 1 is characterized by inductively coupled plasma analysis, powder XRD, infrared spectroscopy and thermogravimetric analysis. Polymer 1 exhibits intense fluorescence at 358 and 377 nm with λexcitation=208 nm in the solid state at room temperature.  相似文献   

7.
Two Ni(II) coordination polymers, [Ni(dmbbbi)(pic)2·3H2O] n (1) and [Ni(dmbbbi)1.5(pdc)·2H2O] n (2) (dmbbbi = 1,1′-(1,4-butanediyl)bis(5,6-dimethylbenzimidazole), Hpic = 2-picolinic acid, H2pdc = pyridine-2,6-dicarboxylic acid), have been hydrothermally synthesized by self-assembly of nickel chloride with a flexible bis(5,6-dimethylbenzimidazole) ligand and two different pyridine carboxylic acids. The compounds were characterized by physico-chemical and spectroscopic methods and by single-crystal diffraction. Compound 1 possesses 1D ribbon-like chains connected by dmbbbi ligands in bis-bridging mode, which are further extended into a 2D supramolecular network through O–H···O hydrogen bonding interactions between pic anions and lattice water molecules, giving a novel trinodal (3,3,4)-connected topology with the point symbol of (4.6.8)2(6.84.10). Compound 2 shows a 2D undulant {63} hexagonal (hcb) network. The structures of the two complexes are further stabilized by intramolecular π···π stacking interactions between the imidazole and N-containing nickel chelate rings. In addition, the fluorescence properties of 1 and 2 have been investigated in the solid state.  相似文献   

8.
Three Salen-like gadolinium complexes, namely, mononuclear (4f) complex [{H2L}Gd(NO3)3] (1), heterodinuclear (3d–4f) complex [{LCu}Gd(NO3)3]·0.25H2O (2) and dimeric heterotrinuclear (3d–4f–3d′) complex [{LCu}Gd(H2O)3{Fe(CN)6}]2·6H2O (3) [H2L = N,N′-ethylene-bis(3-methoxysalicylideneimine)] have been synthesized by stepwise reactions. X-ray diffraction analysis reveals that 1 is of a discrete structure in which H2L coordinates to gadolinium ion through O2O2 moiety. Then, addition of Cu(Ac)2·H2O to the mononuclear lanthanide complex yields expected heterodinuclear (3d–4f) complexes [{LCu}Gd(NO3)3]. 3 features a unique 1D ladder-like topology structure through the intermolecular double links of Cu–N bonds. The measurement of variable-temperature magnetic susceptibility reveals that complex 1 exhibits antiferromagnetic interaction while 2 and 3 exhibit ferromagnetic interaction between spin carriers. The correlations between the structure and magnetism are described and discussed.  相似文献   

9.
An aqueous solution of 2–12% (vol/vol) tetrahydrofuran (THF) induced the selective aggregation of chlorophyll a (Chl a) to form a novel species, A-685, absorbing near 685 nm. The formation of A-685 was closely correlated with a decrease in water activity of the solution. A Raman spectrum of the Chl a species formed in the presence of 6% THF suggests a unique interaction among Chl a, solvent THF and water molecules to give a stacked aggregate (Chl a.THF.H2O.THF.Chl a). The circular dichroic spectrum of the Chl a species formed in the 6% THF aqueous solution showed an intense signal that had negative and positive wings with about 100-fold larger molar ellipticity for the A-685 than for monomer. However, Chl a', the C10 epimer of Chl a, and chlorophyllide, with a phytyl chain replaced by an ethyl group, did not form A-685 in 6% THF. These clearly indicate that 10-methylcarboxylate and the phytyl chain have a significant role in stabilizing A-685. A possible structure for A-685 is proposed as a novel in vitro model for the P-680 Chl a dimer.  相似文献   

10.
A Co(II) complex [Co3(L)4(H2O)6] · 2Cl (I), where L is salicylaldehyde-aminoacetic acid Schiff base, was synthesized and characterized via elemental analysis, UV, and single crystal X-ray crystallography. Complex I crystallizes in the orthorhombic system, space group Pbcn with lattice parameters a = 9.569(4), b = 12.301(5), c = 36.931(14) Å, V = 4347(3) Å3, Z = 4, ρcalcd = 1.608 mg m?3. At the same time, the binding reaction between complex I and bovine serum albumin (BSA) was studied by fluorescence spectroscopy combined with UV-Vis absorption measurements under simulative physiological conditions. The results indicated that its combination reaction is mainly a static quenching process. Complex I bound BSA with a molar ratio of 1: 1 and the binding constant K A values are 3.86 × 105 L mol?1 (25°C) and 1.17 × 105 L mol?1 (36°C). The shortest binding distance r between the donor BSA and acceptor (complex I) is 2.49 nm, which affirms that complex I has partly inserted into the hydrophobic pocket of BSA.  相似文献   

