共查询到20条相似文献,搜索用时 15 毫秒
1.
Jeongsik Kim Yoshikazu OkaTatsuya Morozumi Eun Wha ChoiHiroshi Nakamura 《Tetrahedron》2011,67(26):4814-4819
Benzo-crown ether based chemosensors linked by an amide bond at the 1-, 2- or 9-positions of anthracene rings were synthesized. Their complexation behavior with alkaline earth metal ions in acetonitrile was investigated using fluorescence, UV, and 1H NMR spectroscopy. In the absence of a metal ion, all compounds showed only very slight fluorescence emissions (fluorescence ‘off’ state) because of intramolecular charge/electron transfer process. After the complex formation with Mg2+ and Ca2+, however, only the 2-position analogue gave a fluorescence ‘on’ response by inhibiting the photoinduced electron transfer. Because 2-positioned anthracene was free from steric hindrance of the crown ether ring, a strongly bent complex structure was formed with Mg2+ and Ca2+, which induced a breakdown of π-conjugation between the amide moiety and the benzene ring. 相似文献
2.
The synthesis of the chiral diaza-9-crown-3 derivatives 1 (S,S) and 2 (R,R) is described. These sensors were designed as luminescent chemosensors for lithium where the fluorescence emission from the naphthalene moieties was ‘switched on’ upon Li+ recognition by the crown ether moiety in organic solvents, showing excellent selectivity over other group I and group II cations. Even though the recognition of Li+ was not achieved in water (pH 7.4) or aqueous alcohol solution, the fluorescence (which was switched on at pH 7.4) was substantially modulated by spherical anions, where the fluorescence emission was quenched in the presence of Br− and I− but less by Cl− and not by acetate. This indicates that the emission was quenched by heavy-atom affect. The recognition of Li+ was also investigated by 1H NMR in CD3CN and by observing the changes in the circular dicromism spectra. For the former, the resonances for the crown ether moiety and α-methyl protons adjacent to the ring were sifted upfield and broadened, whereas for 1 the intensity of the CD signal for the π-π transition was substantially modulated upon Li+ recognition. 相似文献
3.
New N-(pyrenylmethyl)naphtho-azacrown-5 (1) was synthesized as an ‘On-Off’ fluorescent chemosensor for Cu2+. Excited at 240 nm corresponding to the absorption of naphthalene unit (energy donor) of 1, emission at 380 nm from pyrene unit (energy acceptor) is observed, indicating that intramolecular fluorescence resonance energy transfer (FRET-On) occurs in 1. When Cu2+ is added to a solution of 1, however, the fluorescence of pyrene is strongly quenched (FRET-Off) whereas that of naphthalene group is revived. Such FRET ‘On-Off’ behavior of 1 is observed only in the case of Cu2+ binding, but not for other metal cations. The high selectivity of 1 toward Cu2+ can be potentially applied to a new kind of FRET-based chemosensor. The FRET On-Off behavior is supported by computational studies. The calculated molecular orbitals of HOMO and LUMOs suggest the excited-state interactions leading to FRET from naphthalene to pyrene in 1, but no electron density changes in 1·Cu2+ complex. 相似文献
4.
New photo-induced electron transfer (PET) probes OMOX and OBOX, carrying an additional binding site in the form of ‘oxadiazole nitrogen’ have been designed to evaluate binding interactions with biologically significant Li+, Na+, K+, Ca2+, Mg2+, and Zn2+ including environmentally toxic Ba2+ and Cd2+ using optical spectral techniques. While Li+, Na+, and K+ did not appreciably perturb either the absorption or emission spectra, Ba2+, Ca2+, Mg2+, Zn2+, and Cd2+ induced slight red shifts (2-8 nm) in the UV-visible spectra as well as pronounced chelation induced enhanced fluorescence (CHEF). Both OMOX and OBOX exhibited the highest CHEF in contact with the zinc ion, whereas Ba2+, Ca2+, Mg2+, and Cd2+ induced relatively less emission enhancements. OBOX, which is a poorer emitter (Φf=0.0062) than OMOX (Φf=0.015), showed highly promising 160-fold emission enhancement in the presence of Zn2+. Potential, therefore is available in OBOX to function as a selective luminescent ‘off-on’ sensor for Zn2+ in the presence of coordinatively competing Ba2+, Ca2+, Mg2+, and Cd2+ ions. 相似文献
5.
