共查询到20条相似文献,搜索用时 140 毫秒
1.
The role of mesomethyl substitution and of steric interaction of peripheral substituents in the formation of nonplanar distortions
of the porphyrin macrocycle is studied for a series of Ni(II)-porphyrins. Resonance Raman spectra are recorded for Ni(II)-5-methyl-2,3,7,8,12,13,17,18-octaethylporphyrin
(1); Ni(II)-2,5,8,12,18-pentamethyl-3,7,13,17-tetraethylporphyrin (2); and Ni(II)-3,5,7,12,17-pentamethyl-2,8,12,17-tetraethylporphyrin
(3). The obtained spectra are compared with spectra of Ni-octaethylporphyrin (Ni-OEP) and Ni-etioporphyrin II. It is found
that introducing one methyl group into a mesoposition leads to significant low-frequency distortions of the structure-sensitive
lines of resonance Raman scattering. Specifically, frequenciesν
3
,ν
11
,ν
19
,ν
2
, andν
10
decrease by 10–44 cm−1 while frequencyν
4
remains practically unchanged. It is shown that the observed spectral variations are caused by nonplanar distortions of the
structure of Ni-porphyrins. The same tendency of the line displacement for tetragonal Ni-OEP and for compounds 1, 2, and 3
indicates that CH3-mesosubstituted Ni-porphyrins have a “corrugated” structure. The degree of nonplanarity is modulated by alkyl groups on pyrrole
rings and increases in the porphyrin series 3→2→1. All mesomethyl-substituted Ni-porphyrins have spectral indications that
the considered compounds are structurally heterogeneous in solution due to the presence of conformers with different degrees
of planarity.
Institute of Molecular and Atomic Physics, National Academy of Sciences of Belarus, 70, F. Skorina Ave., Minsk, 220072, Belarus.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 2, pp. 170–176, March–April, 1999. 相似文献
2.
We have obtained and analyzed the absorption, fluorescence, and fluorescence excitation spectra of indole vapor, N-acetyl-L-tryptophan
vapor, and 3-indole aldehyde vapor. From analysis of the dependence of the fluorescence spectrum of the free indole molecules
on the wavelength of the exciting radiation λex, it follows that emission of fluorescence occurs when the molecules undergo a transition from the one electronically excited
state 1Lb. The fluorescence spectra of the studied compounds are insignificantly different, suggesting a major role for the indole
chromophore in formation of the compounds. The absorption spectrum of N-acetyl-L-tryptophan, in which the group of atoms is
added to the indole ring through a-C-C bond, is similar to the spectrum of indole, while the spectrum of 3-indole aldehyde
is significantly different from the indole spectrum due to the effect of the C=O group conjugated with the indole ring. The
fluorescence excitation spectra are considerably different from the absorption spectra. This is associated with the strong
dependence of the quantum yield for the free molecules on λex. Qualitatively, they are mirror-symmetric to the fluorescence spectra of the stodied compounds. Analysis of the data obtained
provides a basis for assuming that in the case of free molecules of indole and its derivatives, the 1La absorption in the extreme long-wavelength region of the spectrum does not overlap 1Lb absorption.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 2, pp. 218–222, March–April, 2007. 相似文献
3.
L. F. Bakhturova V. V. Bakovets T. M. Levashova I. P. Dolgovesova V. O. Borisov 《Journal of Applied Spectroscopy》2000,67(1):40-44
IR absorption spectra of an intracomplex chelate compound of Cu(II) bis-dipivaloylmethanate in the spectral range 4000–300
cm−1 are investigated. A comparison is made between the spectra of the complex in different aggregative states: as a solution
in heptane and as condensed films. The molar extinction coefficients of absorption bands are calculated. The extinction coefficients
found are used to evaluate the thickness of Cu(dpm)2 films.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 67, No. 1, pp. 34–37, January–February, 2000. 相似文献
4.