11.
New multilayer films were prepared by alternating adsorption of poly(sodium 4-styrenesulfonate) (PSS) and a new complex of [Cu2(Dpq)2(Ac)2(H2O)2] (ClO4)2·H2O (1) (Dpq=dipyrido[3,2-d:2′,3′-f]quinoxaline, Ac=acetate) or a related complex [Cu(Dpq)2(H2O)] (ClO4)2·H2O (1a) by electrostatic layer-by-layer self-assembly technique, respectively. Compounds 1 and 1a have been synthesized and structurally characterized by elemental analyses, IR spectroscopy, and single-crystal X-ray diffraction analyses. Single-crystal X-ray analyses show that complexes 1 and 1a possess a dinuclear and a mononuclear structure, respectively, which are further extended into layered frameworks by π-π stacking and hydrogen-bonding interactions. The multilayer films were characterized by UV-vis spectroscopy, fluorescence spectroscopy, small-angle X-ray reflectivity measurements, and atomic force microscopy (AFM) imaging. UV spectroscopy shows that the deposition process is regular and highly reproducible from layer to layer. AFM image indicates that the film surface is uniform and smooth. The fluorescent properties of the films were studied and the results showed that the forming condition of the films had great influence on their properties.  相似文献   

12.
The effect of oxygen concentration on both absorption and chlorophyll fluorescence spectra was investigated in isolated pea thylakoids at weak actinic light under the steady-state conditions. Upon the rise of oxygen concentration from anaerobiosis up to 412 microM a gradual absorbance increase around both 437 and 670 nm was observed, suggesting the disaggregation of LHCII and destacking of thylakoids. Simultaneously, an increase in oxygen concentration resulted in a decline in the Chl fluorescence at 680 nm to about 60% of the initial value. The plot of normalized Chl fluorescence quenching, F(-O(2))/F(+O(2)), showed discontinuity above 275 microM O(2), revealing two phases of quenching, at both lower and higher oxygen concentrations. The inhibition of photosystem II by DCMU or atrazine as well as that of cyt b(6)f by myxothiazol attenuated the oxygen-induced quenching events observed above 275 microM O(2), but did not modify the first phase of oxygen action. These data imply that the oxygen mediated Chl fluorescence quenching is partially independent on non-cyclic electron flow. The second phase of oxygen-induced decline in Chl fluorescence is diminished in thylakoids with poisoned PSII and cyt b(6)f activities and treated with rotenone or N-ethylmaleimide to inhibit NAD(P)H-plastoquinone dehydrogenase. The data suggest that under weak light and high oxygen concentration the Chl fluorescence quenching results from interactions between oxygen and PSI, cyt b(6)f and Ndh. On the contrary, inhibition of non-cyclic electron flow by antimycin A or uncoupling of thylakoids by carbonyl cyanide m-chlorophenyl hydrazone did not modify the steady-state oxygen effect on Chl fluorescence quenching. The addition of NADH protected thylakoids against oxygen-induced Chl fluorescence quenching, whereas in the presence of exogenic duroquinone the decrease in Chl fluorescence to one half of the initial level did not result from the oxygen effect, probably due to oxygen action as a weak electron acceptor from PQ pool and an insufficient non-photochemical quencher. The data indicate that mechanism of oxygen-induced Chl fluorescence quenching depends significantly on oxygen concentration and is related to both structural rearrangement of thylakoids and the direct oxygen reduction by photosynthetic complexes.  相似文献   

13.
Compounds p-HOOCC6F4COOH · H2O (H2L · H2O), [Tb2(H2O)4(L)3 · 2H2O] n (I), and Tb2(Phen)2(L)3 · 2H2O (II) are synthesized. According to the X-ray structure analysis data, the crystal structure of H2L · H2O is built of centrosymmetric molecules H2L and molecules of water of crystallization. The crystal structure of compound I is built of layers of coordination 2D polymer [Tb2(H2O)4(L)3] n and molecules of water of crystallization. The ligands are the L2? anions performing both the tetradentate bridging and pentadentate bridging-chelating functions. The coordination polyhedron TbO9 is a distorted three-capped trigonal prism. Acid H2L manifests photoluminescence in the UV region (??max = 368 nm). Compounds I and II have the green luminescence characteristic of the Tb3+ ions, and the band with ??max = 545 nm (transition 5 D 4?? 7 F 5) is maximum in intensity. The photoluminescence intensity of compound II is higher than that for compound I.  相似文献   

