共查询到20条相似文献,搜索用时 46 毫秒
1.
Synthesis, Spectroscopy and Photochemistry of Nitro-Azobenzene Dyes Bearing Benzophenone Parts 总被引:1,自引:1,他引:0
Fang Gao Jianchao Wang XiaoJiao Liu Long Yang Nvdan Hu Ting Xie Hongru Li Shengtao Zhang 《Journal of fluorescence》2009,19(3):533-544
Novel nitro-azobenzene dyes bearing one or two benzophenone branches were proposed and synthesized to improve their photophysical
and photochemical properties. The new dyes exhibited double UV/visible bands, and they displayed weak fluorescence emission
as excited at 350 nm. Single crystal X-ray diffraction data showed that two phenyl rings of azobenzene was almost coplanar,
and the benzophenone part was neither coplanar nor linear connection with azobenzene via ether bridged bond, which have good
fit with molecular geometry optimization calculation results. The cyclic voltammeric results of nitro-azobenzene dyes were
firstly reported in this paper, which demonstrated that the electrochemical properties of nitro-azobenzene dyes was altered
by the substitution of benzophenone part. Thermal stabilities of the new dyes were studied by the analysis of differential
scanning calorimetry (DSC) and thermograving (TG) in this paper. Efficient visible-light photoinitiating polymerization of
methyl methacrylate (MMA) by the novel nitro-azobenzene dyes was presented and discussed. 相似文献
2.
Fang Gao Liufeng Yang Long Yang Hongru Li Shengtao Zhang 《Journal of fluorescence》2010,20(1):353-364
Suitable chemical strategy is a useful approach on the tuning color and photoluminescence of organic dyes. This paper presented
tuning novel branched p-nitro-stilbene derivatives efficiently with a new chemical strategy through variation of chemical
bridged bond. Linking bonds played significant effects on the absorption and fluorescence spectroscopy of the branched p-nitro-stilbene
derivatives. A change from “D-π-A” to “A-π-A” chemical structural characteristics occurred for the branched p-nitro-stilbene
derivatives as ester bond was attached. This led to not only large hypsochromic shift of the maximal absorption wavelength
of the branched p-nitro-stilbene derivatives, but considerable reduction of the fluorescence intensity. While in contrast,
the branched p-nitro-stilbene derivatives with ether bond exhibited longer wavelength absorption and much stronger fluorescence
emission in modest polar solvent. The cyclic voltammograms of these branched p-nitro-stilbene derivatives were determined.
Different electrochemistry processes were observed for the branched p-nitro-stilbene derivatives with various linking bonds.
The energies of frontier orbital of the branched p-nitro-stilbene derivatives were estimated from their corresponding redox
potentials. Molecular geometry optimization of the branched p-nitro-stilbene derivatives was performed, and the electron density
distribution of frontier orbital was analyzed. Thermal stabilities of these branched nitro-stilbene derivatives were investigated
via the analysis of the differential scanning calorimetry (DSC) and thermograving (TGA) curves. This paper presented strong
evidences that the absorption and fluorescence spectroscopy of the branched stilbene derivatives could be mediated efficiently
by chemical strategy. 相似文献
3.
In this paper, we have presented a range of new nitro-stilbene derivatives with benzophenones via ether or ester bridged bond.
These nitro-stilbene derivatives with benzophenones have been conveniently obtained by condensation reaction. The linked benzophenones
were efficiently introduced to nitro-stilbene dyes. The structures of these compounds have been characterized with NMR and
element analysis. The single crystals of two target compounds (11 and 12) have been obtained, and their X-ray crystallographic data have been determined and discussed. Remarkably different absorption
and fluorescence spectroscopy was observed for nitro-stilbene derivatives with benzophenones via different linked bonds. The
results show that electron-donating or electron withdrawing bridged bonds have significant influence on the absorption and
fluorescence spectroscopy, which makes it possible for the development of ideal nitro-stilbene dyes with benzophenones through
chemical strategy. 相似文献
4.
