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1.
《Vibrational Spectroscopy》2007,45(2):286-296
Rigorous theoretical treatment of vibrational frequencies is critically important for the interpretation of unassigned experimental vibrational spectra and accurate determination of thermodynamic properties of molecular clusters. IR spectra of trans monomers of sulfuric and acetic acids, sulfuric acid monohydrate and cyclic dimer of the formic acid have been studied using DFT and DF–DFT methods using BLYP, B3LYP and PW91 with 12 different Pople and Dunning basis sets. New data for above-mentioned structures have been reported, scaling factors have been calculated and a comprehensive analysis of the performance of BLYP, B3LYP and PW91 methods has been performed. Comparison of the obtained results with experiments shows that results of pure PW91 and BLYP are better than predictions of well-established hybrid B3LYP method. Our analysis shows on the existence of the considerable difference in scaling factors weighted to high and low frequencies. In the case of formic acid dimer, the deviation the predicted low frequencies from the experimental data is considerable that leads to quite large (∼6–7 kcal mol−1) uncertainties in the absolute values of the cluster Gibbs free energy. In order to determine an efficient computational strategy that comprises accuracy and reasonable computational costs, the effect of density fitting (DF) and basis set superposition error (BSSE) on the vibration frequencies has been investigated. We found that application of the DF that substantially (2.5–3.5 times) increases the performance of pure PW91 and BLYP methods gives excellent results, which are very close to those of conventional DFT. This suggests that DF–DFT is a viable low-cost alternative to conventional DFT in predicting vibrational spectra. It has been found that while vibrational spectra obtained using the counterpoise correction (CP) for the BSSE do not deviate much from uncorrected ones, the difference in absorption intensities between corrected and uncorrected spectra obtained using small and medium-sized basis sets is considerable. This suggests that application of DF–DFT uncorrected for the BSSE with large basis sets is a more efficient strategy of predicting vibrational spectra than the application of conventional DFT with small basis sets. 相似文献
2.
LIU XiaoDong QIU YongQing CHEN Hui LI Na SUN ShiLing & SU ZhongMin Institute of Functional Material Chemistry Faculty of Chemistry Northeast Normal University Changchun China 《中国科学B辑(英文版)》2009,(2)
DFT B3LYP/LANL2DZ method was employed to calculate electron properties and the second-order nonlinear optical(NLO) respond of platinum(Ⅱ) complexes which have been synthesized by Weinstein group.4,7-diphenyl-1,10-phenanthroline shows the ability to push electron in these complexes.Metal Pt plays a balancing charge role.Comparing complex 1b-6b with complex a,the βvec value of complex 1b-5b is larger than one of complex a,while the βvec value of complex 6b is smaller than one of com-plex a.In these seven comp... 相似文献
3.
《Solid State Sciences》2012,14(4):476-487
The Fourier transform infrared (FT-IR) and Fourier transform Raman (FTR) spectra of 4-amino-3(4-chlorophenyl) butanoic acid were recorded in the regions 4000–400 cm−1 and 4000–100 cm−1, respectively, in the solid phase. Molecular electronic energy, geometrical structure, harmonic vibrational spectra, infrared intensities and Raman scattering activities, highest occupied molecular orbital, lowest unoccupied molecular orbital energy, energy gaps and thermodynamical properties such as zero-point vibrational energies, rotational constants, entropies and dipole moment were computed at the Hartree–Fock/6-31G(d,p) and three parameter hybrid functional Lee–Yang–Parr/6-31G(d,p) levels of theory. The vibrational studies were interpreted in terms of potential energy distribution (PED). The results were compared with experimental values with the help of scaling procedures. Most of the modes have wave numbers in the expected range and are in good agreement with computed values. The first order hyperpolarizability (βtotal) of this molecular system and related properties (β, μ, 〈α〉 and Δα) are calculated using HF/6-31G(d,p) and B3LYP/6-31G(d,p) methods based on the finite-field approach. Stability of the molecule arising from hyperconjugative interactions, charge delocalization and intramolecular hydrogen bond-like weak interaction has been analyzed using natural bond orbital (NBO) analysis by using B3LYP/6-31G(d,p) method. The results show that electron density (ED) in the σ1 and π1 antibonding orbitals and second-order delocalization energies E(2) confirm the occurrence of intramolecular charge transfer (ICT) within the molecule. 相似文献
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The i.r. spectra of diiminosuccinonitrile and N,N′-dichlorodiiminosuccinonitrile were recorded as Nujol mulls, as pellets in KBr and polyethylene matrices and as solutions in CH3CN in the region 4000-30 cm−1. Raman spectra of the pure solids were obtained and polarization data were recorded from saturated solutions in CH3CN.The mutual exclusion of i.r. and Raman lines revealed that both compounds existed in the trans conformation and no additional conformers (gauche or cis) were detected in solution.The fundamental frequencies for both molecules were assigned on basis of i.r. and Raman activities, Raman polarization data and the results of normal coordinate analyses. 相似文献
6.
