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1.
Bis(betainium) p-toluenesulfonate monohydrate (abbreviated as BBTSH) was studied at various temperatures by X-ray diffraction, differential scanning calorimetry and vibrational spectroscopy methods. DSC curves of BBTSH show a peak at about 349 K which corresponds to water escape from the crystal, and reveal the “cold crystallization” phenomenon. BBTSH crystallizes in the P21/c space group of monoclinic system. After heating above 349 K the compound dehydrates, the crystal system changes to triclinic, the monocrystalline samples become non-merohedral twins. The BBTSH crystal comprises p-toluenesulfonic anions, monoprotonated betaine dimers and water molecules. Three kinds of hydrogen bonds are present in the crystal: strong, asymmetric and almost linear OH⋯O hydrogen bond (R(O⋯O) = 2.463(2) Å), weak OwH⋯O hydrogen bonds (R(Ow⋯O) = 2.820(2)  2.822(2) Å) and weak CH⋯O hydrogen bonds (R(C⋯O) = 3.295(2)  3.416(2) Å). The νaOHO vibration of the strongest hydrogen bond in the crystal gives rise to an intense broad absorption with numbers of transmission windows in the low wavenumber region of the infrared spectra. Coupling between νCO stretching vibrations of two COO groups of the betaine dimer was detected. The process corresponding to the loss of water is accompanied by the breakage of strong OH⋯O hydrogen bonds in betaine dimers and rearrangement inside half of the betaine dimers. This rearrangement results in formation of the new betaine dimers with OH∙∙∙O hydrogen bond of similar strength as corresponding bond in the hydrated form (BBTSH).  相似文献   

2.
The structure of the complex of dimethylphenyl betaine (DMPB) with dichloroacetic acid (DCA) (1) has been investigated by X-ray diffraction, FTIR and Raman spectroscopy, and B3LYP/6-311 + + G(d,p) calculations. The crystal is monoclinic, space group P21. The acid is connected with betaine through the OH⋯O hydrogen bond of 2.480(2) Å. In the optimized structure the short, asymmetric O⋯O distance is 2.491 Å. FTIR spectrum shows a broad absorption in the 1500–400 cm−1 region characteristic of very short OH⋯O hydrogen bond caused by Fermi resonance between νOH and overtones of δOH and γOH. In the Raman spectrum this broad absorption is not observed. The potential energy distributions (PED) were used for the assignments of IR and Raman frequencies in the experimental and calculated spectra. The FTIR and Raman spectra of the crystal complex are consistent with the X-ray results.  相似文献   

3.
The 1:1 complex of N-methylmorpholinium-acetate, MMB, with hydrobromic acid (1) has been investigated by single-crystal X-ray analysis, infrared spectroscopy and theoretical calculations. The proton-transfer complex has been observed in the crystalline state, with the COOH⋯Br hydrogen bond with the O⋯Br distance of 3.107(2) Å. In the structure optimized at the B3LYP/6-311++G(d,p) levels of theory the proton is closer to the bromide anion, with the BrH⋯OOC distance of 3.069 Å. The potential energy distributions (PED) have been used for the assignments of IR bands. The experimental and theoretical infrared spectra have been discussed.  相似文献   

4.
KOH activation of petroleum coke (PC) was conducted with 30 vol%H2 + 70 vol% N2 as carrier gas. TG-DTG, FTIR, elemental analysis, N2 adsorption, GC and XRD techniques were used to investigate the effects of hydrogen on the activation. During the initial stage of the activation, i.e. the carbonization of the PC, additional CH and CH2 species were formed due to the chemisorption of hydrogen on the nascent sites of the PC created by the removal of the surface heteroatom groups. The formation of the CH and CH2 species increased the quantity of ‘active sites’ which is favorable to the further activation reaction, and developed the porous structure of the activated carbons. The micropore volume and BET surface areas of the activated carbon prepared under 30 vol% H2 + 70 vol% N2 and with a relatively low KOH/PC weight ratio of 2:1 have been increased from 0.78 cm3/g and 1936 m2/g to 0.97 cm3/g and 2477 m2/g, respectively, compared to that prepared in pure N2 atmosphere with the same KOH/PC ratio.  相似文献   