The electronic absorption, excitation and sensitized visible light emission studies of three praseodymium (III) complexes:
[Pr(fod)3(bpy)], [Pr(fod)3(phen)] and [Pr(fod)3(bpm)]n (fod = anion of 6,6,7,7,8,8,8- heptafluoro-2,2-dimethyl-3,5-octanedione; bpy = 2,2'-bipyridyl, phen = 1,10-phenanthroline,
bpm = 2,2'-bipyrimidine) in a series of non–aqueous solvents is presented. The f–f absorption transitions of Pr(III) are environment sensitive which is reflected by the change in the intensity (oscillator
strength) and band shape (stark splitting) upon change in the solvent and/or the ligands. The sensitization of intense Pr(III)
emission, in the visible region, of the complexes in solution upon excitation into the ligand centered π→π* absorption band
is remarkable. The planar phen has pronounced impact and increases considerably the emission intensity of Pr(III) luminescence
than the flexible bpy while bpm has been found least effective in promoting the emission intensity. The intensity of the f-f absorption and sensitized emission are correlated with the nature of the solvents. The donor solvent pyridine enhances the
emission intensity of the [Pr(fod)3(phen)] drastically and of [Pr(fod)3(bpy)] marginally while the luminescent intensity of [Pr(fod)3(bpm)]n is decreased. The combined photophysical studies demonstrate that entry of the solvent molecule(s) to inner coordination
sphere (complex–solvent interaction) is governed by the structure and basicity of the ancillary heterocyclic ligand attached
to the Pr(III) complex. The strong donor DMSO transforms the three complexes into a similar species, [Ln(fod)3(DMSO)2], which results in similar electronic absorption and emission properties of the complexes in this solvent. The results demonstrate
that highly luminescent praseodymium chelates can be designed with ligands containing suitable energy levels and their emission
properties can be further modulated through suitable ancillary ligands and donor solvents, thus opening perspectives for applications
in electroluminescent devices and luminescent probes. 相似文献
5.
dos Santos AM 《Journal of fluorescence》2012,22(1):151-154
The emission behaviour of Aequorea green fluorescent protein (A-GFP) chromophore, in both neutral (N) and anionic (A) form, was studied in the temperature range
from 20 °C to 75 °C and at pH = 7. Excitation wavelengths of 399 nm and 476 nm were applied to probe the N and A forms environment,
respectively. Both forms exhibit distinct fluorescence patterns at high temperature values. The emission quenching rate, following
a temperature increase, is higher for the chromophore N form as a result of the hydrogen bond network weakening. The chromophore
anionic form emission maximum is red shifted, upon temperature increase, due to a charge transfer process occurring after
A form excitation. 相似文献
6.
Spectral properties of novel type of fluorophores consist of a π-conjugated system end-capped with an electron-donating N,N-dimethylaminophenyl group and an electron-withdrawing imidazole-4,5-dicarbonitrile moiety were examined. An additional π-linker
separating these two structural units comprises simple bond (B1P), phenyl (B2B), styryl (B3S) and ethynylphenyl (B4A) moieties.
The absorption and fluorescence spectra were taken in cyclohexane, chloroform, acetonitrile, methanol and in polymer matrices
such as polystyrene, poly(methyl methacrylate) and poly(vinylchloride). The longest-wavelength absorption band was observed
in the range of 300 to 400 nm. Intense fluorescence with quantum yields of 0.2 to 1.0 was observed in cyclohexane, chloroform
and in polymer matrices within the range of 380 to 500 nm. The fluorescence was strongly quenched in neat acetonitrile and
methanol. The fluorescence lifetimes are in the range of 1–4 ns for all measured fluorophores. The large Stokes shift (4,000
to 8,000 cm−1) indicates a large difference in the spatial arrangement of the chromophore in the absorbing and the emitting states. The
observed fluorescence of all fluorophores in chloroform was quenched by 1-oxo-2,2,6,6-tetramethyl-4-hydroxy piperidine by
the diffusion-controlled bimolecular rate (cca 2 × 1010 L mol−1 s−1). Polar solvents such as acetonitrile and methanol quenched the fluorescence as well but probably via a different mechanism. 相似文献
7.