14.
Reaction of Zn(NO3)2·6H2O with p-aminobenzoic acid in a 1:2 molar ratio under ethanol medium at room temperature affords a new three dimensional (3D) coordination polymer [Zn(PABA)2]·H2O (1) (PABA = p-aminobenzoic acid). Single-crystal X-ray diffraction reveals that 1 crystallizes in the orthorhombic system, space group P212121, a = 7.614(2), b = 11.133(3), c = 16.869(4). 1 adopts a 3D open framework with H2O molecules in the cavities. PABA, acting as bridging ligand as well as coordinating ligand, adopts a different coordination mode to bridge Zn atoms and form the 3D supramolecular structure which is further stabilized by N–H?O, O–H?O hydrogen bonding and π–π stacking interactions. Powder second-harmonic generation (SHG) efficiency measurement with Nd:YAG laser (1064 nm) radiation shows that the SHG efficiency of 1 is equivalent to KDP crystal. The present work also demonstrates that the framework of 1 is retained after removal of the guest H2O molecules, and the H2O molecules can be reintroduced into the framework, indicating that this complex may also be used to generate porous materials.  相似文献   

15.
Three cobalt(II) coordination polymers {[Co(L1)(nda)(H2O)2]·2H2O} n (1), [Co(L2)(tbi)(H2O)] n (2) and [Co(L2)(bpdc)(H2O)] n (3) (L1 = 1,3-bis(5,6-dimethylbenzimidazol-1-yl)-2-propanol, L2 = 1,3-bis(benzimidazol-1-yl)-2-propanol, H2nda = 2,6-naphthalenedicarboxylic acid, H2tbi = 5-tert-butyl isophthalic acid and H2bpdc = 4,4′-biphenyldicarboxylic acid) were synthesized and characterized by physicochemical and spectroscopic methods. Complex 1 exhibits a 1D loop-like structure, which is further extended into a 3D 3,3,4T31 network through two O–H···O hydrogen bonding interactions. Complex 2 displays a 1D ladder-like chain, arranged into a 2D supramolecular network with 3,3,4L34 topology via classical O–H···O hydrogen bonding interactions, whereas complex 3 features a 2D 3,4L13 layer structure and further assembles into a 3D framework with a twofold interpenetrating sqc65 topology through O–H···O hydrogen bonding interactions. The fluorescence and catalytic properties of these complexes for the degradation of Congo red in a Fenton-like process have been investigated.  相似文献   

16.
《中国化学快报》2020,31(8):2041-2044
Acetone is an important industrial raw material as well as biomarker in medical diagnosis. The detection of acetone has great significance for safety and health. However, high selectivity and low concentration (ppb level) detection remain challenges for semiconductor gas sensor. Herein, we present a novel sensitive material with bimetallic PtCu nanocrystal modified on WO3·H2O hollow spheres (HS), which shows high sensitivity, excellent selectivity, fast response/recovery speed and low limit of detection (LOD) to acetone detection. Noteworthy, the response (Ra/Rg) of WO3·H2O HS sensor increased by 9.5 times after modification with 0.02% bimetallic PtCu nanocrystals. The response of PtCu/WO3·H2O HS to 50 ppm acetone is as high as 204.9 with short response/recovery times (3.4 s/7.5 s). Finally, the gas-sensitivity mechanism was discussed based on gas sensitivity test results. This research will offer a new route for high efficient acetone detection.  相似文献   

17.
Four homotrinuclear linear coordination compounds with bridging ligand of (m-phenol)-1,2,4-triazole, [Mn3(L)6(H2O)6](ClO4)6 (1), [Ni3(L)6(H2O)6](BF4)6·4DMF (2), [Cd3(L)6(H2O)6](ClO4)6· 2H2O·2DMF·2EtOH (3), [Zn3(L)8(H2O)4](BF4)4(SiF6)·2EtOH·12H2O (4), have been synthesized and structurally determined. The structures consist of three metal ions in linear arrangements, linked to each other by two pairs of three N1, N2 bridging triazole ligands. The negative value of J suggests that antiferromagnetic interaction exists in 1. Green fluorescence of 2 and 4 with emissions at 518 nm for 2 and 524 for 4 is possibly assigned to LMCT. The energy gaps of the compounds 2 and 4 are 1.82 and 1.97 eV, respectively, which suggests that the two materials behave as semiconductors.  相似文献   