5.
FTIR spectra of propionic acid (PA), 2-propanol (PROH) and its binary mixtures with varying molefraction of the PA were recorded in the region 500–3500 cm?1, to investigate the formation of hydrogen bonded complexes in a mixed system. The observed features in ν(CO), ν(CO) and δ(COH) of PA, ν(CO) of PROH and δ(COH) of PA + PROH have been explained in terms of the hydrogen bonding interactions between PROH and PA and dipole–dipole interaction. The dipole moment derivative for the above mentioned vibrational modes have also been predicted from the integrated absorbance. The intrinsic linewidth for the vibrational modes ν(CO) and δ(COH) of PA has been elucidated using Bondarev and Mardaeva model.  相似文献   

6.
The molecular structure of caffeine (3,7-dihydro-1,3,7-trimethyl-1H-purine-2,6-dione) was determined by means of gas electron diffraction. The nozzle temperature was 185 °C. The results of MP2 and B3LYP calculations with the 6-31G7 basis set were used as supporting information. These calculations predicted that caffeine has only one conformer and some of the methyl groups perform low frequency internal rotation. The electron diffraction data were analyzed on this basis. The determined structural parameters (rg and ∠α) of caffeine are as follows: <r(NC)ring> = 1.382(3) Å; r(CC) = 1.382(←) Å; r(CC) = 1.446(18) Å; r(CN) = 1.297(11) Å; <r(NCmethyl)> = 1.459(13) Å; <r(CO)> = 1.206(5) Å; <r(CH)> = 1.085(11) Å; ∠N1C2N3 = 116.5(11)°; ∠N3C4C5 = 121. 5(13)°; ∠C4C5C6 = 122.9(10)°; ∠C4C5N7 = 104.7(14)°; ∠N9–C4=C5 = 111.6(10)°; <∠NCHmethyl> = 108.5(28)°. Angle brackets denote average values; parenthesized values are the estimated limits of error (3σ) referring to the last significant digit; left arrow in parentheses means that this parameter is bound to the preceding one.  相似文献   

7.
《Vibrational Spectroscopy》2009,49(2):259-262
In order to evidence the structural changes induced by CuO and V2O5 in the phosphate glass network and their modifier or former role, x(CuO·V2O5)(100  x)[P2O5·CaO] glass system was prepared and investigated using Raman spectroscopy (0  x  40 mol%).Raman spectra of the studied glasses present the specific bands of the phosphate glasses at low concentration of transition metal (TM) ions, but at higher concentration (x > 7 mol%) a strong depolymerization of the phosphate network appears; non-bridging oxygen atoms are involved in VOP and CuOP bonds and new short units are formed. For a high concentration of V2O5 (x > 10 mol%) the Raman bands of V2O5 prevail in the spectra; this fact suggests that vanadium oxide imposes its structural units in the network acting thus as a network glass former.2D correlation analysis was also applied for the concentration-dependent Raman spectra in order to verify the assignments of the vibration modes and to find correlations in the changes induced by TM ions content. 2D correlation maps indicate a good correlation between the bands at ∼705 cm−1 assigned to POP stretching vibration and at ∼1175 cm−1 assigned to PO2 groups which suggest the depolymerization of the phosphate network. The correlation between the 1270 cm−1 and 930 cm−1 bands also suggests that V2O5 oxide is responsible for PO bonds breaking and POV formation.  相似文献   

8.
Three 1D bimetallic M(II)/Ni(II) (M = Cu, Zn and Cd) complexes, [Cu(OHepy)2Ni(CN)4]n (1), [Zn(OHepy)2Ni(CN)4]n (2) and [Cd(OHepy)2Ni(CN)4]n (3) (2-(2-hydroxyethyl)pyridine abbreviated to OHepy), have been synthesized and characterized by FT-IR and Raman spectroscopy, elemental, thermal analyses and single crystal X-ray diffraction techniques. FT-IR and Raman spectra of OHepy have been experimentally and theoretically investigated in the region of 4000–250 cm−1. The corresponding vibrational assignments of OHepy are examined by means of B3LYP hybrid density functional theory (DFT) method together with 6-311++G(d, p) basis set. Moreover, reliable vibrational assignments have been made on the basis of potential energy distribution (PED). The structures of the complexes consist of one-dimensional polymeric chain M(OHepy)2NCNi(CN)2CNM(OHepy)2−, in which the M(II) and Ni(II) atoms are linked by CN groups. The nickel atom is fourfold coordinated with four cyanide-carbon atoms in a square planar arrangement and the metal(II) atoms are sixfold coordinated with two cyanide nitrogen, two OHepy nitrogen and two OHepy oxygen atoms, in a distorted octahedral arrangement. In all the complexes adjacent chains are connected by π⋯π, CH⋯Ni and OH⋯N hydrogen bonding interactions to form two and three dimensional networks.  相似文献   