Three new pyridylindolizine derivatives, 1, 2, 3-tricarbometoxi-7-(4-pyridyl)-pyrrolo[1, 2-a]pyridine (I), 1,2-dicarboethoxy-3-(4-bromobenzoyl)-7-(4-pyridyl)-pyrrolo[1,2-a]pyridine (II) and its isomer 1,2-dicarboethoxy-3- (4-bromobenzoyl) -5- (2-pyridyl) -pyrrolo[1, 2-a]pyridine (III) have been investigated in different solutions by UV-VIS absorption, steady-state, and time-resolved fluorescence methods. The effects of the substituent and solvent on the spectroscopic properties have been demonstrated. The fluorescence decay data could be fitted to a single-exponential function. The lifetime values are higher in protic polar than in aprotic apolar solvents for compound I. In the case of compounds II and III the fluorescence intensities and lifetimes are very low, with the exception of III in aprotic solvents. The absorption and fluorescence properties of the compounds showed a solvent dependence. 相似文献
8.
A donor-acceptor compound based on Rhodanineacetic acid-pyrene derivative (RAAP), which emits weak yellow-green fluorescence
in the methanol solution, was investigated. RAAP nanoparticles with a mean diameter of 50–60 nm were prepared by a simple
reprecipitation method without surfactants. The observation of RAAP nanoparticles were undertaken through SEM and TEM method.
The emission spectra of RAAP nanoparticles are red-shifted (Δ λem = 86 nm) to red region and the intensity is 40-fold higher than that in the methanol solution. Both the J-aggregation and
aggregation-induced intramolecular planarization are considered to be the probable mechanism of strong emission for RAAP nanoparticles.
The excellent sensibility toward organic vapor which profits from its fluorescence switching behavior is well demonstrated
by vapor experiment. 相似文献
9.
Cheikh?L? Jean-Jacques?Aaron Václav?Kozmík Ji?í?Svoboda Jean-Claude?Brochon Li?Na 《Journal of fluorescence》2010,20(5):1037-1047
The synthesis, electrochemical and optical properties of three fluorescent substituted thieno[3,2-b][1]benzothiophenes (TBT)
derivatives, including 3-methoxythieno[3,2-b][1]benzothiophene (3-MeO-TBT), 2,3-dimethylthieno[3,2-b][1]benzothiophene (2,3-diMe-TBT),
and 6-methoxythieno[3,2-b][1]benzothiophene-2-carboxylate (6-MeO-TBT-2-COOMe), were investigated. The oxidation potential
values varied between 1.40 and 1.20 V/SCE according to the electronic substituent effect, and electropolymerization attempts,
performed in 0.1 M LiClO4 acetonitrile solution, led to the formation of very thin films of poly(3-MeO-TBT) and poly(2,3-di-Me-TBT). Electronic absorption
spectra, fluorescence excitation and emission spectra, fluorescence quantum yields (ΦF) , lifetimes (τF), and other photophysical parameters of the three new TBT derivatives were measured in DMSO solutions at room temperature.
For the methyl-and methoxy-substituted TBT derivatives, the fluorescence emission peak were slightly red shifted relative
to that of unsubstituted TBT (Δλem = 1–12 nm) whereas, in the case of 6-MeO-TBT-2-COOMe, a rather strong red-shift (Δλem = 73 nm) was attributed to the existence of a “push-pull” electronic interaction of the MeO and COOMe groups. All ΦF values were rather high, varying between 0.11 and 0.35, according to the substituent effect. Fluorescence decays were mono-exponential
and τF values were very short, ranging between 0.11 and 0.30 ns for the substituted TBT derivatives until study. 相似文献
10.
