共查询到20条相似文献,搜索用时 312 毫秒
1.
Rmulo A. Ando Rodrigo L. O. R. Cunha Luiz Juliano Antonio C. Borin Paulo S. Santos 《Journal of Raman spectroscopy : JRS》2008,39(4):453-459
The electronic (UV‐vis) and resonance Raman (RR) spectra of a series of para‐substituted trans‐β‐nitrostyrenes were investigated to determine the influence of the electron donating properties of the substituent (X = H, NO2, COOH, Cl, OCH3, OH, N(CH3)2, and O−) on the extent of the charge transfer to the electron‐withdrawing NO2 group directly linked to the ethylenic (C = C) unit. The Raman spectra and quantum chemical calculations show clearly the correlation of the electron donating power of the X group with the wavenumbers of the νs(NO2) and ν (C = C)sty normal modes. In conditions of resonance with the lowest excited electronic state, one observes for X = OH and N(CH3)2 that the symmetric stretching of the NO2, νs(NO2), is the most substantially enhanced mode, whereas for X = O−, the chromophore is extended over the whole molecule, with substantial enhancement of several carbon backbone modes. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
2.
In this work, using density functional theory and time‐dependent density functional theory methods, we theoretically studied the excited‐state behaviors of 3 novel 2‐(2‐hydroxyphenyl)benzothiazole (HBT) derivatives (HBT‐H‐H, HBT‐CN‐H, and HBT‐CN‐CN). Analyses about primary chemical structures such as bond lengths and bond angles, we found that all the intramolecular hydrogen bonds in these 3 structures should be strengthened in the S1 state upon the photoexcitation. Exploring the infrared vibrational spectra at the hydrogen bonds groups, we confirmed that nonsubstitutional HBT‐H‐H structure might play more important roles in the excited‐state intramolecular proton transfer (ESIPT) reaction than HBT‐CN‐H and HBT‐CN‐CN. Further, investigating vertical excitation process, it can be revealed that charge redistribution involved in hydrogen bonding moieties could facilitate the ESIPT reaction. Based on constructing potential energy curves of both S0 and S1 states, we confirmed that the substituents on HBT systems can reasonably regulate and control the ESIPT processes because of the different potential energy barriers. We deem that this present work not only elaborates the different excited‐state behaviors of HBT‐H‐H, HBT‐CN‐H, and HBT‐CN‐CN but also may play important roles in designing and developing new materials and applications involved in HBT systems in future. 相似文献
3.
Estrella Ramos Patricia Guadarrama Gerardo Terán Serguei Fomine 《Journal of Physical Organic Chemistry》2009,22(1):9-16
The electronic properties of the ground state, unrelaxed and relaxed first excited states of push–pull hyperbranched molecules bearing amino and nitro terminal groups have been studied at BB1K/cc‐pvdz//HF/6‐31g(d), TD‐BB1K/cc‐pvdz//HF/6‐31g(d) and TD‐BB1K/cc‐pvdz//CIS/6‐31g(d) levels of theory, respectively. It was demonstrated that dendritic architecture of push–pull molecules favours the charge transfer in the excited state compared to linear molecules. The possibility of adopting a plane conformation is an important condition for the charge transfer in an excited state. According to the calculations 1:1 ratio of donor and acceptor groups is another important precondition for the manifestation of strong charge separation in the excited state. In case of excess of nitro groups over the amino, some of the excitations participating in the S0 → S1 transition favour the charge transfer in the excited state in the opposite directions, thus decreasing the charge separation. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
4.
Emilio Squitieri 《Journal of Physical Organic Chemistry》2003,16(11):875-879
The nuclear relaxation first hyperpolarizability of a push–pull molecule was studied using the simple valence‐bond charge‐transfer model and analytical evaluation of electrical properties method. A relationship between the nuclear relaxation and electronic contributions to the first hyperpolarizability was derived, which incorporates the harmonic and anharmonic terms associated with the ground‐state potential energy. We show that the anharmonic contribution is as important as that of the harmonic contribution and it follows the trend of the electronic contribution. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
5.
