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1.
A new binaphthalene (R)-1 with two substituted TTF and trichloroquinone units is reported. Both absorption and ESR spectral studies show that electron transfer occurs between TTF and trichloroquinone units of (R)-1 in the presence of metal ions (Pb2+, Sc3+, Zn2+, and Ca2+). We also propose a possible mechanism for this electron transfer process. But, the CD spectral change of (R)-1 in the presence of metal ions is rather small.  相似文献   

2.
Tetrathiafulvalene-flavin dyads 1 and 2 are reported. Both absorption and ESR spectral studies show that the intramolecular electron transfer occurs from TTF to flavin units in dyads 1 and 2 in the presence of Pb2+/Sc3+. But, the electron transfer is more efficient for dyad 1 in the presence of Pb2+/Sc3+. Electrochemical studies manifest that coordination of dyads 1 and 2 with Pb2+/Sc3+ play an important role in facilitating the electron transfer within dyads 1 and 2.  相似文献   

3.
Two tetrathiafulvalene-calix[4]arene assemblies(TTF-calix-1 and TTF-calix-2) have been synthesized by the click reaction.Both their cyclic voltammograms show,as expected,two one-electron quasi-reversible redox behavior.The UV-vis absorption spectra studies show that these two assemblies undergo progressive oxidation at the TTF moiety in presence of increasing amounts of Cu2+ or Hg2+. Moreover,the absorption studies show intermolecular electron transfer between compounds TTF-calix- 1 or TTF-calix-2 and p-chloranil may be promoted by specific metal ions such as Pb2+,Sc3+ etc.  相似文献   

4.
Two crown ethers carrying pyrene side arms with nitrogen-sulfur donor atom were designed and synthesized by the reaction of the corresponding macrocyclic compounds and 1-bromomethyl-pyrene. The influence of metal cations such as Al3+, Zn2+, Fe2+, Fe3+, Co2+, Ni2+, Mn2+, Cu2+, Cd2+, Hg2+ and Pb2+ on the spectroscopic properties of the ligands was investigated in acetonitrile-tetrahydrofuran (1:1) by means of absorption and emission spectrometry. Absorption spectra show isosbestic points in the spectrophotometric titration of Al3+, Zn2+, Fe2+, Ni2+, Cu2+, and Pb2+ with 16-membered crown ether. Similar results were obtained for Al3+, Fe2+, Hg2+, Cu2+ and Pb2+ with 14-membered crown ether. The results of spectrophotometric titration experiments disclosed the complexation stoichiometry and complex stability constants of the novel ligands with these cations. According to spectrofluorimetric titration measurements the 14-membered diazadithia crown ether showed sensitivity for Pb2+ with linear range and detection limit of 1.3 × 10?6 to 5.2 × 10?5 M and 5.2 × 10?7 M, respectively. The 16-membered diazadithia crown ether showed sensitivity for Ni2+ with linear range and detection limit of 1.3 × 10?7 to 5.2 × 10?6 M and 4.1 × 10?8 M, respectively.  相似文献   

5.
A water in soluble long‐chain crown ether alkyl (C18)‐benzo‐15‐crown‐5 was synthesized and applied as a coating material on quartz crystal membranes of a liquid flow piezo electric crystal sensor. The oscillating crown ether‐coated piezo electric (PZ) crystal with a home‐made computer inter face was prepared as a liquid chromato graphic (LC) detector for organic species and metal ions in aqueous solutions. The oscillating frequency of the quartz crystal decreased due to the adsorption of organic molecules or metal ions on crown ether molecules. Effects of functional group, molar mass, steric hindrance, and polarity of organic molecules on frequency responses of the crown ether coated PZ crystal detector were investigated. The frequency responses of the crown ether coated PZ crystal detector for various molecules were in the order: amines > carboxylic acids > alcohols > ketones. The crown ether PZ detector also exhibited good sensitivity for some heavy metal ions and the frequency shifts were in the order: Cr3+ » Pb2+ > Co2+ > Cd2+ > Ni2+ > Cu2+. The crown ether coated piezo electric crystal LC detector demonstrated low detection limits for various polar organic molecules, e.g., 6.0 × 10?5 M for propylamine, and metal ions, e.g., 2.9 × 10?5 M (1.8 ppm) for Cu2+; the crown ether PZ detector also gave good reproducibility when re used. A quite sensitive electrochemical quartz crystal microbalance (EQCM) detection system was also set‐up for detecting trace heavy metal ions in solutions. The variation in frequency of the PZ crystal and the diffusion current were observed simultaneously after the reduction in heavy metal ions such as Cu2+ and Ni2+. The EQCM detection system exhibited fairly good sensitivity, e.g., 112 Hz/ppm for Cu2+ and a good detection limit, e.g., 0.13 ppm for Cu2+ ions. Comparison between EQCM and PZ detection systems was made and discussed.  相似文献   