Compounds with strong absorptions in the ultraviolet (UV) region of the spectrum, particularly the UVA and UVB, have seen much interest as UV screeners or absorbers in a wide variety of commercial products. A series of benzisoxazole 2‐oxides have been synthesized and characterized by UV–vis spectroscopy. A number of derivatives have been shown to posses moderate to strong molar absorption coefficients in the UVB range (ca. 300 nm), the strongest being those derived from benzophenones. Three other derivatives containing additional electron withdrawing groups showed strong molar absorption coefficients in the UVA (ca. 340 nm). Solvent effects on the parent derivatives show changes in the molar absorption coefficients with little changes in the λmax values. Preliminary studies of these compounds as potential additives to prevent photooxidation of polystyrene showed considerable inhibition of polymer degradation with the parent unsubstituted benzisoxazole 2‐oxide compounds being the most effective. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
11.
G. K. Raghuraman Jürgen Rühe Raghavachari Dhamodharan 《Journal of nanoparticle research》2008,10(3):415-427
Stable dispersion of titania nanoparticles in organic solvents are obtained by grafting poly(methyl methacrylate) layer on
to the surface. Titania nanoparticles are synthesized through the hydrolysis of titanium (IV) isopropoxide. The average size
of the titania particles is found to be 15 ± 2 nm. The polymer layer was introduced onto the surface by immobilizing the initiating
moiety. Azo initiator moiety required for surface-initiated conventional free radical polymerization and a tertiary bromide
initiator moiety required for ATRP are attached covalently to the titania nanoparticulate surface through the surface hydroxyl
groups. The “encapsulation” of PMMA layer results in the steric stabilization of the titania nanoparticles. Another important
finding is that it is possible to grow polymer layer in a controlled fashion. 相似文献
12.
Abstract Absorption and emission spectroscopy in the ultraviolet and visible regions, apart from being the earliest physical techniques of analysis, have great utility in solving a variety of structural and analytical problems [l-41. However, in many cases the quantitative determination of individual components in a mixture by UV-VIS spectroscopy becomes very difficult owing to the spectral similarities and overlapping of weak absorption bands of one component by strong absorption bands of other components. It was recently recognized that derivative spectrophotometry, introduced about three decades ago [5-81 and originally proposed by Rutherford [9], can be a very useful analytical tool for characterizing an analyte band that is overlapped by other absorption bands with different halfwidths. On differentiation, the intensity of the absorption band with a small halfwidth increases more than that of a band with a large halfwidth [10]. The central idea behind the development of the science of derivatized spectra rests upon the measurement of the first or the higher derivatives of the absorbance A or the luminescence intensity I with respect to the wavelength λ, e.g., dI/dλ, dA/dλ, d2I/dλ2, etc. These derivatives, when plotted or scanned against wavelength, yield an array of derivative spectra. 相似文献
13.
Yang Li Dong Wang Lei Wang Zhengqiang Li Qing Cui Haiquan Zhang Huai Yang 《Journal of luminescence》2012,132(4):1010-1014
A series of novel substituted pyrene derivatives with asymmetrical groups have been successfully synthesized in excellent yield. Structures of the asymmetrical compound were fully characterized by 1H-NMR, IR spectroscopy and mass spectrometry. By introducing ethynyl functions to pyrene, we obtained highly efficient blue and green light emitting materials. It has been demonstrated that the emission characteristics of pyrene derivatives have been bathochromatically tuned in the visible region by extending the π-conjugation. The photophysical properties of these compounds were carefully examined in different organic solvents and different concentrations. The electrochemical properties and geometrical electronic structures of the new pyrene derivatives have been investigated by cyclic voltammograms and density functional theory (DFT) calculations. 相似文献
14.
M. K. Mundra C. J. Ellison P. Rittigstein J. M. Torkelson 《The European physical journal. Special topics》2007,141(1):143-151
Confinement effects in polystyrene and poly(methyl
methacrylate) films and nanocomposites are studied by fluorescence.
