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1.
A new class of red emitting extensively conjugated donor-π-acceptor type dyes bearing coumarin units have been synthesized by condensation of 7-(diethylamino)-2-oxo-2 H-chromene-3-carbaldehyde with different active methylenes. All the dyes are characterized by 1H NMR, 13C NMR and HRMS spectroscopy. The photophysical behaviour and the relation between structure and properties of the coumarin “push–pull” derivatives were investigated experimentally. The dyes exhibited positive solvatochromism and solvatofluorism in solution of varying polarity. These coumarin dyes show aggregation induced emission properties with red emitting fluorescence. They show absorption in the range of 501–528 and emission in the range of 547–630 nm. We evaluated photophysical properties of coumarin dyes using solvotochromism and solvent dependent shift in the emission wavelength. All the synthesized coumarin dyes COS1- COS4 are showing very good solvatochromic properties. 相似文献
2.
Abstract Reaction of 2-aminothiazoline with an aromatic aldehyde and diethylmalonate, in basic medium afforded two kinds of regioisomers: 5-oxo and 7-oxo-tetrahydrothioazolopyrimidines. Assignment of the structures of 5-oxo-7-phenyl-2,3,6,7-tetrahydro-5 H -thiazolo[3,2-a] pyrimidine-6-ethylcarboxylate ( 1) and 7-oxo-5-phenyl-2,3,5,6-tetrahydro-7 H -thiazolo[3,2-a] pyrimidine-6-ethylcarboxylate ( 2) were performed using 1H and 13C NMR spectroscopy, including NOE experiments. For each regioisomer, only R? S? trans-diaxial diastereoisomers were isolated and characterized. 相似文献
3.
An unusual and unexpected synthesis of 3-(2-(arylamino)thiazol-4-yl)-2H-chromen-2-ones has been observed by the reaction of ethyl 2-(chloromethyl)-2-hydroxy-2H-chromene-3-carboxylate with various arylthioureas in ethanol under mild reaction conditions with excellent yields. The ambiguity in the structure of the obtained products has been solved by recording its single-crystal X-ray analysis. This protocol has been found to be a novel approach for the preparation of title compounds via benzopyran ring opening. A systematic plausible mechanism has been proposed for the formation of the product. Also, an efficient one-pot three-component method has been demonstrated for the formation of title compounds starting from salicylaldehyde. 相似文献
4.
In the past, non‐invasive in vivo FT‐Raman spectroscopy has been used to detect H 2O 2‐mediated oxidation of methionine to methionine sulfoxide and methionine sulfone, as well as cysteine to cysteic acid, in the sequence of proteins in the epidermis of patients with vitiligo. L ‐tryptophan (Trp) is another potential target for this oxidation. Owing to the presence of 10 −3M epidermal albumin which contains one Trp residue, it was tempting to follow the oxidation of this amino acid. Using in vivo and in vitro FT‐Raman spectroscopy, we show for the first time that epidermal Trp is oxidised in patients with vitiligo, yielding 5‐OH‐Trp at 930 cm −1 and other oxidation products (i.e. N‐formyl kynurenine and kynurenine) from indole ring oxidation peaking at 1050 cm −1. On the basis of detailed in vitro results, we could conclude that 5‐OH‐Trp as well as formyl kynurenine and kynurenine are formed via H 2O 2‐mediated Fenton chemistry. These results once again bring out the strength of non‐invasive in vivo FT‐Raman Spectroscopy in dermatology to follow the effect of oxidative stress in the skin of patients with vitiligo. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
5.
An efficient synthesis of 2-hydroxy-3-[2-oxo-2-phenylethylidene]-2-phenyl-2, 3-dihydro-4 H-furo[3, 2-c]chromene-4(2 H)-one is described. This involves the reaction between dibenzoylacetylene and 4-hydroxycoumarine in the presence of NaH (10 mol
%) in nearly quantitative yield. Treatment of this heterocyclic system with trimethyl chlorosilane in CHCl 3 leads quantitatively to 4-oxo-3-[2-oxo-2-phenylethylidene]-2-phenyl-3 H, 4 H-furo[3,2-c]chromene-1-ium chloride. Direct addition of nucleophiles, such as alcohols, amines or trialkyl phosphites to this
salt in water as the solvent produces functionalized 2-phenyl-4 H-furo[3,2-c] chromen derivatives in excellent yields. 相似文献
6.