The Fourier transform Raman and Fourier transform infrared spectra of fenbufen (γ-oxo [1,1′-biphenyl]-4-butanoic acid) were
recorded in the solid phase. The gas-phase structure and conformational properties of fenbufen were determined by quantum-chemical
calculations (HF and DFT/B3LYP with 6-311++G(d,p) basis set). The harmonic wave numbers were calculated by the density functional
theory (DFT) calculations with B3LYP functional and 6-311++G(d,p) basis set, and the scaled values were in good agreement
with the majority of the experimental observations. A complete assignment of the fundamentals was proposed based on the total
energy distribution (TED) calculation. The possible interaction between fenbufen and ofloxacin which is a synthetic antimicrobial
agent was investigated. The changes observed in some bands of mixed drug indicated that there is an interaction between the
two drug molecules. 相似文献
7.
Çırak Ç Demir S Ucun F Çubuk O 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2011,79(3):529-532
Experimental and theoretical vibrational spectra of β-2-aminopyridinium dihydrogenphosphate (β-2APDP) have been investigated. The FT-IR spectrum of β-2APDP was recorded in the region 4000-400 cm(-1). The optimized molecular structure and theoretical vibrational frequencies of β-2APDP have been investigated using ab initio Hartree-Fock (HF) and density functional B3LYP method with 6-311++G(d,p) basis set. The optimized geometric parameters (bond lengths and bond angles) and theoretical frequencies have been compared with the corresponding experimental data and it is found that they agree well with each other. All the assignments of the theoretical frequencies were performed by potential energy distributions using VEDA 4 program. Furthermore, the used scale factors were obtained from the ratio of the frequency values of the strongest peaks in the experimental and theoretical IR spectra. From the results it was concluded that the B3LYP method is superior to the HF method for the vibrational frequencies. 相似文献
8.
《中国科学:化学(英文版)》2012,(7):1439-1445
The dynamic first hyperpolarizabilities of a series of 1,10-phenanthroline Ru(Ⅱ) complexes were carried out using density functional theory(DFT).The results indicate that these complexes have large second-order nonlinear optical(NLO) responses.Specially,complex 6b has a maximal first hyperpolarizability βtot value.The first hyperpolarizabilities can be tuned by changing the ancillary ligand,introducing electron-acceptor group NO2 and/or increasing π-conjugation on phenanthroline.Calculations on absorption spectra demonstrate that the second-order NLO responses of complexes in series a are ascribed to the intraligand charge transfer(ILCT),while the complexes in series b exhibit metal-to-ligand charge transfer(MLCT) and ligand-to-ligand charge transfer(LLCT) transition at relatively low-energy absorptions. 相似文献
9.
Thebluelighttransparentorganicfrequencydoublingmaterialsareoneofthemostimportantfieldinthedevelopmentofnewwavelengthconversionmaterials.Beingpracticalfrequencydoublingmaterials,theymusthavenotonlylargemolecularfirsthyperpolarizabilityβ,butalsogoodtran… 相似文献
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Anoop Kumar Pandey D.V. Shukla Vijay Narayan Mishra Vijay Singh O.P. Yadav Apoorva Dwivedi 《印度化学会志》2022,99(4):100396
Proflavine, having the molecular formula C13H11N3, is a well-known urinary antiseptic and anticancer medication (3,6-diaminoacridine). In this communication, Quantum chemical computations of Proflavine's geometry have been performed and examined in the ground state. The optimized structure and wavenumbers of the molecule's vibrational bands were investigated using the DFT/B3LYP method and 6–311G (d, p) as the basis set. The calculated vibrational frequencies are compared to experimental IR spectra. The link between thermodynamic characteristics and temperature has been studied. The computed IR frequencies correlate well with the experiments, as indicated by the correlation factor (R2 = 0.99). The UV spectra of the title molecule are calculated by using Time Dependent Density Functional Theory (TD-DFT). The molecule's interactions with other species were described using an analysis of a HOMO (Highest Occupied Molecular Orbital) and LUMO (Lowest Unoccupied Molecular Orbital). Natural bond orbitals (NBO) analysis was used to investigate intramolecular and intermolecular hydrogen bonding and their second-order stabilization energies and conjugative and hyperconjugative interactions. By computing the first hyperpolarizability, nonlinear optical (NLO) analysis was utilized to explore the molecule's nonlinear optical properties. 相似文献
12.