The ability to employ an intensive measurable, the excited-state
fluorescence lifetime, in defining the glass transition temperature,
Tg, of polymers is demonstrated and compared to the use of an
extensive measurable, fluorescence intensity. In addition, intrinsic
fluorescence from the phenyl groups in polystyrene is used to
determine the Tg-confinement effect in films as thin as
~15 nm. The decrease in Tg with decreasing film thickness
(below ∼60 nm) agrees well with results obtained by extrinsic
pyrene fluorescence. Dye label fluorescence is used to quantify the
enhancement in Tg observed with decreasing thickness (below
~90 nm) in poly(methyl methacrylate) films; addition of
2–4 wt% dioctyl phthalate plasticizer reduces or eliminates the
Tg-confinement effect in films down to 20 nm
thickness. Intrinsic polystyrene fluorescence, which is sensitive to
local conformation, is used to quantify the time scales (some tens
of minutes) associated with stress relaxation in thin and ultrathin
spin-coated films at Tg + 10 K. Finally, the shape of the
fluorescence spectrum of pyrene doped at trace levels in polystyrene
films and polystyrene-silica nanocomposites is used to determine
effects of confinement on microenvironment polarity. 相似文献
15.
In the context, a modified sol-gel technology was afford to the synthesis of rare earth composite ceramic phosphors MM′O3/CeO2 and MM′O3/CeO2: Pr3+ (M = Ca, Sr; M′ = Ti, Zr) with multicomponent hybrid precursors were composed. The micromorphology, particle size and photoluminescence
properties were studied with XRD, SEM and luminescent spectroscopy in detail. Both XRD and SEM indicated the particle sizes
were in the submicrometer range of 100 ∼ 300 nm. The photoluminescence for these ceramic phosphors were studied in details
with the different component of host (molecular ratio of Sr, Ca and Ti, Zr), presenting a broad spectral band in the visible
blue-violet region with the maximum excitation peak at 449 nm and a wide emission range with a maximum peak at 619 nm, which
was ascribed to be the characteristic transition of Pr3+ (1D2 → 3H4). These phosphors can be expected for visible light conversion (blue → red) materials. Especially it can be found that the
introduction of CeO2 can enhance the luminescence intensity of MM′O3 and MM′O3: Pr3+. 相似文献
16.
A. Antony Muthu Prabhu S. Siva R. K. Sankaranarayanan N. Rajendiran 《Journal of fluorescence》2010,20(1):43-54
The photophysical behaviour of 2,6-diaminopyridine (DAP) has been studied in solvents of different polarity, pH, β-cyclodextrin
(β-CD) and compared with 2-amino pyridine (2AP). The inclusion complex of both molecules with β-CD are analysed by UV-visible,
fluorimetry, FT-IR, 1H NMR, SEM and AM1 methods. The solvent studies shows i) DAP gives more red shifted absorption and emission maxima than 2AP
molecule and ii) addition of amino group in 2AP effectively increase the resonance interaction in the pyridine ring. A regular
red shift observed in acidic pH solutions suggests intramolecular proton transfer (IPT) present in both molecules. β-CD studies
indicates i) in pH ~ 7, a regular red shifted absorption and emission maxima observed in AP molecules suggests pyridine ring
encapsulated in to the β-CD cavity (1:1 inclusion complex formed) and ii) in pH ~ 1, a blue shifted absorption maxima noticed
in 2AP, is due to protonated amino group deeply encapsulated in to the hydrophobic part of the β-CD cavity. 相似文献
17.
Li Wan Xianbao Wang Shimin Wang Shaoqing Li Qin Li Rong Tian Mingjian Li 《Journal of Physical Organic Chemistry》2009,22(4):331-336
The imidazole derivatives functionalized single‐walled carbon nanotubes (SWNTs) were synthesized by a diazonium‐based reaction. We have designed and synthesized two imidazole derivatives to modify SWNTs. The resulting products were characterized by Fourier transform infrared (FT‐IR) spectroscopy, Raman spectroscopy, ultraviolet visible (UV/Vis) spectroscopy, thermo gravimetric analysis (TGA), energy dispersive X‐ray spectroscopy (EDX), transmission electron microscopy (TEM), and atomic force microscopy (AFM). Electrochemical measurements via a cyclic voltammetry method revealed that the weak intramolecular electronic interactions presented between the attached imidazole derivatives groups and the nanotubes. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
18.