The title molecules, N-(1,5-dimethyl-3-oxo-2-phenyl-1 H-3-(2 H)-pyrazolyl)4-nitrobenzamide (C 18H 16N 4O 4·H 2O) (I) and 2,2-dimethyl-3-(4-nitrobenzoyl)-5-(phenylamino)-2,3-dihydro-1,3,4-thiyadiazole (C 17H 16N 4O 3S) (II), were prepared and characterised by 1H NMR, 13C NMR, infrared spectroscopy (IR) and structural X-ray diffraction (XRD) techniques. The molecular geometries, vibrational frequencies of the title compounds in the ground state have been calculated by using the density functional theory (DFT) method with 6-31G(d) basis set, and compared with the experimental data. The calculated results showed that the optimised geometries from the DFT method agree with the X-ray structures well for both compounds. Theoretical calculations of harmonic vibration frequencies are in good agreement with experimental results. To determine conformational flexibility, the molecular energy profiles of the title compounds were obtained. Besides, molecular electrostatic potential (MEP), frontier molecular orbitals (FMO) analysis and thermodynamic properties of the title compounds were investigated by theoretical calculations. 相似文献
7.
A concise, efficient one-pot synthesis of functionalized chromeno[4,3- b]pyridine derivatives via a three-component reaction of 4-oxo-4 H-chromene-3-carbaldehydes, malononitrile or cyanoacetates, and aromatic amines under catalyst-free conditions in an environmentally friendly medium (ethanol–water, 3:1 v/v) is described. This synthesis involves a group-assisted purification process, which avoids traditional recrystallization and chromatographic purification methods. 相似文献
8.
Geometries, excitation energies, dipole moments and dipole polarisability tensor components of the ground and four lowest excited states 3 B 1, 1 B 1, 3 A 2, 1 A 2 of the H 2O and H 2S molecules were calculated at the CASSCF, CASPT2, CCSD and CCSD(T) level of approximation. Vertical excitation and equilibrium transition energies of these states, having the Rydberg character, are reported too. Properties of both molecules in the ground and in low lying excited states are compared and discussed from the point of view of their molecular electronic structure. Upon excitation we observe dramatic changes of dipole moments and polarisabilities with respect to the ground state. We stress the change of the polarity of H 2O in all excited states accompanied by the enhancement of the dipole polarisability by an order of magnitude. Large, even if less pronounced, are changes of electric properties of H 2S in its excited states. Dipole moments and dipole polarisabilities of 3 B 1, 1 B 1 states of H 2S and H 2O behave quite analogously in comparison to their respective ground state. The general pattern of properties for both molecules in their 3 A 2 and 1 A 2 excited states is more different due to a pronounced participation of the sulphur d-orbitals in these states of the H 2S molecule. 相似文献
9.
Abstract The synthesis of 2‐(2‐nitrophenyl)‐1 H‐benzimidazole ( 1), 1‐benzoyl‐2‐(2‐nitrophenyl)‐1 H ‐benzimidazole ( 2), and 1‐acetyl‐2‐(2‐nitrophenyl)‐1 H‐benzimidazole ( 3) is reported. Stable radical anions ( 1 ·?, 2 ·?, and 3 ·?) were generated by chemical reduction in DMSO and studied by ESR spectroscopy. The interpretation of the ESR spectra was done by means of computational simulation process. Hyperfine coupling constants were assigned by comparison with related compounds, and on the basis of calculation based on SCF INDO MO method in the unrestricted Hartree–Fock scheme. 相似文献
10.
Proton-conducting polymer complex electrolytes were prepared by incorporation of boric acid, H 3BO 3 into poly(vinylalcohol), PVA, to form hydrated PVA xH 3BO 3 where x denotes the number of moles of boric acid per polymer repeat unit. The dried materials were characterized via Fourier transform
infrared spectroscopy, thermogravimetry, and X-ray diffraction. The proton conductivity of the hydrated complex electrolytes
was measured by AC impedance spectroscopy. PVA2H 3BO 3 with RH ∼25% was found to be optimum composition that exhibited proton conductivity of 1.3 × 10 −3 S/cm at 80 °C. 相似文献
11.
The a type transitions of the microwave rotational spectra of cyanophosphaacetylene, H 2PCCCN, have been investigated in the frequency region between 5 and 26.5 GHz by Fourier transformation microwave (FTMW) spectroscopy. Rotational, centrifugal distortion and 14N nuclear quadrupole coupling constants have been determined. Density functional theory level ab initio calculations were performed to predict the molecular constants, and the predicted values are in good agreement with our experimentally determined results. The 13C and 15N isotopomer transitions were also observed. The derived r0 structure is quite comparable to the calculated H 2PCCCN equilibrium geometry. 相似文献
12.