6.
The site of electron‐transfer reduction of AuPQ+ (PQ=5,10,15,20‐tetrakis(3,5‐di‐tert‐butylphenyl)quino‐xalino[2, 3?b′]porphyrin) and AuQPQ+ (QPQ=5,10,15,20‐tetrakis(3,5‐di‐tert‐butylphenyl)bisquinoxalino[2,3‐b′:12,13‐b′′]porphyrin) is changed from the AuIII center to the quinoxaline part of the PQ macrocycle in the presence of Sc3+ in benzonitrile because of strong binding of Sc3+ to the two nitrogen atoms of the quinoxaline moiety. Strong binding of Sc3+ to the corresponding nitrogen atoms on the quinoxaline unit of ZnPQ also occurs for the neutral form. The effects of Sc3+ on the photodynamics of an electron donor–acceptor compound containing a linked ZnII and AuIII porphyrin ([ZnPQ–AuPQ]PF6) have been examined by femto‐ and nanosecond laser flash photolysis measurements. The observed transient absorption bands at 630 and 670 nm after laser pulse irradiation in the absence of Sc3+ in benzonitrile are assigned to the charge‐shifted (CS) state (ZnPQ . +–AuPQ). The CS state decays through back electron transfer (BET) to the ground state rather than to the triplet excited state. The BET rate was determined from the disappearance of the absorption band due to the CS state. The decay of the CS state obeys first‐order kinetics. The CS lifetime was determined to be 250 ps in benzonitrile. Addition of Sc3+ to a solution of ZnPQ–AuPQ+ in benzonitrile caused a drastic lengthening of the CS lifetime that was determined to be 430 ns, a value 1700 times longer than the 250 ps lifetime measured in the absence of Sc3+. Such remarkable prolongation of the CS lifetime in the presence of Sc3+ results from a change in the site of electron transfer from the AuIII center to the quinoxaline part of the PQ macrocycle when Sc3+ binds to the quinoxaline moiety, which decelerate BET due to a large reorganization energy of electron transfer. The change in the site of electron transfer was confirmed by ESR measurements, redox potentials, and UV/Vis spectra of the singly reduced products.  相似文献   

7.
The effect of metal ions on the, reduction of 1,10-phenanthroline-5,6-quinone (1), 5,8-quinolinequinone (II) and 6,7-dichloro-5, 8-quinolinequinone (III) has been investigated in 50% dimethylsulfoxide+water solvent. 1 contains the 1,10-phenanthroline structure in both its quinone and hydroquinone forms, while II and III contain the 8-hydroxyquinoline structure in the hydroquinone forms. Complexation of the hydroquinones of II and III by metal ions causes positive shifts in the quinone half-wave potentials. These shifts have been used to calculate conditional formation constants for Pb2+(II) and Pb2+ and Zn2+(III). The quinone form of I binds strongly to Ni2+, Co2+ and Zn2+ but not to Ca2+. Mg2+. Mg2+. Mn2+ and Pb2+. With the latter four metals, binding to the hydroquinone from of I was detected and formation constants were determined. In addition to binding both the quinone and hydroquinone forms at the nitrogen atoms, Ni2+ Co2+ and Zn2+ formed complexes at the 1,2-dihydroxy site of the hydroquinone of I.  相似文献   

8.
The synthesis of a new ligand (L1) containing two 1,4,7‐triazacyclononane ([9]aneN3) moieties linked by a 4,5‐dimethylenacridine unit is reported. The binding and fluorescence sensing properties toward Cu2+, Zn2+, Cd2+, and Pb2+ of L1 and receptor L2, composed of two [9]aneN3 macrocycles bridged by a 6,6′′‐dimethylen‐2,2′:6′,2′′‐terpyridine unit, have been studied by coupling potentiometric, UV/Vis absorption, and emission measurements in aqueous media. Both receptors can selectively detect Zn2+ thanks to fluorescence emission enhancement upon metal binding. The analysis of the binding and sensing properties of the Zn2+ complexes toward inorganic anions revealed that the dinuclear Zn2+ complex of L1 selectively binds and senses the triphosphate anion (TP), whereas the mononuclear Zn2+ complex of L2 displays selective recognition of diphosphate (DP). Binding of TP or DP induces emission quenching of the Zn2+ complexes with L1 and L2, respectively. These results are exploited to discuss the role played by pH, number of coordinated metal cations, and binding ability of the bridging units in metal and/or anion coordination and sensing.  相似文献   

