共查询到20条相似文献,搜索用时 15 毫秒
1.
T. Vijayakumar I. Hubert Joe C. P. Reghunadhan Nair V. S. Jayakumar 《Journal of Raman spectroscopy : JRS》2009,40(1):18-30
The near infrared Fourier‐transform (NIR FT)‐Raman and Fourier‐transform infrared (FT‐IR) spectroscopies supported by HF/6‐31G(d) computations have been employed to derive equilibrium geometry, vibrational wavenumbers and the first hyperpolarizability of the nonlinear optical (NLO) material, L ‐arginine nitrate (LAN) hemihydrate. The reasonable NLO efficiency, predicted for the first time in this novel compound, has been confirmed by Kurtz–Perry powder second harmonic generation (SHG) experiments. The changes in the atomic charge distribution among different groups due to the presence of strong electronegative atoms and the shrinking of N O bonds of nitrate anion and C N bonds of guanidyl group have been analyzed. The splitting of the carboxylate stretching modes, blue shifting of methine vibrations and the electronic effects such as backdonation and induction on the methylene hydrogen atoms have also been examined in detail. The intense low wavenumber H‐bond Raman vibrations due to electron–phonon coupling and nonbonded interactions in making the LAN molecule NLO active have been discussed based on the vibrational spectral features. The natural bond orbital (NBO) analysis and HF computations confirm the occurrence of strong intra‐ and intermolecular N H·O and O H·O ionic hydrogen bonding between charged species providing the noncentrosymmetric structure in the LAN crystal. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
2.
John S. Lomas 《Journal of Physical Organic Chemistry》2011,24(2):129-139
The 1H NMR titration method is used to investigate through‐space and through‐bond effects on the association of diols with pyridine in benzene. Alkan‐1,n‐diols (n goes from 2 to 10), DL and meso isomers of butan‐2,3‐, pentan‐2,4‐ and hexan‐2,5‐diols, two adamantane diols and a bicyclo[2.2.2]octane diol are compared with alkanols. The –CH2OH groups of the tri‐ and bicyclic compounds behave as if they were independent, with limiting OH proton shifts (at very low concentration) and both the first and the second association constants similar to those of a primary alcohol. In contrast, the alkane diols, with n = 2–4, display unusually high limiting shifts, ranging from 1.0 to 1.5 ppm (2.1 ppm for one methyl‐substituted diol). For these diols the first dissociation constant and the sum of the OH proton shifts in the 1:1 pyridine: diol complex are enhanced. This may be attributed to small cooperative effects, implying intramolecular hydrogen bonding, for n = 3 and 4, but for n = 2 a through‐bond effect accounts for most of the increase. Substituent interaction falls off sharply for n = 5 and is practically negligible for n = 10, for which the second association constant is close to the first. A sterically hindered BiEDOT diol, 2,2′‐bis{(3,4‐ethylenedioxythienyl)‐5‐[3‐(2,2,4,4‐tetramethylpentan‐3‐ol)]} behaves like the polycyclic compounds, with the two ? C(t‐Bu)2OH groups independent. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
3.
Mohammad Solimannejad Mohaddeseh Rabbani Amineh Ahmadi Mehdi D. Esrafili 《Molecular physics》2014,112(15):2017-2022
Ternary complexes of NaC3N with HMgH and HCN (HNC) are connected by sodium, hydrogen and dihydrogen bonds. Molecular geometries and interaction energies of dyads and triads are investigated at the MøllerPlesset perturbation theory of the second order/aug-cc-pVDZ computational level. Particular attention is paid to parameters, such as cooperative energies and many-body interaction energies. Triads with the HMgH molecule located at the end of the chain show an energetic cooperativity ranging between ?2.13 and ?10.53 kJ mol?1. When the HMgH molecule is located in the middle, the obtained cluster is diminutive with an energetic effect with values 4.39 and 6.77 kJ mol?1. The electronic properties of the complexes are analysed using parameters derived from the atoms in molecules methodology. Based on the energy decomposition analysis, it can be seen that the stabilities of the complexes are predicted to be attributable mainly to electrostatic effects. 相似文献
4.