利用电子束蒸发方法将MgB 2超导薄膜沉积到Al 2O 3(001)衬底上.采用标准的四引线法研究了磁场平行和垂直超导薄膜 ab平面下的电阻转变.一个激活能模型 U( T, H)= U0(1- T/( Tc+ δ)) n(1- H/ H
关键词:
2/Al 2O 3')" href="#">MgB 2/Al 2O 3
超导体
电阻转变
各向异性 相似文献
13.
Raman spectroscopic technique has been used to characterize a Ru/TiO 2 catalyst and to follow in situ their structural changes during the CO selective methanation reaction (S‐MET). For a better comprehension of the catalytic mechanism, the in‐situ Raman study of the catalysts activation (reduction) process, the isolated CO and CO 2 methanation reactions and the effect of the composition of the reactive stream (H 2O and CO 2 presence) have been carried out. Raman spectroscopy evidences that the catalyst is composed by islands of TiO 2–RuO 2 solid solutions, constituting Ru–TiO 2 interphases in the form of Ru xTi 1 − xO 2 rutile type solid solutions. The activation procedure with H 2 at 300 °C promotes the reduction of the RuO 2–TiO 2 islands generating Ru o–Ti 3+ centers. The spectroscopic changes are in agreement with the strong increase in chemical reactivity as increasing the carbonaceous intermediates observed. The selective methanation of CO proceeds after their adsorption on these Ru o–Ti 3+ active centers and subsequent C―O dissociation throughout the formation of CH x/C nH x/C nH xO/CH x―CO species. These intermediates are transformed into CH 4 by a combination of hydrogenation reactions. The formation of carbonaceous species during the methanation of CO and CO 2 suggests that the CO presence is required to promote the CO 2 methanation. Similar carbonaceous species are detected when the selective CO methanation is carried out with water in the stream. However, the activation of the catalysts occurs at much lower temperatures, and the carbon oxidation is favored by the oxidative effect of water. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
14.
用二次组态相关(QCISD)和密度泛函(B3LYP)方法, 选用6-311++g(d,p), 6-311++g(3df,3pd)和D95(3df,3pd)基组对H 2, BeH和BeH 2分子的结构进行优化. 得到它们的基态电子态分别为H 2( 1Σg), BeH( 2Σ)和BeH 2( 1Σg
关键词:
BeH
2')" href="#">BeH 2
2')" href="#">H 2
二次组态相关(QCISD)
势能函数 相似文献
15.
In this article, the isomerisation mechanisms of HN(NO 2) 2 to O 2NNN(O)OH without and with catalyst X ( X = H 2O, (H 2O) 2, (H 2O) 3, HCOOH, H 2SO 4, CH 3CH 2COOH and HN(NO 2) 2) have been investigated theoretically at the CBS-QB3 level of theory. Our results show that the catalyst X ( X = H 2O, (H 2O) 2, (H 2O) 3, HCOOH, H 2SO 4 and CH 3CH 2COOH) shows different positive catalytic effects on reducing the apparent activation energy of the isomerisation reaction processes. Such different catalytic effects are mainly related to the number of hydrogen bonds and the size of the ring structure in X ( X = H 2O, (H 2O) 2 and (H 2O) 3)-assisted transition states, as well as different values of p Ka for H 2SO 4, HCOOH and CH 3CH 2COOH. Very interesting is also the fact that H 2SO 4-assisted reaction is the most favourable for the hydrogen transfer from HN(NO 2) 2 to O 2NNN(O)OH, due to the smallest p Ka (?3.0) value of H 2SO 4 than H 2O, HCOOH, H 2SO 4 and CH 3CH 2COOH, and also because of the largest ∠X???H???Y (the angle between the hydrogen bond donor and acceptor) involved in H 2SO 4-assisted transition state. Compared to the self-catalysis of the isomerisation mechanisms of HN(NO 2) 2 to O 2NNN(O)OH, the apparent activation energy of H 2SO 4-assisted channel also reduces by 9.6 kcal?mol ?1, indicating that H 2SO 4 can affect the isomerisation of HN(NO 2) 2 to O 2NNN(O)OH, most obvious among all the catalysts H 2O, (H 2O) 2, (H 2O) 3, HCOOH, H 2SO 4, CH 3CH 2COOH and HN(NO 2) 2. 相似文献
16.