9.
A chloroform membrane system containing a given mixture of dibenzyldiaza‐18‐crown‐6 and palmetic acid was applied for transport of Pb2+ ions. The transport was capable of moving metal ions “uphill”. Thus, it was possible to follow the transfer of Pb(II) from the aqueous source phase to the organic layer and from the organic layer to the receiving phase. The effects of thiosulfate concentration in the receiving phase, palmetic acid and dibenzyldiaza‐18‐crown‐6 concentration in the organic phase on the efficiency of the transport system were examined. By using S2O32? ion as metal ion acceptor in the receiving phase, the amount of lead ion transport across the liquid membrane after 150 minutes is 96 ± 1.5%. The selectivity and efficiency of lead transport from aqueous solution containing Cu2+, Tl+, Ag+, Co2+, Ni2+, Mg2+, Zn2+, Hg2+, Cd2+, Ca2+ were investigated. In the presence of thiosulfate as a suitable masking agent in the source phase, the interfering effects of Ag+ and Cu2+ were diminished drastically.  相似文献   

10.
A series of lead‐sensitive poly(N‐isopropylacrylamide) microgels with pendant crown ether groups were prepared. Their cation‐sensitive behaviors were studied by dynamic light scattering. When ionic strength is not controlled, adding salts causes the microgel particles to deswell. However, when the salt effect is ruled out by keeping a constant ionic strength, adding Pb2+ results in much larger swelling. The Pb2+‐induced swelling was explained by the formation of host–guest complex between Pb2+ and the pendant crown ether groups, which increases the hydrophilicity of the polymer and accordingly the degree of swelling. The lead sensitivity of the microgels increases with increasing crown ether content. For the modified microgel with the highest crown ether content, it swells to ~430% of its original volume at [Pb2+] = 10 mM. Other cations also increase the swelling degree of the modified microgels. The extent of the cation‐induced swelling mainly depends on their affinity to the pendant crown ether groups. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4120–4127, 2010  相似文献   

11.
The heteroditopic crown ether‐based ligand 1 containing the diazafluorenylimino group as a binding site for the Zn2+ and Cs+ was synthesized. The ligand 1 can be gelated in DMSO/water with and without Cs+ in the presence of the Zn2+ ion. Interestingly, the remarkable gelation reinforcement of gel 1 occurred with Cs+ in the presence of Zn2+, which is due to the formation of a sandwich complex. According to DFT calculations, one Zn2+ is bound to two diazafluorenylimino moieties in a tetrahedral structure. In addition, one Cs+ ion is bound to two crown‐rings. The Zn2+‐diazafluorenylimino ligand gel without Cs+ shows a spherical structure with 250–800 nm diameter, whereas the Zn2+‐diazafluorenylimino‐based ligand gel with Cs+ shows a fiber structure with 60–70 nm diameter and several micrometers of lengths. The rheological properties of the Zn2+‐ diazafluorenylimino‐based ligand gel were strongly dependent on the presence of Cs+.  相似文献   

12.
Two water‐soluble para‐xylylene‐connected 4,4′‐bipyridinium (BIPY2+) polymers have been prepared. UV‐Vis absorption, 1H NMR spectroscopy, and cyclic voltammetry experiments support that in water the BIPY2+ units in the polymers form stable 1:1 charge‐transfer complexes with tetrathiafulvalene (TTF) guests that bear two or four carboxylate groups. These charge‐transfer complexes are stabilized by the donor–acceptor interaction between electron‐rich TTF and electron‐deficient BIPY2+ units and electrostatic attraction between the dicationic BIPY2+ units and the anionic carboxylate groups attached to the TTF core. On the basis of UV‐Vis experiments, a lower limit to the apparent association constant of the TTF?BIPY2+ complexes of the mixtures, 1.8×106 m ?1, has been estimated in water. Control experiments reveal substantially reduced binding ability of the neutral TTF di‐ and tetracarboxylic acids to the BIPY2+ molecules and polymers. Moreover, the stability of the charge‐transfer complexes formed by the BIPY2+ units of the polymers are considerably higher than that of the complexes formed between two monomeric BIPY2+ controls and the dicarboxylate‐TTF donor; this has been attributed to the mutually strengthened electron‐deficient nature of the BIPY2+ units of the polymers due to the electron‐withdrawing effect of the BIPY2+ units.  相似文献   