9.
An overview is given on synthesis and structures of new bidentate phosphaalkene ligands [(RMe2Si)2CP]2E (E = O, NR, N?) and (RMe2Si)2CPN(R′)PR′′2. Exceptional properties of these ligands, extending beyond predictable properties of phosphaalkenes are: (i) the NSi bond cleavage of [(iPrMe2Si)2CP]2NSiMe3 with AuI and RhI chloro complexes under mild conditions leading to binuclear complexes of the 6π-delocalised imidobisphosphaalkene anion [(iPrMe2Si)2CP]2N?, and (ii) the chlorotropic formation of molecular 1:2 PdII and PtII metallochloroylid complexes with novel ylid-type ligands [(RMe2Si)2CP(Cl)N(R)PR2]?, and the transformation of a P-platina-P-chloroylid complex into a C-platina phosphaalkene by intramolecular chlorosilane elimination. Properties of the heavier congeners [(RMe2Si)2CP]2E (E = S, Se, Te, PR, P?, As?) and (RMe2Si)2CPEPR′′2 (E = S, Se, Te) are also described.  相似文献   

10.
In this work, the interaction between dehydroindigo (an intermediary oxidized form of indigo) and Laponite clay was investigated. Dehydroindigo (DHI) has been detected when indigo is adsorbed by clay minerals, but it is relatively unstable and in the presence of water it turns back into indigo. It is, therefore, important to understand the factors that extend its stability and Laponite was chosen because the small aspect ratio implies in a large amount of silanol groups (SiOH) which would thus favor the DHI interaction through hydrogen bonding.A significant bathochromic shift (65 nm) of the DHI π®π* transition band in the visible region and changes in the relative intensities and position of the Raman bands at 1530, 1378 and 1167 cm−1 assigned to ν(NCCN), δ(CN) and ν(CN) respectively, indicate that the interaction is stronger than expected for the van der Waals and polarization forces involved in the external surfaces interactions with the siloxane groups. It was also observed that DHI presents an enhanced photochemical stability when interacting with Laponite. These results indicate that hydrogen bonding between a DHI nitrogen atom and the −SiOH or MOH groups is mainly responsible for the behavior present in the DHI + Lap system.  相似文献   

11.
In this paper, we report the gas phase infrared spectra of fluorene and its methylated derivatives using a heated multipass cell and argon as a carrier gas. The observed spectra in the 4000–400 cm−1 range have been fitted using the modified scaled quantum mechanical force field (SQMFF) calculation with the 6-311G** basis. The advantage of using the modified SQMFF method is that it scales the force constants to find the best fit to the observed spectral lines by minimizing the fitting error. In this way we are able to assign all the observed fundamental bands in the spectra. With consecutive methyl substitutions two sets of bands are found to shift in a systematic way. The set of four aromatic CH stretching vibrations around 3000 cm−1 shifts toward lower frequencies while the single most intense aromatic CH out-of-plane bending mode around 750 cm−1 shifts toward higher frequencies. The reason for shifting of aromatic CH stretching frequency toward lower wave numbers with gradual methyl substitution has been attributed to the lengthening of the CH bonds due to the +I effect of the methyl groups to the ring current as revealed from the calculations. While the unexpected shifting of the aromatic CH out-of-plane bend toward higher wave numbers with increasing methyl substitution is ascribed to the lowering of the number of adjacent aromatic CH bonds on the plane of the benzene ring with gradual methyl substitutions.  相似文献   

12.
The natural vermiculites from different localities (Bulgaria, Brazil, and South Africa) after acid treatment were used for this study. Differently acidified vermiculite samples were prepared from the natural vermiculite sample using different concentrations of hydrochloric acid (0.5 M and 1 M) and different reaction time (2 h and 4 h) at 80 °C. Natural vermiculites and acid treated vermiculites were analyzed by elemental analysis, X-ray diffraction (XRD) analysis and studied using Fourier transform infrared (FTIR) spectroscopy and dispersive Raman spectroscopy. According to the XRD analysis vermiculites are interstratified structures created in the different two-one-zero sheet hydrated phases. Ratio of intensities of spectrally deconvoluted bands at 1075 cm−1 and 1000 cm−1 (stretching vibration of SiO bonds of vermiculites and stretching vibration of SiO bonds of amorphous silica, respectively) was used to determine the content of amorphous silica in acid treated vermiculite samples. Study of the infrared and Raman spectra of the acidified vermiculites enable a comparison of these two spectroscopic data that have not yet been performed.  相似文献   