采用高温固相法制备了SrAl2B2O7:Dy3+发光材料.在350nm紫外光激发下,测得SrAl2B2O7:Dy3+材料的发射光谱为一个多峰宽谱,主峰分别为480,573和678nm;分别和Dy3+的4F9/2→6H15/2,4F9/2→6H13/2,4F9/2→6H11/2的跃迁发射相对应;监测573nm的发射峰,得到材料的激发光谱为一个多峰宽谱,主峰分别为295,325,350,365,400nm.研究了Dy3+掺杂浓度对SrAl2B2O7:Dy3+材料发射光谱的影响,随着Dy3+掺杂浓度的增大,SrAl2B2O7:Dy3+材料的Iy/Ib逐渐增大,根据Judd-Ofelt理论解释了其原因.随着Dy3+掺杂浓度的增大,Dy3+的4F9/2→6H13/2跃迁产生的573nm发射峰强度先增大,在4%时达到最大值,之后减小,其自身的浓度猝灭机理为电偶极-电偶极相互作用.不同的电荷补偿剂Li+,Na+,K+的引入均使发光强度得到提高,尤其以Li+最佳,发光强度提高了大约33%. 相似文献
17.
Ferrimagnetic spinel selenide CuCr 2Se 4 has been investigated by the
electron spin resonance (ESR) spectroscopy. Experimental results reveal that ESR signals
originate from the localized d-shell electrons of Cr 3+ ions.
In addition, the ESR linewidth Δ H
PP
increases
linearly with decreasing temperature. It is suggested that the spin-orbit coupling may be
one of the contributions to the broadening of
Δ H
PP
. Our ESR results support the model of
the ferrimagnetic hybridization between localized 3 d
3
electrons of Cr 3+ with delocalized holes of Se 4 p band. 相似文献
18.
The 2 H polytype of a SnS 2 layered crystal has been studied using Raman spectroscopy at pressures of up to 5 GPa in a diamond anvil cell. The Raman
frequency of the intralayer mode increases linearly with increasing pressure at baric coefficients of 5.2 cm −1/GPa for P<3 GPa and 3.4 cm −1/GPa for P>3 GPa. This change in the baric coefficient for Raman scattering and the available data on X-ray measurements of the compressibility
of 2 H-SnS 2up to 10 GPa suggest that the crystal structure undergoes a transformation at about 3 GPa. 相似文献
19.
The reaction of alkyl isocyanides with dimethyl 1,3-acetonedicarboxylate in the presence of dialkyl acetylenedicarboxylates
in CH 2Cl 2 at ambient temperature leads to highly functionalized 2-amino-4 H-pyrans and 1,2-dialkyl 4,6-dimethyl-(1 E, 3 E)-3 (alkylamino)-5-oxo-1,3-hexadiene-1,2,4,6-tetracarboxylates. 相似文献
20.
40 absolute line wavenumbers in the 3 v 3 band of 12C 16O 2 between 6927 cm ?1 and 6989 cm ?1 and 626 absolute line wavenumbers in the near infrared absorption spectrum of 12C 2H 2 between 7060 cm ?1 and 9900 cm ?1 have been measured using high resolution Fourier transform spectroscopy. The calibration of the CO 2 line wavenumbers relied on heterodyne frequencies available in the v 1 + v 3 band of 12C 2H 2 near 6556 cm ?1. The absolute uncertainty of the calibrated CO 2 line wavenumbers is estimated to 0.000 08 cm ?1. The acetylene spectra were calibrated using heterodyne frequencies available in the 2—0 band of 12C 16O and the line wavenumbers obtained in the 3 v 3 band of 12C 16O 2. The absolute uncertainty of the calibrated acetylene line wavenumbers is estimated to range from 0.0003 cm ?1 to 0.006 cm ?1 for strong to very weak isolated lines. Comparison with absolute line wavenumbers obtained independently at JPL in the 3 v 3 band of 12C 2H 2 near 9649 cm ?1, calibrated using absolute wavenumbers available in the 2—0 and 3—0 (near 6350 cm ?1) bands of 12C 16O, shows very good agreement. Also, the vibration—rotation constants for the observed upper vibrational states of 12C 2H 2 were determined, but without accounting for the perturbations affecting these states. 相似文献
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