We have developed a FRET-based ratiometric fluorescent probe for the detection of CN− using a fluorescein–Zn–naphthalene ensemble (NFH·Zn2+). The sensing mechanism was ascribed by displacement approach. The chemosensor exhibits high selectivity and sensibility for CN−. The speculation was supported by fluorescence emission spectra, UV–vis spectrum, 1H NMR titration experiments, and mass spectra. The interconversion of probe NFH and NFH·Zn2+ via the complexation/decomplexation by the modulation of Zn2+/CN− mimics INHIBIT gate. In addition, it also shows an excellent performance in ‘dip stick’ method. 相似文献
6.
Zhanxian LiWanying Zhao Yuna ZhangLifeng Zhang Mingming Yu Jinxia Liu Hongyan Zhang 《Tetrahedron》2011,67(37):7096-7100
A ‘switching-on’ fluorescent chemosensor for the selective and sensitive signaling of intraceullar Cr3+ has been designed and synthesized exploiting the guest-induced prohibition of the photoinduced electron transfer process between naphthyridine moiety and 7,10-diphenylfluoranthene moiety, the system shows a Cr3+-selective chelation-enhanced fluorescence response not only in ethanol but in cell. 相似文献
7.
A series of novel, water-soluble benzimidazolium salts with common ‘fluorophore–spacer–receptor’ PET design has been synthesized. Despite the common PET scaffold these benzimidazolium salts displayed diverse emission intensities in pure aqueous solutions. The observed emission intensities were found to be influenced by the functionalized alkyl side arms present on the benzimidazolium ring. These benzimidazolium salts were also found to act as selective sensors for Fe3+ ions over other metal ions like Na+, K+, Ca2+, Mg2+, Ba2+, Al3+, Cr3+, Co2+, Ni2+, Mn2+, Zn2+, Pb2+, Ag+, Cu2+ and Hg2+ in pure aqueous media. 相似文献
8.
Satomi HagiwaraYohei Ishida Dai MasuiTetsuya Shimada Shinsuke Takagi 《Tetrahedron letters》2012,53(43):5800-5802
Novel tetracationic pyrene derivative (1,3,6,8-tetrakis(N-methylpyridinium-4-yl)pyrene, Py4+) was synthesized. Photochemical properties such as fluorescence quantum yield and fluorescence lifetime were observed for Py4+ and Py4+/clay complexes. Judging from Lambert-Beer plot analysis, Py4+ molecules adsorb on the clay surface without aggregation up to 69% versus cation exchange capacity of the clay. Py4+ molecule emits strong fluorescence from an excited state of monomer, while the emission from excimer was not detected, in spite of high density adsorption condition on the solid surface. It is supposed that strong interaction between host and guest by the ‘Size-Matching Effect’ inhibits the formation of excimer on the clay surface. 相似文献
9.
Thorfinnur Gunnlaugsson Paul E. KrugerT.Clive Lee Raman ParkeshFrederick M. Pfeffer Gillian M. Hussey 《Tetrahedron letters》2003,44(35):6575-6578
The design and synthesis of two novel fluorescent PET anion sensors is described, based on the principle of ‘fluorophore-spacer-(anion)receptor’. The sensors 1 and 2 employ simple diaromatic thioureas as anion receptors, and the fluorophore is a naphthalimide moiety that absorbs in the visible part of the spectrum and emits in the green. Upon recognition of anions such as F− and AcO− in DMSO, the fluorescence emission of 1 and 2 was ‘switched off’, with no significant changes in the UV-vis spectra. This recognition shows a 1:1 binding between the receptor and the anions. In the case of F−, further additions of the anion, gave rise to large changes in the UV-vis spectra, where the λmax at 455 nm was shifted to 550 nm. These changes are thought to be due to the deprotonation of the 4-amino moiety of the naphthalimide fluorophore. This was in fact found to be the case, using simple naphthalimide derivatives such as 6. Sensors 1 and 2 can thus display dual sensing action; where at low concentrations, the fluorescence emission is quenched, and at higher concentrations the absorption spectra are modulated. 相似文献
10.