13.
The curing dynamics and network formation of cyanate ester resin/graphene oxide (GO) nanocomposites were studied by means of Differential Scanning Calorimetry (DSC), Fourier Transform Infrared (FT-IR) and Raman spectroscopies. The incorporation of GO into the resin showed a strong catalytic effect on the cure of the resin, especially in the initial stages. Addition of 4 wt.% GO resulted in the decrease of curing temperature significantly about 97 °C. Activation energy of the nanocomposites also maintained at a low level till the end of the cure. The most effective catalytic behavior was observed with 1 wt.% GO. Both FT-IR and Raman spectra revealed that OH group in GO reacted with cyanate group OCN in the resin to form O(CNH)O bond in the early stages of the cure. These results could provide a low temperature curing route for cyanate ester resins with improved curing efficiency.  相似文献   

14.
With the aid of differential phonon spectrometrics (DPS) and surface stress detection, we show that HI and NaI solvation transforms different fractions of the HO stretching phonons from the mode of ordinary water centred at ∼3200 to the mode of hydration shell at ∼3500 cm−1. Observations suggest that an addition of the H  H anti-hydrogen-bond to the Zundel notion, [H(H2O)2]+, would be necessary as the HO bond due H3O+ has a 4.0 eV energy, and the H  H fragilization disrupts the solution network and the surface stress. The I and Na+ ions form each a charge centre that aligns, stretches, and polarize the O:HO bond, resulting in shortening the HO bond and its phonon blue shift in the hydration shell or at the solute-solvent interface. The solute capabilities of bond-number-fraction transition follow: fH = 0, fNa  C, and fI  1  exp(−C/C0) toward saturation, with C being the solute molar concentration and C0 the decay constant. The fH = 0 evidences the non-polarizability of the H+ because of the H  H formation. The linear fNa(C) suggests the invariance of the Na+ hydration shell size because of the fully-screened cationic potential by the H2O dipoles in the hydration shell but the nonlinear fI(C) fingerprints the I  I interactions at higher concentrations. Concentration trend consistency between Jones–Dole’s viscosity and the fNaI(C) coefficient may evidence the same polarization origin of the solution viscosity and surface stress.  相似文献   

15.
A new liquid crystalline material containing diester linking group ethyl-[4-(4′-decyloxy)benzoyloxy]-benzoate (4-EDBB) was synthesized. The phase transition temperatures were noted by differential scanning calorimetry (DSC), the texture pattern were observed by polarizing optical microscopy (POM) and temperature dependent Raman study was employed to observe the transitions as well as to understand the molecular rearrangement during phase transition. The transitions were observed with all the three techniques but the Raman signature of crystal  smectic A transition is many fold and more precise and accurate. The correlation between intermolecular interaction and phase behaviour has been discussed using temperature dependence Raman data of CH in-plane bending and CO stretching vibrations. With the help of DFT method the possible dimers of 4-EDBB were optimized and the rotational isomers were also investigated. There exists weak hydrogen bonds at room temperature, which breaks as the temperature is increased causing the CH in-plane bending to shift lower and CO stretching vibrations to shift higher. The discussion of the temperature dependent Raman data reveals that at crystal  smectic A transition as a result of intra-molecular rotation the molecules transform from trans- to cis- conformer.  相似文献   

16.
《Fluid Phase Equilibria》2005,235(1):83-91
Densities and speeds of sound for the binary mixtures acetone, 2-butanone and 2-pentanone + diethyl carbonate, over the whole composition range, at T = 298.15 K and atmospheric pressure have been measured. Excess molar volumes and deviations in isentropic compressibility for the binary systems were fitted to the Redlich–Kister polynomial. Isobaric vapor–liquid equilibria for the binary systems acetone + diethyl carbonate, 2-butanone + diethyl carbonate and 2-pentanone + diethyl carbonate at P = 101.3 kPa have been determined. The activity coefficients were calculated to be thermodynamically consistent and they were correlated with the Wilson, NRTL, UNIQUAC and Redlich–Kister equations. Interaction parameters related to the carbonate (OCOO) and ketone (CO) groups, in ASOG and UNIFAC methods, have been determined using our experimental VLE data.  相似文献   