G. A. Zalesskaya V. S. Ulashchik N. P. Mit’kovskaya O. V. Laskina A. V. Kuchinskii 《Journal of Applied Spectroscopy》2007,74(5):738-743
We used IR Fourier absorption spectra of blood to study changes in the structure of globular blood proteins with extracorporeal
autohemomagnetotherapy, used to treat ischemic heart disease. We compare the spectra of blood before and after magnetotherapy
in the regions: amide I (1655 cm−1), amide II (1545 cm−1), amide III (1230–1350 cm−1), amide IV and amide V (400–700 cm−1). We have shown that pronounced changes in the spectra in the indicated regions on direct exposure of blood in vivo to a
low-frequency pulsed magnetic field are connected with conformational changes in the secondary structure of globular blood
proteins, which are apparent in the increase in the contribution of the α-helix conformation. We discuss the magnetotherapy-initiated
appearance of new IR absorption bands at 1018 and 1038 cm−1 and an increase in the intensity of a number of other bands located in the 1000–1200 cm−1 region, which suggests a change in the concentration of some blood components.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 5, pp. 665–669, September–October, 2007. 相似文献
5.
A. V. Borodin V. Ya. Gayvoronsky O. D. Kachkovsky Ya. A. Prostota A. V. Kargovski? M. M. Nazarov D. A. Sapozhnikov Yu. L. Slominski? I. N. Smirnova A. P. Shkurinov 《Optics and Spectroscopy》2009,107(4):505-514
The low-frequency vibrational modes of the series of merocyanines (malononitrile derivative) have been investigated by pulsed
terahertz spectroscopy. The terahertz absorption spectra are shown to contain both intermolecular and intramolecular vibrational
modes in the range of 0.15–3.45 THz (5–115 cm−1). An unambiguous correlation is established between the purposeful modification of the molecular structure of merocyanine
dyes and the change in their terahertz absorption spectra. 相似文献
6.
We have recorded the fluorescence excitation spectra of three heterocyclic compounds with a chain structure [BPO (2-phenyl-5-(4-diphenylyl)oxazole),
POPOP (1,4-di[2-(5-phenyloxazolyl)]benzene, and TOPOT (1,4-di[2-(5-n-tolyloxazolyl)]benzene] and the fluorescence spectra
of POPOP, under conditions where the molecules were cooled in an ultrasonic helium jet. A line structure is observed in the
spectra of POPOP and TOPOT; for the BPO molecules, whose configuration changes considerably during electronic excitation,
vibrational structure is apparent only in the low-frequency region of the excitation spectrum, and a diffuse spectrum is recorded
starting from ν
0
0
+ 200 cm−1. For all the compounds, in the spectra we recorded vibrations with frequencies up to 100 cm−1, arising due to the flexibility of the molecular structure. The rotational contours of the lines for the electronic and vibronic
transitions of the POPOP molecules (Trot = 10.5 K) and TOPOT molecules (Trot = 15 K) are structureless and bell-shaped. The degree of polarization of the fluorescence Pfl for the jet-cooled POPOP molecules for excitation of vibrations along the absorption band up to 2000 cm−1 above ν
0
0
is practically constant (∼8.4%) and matches Pfl for high-temperature vapors.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 6, pp. 728–734, November–December, 2006. 相似文献
7.
8.
J. Thirumalai R. Chandramohan M. Sekar R. Rajachandrasekar 《Journal of nanoparticle research》2008,10(3):455-463
Small particles of trivalent europium doped yttrium oxysulfide nanocrystals (ϕ ∼ 7 nm) were synthesized using sol–gel polymer
thermolysis. The nanocrystals show significant change in the excitation bands corresponding to fundamental absorption and
charge transfer absorption bands. The optical spectra essentially comprise of two parts: fundamental absorption (∼260 nm)
and Eu3+–X2− ligand (O2−/S2−) charge transfer (∼290 nm) bands. They show significant blue shifts (0.24–0.30 eV), respectively, with respect to the bulk
counterpart. These may be explained by considering possible size dependent changes associated with quantum confinement effect
in this large bandgap semiconductor system. FT-IR spectra revealed the difference in chemisorbed species between bulk and
nanocrystalline samples. The results of the solid-state photo-induced electrical impedance spectroscopy studies are reported. 相似文献
9.