The time‐dependent density functional theory (TDDFT) method was performed to investigate the excited‐state hydrogen bonding dynamics of 4‐amino‐1,8‐naphthalimide (4ANI) as hydrogen bond acceptor in hydrogen donating methanol (MeOH) solvent. The ground‐state geometry optimizations, electronic transition energies and corresponding oscillation strengths of the low‐lying electronically excited states for the isolated 4ANi and hydrogen‐bonded 4ANi‐(MeOH)1,4 complexes were calculated by the DFT and TDDFT methods, respectively. We demonstrated that the intermolecular hydrogen bond C═O···H–O and N–H···O–H in the hydrogen‐bonded 4ANi‐(MeOH)1,4 is strengthened in the electronically excited state, because the electronic excitation energies of the hydrogen‐bonded complex are correspondingly decreased compared with that of the isolated 4ANi. The calculated results are consistent with the mechanism of the hydrogen bond strengthening in the electronically excited state, while contrast with mechanism of hydrogen bond cleavage. Furthermore, we believe that the transient hydrogen bond strengthening behavior in electronically excited state of fluorescent dye in hydrogen‐donating solvents exists in many other systems in solution. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
5.
Thomas F. Whale Stewart J. Clark John L. Finney Christoph G. Salzmann 《Journal of Raman spectroscopy : JRS》2013,44(2):290-298
The vibrational spectra of the condensed phases of water often show broad and strongly overlapping spectral features which can make spectroscopic interpretations and peak assignments difficult. The Raman spectra of hydrogen‐ordered H2O and D2O ice XV are reported here, and it is shown that the spectra can be fully interpreted in terms of assigning normal modes to the various spectral features by using density functional theory (DFT) calculations. The calculated lattice‐vibration spectrum of the experimental antiferroelectric structure is in good agreement with the experimental data whereas the spectrum of a ferroelectric Cc structure, which computational studies have suggested as the crystal structure of ice XV, differs substantially. Moreover, the calculated coupled O–H stretch spectrum also seems in better agreement with the experiment than the calculated spectrum for the Cc structure. Both the hydrogen bonds as well as the covalent bonds appear to be stronger in hydrogen‐ordered ice XV than in the hydrogen‐disordered counterpart ice VI. A new type of stretching mode is identified, and it is speculated that this kind of mode might be relevant for other condensed water phases as well. Furthermore, the ice XV spectra are compared to the spectra of ice VIII which is the only other high‐pressure phase of ice for which detailed spectroscopic assignments have been made so far. In summary, we have established a link between crystallographic data and spectroscopic information in the case of ice XV by using DFT‐calculated spectra. Such correlations may eventually help interpreting the vibrational spectra of more structurally‐disordered aqueous systems. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
6.
John S. Lomas François Maurel Alain Adenier 《Journal of Physical Organic Chemistry》2011,24(9):798-808
The 1H NMR titration method is used to investigate the association of non‐symmetrical 1,2‐ and 1,3‐diols with pyridine in benzene. These diols give well‐defined titration curves for the two non‐equivalent OH protons, but it is not possible to determine individual association constants. Only the sum of the first association constants for the two protons and the product of the first and second association constants are accessible. The sum is significantly higher than that of the association constants of the corresponding primary and secondary alcohols, but close to an estimate based on symmetrical diols. The product leads to second association constants similar to those found for symmetrical diols. The sum of the chemical shifts of the associated and non‐associated OH protons in either 1:1 pyridine complex is higher than that of the shifts in the free diol and the 2:1 complex. These features are consistent with small cooperative effects, amounting to an average increase in the reaction free energy of 1.3 kJ mol?1 compared to monohydric alcohols. Infrared (IR) spectra of non‐symmetrical diols and quantum mechanical (QM) calculation of the energies and 1H NMR shifts of the OH protons in several conformers of propan‐1,2‐ and butan‐1,3‐diols indicate that both the primary and the secondary OH groups act as “donor” or “acceptor” in the free molecule. Gauche interactions in propan‐1,2‐diol enhance chemical shifts considerably less than does the intramolecular hydrogen bond in butan‐1,3‐diol. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
7.