13.
A series of tetrathiafulvalene (TTF)‐annulated porphyrins, and their corresponding ZnII complexes, have been synthesized. Detailed electrochemical, photophysical, and theoretical studies reveal the effects of intramolecular charge‐transfer transitions that originate from the TTF fragments to the macrocyclic core. The incremental synthetic addition of TTF moieties to the porphyrin core makes the species more susceptible to these charge‐transfer (CT) effects as evidenced by spectroscopic studies. On the other hand, regular positive shifts in the reduction signals are seen in the square‐wave voltammograms as the number of TTF subunits increases. Structural studies that involve the tetrakis‐substituted TTF–porphyrin (both free‐base and ZnII complex) reveal only modest deviations from planarity. The effect of TTF substitution is thus ascribed to electronic overlap between annulated TTF subunits rather than steric effects. The directly linked thiafulvalene subunits function as both π acceptors as well as σ donors. Whereas σ donation accounts for the substituent‐dependent charge‐transfer transitions, it is the π‐acceptor nature of the appended tetrathiafulvalene groups that dominates the redox chemistry. Interactions between the subunits are also reflected in the square‐wave voltammograms. In the case of the free‐base derivatives that bear multiple TTF subunits, the neighboring TTF units, as well as the TTF ? + generated through one‐electron oxidation, can interact with each other; this gives rise to multiple signals in the square‐wave voltammograms. On the other hand, after metalation, the electronic communication between the separate TTF moieties becomes restricted and they act as separate redox centers under conditions of oxidation. Thus only two signals, which correspond to TTF . + and TTF2+, are observed. The reduction potentials are also seen to shift towards more negative values after metalation, a finding that is considered to reflect an increased HOMO–LUMO gap. To probe the excited‐state dynamics and internal CT character, transient absorption spectral studies were performed. These analyses revealed that all the TTF–porphyrins of this study display relatively short excited‐state lifetimes, which range from 1 to 20 ps. This reflects a very fast decay to the ground state and is consistent with the proposed intramolecular charge‐transfer effects inferred from the ground‐state studies. Complementary DFT calculations provide a mechanistic rationale for the electron flow within the TTF–porphyrins and support the proposed intramolecular charge‐transfer interactions and π‐acceptor effects.  相似文献   

14.
A practical, two‐step synthesis of novel 4‐(substituted bis‐indolyl)methyl)benzo‐15‐crown‐5 has been reported. The strategy employed for the synthesis of the desired molecules involved Duff formylation of benzo‐15‐crown‐5 to get 4‐formyl benzo‐15‐crown‐5 followed by subsequent reactions with substituted indoles in trifluoroacetic acid to yield novel 4‐(substituted bis‐indolyl)methyl)benzo‐15‐crown‐5 in moderate to good yield. One of the reported novel molecule tested for the complexation behavior with various metal cations, such as Li+, Na+, K+, Mg2+ Ca2+, Al3+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Sn2+, Ba2+, Hg2+, and Pb2+, showed a visual colorimetric probe for the detection of mercury cations (Hg2+) in an aqueous medium.  相似文献   

15.
The promiscuous encapsulation of π‐electron‐rich guests by the π‐electron‐deficient host, cyclobis(paraquat‐p‐phenylene) (CBPQT4+), involves the formation of 1:1 inclusion complexes. One of the most intensely investigated charge‐transfer (CT) bands, assumed to result from inclusion of a guest molecule inside the cavity of CBPQT4+, is an emerald‐green band associated with the complexation of tetrathiafulvalene (TTF) and its derivatives. This interpretation was called into question recently in this journal based on theoretical gas‐phase calculations that reinterpreted this CT band in terms of an intermolecular side‐on interaction of TTF with one of the bipyridinium (BIPY2+) units of CBPQT4+, rather than the encapsulation of TTF inside the cavity of CBPQT4+. We carried out DFT calculations, including solvation, that reveal conclusively that the CT band emerging upon mixing TTF with CBPQT4+ arises from the formation of a 1:1 inclusion complex. In support of this conclusion, we have performed additional experiments on a [2]rotaxane in which a TTF unit, located in the middle of its short dumbbell, is prevented sterically from interacting with either one of the two BIPY2+ units of a CBPQT4+ ring residing on a separate [2]rotaxane in a side‐on fashion. This [2]rotaxane has similar UV/Vis and 1H NMR spectroscopic properties with those of 1:1 inclusion complexes of TTF and its derivatives with CBPQT4+. The [2]rotaxane exists as an equimolar mixture of cis‐ and trans‐isomers associated with the disubstituted TTF unit in its dumbbell component. Solid‐state structures were obtained for both isomers, validating the conclusion that the TTF unit, which gives rise to the CT band, resides inside CBPQT4+.  相似文献   