Marchewka MK Drozd M Janczak J 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2011,79(4):758-766
The N-(4-nitrophenyl)-β-alanine in crystalline form directly by the addition of 4-nitroaniline to the acrylic acid in aqueous solution has been obtained. The title β-alanine derivative crystallizes in the P2(1)/c space group of monoclinic system with four molecules per unit cell. The X-ray geometry of β-alanine derivative molecule has been compared with those obtained by molecular orbital calculations corresponding to the gas phase. In the crystal the molecules related by an inversion center interact via symmetrically equivalent O-H···O hydrogen bonds with O···O distance of 2.656(2) ? forming a dimeric structure. The dimers of β-alanine derivative weakly interact via N-H···O hydrogen bonds between the H atom of β-amine groups and one of O atom of nitro groups. The room temperature powder vibrational (infrared and Raman) measurements are in accordance with the X-ray analysis. In aqueous solution of 4-nitroaniline and acrylic acid, the double CC bond of vinyl group of acrylic acid breaks as result of 4-nitroaniline addition. 相似文献
13.
Cai-Feng Wang He-Yi Xie Yu-Peng Cheng Li Chen Michael Z. Hu Su Chen 《Colloid and polymer science》2011,289(4):395-400
This paper describes the first synthesis of cadmium sulfide (CdS)-poly(lactic acid) (PLA) nanocomposites and their transparent
fluorescent films by covalently grafting PLA onto the surfaces of CdS nanocrystals (NCs). Synthesis of the nanocomposites
involved two steps. Lactic acid (LA)-capped CdS NCs were first prepared by reacting cadmium chloride (CdCl2) with sodium sulfide (Na2S) using LA as the organic ligand in H2O/N,N-dimethylformamide (DMF) solution. CdS–PLA nanocomposites were then formed by in situ ring-opening polymerization of lactide
on the surface of modified CdS NCs. We also demonstrated herein the fabrication of the transparent fluorescent films of CdS–PLA
nanocomposites by blending as-prepared nanocomposites with high-molecular-weight PLA. The as-prepared CdS NCs and their nanocomposites
were studied by transmission electron microscopic imaging, thermogravimetric analyses, and spectroscopic measurements (ultraviolet–visible
absorption and photoluminescence). The results revealed that the CdS–polymer nanocomposites exhibited good optical properties
in terms of their photoluminescence and transparency. 相似文献
14.
Xing-Hai Liu Wei-Guang Zhao Bao-Lei Wang Zheng-Ming Li 《Research on Chemical Intermediates》2012,38(8):1999-2008
A series of novel 1,2,3-thiadiazole derivatives were designed and synthesized. Their structures were characterized by 1H NMR, MS and HRMS. The bioactivity tests indicated that compound 9b exhibits a favorable KARI inhibition rate, and some of these novel compounds also showed moderate herbicidal activity against Brassica campestris. 相似文献
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《Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy》1988,44(4):409-422
A safe method for the synthesis of azidoethane from ethylbromide is given and 1H and 13C NMR data are reported.The i.r. and Raman spectra of azidoethane have been recorded in the region 4000-40 cm−1 and interpreted in terms of two conformers, anti and gauche, present in the vapour and in the liquid and of the gauche conformer in the crystalline solid. Matrix isolation studies reveal the gauche conformation to be the more stable in argon and in nitrogen matrices and probably also more stable in the vapour. The enthalpy difference between the conformers is calculated to be ΔH0a→g (N2 matrix) ≈ ΔH0a→g (vap.) = −0.56(10) kJ mol−1, and the barrier to rotational isomerism (anti → gauche) as 9.0(10) kJ mol−1 in the nitrogen matrix and less than 6 kJ mol−1 in the argon matrix. Careful Raman studies of the liquid at 140–290 K reveal the gauche conformation to be the more stable in the liquid phase as well, the enthalpy difference being ΔH0a→g (liq.) = − 1.15 (5) kJ mol−1.The majority of the fundamentals for both conformers have been assigned with the aid of normal coordinate calculations using previously developed scaled quantum mechanical force fields which are also presented. 相似文献
17.