M. Snehalatha I. Hubert Joe C. Ravikumar V. S. Jayakumar 《Journal of Raman spectroscopy : JRS》2009,40(2):176-182
Fourier transform Raman and IR as well as UV–visible spectra of the phenothiazine dye Azure A chloride, 3‐amino‐7‐(dimethylamino) phenothiazin‐5‐ium chloride were recorded and analyzed. The spectral interpretation was done following full structure optimization and vibrational wavenumber calculations based on the density functional theory (DFT) using the standard B3LYP/6‐31G(d) basis set. The N H stretching wavenumber is found to be lowered owing to intermolecular N H···S hydrogen bonding. The downshift of C H stretching wavenumber is discussed. The first hyperpolarizability of the dye is calculated. Time‐dependent density functional theory (TD‐DFT) calculations of electronic spectra were performed on the optimized structure and compared with the experimental UV–visible spectrum. The atomic net charges of the molecule reveal the M effect of the nitrogen atoms in the molecule. Stability of the molecule arising from hyperconjugative interactions leading to its nonlinearity and bioactivity, charge delocalization and mesomeric effects have been analyzed using natural bond orbital (NBO) analysis. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
6.
M. Snehalatha C. Ravikumar I. Hubert Joe V. S. Jayakumar 《Journal of Raman spectroscopy : JRS》2009,40(9):1121-1126
The FT‐IR and Raman spectra of Martius Yellow sodium salt Monohydrate (MYM) [2, 4‐dinitro‐1‐naphthol sodium salt] in solid‐phase have been measured. The geometry, intramolecular hydrogen bonding and harmonic vibrational wavenumbers of MYM have been investigated with the help of B3LYP density functional theory (DFT) methods. The detailed interpretation of the vibrational spectra has been carried out with the aid of normal coordinate analysis (NCA) following the scaled quantum mechanical force field methodology (SQMFF). The existence of intramolecular C H···O improper, blue‐shifted hydrogen bonding was investigated by means of the NBO analysis. The infrared and Raman spectra were predicted theoretically from the calculated intensities. The observed and the calculated spectra were found to be in good agreement. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
7.
8.
Ewa D. Raczyska Micha K. Cyraski Maciej Gutowski Janusz Rak Jean‐Franois Gal Pierre‐Charles Maria Magorzata Darowska Kinga Duczmal 《Journal of Physical Organic Chemistry》2003,16(2):91-106
Consequences of proton‐transfer reactions in guanidine in the solid state, solution and gas phase are discussed. Y‐delocalization, resonance and symmetry strongly influence the basicity of guanidine in the gas phase. These effects are, however, insufficient to explain the basicity of guanidine which in aqueous solution is stronger than that of trisubstituted alkylamines and proton sponge (DMAN). The intrinsic (gas‐phase) basicity of guanidine is close to that of triethylamine. The large difference between the basicities of amines and guanidine in solution is attributed to the important role played by effects such as polarizability and internal and external solvation. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
9.
10.
A new merocyanine dye, 1,3‐Dimethyl‐5‐{(thien‐2‐yl)‐[4‐(1‐piperidyl)phenyl]methylidene}‐ (1H, 3H)‐pyrimidine‐2,4,6‐trione 3 , has been synthesized by condensation of 2‐[4‐(piperidyl)benzoyl]thiophene 1 with N,N′‐dimethyl barbituric acid 2 . The solvatochromic response of 3 dissolved in 26 solvents of different polarity has been measured. The solvent‐dependent long‐wavelength UV/Vis spectroscopic absorption maxima, vmax, are analyzed using the empirical Kamlet–Taft solvent parameters π* (dipolarity/polarizability), α (hydrogen‐bond donating capacity), and β (hydrogen‐bond accepting ability) in terms of the well‐established linear solvation energy relationship (LSER): (1) The solvent independent coefficients s , a , and b and (vmax)0 have been determined. The McRae equation and the empirical solvent polarity index, ET(30) have been also used to study the solvatochromism of 3 . Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
11.
The gluon and Goldstone boson induced tensor interaction effect on
the dibaryon mass and the D-wave decay width has been studied in
the quark delocalization, color screening model. The effective S-D
wave transition interactions induced by gluon and Goldstone boson exchanges decrease quickly as the increasing of the channel strangeness. The K and η meson tensor contribution is
negligible in this model. No six-quark state in the light flavor world can become a bound one by the help of these tensor interactions except the deuteron. The partial D-wave decay width
of IJp=\frac{1}{2}2+ NΩ state to spin 0, 1 ΛΞ
final state is 20.7 keV and 63.1 keV respectively. It is a very narrow
dibaryon resonance and might be detected in the
relativistic heavy ion reaction by the existing RHIC
detectors through the reconstruction of the ΛΞ vertex
mass and the future COMPAS detector at CERN and FAIR project
in Germany. 相似文献
12.