18.
A new complex [Co(phen)3] · (H3btec) · (H2btec)0.5 · DMF · 6H2O (1) (H4btec = 1,2,4,5-Benzenetetracarboxylic acid, phen = 1,10-phenanthroline, DMF = dimethylformamide) was synthesized by the reaction of pyromellitic dianhydride, phen · H2O and CoSO4 · 7H2O. Complex 1 crystallizes in the triclinic system, space group P-1 with a = 11.8123(14) ?, b = 13.0356(16) ?, c = 17.575(2) ?, ?? = 91.461(2)°, ?? = 101.347(2)°, ?? = 99.830(2)°, FW = 1159.94, Z = 2, V = 2609.5(5) ?3. X-ray crystal structural determination indicates that the Co(II) ion is octahedral coordinated by six nitrogen atoms of three phenanthroline ligands. The [Co(phen)3]2+ cation engages its phen ligands in ??-?? interactions with H2btec anion. Extensive hydrogen bonding interactions occur between water molecules, DMF, H3btec and H2btec anions. The highly-crystalline compounds 1, which are insoluble in water as well as common organic solvents, have been characterized in the solid-state by elemental analysis, thermogravimetric analysis and IR spectra. Moreover, the study of the electrochemistry of complex 1 was carried out by using cyclic voltammetry. It revealed that the Co(II) complex exhibits a quasi-reversible one-electron redox process.  相似文献   

19.
New luminescent mononuclear and dinuclear copper(II) (S = 1/2) complexes [Cu(HL)(H2O)2](ClO4)2 (1a) and [Cu2(HL)2(μ-SO4)2]·2H2O (1b) were synthesized with the acyclic tridentate pyridine-2-carboxaldehyde-2-pyridylhydrazone ligand, HL (1). Interestingly, the mononuclear complex 1a can be converted into the disulfate bridged dimeric copper(II) complex 1b by passing freshly prepared SO2 through the basic medium. On excitation at 290 nm, the ligand fluoresces at 364 nm due to an intraligand 1(π–π1) transition. Upon complexation with copper(II), the emission peak is slightly blue shifted (356 nm, F/F0 0.76 for 1a and 354 nm, F/F0 0.89 for 1b) with a little quenching in the emission intensity. The association constants (Kass (5.06 ± 0.004) × 104 for 1a and Kass (5.46 ± 0.006) × 104 for 1b at 298 K) and the thermodynamic parameters have been determined by UV–Vis spectroscopy. The molecular structure of the complex 1b (Cu?Cu 4.456 Å) has been determined by single crystal X-ray diffraction studies. The complex 1b exhibits a strong interaction towards DNA as revealed from the Kb (intrinsic binding constant) 6.3 × 104 M?1 and Ksv (Stern–Volmer quenching constant) 2.93 values.  相似文献   

20.
Qualitative single crystals of ??-complexes Cu(H+L)(ClO4)]ClO4 · H2O (I), Cu(H+L)(BF4)]BF4 · H2O (II), and [Cu(H+L)(H2O)]SiF6 · H2O (III) are synthesized from solutions of 3-(diallylamino)propanenitrile (L) in propanol, ethanol, and methanol-water acidified with the corresponding acid to pH 3.5?C5 and from the copper(II) salts (Cu(ClO4)2 · 6H2O, Cu(BF4)2 · 6H2O, and CuSiF6 · 4H2O) using the alternating-current electrochemical method on copper wire electrodes. The crystal structures of the complexes are determined. All compounds crystallize in the monoclinic crystal system: complexes I and II are isostructural, space group P21/n, Z = 4. For compound III, space group P21/c, Z = 8. Unit cell parameters: for I a =7.8153(3), b = 16.7824(7), c = 12.4426(5) ?, ?? = 93.410(2)°, V = 1629.1(1) ?3; for II, a = 7.6755(4), b = 16.7119(7), c = 12.3784(6) ?, ?? = 94.354(2)°, V = 1583.2(1); and for III a = 9.826(2), b = 24.009(3), c = 12.061(2) ?, ?? = 91.820(6)°, V = 2843.9(7) ?3. The trigonal pyramidal coordination of the copper atom in complexes I-III is formed by two C=C bonds of the allyl groups of H+L, the nitrile N atom of the adjacent cation of the ligand, and the O or F atom of the ClO 4 ? or BF 4 ? anions. In structure III, the apical position of the pyramid is occupied by the O atom of the water molecule, since the SiF 6 2? anion is considerably remote from the copper(I) atom. However, this anion is bound to the organic cation by hydrogen bonds F??H (2.05?C2.51 ?).  相似文献   

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