《Journal of Saudi Chemical Society》2014,18(5):574-580
The ground state structures of 5,5″-diperfluorophenyl-2,2′:5′,2″:5″,2‴-quaterthiophene (1), 5,5′-bis{1-[4-(thien-2-yl)perfluorophenyl]}-2,2′-dithiophene (2), 4,4′-bis[5-(2,2′-dithiophenyl)]-perfluorobiphenyl (3), 5,5″-diperfluorophenyl-2,2′:5′,2″-tertthiophene (4), 5,5′-diperfluorophenyl-2,2′-dihiophene (5), and 5,5-diperfluorophenylthiophene (6) have been optimized at the B3LYP/6-31G(d), B3LYP/6-31G(d,p), PBE0/6-31G(d), and PBE0/6-31G(d,p) level of theories. The B3LYP/6-31+G(d) and PBE0/6-31+G(d) level of theories have been applied to investigate the absorption spectra. The PBE0 functional is good to predict the C–S bond lengths while the C–F bond lengths are good envisaged with B3LYP functional. The increment of thiophene rings between two perfluoroarene rings leads to red shift in absorption spectra. The electron affinities are energetically destabilized while energetic stabilization of the radical-cation increases by decreasing the thiophene rings from four to one. The perfluoroarene rings leads to enhance the electron injection. 相似文献
18.
NaNa Ma YongQing Qiu ShiLing Sun ChunGuang Liu Min Fan ZhongMin Su 《中国科学:化学(英文版)》2010,53(5):1149-1154
The structures, electronic spectra, polarizability and third-order nonlinear optical properties of six gold compounds [X-“Au(PMe3)”2] were investigated by density functional theory (DFT) B3LYP and BhandHLYP methods. It was found that the calculation methods and basis set are rational for the object of study, and molecular structures change slightly when PPh3 is replaced by PMe3. The spatial effects of the bridging section have a significant influence on the polarizability, but indistinctive to the third-order nonlinear optical (NLO) coefficient. As a result of the conjugated effect in different compounds, the third-order polarizability of molecule 1a is the smallest, while that of molecule 2a is the largest. Au has donor ability in molecule 1a but acceptor ability in molecules 2a–6a by analyzing the electronic spectra and frontier molecular orbitals constitute maximal absorption, which indicates the contribution of Au to NLO properties in the six molecules is different. 相似文献
19.
FaQian Liu Lei Wang JiXi Guo WeiHua Li ChaoQin Li YanLing Jin RongXun Li FangFang Jian 《中国科学:化学(英文版)》2014,57(9):1235-1245
Three polymeric heterometallic clusters with 1D, 2D, and 3D frameworks, constructed from a cyclic vanadate {V4O12}4-building block and three geometric constraint ligands, were synthesized by a one-pot self-assembly reaction. Z-scan experiments demonstrated that all the three cluster polymers have large hyperpolarizability γ values. TD-DFT calculations afforded insight into the electronic transitions and spectral characterization of these novel NLO molecular materials. 相似文献
20.
Iron(III)-5-fluorosalicylic acid systems were investigated in water by pH potentiometry combined with UV-VIS spectrophotometry.
The data revealed that stable aquated mono-, bis-, and tris(5-fluorosalicylato) iron(III) complexes are formed together with
their monohydroxo and dihydroxo analogues. The stability constants of all present iron(III) species were calculated. Based
on pH and the metal: ligand ratio dependent distribution of the species, electronic absorption spectra of the complexes in
the visible region were obtained. Redox stability was monitored as an ability to undergo both spontaneous and photoinduced
reduction of iron(III) to iron(II). Complexes do not undergo any redox changes when in dark neither in methanol nor in water.
While aqueous solutions of complexes are stable under the influence of incident visible radiation, steady-state irradiation
of the methanolic systems by visible light led to photoreduction of iron(III) to iron(II), the quantum yield of iron(II) photoformation
was determined.
Dedicated to Professor Milan Melník on the occasion of his 70th birthday 相似文献