Nathan Harris Wu Wei William H. Saunders Sason Shaik 《Journal of Physical Organic Chemistry》1999,12(3):259-262
Direct computational evidence is presented that the lag in delocalization at the transition state in proton transfers from carbon acids yielding delocalized anions provides the lowest energy path. It does not, contrary to a common assumption, deprive the transition structure of all resonance stabilization that could otherwise lower the barrier. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
13.
Martha E. Buschbeck‐Alvarado Gabriel Hernández‐Fernández Jesús Hernández‐Trujillo Fernando Cortés‐Guzmán Gabriel Cuevas 《Journal of Physical Organic Chemistry》2018,31(4)
Every day, more evidence accumulates, leading to the conclusion that the stereoelectronic model through the nO → σ*C─O interaction is of minor relevance or even inoperative to explain conformational preference in the specific O─C─O segment. In the present study, dimethoxymethane (DMM) and some model spiroketals were chosen to develop a reliable and easy to apply methodology that is simple to interpret by experimental chemists. The general conformation observed in these molecules, present in many biologically active natural products, is the gauche‐gauche (g,g) in DMM and bis‐diaxial in spiroketals. To study this conformational preference, this paper presents a new approach, where general trends for the atomic and molecular energetic components, as well as localization and delocalization indices, and their bonded (Δb) and nonbonded (Δnb) electronic contributions are analyzed. In addition, group contributions to the electron localization and polarization are also defined, agreeing with the conformational preference. It is clear that electronic localization/delocalization is capable of reproducing experimental observations, showing an adequate correlation of this property to the cos θ term in the context of Pople's analysis. It is proposed that electron delocalization between electronegative atoms or total delocalization between nonbonded atoms is not the major contributors to the axial conformational preference observed in spiroketals. Conformational preference shows defined trends in terms of group delocalization in DMM and ring localization and charge transfer between groups in spiroketals. This way, electronic delocalization can be used to evaluate the anomeric effect, using just a few parameters, which makes the method broadly functional. 相似文献
14.
《Advanced Optical Materials》2018,6(7)
Infrared organic photodetector materials are investigated using transient absorption spectroscopy, demonstrating that ultrafast charge generation assisted by polymer aggregation is essential to compensate for the energy gap law, which dictates that excited state lifetimes decrease as the band gap narrows. Short sub‐picosecond singlet exciton lifetimes are measured in a structurally related series of infrared‐absorbing copolymers that consist of alternating cyclopentadithiophene electron‐rich “push” units and strong electron‐deficient “pull” units, including benzothiadiazole, benzoselenadiazole, pyridalselenadiazole, or thiadiazoloquinoxaline. While the ultrafast lifetimes of excitons localized on individual polymer chains suggest that charge carrier generation will be inefficient, high detectivity for polymer:PC71BM infrared photodetectors is measured in the 0.6 < λ < 1.5 µm range. The photophysical processes leading to charge generation are investigated by performing a global analysis on transient absorption data of blended polymer:PC71BM films. In these blends, charge carriers form primarily at polymer aggregate sites on the ultrafast time scale (within our instrument response), leaving quickly decaying single‐chain excitons unquenched. The results have important implications for the further development of organic infrared optoelectronic devices, where targeting processes such as excited state delocalization over aggregates may be necessary to mitigate losses to ultrafast exciton decay as materials with even lower band gaps are developed. 相似文献
15.
Intraparticle charge delocalization occurs when metal nanoparticles are functionalized with organic capping ligands through conjugated metal-ligand interfacial bonds. In this study, metal nanoparticles of 5d metals (Ir, Pt, and Au) and 4d metals (Ru, Rh, and Pd) were prepared and capped with ethynylphenylacetylene and the impacts of the number of metal d electrons on the nanoparticle optoelectronic properties were examined. Both FTIR and photoluminescence measurements indicate that intraparticle charge delocalization was enhanced with the increase of the number of d electrons in the same period with palladium being an exception. 相似文献
16.