Subhodip Samanta Pinki Saha Sardar Shyam Sundar Maity Anirban Pal Maitrayee Basu Roy Sanjib Ghosh 《Journal of Chemical Sciences》2007,119(2):175-183
A comparative time-resolved emission studies of several naphtho-crown ethers I–V, where metal ions can be complexed in a predetermined orientation with respect to the naphthalene (Naph) π-plane and naphthalene-linked aza crown ethers (L1 and L2) have been presented. In both the systems, crown ethers and aza
crown ethers, naphthalene fluorescence gets quenched. In the systems I to V, the quenching is mainly due to efficient spin-orbit coupling (SOC) leading to greater population of the lowest triplet state
of naphthalene. This SOC depends on the orientation of the crown ring with respect to the Naph-π-plane. However, in the systems L1 and L2, the quenching is due to photoinduced electron transfer (PET) from nitrogen lone
pair of the aza crown ring to naphthalene moiety and consequent exciplex formation. The results have been interpreted using
the time-resolved emission studies of all the compounds in various solvents, their alkali metal ion complexes, and protonated
ligands. 相似文献
11.
Yi-Bin RuanJuan Xie 《Tetrahedron》2011,67(45):8717-8723
Methylated fluorescein 1 was explored for fluorescence ‘turn-on’ and ratiometric detection of Hg2+ in THF and CH2Cl2/MeOH (v/v=9:1), respectively, with unexpected high selectivity. In the presence of Hg2+, characteristic structured absorption band of 1 diminished and a new sharp band appeared at 445 nm. Meanwhile a blue shifted and enhanced emission was observed. The ratio of the fluorescence intensity at 559 and 478 nm increased linearly with [Hg2+], and solution color changing from yellow to cyan under irradiation at 365 nm in CH2Cl2/MeOH. Job plot indicated a 1:1 stoichiometry for 1-Hg2+ complex in solution. 1H NMR titration and IR spectra suggested the coordination of carbonyl group in xanthene moiety to Hg2+, affording its spectral behavior. Compound 2 bearing two triazolyl amino esters in place of methyl group showed quite similar behavior to Hg2+, which indicated that substituents did not interfere with the specific binding behavior of fluorescein platform. Our work presents a new way to explore xanthene dyes as new chemosensors by modulating electron density on the xanthene ring through non-covalent interactions with carbonyl group. 相似文献
12.
A novel ‘turn-on’ fluorescent probe with perylene tetracarboxylic bisimide (PBI) as the fluorophore and di(2-(salicylideneamino))ethylamine (DSEA) as the metal ion receptor was designed. The capability of the prepared probe to detect metal ions was evaluated by the changes in its emission intensity. The probe demonstrated a considerable emission enhancement (ca. 110-fold) in the presence of Al3+ in MeCN with high selectivity and sensitivity. Furthermore, the considerably ‘off–on’ fluorescence response concomitantly led to the apparent color change from colorless to brilliant yellow, which could also be identified by naked eye easily under UV lamp. 相似文献
13.
A new thiacalix[4]arene based fluorescent sensor 1 bearing two naphthyl groups has been synthesized in 1,3-alternate conformation. In the absence of fluoride ion, the receptor 1 is in ‘off-state’ showing no fluorescence emission. The presence of fluoride ion triggered the fluorescence emission to ‘on-state’. The receptor shows pronounced selectivity for fluoride ions. In THF, the presence of F− ions induces the formation of a 1:1 (G:H) complex. 相似文献
14.