G.V. Bondarenko 《Molecular physics》2013,111(5):783-788
The ternary system NaClO4–H2O–D2O has been studied, using the Raman spectroscopy. Analysis of the uncoupled OD band of HDO clearly shows that the contour of the band consists of two components only. A new approach has been developed for the quantitative evaluation of the mole fraction of bonded OD groups as a function of perchlorate concentration. It is practically impossible to measure the absolute intensity of Raman scattering. Nevertheless, it is feasible to obtain the specific coefficients of scattering per bonded OD group from the ratio of integrated intensities of the components. For this purpose, the concept of negative ‘phantom’ concentration was introduced, at which all the OD groups must be bonded. As a result, the concentration dependence of the mole fraction of bonded OD groups has been derived. It was found that the infinite network of hydrogen bonds in bulk water ceases to exist at a mole fraction of NaClO4 above ~0.03–0.035. At higher concentration of perchlorate only residual finite clusters of water molecules can take place. However, the infinite percolation in the system remains. The important fact resulting from the data treatment is that the average number of hydrogen bonds per water molecule in pure water is 2.6?±?0.2. 相似文献
8.
Hydrogen bonding and excited state properties of the photoexcited hydrogen‐bonded (E)‐S‐(2‐aminopropyl) 3‐(4‐hydroxyphenyl)prop‐2‐enethioate complexes
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The time‐dependent density functional theory (TDDFT) method has been performed to investigate the excited state and hydrogen bonding dynamics of a series of photoinduced hydrogen‐bonded complexes formed by (E)‐S‐(2‐aminopropyl) 3‐(4‐hydroxyphenyl)prop‐2‐enethioate with water molecules in vacuum. The ground state geometric optimizations and electronic transition energies as well as corresponding oscillator strengths of the low‐lying electronic excited states of the (E)‐S‐(2‐aminopropyl) 3‐(4‐hydroxyphenyl)prop‐2‐enethioate monomer and its hydrogen‐bonded complexes O1‐H2O, O2‐H2O, and O1O2‐(H2O)2 were calculated by the density functional theory and TDDFT methods, respectively. It is found that in the excited states S1 and S2, the intermolecular hydrogen bond formed with carbonyl oxygen is strengthened and induces an excitation energy redshift, whereas the hydrogen bond formed with phenolate oxygen is weakened and results in an excitation energy blueshift. This can be confirmed based on the excited state geometric optimizations by the TDDFT method. Furthermore, the frontier molecular orbital analysis reveals that the states with the maximum oscillator strength are mainly contributed by the orbital transition from the highest occupied molecular orbital to the lowest unoccupied molecular orbital. These states are of locally excited character, and they correspond to single‐bond isomerization while the double bond remains unchanged in vacuum. 相似文献
9.
Isabel Rozas Goar Sánchez‐Sanz Ibon Alkorta José Elguero 《Journal of Physical Organic Chemistry》2013,26(5):378-385
We have calculated the complexes formed by guanidine/guanidinium and HCl/Cl?, HNO3/NO3? and H2SO4/HSO4? both in the gas and aqueous Polarizable Continuum Model (PCM) phase to understand the effect that solvation has on their interaction energies. In the gas phase, the cation–anion complexes are much more stable than the rest; however, when PCM‐water is considered, this energetic difference is not as large due to the extra stabilization that the ions suffer when in aqueous solution. All the complexes were analyzed in terms of their AIM and NBO properties. In all cases, water solvation seems to “dampen” those properties observed in the gas phase. The values of Nucleus Independent Chemical Shift (NICS)(1) and NICS(2) indicate a huge influence of the proximity of the carbon atom for short distances; thus, the 3D NICS values on the van der Waal isosurfaces have been used to evaluate the possible Y‐aromaticity of the guanidinium system. The isosurface in this system is more similar to cyclohexane than to benzene as indication of poor aromaticity. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
10.