17.
《Vibrational Spectroscopy》2007,43(1):104-110
The Raman spectra of serine [α-amino-β-hydroxypropionic acid; HOCH2CH(NH3)+COO] and 3,3-dideutero-serine [HOCD2CH(NH3)+COO] in aqueous solution were studied in the range 4000–300 cm−1. The data obtained for the deuterated compound are novel and provide compelling evidence that previously reported assignments for the undeuterated amino acid should be revised.  相似文献   

18.
Methyl aziridine-2-carboxylate (MA2C) has been isolated in low temperature argon and xenon matrices and its structure and photochemistry were studied by FTIR spectroscopy. The reactant as well as the main photoproducts were characterized by comparison of their experimental IR spectra with spectra calculated at the DFT(B3LYP)/6-311++G(d,p) level. The theoretical calculations predicted the existence of two low energy MA2C conformers, differing by the orientation of the OCCN dihedral angle. Both conformers were identified in the studied matrices. Both narrowband tunable and broadband UV irradiations of matrix-isolated MA2C yielded isomerization photoproducts resulting from cleavage of the CC and weakest CN bonds of the aziridine ring. Irradiation with UV laser-light at λ = 235 nm resulted in the formation of the E isomer of methyl 2-(methylimino)-acetate (MMIA) and the Z isomer of methyl 3-iminopropanoate (M3IP). Subsequent irradiation at 290 nm led to observation of new bands resulting from E  Z isomerization of MMIA, while bands due to M3IP remained unchanged. The photoproduced Z isomer of MMIA could be subsequently consumed upon higher-wavelength irradiation (λ = 330 nm). The initially produced MMIA conformer was found to obey the nonequilibrium of excited rotamers (NEER) principle. No photoproducts resulting from the cleavage of the strongest CN bond of the MA2C aziridine ring were observed, nor that of methyl 3-aminoacrylate (M3AA), which could in principle be obtained also by cleavage of the weakest CN bond of the MA2C aziridine ring, but would imply a different H-atom migration simultaneous with the ring opening process. These results indicate that both the differential electronic characteristics of the CN bonds of substituted aziridine rings and the type of required H-atom migration are major factors in determining the specific photochemistries of substituted aziridines. Photofragmentation reactions of MA2C were also observed, through identification of various related products, e.g., acetonitrile, methanol, methane, CO and CO2.  相似文献   

19.
《Vibrational Spectroscopy》2006,40(1):142-147
A novel compound, (4,4′-Hbpy)2(K2Mo8O26) 1 (bpy = bipydine), was synthesized by hydrothermal method and characterized by X-ray single analysis, thermalgravimetric analysis, one-dimensional (1D) infrared spectroscopy and two-dimensional (2D) correlation infrared spectroscopy under thermal perturbation. In the compound 1, the [Mo8O26] units link to potassium ions to form layer structure, and the protonated 4,4′-bpy are linked to chains by hydrogen bonds. The 2D IR correlation spectroscopy study indicates that the intensity changes of MoO, NH and CC stretching vibration are sensitive to the temperature variation, and the intensity changes of asymmetry stretching vibration of the terminal MoO occur prior to that of terminal MoO linked by K atom. At the same time, the peaks of asymmetry stretching vibrations of the terminal MoO and the stretching vibrations of NH split into two peaks respectively in 2D IR correlation spectroscopy.  相似文献   

20.
Three structural isomers of pyridinecarboxaldehydes (2-, 3- and 4-pyridinecarboxaldehyde) have been investigated in detail with matrix-isolation infrared spectroscopy in the 3000–600 cm−1 region, combined with the UV photo-excitation and density-functional theory (DFT) calculations. Two rotamers (anti and syn) for 2- and 3-pyridinecarboxaldehyde (2- and 3-PCA, respectively) and one rotamer for 4-pyridinecarboxaldehyde (4-PCA) were identified upon photo-excitation. Most of the observed bands of each rotamer have been assigned. Both the infrared data and the results of the DFT calculations agree that the syn rotamer is a less stable isomer for 2- and 3-PCA. Formation of an intramolecular CH⋯N hydrogen bond in the anti rotamer of 2-PCA results in a shortening of the aldehyde CH bond length. The CO bond length is shortened in the syn rotamer due to the repulsion between the N and aldehyde O atoms. With 2-PCA, both photoinduced rotational isomerism and photolysis were observed upon UV irradiation.  相似文献   

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