The present paper deals with data interpretation of monitoring of various atmospheric events (cloud water, aerosol and rainwater) at three different elevation levels at Achenkirch profile in an Alpine valley, Tyrol, Austria (Christlumkopf-1758 m, Christlumalm-1280 m and Talboden-930 m a.s.l.) by the use of principal components analysis. From October 1995 to September 1996 sampling sessions for all sites from the profile and for all events were performed for the major ions NH4+, Na+, K+, Ca2+, Mg2+, Cl−, NO3−, SO42−-44 cases with eight variables for rainwater; 117 cases with eight variables for cloud water samples and 50 cases with seven variables for aerosol (the major ions as in rain- and cloud water but without magnesium) at any of the elevations. The aim of the multivariate statistical treatment was to extract information about latent factors determining the data structure in all of the cases in order to compare and interpret similarities and dissimilarities with respect to the elevation or the type of the atmospheric event. Four latent factors seem to explain over 85% of the total variance for almost all sites and events but the factors have different identification for the different events or sites (e.g. ‘anthropogenic’, ‘crustal’, ‘neutralization’, ‘salt’). Thus, a comparison between sites and between events becomes possible. It was found that cloud water and aerosol events are much more similar with respect to data structure (relevant to emission sources or processes of formation) than the same events and rainwater. Further, the upper sites of the profile (Christlumkopf and Christlumalm) also reveal data structure similarity differing from that of the lowest site Talboden. 相似文献
15.
Prabhpreet Singh 《Tetrahedron》2006,62(26):6379-6387
The dipod 1,2-bis(8-hydroxyquinolinoxymethyl)benzene (3) and tetrapod 1,2,4,5-tetrakis(8-hydroxyquinolinoxymethyl)benzene (5) have been synthesized through nucleophilic substitution of respective 1,2-bis(bromomethyl)benzene (2) and 1,2,4,5-tetra(bromomethyl)benzene (4) with 8-hydroxyquinoline (1). For comparison, 1,3,5-tris(8-hydroxyquinolinoxymethyl)benzene derivatives (7a and 7b) have been obtained. The complexation behavior of these podands towards Ag+, Co2+, Ni2+, Cu2+, Zn2+, and Cd2+ metal ions has been investigated in acetonitrile by fluorescence spectroscopy. The sterically crowded 1,2,4,5-tetrapod 5 displays unique fluorescence ‘ON-OFF-ON’ switching through fluorescence quenching (λmax 395 nm, switch OFF) with <1.0 equiv of Ag+ and fluorescence enhancement (λmax 495 nm, switch ON) with >3 equiv Ag+ and can be used for estimation of two different concentrations of Ag+ at two different wavelengths. The addition of Cu2+, Ni2+, and Co2+ metal ions to tetrapod 5 causes fluorescence quenching, i.e., ‘ON-OFF’ phenomena at λmax 395 nm for <10 μM (1 equiv) of these ions but addition of Zn2+ and Cd2+ to tetrapod 5 results in fluorescence enhancement with a gradual shift of λem from 395 to 432 and 418 nm, respectively. Similarly, dipod 3 behaves as an ‘ON-OFF-ON’ switch with Ag+, an ‘ON-OFF’ switch with Cu2+, and an ‘OFF-ON’ switch with Zn2+. The placement of quinolinoxymethyl groups at the 1,3,5-positions of benzene ring in tripod 7a-b leads to simultaneous fluorescence quenching at λmax 380 nm and enhancement at λmax 490 nm with both Ag+ and Cu2+. This behavior is in parallel with 8-methoxyquinoline 8. The rationalization of these results in terms of metal ion coordination and protonation of podands shows that 1,2 placement of quinoline units in tetrapod 5 and dipod 3 causes three different fluorescent responses, i.e., ‘ON-OFF-ON’, ‘ON-OFF’, and ‘OFF-ON’ due to metal ion coordination of different transition metal ions and 1, 3, and 5 placement of three quinolines in tripod 7, the protonation of quinolines is preferred over metal ion coordination. In general, the greater number of quinoline units coordinated per metal ion in 5 compared with the other podands points to organization of the four quinoline moieties around metal ions in the case of 5. 相似文献
16.