Pressure effects on the Raman spectra due to the inter‐ and intramolecular vibrations of the L ‐ascorbic acid crystal were studied. The intensity of the Raman bands due to the intermolecular vibrations varies in three different ways by application of pressure. The bands of the first group become stronger, those of the second one become weaker and the third group shows no prominent change in their intensity with increasing pressure. The bands due to the intermolecular vibrations show a blue shift, while the bands due to the intramolecular vibrations shift to the blue or red depending on the vibrational modes by application of pressure. The bands assigned to the O H stretching vibrations shift to the red, the bands assigned to the CO and CC stretching vibrations shift a little to the red and the bands assigned to the other vibrations shift to the blue under high pressure. The following conclusions were derived. (1) The hydrogen bonds forming helixes become stronger and the isolated hydrogen bond becomes weaker with increasing pressure. (2) The bands of the first group owing to the intermolecular vibrations are ascribed to the vibrations related to the helix hydrogen bonds and the second group bands to the isolated hydrogen bond. (3) The CO stretching vibration couples with the CC stretching vibration. (4) The phase transitions take place at 1.8 and 4 GPa in the crystal. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
11.
Atena Najdian Mehdi Shakourian‐Fard Alireza Fattahi 《Journal of Physical Organic Chemistry》2014,27(7):604-612
Density functional theory method and B3LYP/6‐311++G(d,p) level of theory were used to determine the acidity of alkyl sulfonic acids and polyolalkyl sulfonic acids in the gas and solution (H2O, DMSO, and CH3CN) phase. Polarized continuum model was applied to calculate pKa values of alkyl sulfonic acids and polyolalkyl sulfonic acids. A comparison between acidity of alkyl sulfonic acids and polyolalkyl sulfonic acids in the gas and solution phase indicates that the acidity strength of polyolalkyl sulfonic acids enhances with the increase of the cooperativity effect of intramolecular hydrogen bonds in polyolalkyl sulfonic acids. Natural bond orbital and quantum theory of atoms in molecules analyses also confirm the role of cooperativity effect on the acidity of polyolalkyl sulfonic acids. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
12.
M. Sethu Raman V. Ponnuswamy P. Kolandaivel K. Perumal 《Journal of Molecular Liquids》2008,142(1-3):10-16
The experimental measurements of density, viscosity and ultrasonic velocity of aqueous glycerol solutions were carried out as functions of concentration (0.1 ≤ m [mol kg− 1] ≤ 1.0) and temperature (303.15 ≤ T [K] ≤323.15). The isentropic compressibility (βs), acoustic impedance (Z), hydration number (Hn), intermolecular free length (Lf), classical sound absorption (α/f2)class and shear relaxation time (τ) were calculated by using the measured data. These parameters have been interpreted in terms of solute–solvent interactions. The quantum chemical calculations were performed to study the hydrogen bonding in interacting complex formed between glycerol and water molecules. Computations have been done by using Density Functional Theory (DFT) method at B3LYP/6–31 + g(d) level of theory to study the equilibrium structure of glycerol, glycerol–water interacting complex and vibrational frequencies. The solution phase study was carried out using Onsager's reaction field model in water solvent. The computed vibrational frequencies are in good agreement with the main features of the experimental spectrum when four water molecules are considered explicitly with glycerol. The interaction energy (Etotal), hydrogen bond lengths and dipole moment (µm) of the interacting complex are also presented and discussed with in the light of solute–solvent interactions. 相似文献
13.
Mahboob Mohammad Asma Rauf Saba Rauf Muhammad Tariq 《Journal of Physical Organic Chemistry》2012,25(12):1269-1274
To explore the possibility of hydrogen bonding of a stable anion radical with DNA – component sugar, hormones, steroid, and so on (through hydroxyl group), as a first step, the possibility of hydrogen bonding of 1,3‐dinitrobenzene anion radical (1,3‐DNB??) with aliphatic alcohols was studied. It was found that 1,3‐DNB?? anion radical undergoes hydrogen bonding with alcohols: methanol, ethanol, and 2‐proponal. The hydrogen‐bonding equilibrium constant Keq and the (hydrogen‐bonding) rate constants k2 were evaluated through the use of linear scan and cyclic voltammetry theory and techniques. The Keq was found to be in the range of 1.4–6.0 m ?1, whereas the rate constants k2 were found to be in the range of 1.5–3.6 m ?1 s?1, depending upon the hydrogen‐bonding agent and the equation used for the calculation of the rate constants. The hydrogen‐bonding number n was found to be around 0.5 or 1.0. The implication of this study in, for example, the replication of DNA, the prevention of the formation of super oxide, and so on is discussed. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
14.