Using data on the stability of complex forms, electron absorption spectra of copper (I)-, silver (I)-, and gold (I)—thiourea
complexes in an aqueous solution Mituj (Ag: i=1, 2, j=1–3; Cu: j=1, 2; Au: j=2) are calculated from the spectra of solutions of a known analytical composition.
Parameters of particular bands of the absorption spectra of these complexes are given. It is found that the integral intensity
of the spectra of the solutions is proportional to the concentration of thiourea in the solution with high accuracy. The same
is also valid for the spectra in solutions that contain mercury (II) and thiourea. The total intensity of longwave bands in
the spectra of the complexes is proportional to the number of ligands in a molecule of the complex.
Institute of Ionorganic Chemistry, Siberian Branch of the Russian Academy of Sciences, 3, Lavrent’ev Ave., 630090, Novosibirsk-90,
Russia, Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 4, pp. 458–462, July–August, 1997. 相似文献
10.
Fatemah M. Al-Douseri Yunqing Chen X.-C. Zhang 《International Journal of Infrared and Millimeter Waves》2006,27(4):481-503
We present the results of terahertz (THz) sensing of gasoline products. The frequency-dependent absorption coefficients, refractive
indices, and complex dielectric constants of gasoline and xylene isomers were extracted in the spectral range from 0.5–3.0
THz. The THz spectra of gasoline (#87, #89, #93) and related BTEX (benzene, toluene, ethylbenzene, and xylene) compounds were
studied by using Fourier transform infrared spectroscopy (FTIR) in the 1.5–20 THz (50–660 cm−1). The xylene isomers, which are used as antiknock agent in gasoline were determined quantitatively in gasoline in the THz
range. Our investigations show the potential of THz technology for the petroleum industrial applications. 相似文献
11.
This paper presents a calculation of the defect vibrations induced in a ZnO:Ni crystal by the Ni+2 impurity. The computations are done by a recursive method in the shell model. Based on the model calculations, the vibronic
structure in the absorption spectra of the intracenter d-d transitions in the ZnO:Ni crystal is interpreted.
Fiz. Tverd. Tela (St. Petersburg) 40, 2213–2216 (December 1998) 相似文献
12.
We have used the IR absorption spectra of blood, plasma, and packed erythrocytes to study the effect of in vivo exposure of
blood to low-intensity emission from a He–Ne laser (λ = 632.8 nm, 4 mW/cm2) on the molecular components of blood. In comparing the IR spectra of samples of blood sample and blood components before
and after irradiation, we identified changes in the amide A, amide I, amide II, amide III absorption regions and also in the
absorption bands of methyl, methylene, and phosphate groups. We conclude that exposure of blood in vivo to emission from a
He–Ne laser leads to a decrease in the contribution of the α-helix conformation in the secondary structure of the blood proteins. 相似文献
13.
Strong green luminescence of Ni2+-doped ZnS nanocrystals 总被引:1,自引:0,他引:1
P. Yang M. Lü D. Xü D. Yuan J. Chang G. Zhou M. Pan 《Applied Physics A: Materials Science & Processing》2002,74(2):257-259
ZnS nanoparticles doped with Ni2+ have been obtained by chemical co-precipitation from homogeneous solutions of zinc and nickel salt compounds, with S2- as precipitating anion, formed by decomposition of thioacetamide (TAA). The average size of particles doped with different
mole ratios, estimated from the Debye–Scherrer formula, is about 2–2.5 nm. The nanoparticles could be doped with nickel during
synthesis without altering the X-ray diffraction pattern. A Hitachi M-850 fluorescence spectrophotometer reveals the emission
spectra of samples. The absorption spectra show that the excitation spectra of Ni-doped ZnS nanocrystallites are almost the
same as those of pure ZnS nanocrystallites (λex=308–310 nm). Because a Ni2+ luminescent center is formed in ZnS nanocrystallites, the photoluminescence intensity increases with the amount of ZnS nanoparticles
doped with Ni2+. Stronger and stable green-light emission (520 nm) (its intensity is about two times that of pure ZnS nanoparticles) has
been observed from ZnS nanoparticles doped with Ni2+.