16.
Four cone calix[4]arene-1,2-crown ethers each with two ionisable side arms containing dansyl groups are synthesised. The crown ether ring on the lower rim is varied from crown-4 to crown-5 with hydrogen or tert-butyl groups on the para position of the upper rim. Di(tetramethylammonium) salts of the di-ionised ligands are utilised for spectrofluorimetric titration experiments in MeCN. The influence of alkali metal, alkaline earth metal and selected transition and heavy metal (Co2+, Fe2+, Hg2+, Mn2+, Pb2+, Zn2+ and Fe3+) cations on the spectroscopic properties of the two dansyl groups linked to the lower rim of the conformationally locked, di-ionised calix[4]arene-1,2-crown ether frameworks is investigated by emission spectrophotometry. All of the metal cations induce red shifts in the emission spectra of the di-ionised ligands. The metal cations produce enhancement or quenching of the fluorescence emissions. Changes in the fluorescence emission as a function of the metal cation identity, the lower rim crown ether ring size and the absence or presence of upper rim tert-butyl groups are investigated.  相似文献   

17.
Rigid N‐(substituted)‐2‐aza‐[3]‐ferrocenophanes L1 and L2 were easily synthesized from 1,1 ‐dicarboxyaldehydeferrocene and the corresponding amines. Ligands L1 and L2 were characterized by 1H NMR, 13C NMR and single‐crystal X‐ray crystallography. The coordination abilities of L1 and L2 with metal ions such as Cu2+, Mg2+, Ni2+, Zn2+, Pb2+ and Cd2+ were evaluated by cyclic voltammetry. The electrochemical shift (ΔE1/2) of 125 mV was observed in the presence of Cu2+ ion, while no significant shift of the Fc/Fc + couple was observed when Mg2+, Ni2+, Zn2+, Pb2+, Cd2+ metal ions were added to the solution of L1 in the mixture of MeOH and H2O. Moreover, the extent of the anodic shift of redox potentials was approximately equal to that induced by Cu2+ alone when a mixture of Cu2+, Mg2+, Ni2+, Zn2+, Pb2+ and Cd2+ was added to a solution of L1. Ligand L1 was proved to selectively sense Cu2+ in the presence of large, excessive first‐row transition and late‐transition metal cations. The coordination model was proposed from the results of controlled experiments and quantum calculations. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

18.
In the present work, we have reported the synthesis of benzimidazoles functionalized crown ether derivatives of 4-formyl benzo-15-crown-5/4,4′-diformyl dibenzo-15-crown-5 and substituted diamine pyridine using sulfamic acid as a catalyst in DMSO. These molecules are used for the colorimetric determination of Au3+ selectively among other metal cations such as Fe2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Pb2+, Hg2+, Au3+ and Ag+ ions.  相似文献   

19.
This research concerns the analysis of the metal ion binding of benzo‐ and pyridine‐azacrown ether compounds of different structures and sizes by potentiometric method. The ligands are able to form 1 : 1 complexes with heavy metal ions (Cu+2, Pb+2, Cd+2, Ag+, Ni+2, Zn+2) in water of middle or high stability. To understand the selectivity in cation binding, different factors were considered.  相似文献   

20.
A new 14-membered crown ether with nitrogen–sulfur donor atom carrying two anthryl groups was designed and synthesized by the reaction of the corresponding macrocyclic compound and 9-(chloromethyl) anthracene. The influence of metal cations such as Al3+, Zn2+, Fe2+, Fe3+, Co2+, Ni2+, Mn2+, Cu2+, Cd2+, Hg2+ and Pb2+ on the spectroscopic properties of the ligand was investigated in acetonitrile–dioxane solution (1/1) by means of absorption and emission spectrometry. The results of spectrophotometric titration experiments disclosed the complexation stoichiometry and complex stability constant of the novel ligand with Fe2+, Fe3+, Al3+, Cd2+, Cu2+, Zn2+, Pb2+ and Hg2+ cations. Absorption spectra show isobestic points in the spectrophotometric titration of these cations. The presence of excess of Al3+, Zn2+, Fe2+, Fe3+, Co2+, Ni2+, Mn2+, Cu2+, Cd2+, Hg2+ and Pb2+ cations caused an enhancement of anthryl fluorescence. Especially, the enhancement in case of the interaction of Hg2+ and Al3+ cations with the ligand was pronounced.  相似文献   

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