A series of 1,3‐bis(2′‐hydroxyethyl)imidazolium ionic liquids is reported where 1H NMR chemical shift values and thermal stabilities (Td), as determined by thermogravimetric analysis, are correlated with the hydrogen bonding capability of various anions ([Cl?], [Br?], [CF3CO2?], [NO2?], [MsO?], [NO3?], [TfO?], [BF4?], [NTf2?], and [PF6?]). Use of anions with the strongest hydrogen bonding capability, such as chloride [Cl?], bromide [Br?], and trifluoroacetate [CF3CO2?], led to the furthest observed downfield chemical shift values in DMSO‐d6 and the poorest thermal stabilities ([CF3CO2?] < 200 °C). Thermal stabilities in excess of 350 °C and upfield chemical shift values were observed for ionic liquids, which employed the weakly coordinating triflate [OTf?], tetrafluoroborate [BF4?], or bis(trifluoromethylsulfonyl)imide [NTf2?] anion. Optimized structures of selected ionic liquids, as determined by density functional theory calculations at the B3LYP/6‐31G + (d,p) level, indicated that the anion preferred to be located above the imidazolium ring and in close proximity to the hydroxyl groups. Calculated dissociation energies (ΔE) and a comparison of key bonding distances (C2―H, (C2)H···X, O―H, and (O)H···X) also confirmed this structural preference. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
15.
Bharat Bhooshan Sharma Chitra Murli R. Chitra Surinder M. Sharma 《Journal of Raman spectroscopy : JRS》2012,43(1):138-145
Recent spectroscopic investigations of various amino acids report intriguing high‐pressure and low‐temperature behavior of NH3+ groups and their influence on various hydrogen bonds in the system. In particular, the variation of the intensity of NH3+ torsional mode at different temperatures and pressures has received much attention. We report here the first in situ Raman investigations of fully deuterated α‐glycine up to ∼20 GPa. The discontinuous changes in COO− and ND3+ modes across ∼3 GPa indicate subtle structural rearrangements in fully deuterated α‐glycine. The decrease in the intensity of ND3+ torsional mode is found to be similar to that of undeuterated α‐glycine. The pressure‐induced stiffening of N D and CD2 stretching modes are discussed in the context of changes in the hydrogen‐bonding interactions. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
16.
Sunil K. Srivastava Sebastian Schlücker Wagner A. Alves 《Journal of Raman spectroscopy : JRS》2010,41(12):1714-1719
High‐resolution Raman spectra of pyrimidine (PD) and formamide (FA) mixtures with different compositions recorded in the ring breathing region of PD (ν1 ∼ 991 cm−1) are presented. The dilution of PD with FA leads to the appearance of a new band at ν1′ ∼ 994 cm−1, which is assigned to hydrogen‐bonded PD:FA species. From a quantitative analysis of the concentration‐dependent Raman spectra, the average number of FA molecules in the first solvation sphere of PD is determined as being equal to 2. This value is supported by density functional theory (DFT) calculations: a symmetric 1:2 complex is the most stable species among various hydrogen‐bonded PD:FA clusters with stoichiometries ranging from 1:1 to 1:4. A qualitative explanation for the blue shift of the ν1 mode upon complexation is given. Additionally, we have observed not only similarities but also some differences with respect to the PD:water system. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
17.