A novel β-aminobisphosphonate receptor has been combined with naphthalene in the fluorophore-spacer-receptor format of a typical photoinduced electron transfer (PET) based sensor. The sensor was synthesised in two steps by first reacting aminomethylnaphthalene with diethyl vinylphosphonate to produce the parent tetraester, followed by deprotection with bromotrimethylsilane to afford the desired sensor. The fluorescence emission of the sensor was observed to remain ‘On’ over a wide pH range (2-10). Cu(II) was found to bind strongly to the sensor resulting in an ‘On-Off’ fluorescent response with sensitivity in the μM range. 相似文献
17.
18.
Fluorescent nucleosides and oligonucleotides functionalized with pyrene were synthesized using ‘click’ chemistry or the Sonogashira cross-coupling reaction. The dye was connected to position-7 of 7-deaza-2′-deoxyguanosine or to the 2′-deoxyribofuranose moiety. Four different DNA-dye connectors with 1,2,3-triazolyl residues or triple bonds were constructed. Phosphoramidites of the pyrene conjugates (9, 14, 25) were prepared and used in solid-phase synthesis. Short linkers (2, 4) destabilize DNA, while long linkers (1) increased duplex stability. Nucleosides and oligonucleotides with single dye incorporations show linker dependent fluorescence. Linker dependent excimer emission with pyrenes in proximal positions was also observed. A ‘superchromophore’ formed by the 7-deaza-2′-deoxyguanosine ethynylpyrene conjugate shows strong red shifted fluorescence emission at 495 nm. 相似文献
19.
Han Zhang 《Tetrahedron letters》2007,48(23):3959-3962
Novel turn-on fluoroionophores 2 and 3 based on highly fluorescent 8-methoxyquinoline were developed in which a sequential singlet-singlet energy transfer, ISC, and triplet-triplet energy transfer occurred leading to a fluorescence ‘off’ state. They showed substantially enhanced fluorescence in the presence of transition metal ions such as Zn2+, Cu2+, Pb2+, and Hg2+ and an extremely high selectivity toward Zn2+ by 3. 相似文献
20.
A series of 1-naphthanilides (1) and 2-naphthanilides (2) with varied substituents at the para- or meta-position of anilino phenyl ring were prepared and their absorption and fluorescence spectra in a nonpolar solvent cyclohexane were investigated. An abnormal long wavelength emission assigned to the charge transfer (CT) state was found for all of the prepared naphthanilides in cyclohexane. A linear free energy correlation between the CT emission energies and the Hammett constants of the substituent was found within series 1 and 2. The value of the linear slope with 1 (0.42 eV) was higher than that with 2 (0.32 eV) being close to that of the substituted benzanilides 3 (0.31 eV) The higher slope value suggested higher charge separation extent in the CT state of 1 than that of 2. It was found that the corresponding linear slope of anilino-substituted benzanilides remained unchanged when para-, meta-, ortho-, or ortho, ortho-methyls were introduced into the anilino moiety, which ruled out the possible contribution of the difference in the steric effect and the electron accepting ability of the naphthoyl acceptor in 1 and 2. Compared with the early reported N-substituted-benzoyl-aminonaphthalene derivatives 4 and 5, it was considered that 1-naphthoyl enhanced the charge transfer in 1 and the proximity of its ^1La and ^1Lb states was suggested to be responsible. It was shown that 1- and/or 2-substituted naphthalene cores acting as either electron acceptor (naphthoyl) or electron donor (aminonaphthalene) were different in not only electron accepting (donating) ability but also shaping the charge transfer pathway. 相似文献