Received: 18 December 2000 / Accepted: 17 March 2001 / Published online: 20 June 2001 相似文献
14.
Xiaoyi Li Yiqun Wu Donghong Gu Fuxi Gan 《Applied Physics A: Materials Science & Processing》2011,102(3):719-724
Three novel metal(II) complexes, CoL2, NiL2 and CuL2 (L = (Z)-4-(2-(1,3-dimethyl-5-oxo-1H-pyrazol-4(5H)-ylidene)hydrazinyl)-1,5-dimethyl-2-phenyl-1,2-dihydropyrazol-3-one were
synthesized. Their structures were postulated based on elemental analyses, 1H NMR, ESI-MS, FT-IR spectra and UV-vis spectra. The effect of different central metal(II) ions on absorption bands of the
metal(II) complexes in CHCl3 solutions was researched. The result indicates that the bathochromic shift is CuL2 > NiL2 > CoL2. The absorption properties of thin films and thermal stability of these complexes are also discussed. In addition, the optical
constants (complex refractive index N=n+ik) and thickness of the complex thin films on polished single-crystal silicon substrates were measured by spectroscopic ellipsometry.
Results indicate that the metal(II) complexes would be a promising recording medium candidate for blu-ray recordable optical
storage system due to good absorption at 405 nm, high thermal stability and sharp thermal decomposition, and a high n values of 1.35–1.45 and a low k values of 0.33–0.39. 相似文献
15.
B. Grouiez V. Zeninari L. Joly B. Parvitte 《Applied physics. B, Lasers and optics》2010,100(2):265-273
Pulsed quantum-cascade-laser spectrometers are usually used to detect atmospheric gases with either the interpulse technique
(short pulses, typically 5–20 ns) or the intrapulse technique (long pulses, typically 500–800 ns). Each of these techniques
has its drawbacks. Particularly the gas absorption spectra are generally distorted. We have previously developed another technique
called intermediate-size pulses (typically 50–100 ns) technique for gas detection using pulsed QCL spectrometers. In this
paper, infrared spectra of ammonia recorded with this technique in the 10 μm region are presented. For the NH3 spectra recorded at low pressure (i.e. in the mbar range), the spectra show typical oscillations after the absorption. The
Beer–Lambert law cannot explain these oscillations, termed the rapid-passage effect. Comparisons between experimental and
calculated spectra will be realized. This phenomenon is not satisfactory from a spectroscopic point of view and spectra must
be recorded at higher pressures. For the NH3 spectra recorded at higher pressure (i.e. in the 50 mbar range), the oscillations disappear and the Beer–Lambert law could
be reused. This paper will demonstrate that the intermediate-size technique gives reliable measurements for NH3 detection. Moreover the typical apparatus function (0.003 cm−1 HWHM) is far lower from the typical apparatus function of the interpulse QCL spectrometers (0.015 cm−1 HWHM). 相似文献
16.
We report the vibrational properties of lithium-intercalated SnSySe2−y (0≤y≤2) layered compounds. Infrared absorption spectra have been recorded as a function of temperature in the frequency range
50–600 cm−1. The new bands are interpreted as vibrational modes of lithium atoms against the nearest-neighbouring-chalcogen atoms located
in the van der Waals gap. Results are analyzed in terms of stretching vibrations of Li-S4 and Li-S6 entities. From a comparison of the spectra, it is concluded that lithium ions are more likely to occupy tetrahedral sites
in the lithium-rich phases. Using a simple model of lattice dynamics, the coupling force constants are determined and compared
with those of the pristine materials.