Nicolas Zorn Morales;Daniel Steffen Rühl;Emil List-Kratochvil;Sylke Blumstengel; 《physica status solidi (a)》2024,221(1):2300186
Combining materials with diverse properties into two-dimensional (2D) van der Waals heterostructures lies at the heart of electronic, optoelectronic, and photonic applications. Prerequisite is a significant degree of electronic or photonic coupling of the constituents across the heterointerface. Understanding and controlling these interactions is mandatory to achieve the desired functionality. This review focuses on the charge and energy transfer processes and their dynamics in a specific class of van der Waals heterostructures, namely such composed of semiconducting transition metal dichalcogenides and conjugated organic molecules. With the help of prototypical material combinations, the importance of a precise knowledge of the interfacial electronic structure is demonstrated as it governs the excited-state dynamics. This review aims at providing basic design guidelines to achieve functional 2D organic/inorganic van der Waals heterostructures with final properties that can be designed by careful selection of the organic component. 相似文献
17.
《Journal of Raman spectroscopy : JRS》2018,49(3):438-451
Graphene‐mediated surface enhanced Raman scattering is a recent phenomenon that produces clean and reproducible signals from chemical analytes. In this work, we report on the development of graphene‐family nanomaterials (graphene oxide; GO, reduced GO; rGO, and multilayer graphene; MLG) decorated with physisorbed silver (AgNP) and gold (AuNP) nanoparticles and as layered architectures for detection of methylene blue and rhodamine 6G dyes in view of optical and biological significance. The experimental results illustrate four orders of magnitude graphene‐mediated surface enhanced Raman scattering enhancement in the order rGO/AgNP > GO/AgNP > MLG/AgNP for physisorbed and cascade amplified signal on multilayer architectures, larger than those only on graphene and metal nanoparticles, which is achieved at optimal size of Ag (30 nm) and Au (40 nm) on rGO. Moreover, highly‐sensitive graphene‐decorated nanoparticle are capable of molecular detection over a broad concentration range 10 pM–100 μM. The findings are discussed in terms of (a) strong graphene‐metal nanoparticle coupling leading to local interfacial hybridization and polarization, (b) molecular structural symmetry of analytes in relation to nanoparticle‐graphene functionalities, and (c) effective charge transfer and exchange or sharing of charges between analyte and nanoparticles decorated graphene. Optimized metal nanoparticle‐graphene geometries and electronic properties are determined from density functional theory calculations. They identify preferred metal nanoparticle adsorption sites and long‐range electrostatic interactions and determine relative resonant charge transfer population (alternatively, chemical enhancement mechanism) values derived from the Mulliken population thus gaining insights into effective enhancement factors. These findings will help to design advanced SERS platforms for ultrasensitive detection of chemicals and biological molecules useful in bio‐nanotechnology. 相似文献
18.
G. Ares de Parga 《Foundations of Physics》2006,36(10):1474-1510
A new scheme is proposed in order to deduce an equation of motion for a spinless charged point particle leading to an equivalent Landau–Lifshitz equation of motion. Consequently Larmor’s formula must be substituted by a new expression for the large distance radiation rate of energy. A constraint appears on the applicability of the Maxwell electromagnetic tensor. The particular case of a sudden force is analyzed in order to show the physical results predicted by the new model. A geometrical rearrangement of the energy explains the balance. 相似文献
19.
Single‐electron oxidants are the primary reagents for investigations of the new oxidants and the development of electron‐accepting materials for application in optoelectronics. Quinones are the well‐known class of the neutral single‐electron oxidants. Here, we present the properties of the strongest neutral electron acceptor of this class tetracyanoquinone (cyanil) and investigate its electron‐accepting strength by analyzing the charge‐transfer complex formations with the aromatic donor molecules. Charge‐transfer complexes of tetracyanoquinone with aromatic electron donors are characterized spectroscopically in solution and isolated as the single crystals. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
20.
The ratios of transfer ionization to single capture for isocharge C^{q+}, N^{q+}, O^{q+}, Ne^{q+} ions on Ar atoms are measured by using position-sensitive and time-of-flight techniques. It is found that the ratio R_{1} increases with nuclear charge Z in a q=4 sequence, and the ratio R_{1} sequences have the minimum values at Z=7 and Z=8 in q=5 and q=6 sequences, respectively, and the ratio R_{1} decreases with the increase in the nuclear charge Z in a q=7 sequence. The results may be explained within the frame of the statistical model. It may be concluded that the transfer ionization depends remarkably upon the electronic structure of the projectile. The projectiles used in this study have the same charge state and velocity, but different electronic structures. The dependence of the ratio R_{1} on q is studied for Ne^{q+}-Ar collisions. The ratio R_{1} is found to increase as q increases for Ne^{q+}-Ar collisions. The measured dependence of the ratio R_{1} on q is compared with the calculation using the molecular Coulomb over-barrier model. 相似文献