Some novel Y-shaped imidazole derivatives were developed and characterized by NMR and mass spectral techniques. The photophysical
properties of these imidazole derivatives were studied in several solvents. The Kamlet-Taft and Catalan’s solvent scales were
found to be the most suitable for describing the solvatochromic shifts of the absorption and fluorescence emission. The adjusted
coefficient representing the electron releasing ability or basicity of the solvent, C
β
or C
SB has a negative value, suggesting that the absorption and fluorescence bands shift to lower energies with the increasing electron-donating
ability of the solvent. This effect can be interpreted in terms of the stabilization of the resonance structures of the chromophore.
The observed lower fluorescence quantum yield may be due to an increase in the non-radiative deactivation rate constant. This
is attributed to the loss of planarity in the excited state provided by the non co-planarity of the cinnamaldehyde ring attached
to C(2) atom of the imidazole ring. Such a geometrical change in the excited state leads to an important Stokes shift, reducing
the reabsorption and reemission effects in the detected emission in highly concentrated solutions. 相似文献
19.
Aurones, derivatives of 2-benylidenebenzofuran-3(2H)-one, are natural products that serve as plant pigments. There have been reports that some of these substances fluoresce,
but little information about their optical properties is in the literature. In this report, series of aurone derivatives were
synthesized as possible fluorescent probes that can be excited by visible light. We found that an amine substituent shifted
the lowest energy absorption band from the near-UV to the visible region of the electromagnetic spectrum. Four amine-substituted
aurone derivatives were synthesized to explore the effect of this substituent on the absorption and emission properties of
the aurone chromophore. The emission maxima and intensities of the molecules are strongly dependent on the nature of the substituent
and the solvent polarity. Overall, the emission intensity increases and the maximum wavelength decreases in less polar solvents;
thus, the aurones may be useful probes for hydrophobic sites on biological molecules. A limited investigation with model protein,
nucleic acid and fixed cells supports this idea. It is known that the sulfur analog of aurone can undergo photo-induced E/Z isomerization. This possibility was investigated for one of the aminoaurones, which was observed to reversible photoisomerize.
The two isomers have similar absorption spectra, but the emission properties are distinct. We conclude that appropriately
substituted aurones are potentially useful as biological probes and photoswitches. 相似文献
20.
The spectral properties of a novel type of Y-shaped fluorophores consisting of an imidazole ring end-capped with two electron-donating N,N-dimethylaminophenyl groups at positions C4 and C5 and one electron-withdrawing cyano group on the imidazole moiety at position C2 were examined. The π-linker separating the 4,5-bis[4-(N,N-dimethylamino)phenyl]-1H-imidazole donor moiety and the cyano group comprises 1,4-phenylene (1), (E)-phenylethenyl (2), (E)-phenylbuta-1,3-dienyl (3), biphenyl (4), (E)-phenylethenylphenyl (5) and phenylethynylphenyl (6) conjugated paths. The absorption and fluorescence spectra were obtained in toluene, dichloromethane, acetonitrile and methanol and in polymer matrices such as polystyrene (PS), poly(methyl methacrylate) (PMMA) and poly(vinylchloride) (PVC). The most intense absorption bands of fluorophores 1-6 were observed within the range of 283 to 330?nm. Less intense but longer-wavelength absorption bands designated as charge-transfer bands were observed at approximately 380-430?nm depending on the medium. The fluorophores exhibited strong fluorescence in the visible region with a Stokes shift of approximately 4300-5800?cm(-1) in non-polar toluene and polystyrene, whereas very low intensity of fluorescence was observed with a Stokes shift in the 6500-7800?cm(-1) region in polar methanol and acetonitrile. The large Stokes shift indicates a large difference in the spatial arrangement of the chromophore in the absorbing and emitting states. A relatively intense fluorescence (quantum yields of 0.12-0.69) was observed only for derivative 1 in all media except methanol. The fluorophores doped in matrices yielded more intense fluorescence compared with the fluorescence in liquid media. The use of solid polymer matrices lowers the probability of forming non-emissive excited states. The fluorescence lifetimes were short (1-4?ns) for all of the fluorophores in solvents and in polymer matrices. 相似文献