Tadeusz M. Krygowski Joanna E. Zachara‐Horeglad 《Journal of Physical Organic Chemistry》2007,20(8):594-599
B3LYP/6–311+G** optimization was carried out for azulene and its analogs, in which CH? CH? CH fragment was replaced with O···X···O (X = H or Li). π‐electron delocalization in four possible derivatives with H‐bonding and three possible derivatives with Li‐bonding was described by the use of HOMA index. All derivatives with Li‐bonding exhibit high π‐electron delocalization similar to that found for azulene. Among four H‐bonded systems, two exhibit lower π‐electron delocalization (HOMA < 0.39) and higher total electron energy than the other two derivatives. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
18.
Piotr Matczak 《Molecular physics》2018,116(3):338-350
In this work, a series of model complexes (MH3X)(HNC)(N'C’H’), where M = C–Pb and X = Cl–At, is studied using a first-principles computational approach. Each of these complexes possesses a halogen atom (X) simultaneously acting as the Lewis base for X···H hydrogen bonding (HB) with HNC and as the Lewis acid for X···N’ halogen bonding (XB) with N'C’H’. The strengths of these non-covalent interactions are tuned by sharing the same halogen centre and by substituting M and X with consecutive elements from groups 14 and 17. Variations in the strengths are estimated mostly by means of various energetic quantities, such as the total interaction energy (Eint), two- and three-body contributions to Eint, their fundamental physical components and donor–acceptor orbital interaction energies. The coexistence of HB and XB involving the same X-centre weakens these interactions, but the magnitude of the total interaction in the complexes increases due to the three-body interaction and the appearance of additional lateral non-covalent interaction between HNC and N'C’H’. Substituting M and X with consecutive elements from groups 14 and 17 leads to several regularities in the changes of Eint. A dependence of three-body interaction on the kinds of M and X is also detected. 相似文献
19.
Matheus P. Freitas Roberto Rittner Cláudio F. Tormena Raymond J. Abraham 《Journal of Physical Organic Chemistry》2008,21(6):505-509
The rotational isomerism of model phosphorus‐containing compounds was evaluated by using theoretical methodologies. The trans rotamer of chloromethylphosphonic acid dichloride ( 1 ) was found to be the prevailing form in the gas phase and in non‐polar solvents, with an inverse behaviour from chloroform solution. Although the use of direct spin–spin coupling constants (SSCCs) do not apply for the quantitative determination of conformers in 1 , due to the small dependence of J with conformation, the observed measurements and calculated individual couplings suggest that the gauche conformer is progressively stabilized with increasing the solvent polarity. In addition, theoretical calculations at the CBS‐Q level for the corresponding phosphine of 1 (compound 2 ) showed the gauche rotamer as the prevailing one in the isolated state. Natural Bond Orbital (NBO) analysis indicated that steric and electrostatic effects rule the rotational isomerism of 1 , while the anomeric effect nP → σ*CCl also plays an important role on the conformational equilibrium of 2 . Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
20.
Animesh K. Ojha Sunil K. Srivastava S. Schlücker W. Kiefer B. P. Asthana Ranjan K. Singh 《Journal of Raman spectroscopy : JRS》2007,38(12):1656-1664
A concentration‐dependent Raman study of the ν(C Br) stretching and trigonal bending modes of 2‐ and 3‐Br‐pyridine (2Br‐p and 3Br‐p) in CH3OH was performed at different mole fractions of the reference molecule, 2Br‐p/3Br‐p, from 0.1 to 0.9 in order to understand the origin of blue/red wavenumber shifts of the vibrational modes due to hydrogen‐bond formation. The appearance of additional Raman bands in these binary systems at ∼617 cm−1in the case of 2Br‐p and at ∼618 cm−1 in the case of 3Br‐p compared to neat bromopyridine derivatives were attributed to specific hydrogen‐bonded complexes formed in the mixtures. The interpretation of experimental results is supported by density functional calculations on optimized geometries and vibrational wavenumbers of 2Br‐p and 3Br‐p and a series of hydrogen‐bonded complexes with methanol. The parameters obtained from these calculations were used for a qualitative explanation of the blue/red shifts. The wavenumber shifts and linewidth changes for the ν(C Br) stretching and trigonal bending modes as a function of concentration reveal that the caging effects leading to motional narrowing and diffusion‐causing line broadening are simultaneously operative, in addition to the blue shift caused due to hydrogen bonding. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献