Paper presented at the 2nd Euroconference on Solid State Ionics, Funchal, Madeira, Portugal, Sept. 10–16, 1995 相似文献
17.
We have used electronic spectroscopy in the 160–1100 nm range to study the polyvinyl alcohol-nickel(II) chloride system. Based
on the results obtained, we hypothesize formation of mixed-ligand complexes of the type [Ni(H2O)6-nCln]2-n (n = 0, 1,..., 5) in the polyvinyl alcohol matrix. Transformation of the coordination sphere as the NiCl2 concentration changes is apparent both in the region of the d-d transition bands (350–1100 nm) and in the region of the charge
transfer bands (160–250 nm). We propose assigning the absorption bands separated by mathematical treatment to complexes of
specific compositions.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 1, pp. 136–138, January–February, 2006. 相似文献
18.
A. M. Efimov A. I. Ignat’ev N. V. Nikonorov E. S. Postnikov 《Optics and Spectroscopy》2011,111(3):426-433
We have measured the UV absorption spectra of photothermorefractive glasses of the system Na2O-ZnO-Al2O3-NaF-SiO2 doped by cerium oxide in the range of (2.8–5.0) × 104 cm−1 (360–200 nm). The spectra have been processed by the method of dispersion analysis based on the analytical convolution model
for the complex dielectric function of glasses. We show that the absorption band centered at 3.3 × 104 cm−1 (∼303 nm) that is attributed to the transition 2F
5/2 → 5d in the Ce3+ ion, is an envelope of three spectral components. The broad absorption range (3.5–4.7) × 104 cm−1 (200–270 nm) that is commonly interpreted as a charge transfer band of the Ce(IV) valence state, is an envelope of at least
three spectral components. 相似文献
19.
E. Birckner U.-W. Grummt H. Rost A. Hartmann S. Pfeiffer H. Tillmann H.-H. Hörhold 《Journal of fluorescence》1998,8(1):73-80
The absorption and fluorescence of substituted distyrylbenzene (DSB) derivatives and segmented poly(phenylene vinylene) (PPV)
derivatives are characterized by long-wavelength absorption maxima and absorption coefficients of λa = 380–450 nm, ε = 20,000–60,000 M−1 cm1 and fluorescence maxima, quantum yields, and decay times of λr = 440–530 nm, Φf = 0.2–0.9, and Τ = 0.8–2.5 ns, respectively. Alkoxy substituents at the central phenylene ring of DSB groups increase the
bathochromic shift in the spectra in comparison to DSB, without a significant decrease in the high DSB fluorescence quantum
yield. Both phenyl and cyano substitutions at the vinylene bridge lead to a further bathochromic shift of the fluorescence
and a decrease in the quantum yield to ca. 0.4. The DSB derivatives and the related segmented PPV derivatives show nearly
the same absorption spectra, fluorescence spectra, and radiative rate constantsk
f= Φf/Τ, indicating the efficacy of the segmentation of the polymer chain. The radiative rate constants determined by the Φf and Τ values and by the Strickler/Berg formula are in reasonable agreement. This supports the possibility of interpreting
the properties of the polymers in terms of their DSB units. The decrease in the emission anisotropy can be ascribed to multistep
energy transfer processes between different oriented segments. 相似文献
20.
L. L. Gladkov Yu. D. Khamchukov I. Yu. Sychev A. V. Lyubimov 《Journal of Applied Spectroscopy》2012,79(1):31-37
IR absorption spectra of indolinospironaphthooxazine (ISNO) are presented. The geometric structure and normal coordinates
of the ISNO molecule have been calculated using a quantum mechanical DFT method. The IR spectrum of ISNO in its original spiro
form has been interpreted for the first time. Four normal modes in the range 800–1200 cm–1 with the largest amplitudes of Cspiro–O bond change are identified. The excited ISNO molecule spiro form may experience photoconversion to the merocyanine form
through them. 相似文献