首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 46 毫秒
1.
Raman and i.r. spectra of tetramethylcyclobutane-1-one-3-thione (TMCBOT) and the fully deuterated derivative TMCBOT-d12 have been recorded. A fairly complete set of vibrational frequencies and assignments are given for the two molecules. The CO stretching mode was observed as a very strong Fermi doublet in the infrared spectrum of TMCBOT at 1811/1782 cm−1. For TMCBOT-d12 a similar doublet was observed at 1808/1775 cm−1. The CS stretching mode was assigned to bands at 1303 cm−1 for TMCBOT and 1307 cm−1 for the deuterated molecule.  相似文献   

2.
《Chemical physics letters》1986,129(4):342-345
A novel emission spectrum extending from 5500 to 8600 Å has been observed during the gas-phase reaction of F2 with CS2. Long progressions in the lower-state (presumably the ground-state) bending frequency and shorter progressions in a ground-state stretching frequency were observed. A partial vibrational analysis is reported, from which two new frequencies are obtained: v2 = 356 ± 5 and v3 = 8 31 ± 8 cm−1 .The electronic origin lies near 18500 ± 1200 cm−1. The spectrum is tentatively assigned to the FCS radical.  相似文献   

3.
The Raman spectra (3400 to 10 cm−1 of gaseous, liquid (with qualitative depolarization values) and solid cyclobutyl acetylene, c-C4H7CCH, have been recorded. Additionally, the infrared spectra (3500 to 90 cm−1 of the gas and solid have been obtained. The spectra of the fluid phases are consistent with two stable conformers existing at ambient temperature. These data have been interpreted on the basis that the equatorial conformer is more stable than the high energy axial form in both the gas- and liquid-phases, and is the only conformer present in the solid. Two Q-branches are observed in the low frequency vibrational spectra of the gas at 133 and 118 cm−1 and are assigned to the fundamental ring puckering vibration and an associated upper state transition of the low energy equatorial conformer. These data have been used to approximate the form of the potential function governing ring inversion. Experimental values for the enthalpy difference between the two conformers have been determined for both the gas, 282 ± 49 cm−1, and the liquid, 181 ± 15 cm−1, from relative intensities of a pair of Raman lines over 71 and 100°C temperature ranges, respectively. The structure, conformational stability, inversion barrier and vibrational frequencies have been determined by ab initio calculations using the 3-21G and/or 6-31G* basis sets. These calculated results are discussed in comparison to those determined from experiment and to corresponding quantities for some similar molecules.  相似文献   

4.
《Chemical physics letters》1986,125(2):165-169
The lowest six vibrational hot bands of CF+ have been measured in a helium/C2F6 discharge by velocity modulation laser spectroscopy. A total of 56 transitions has been fitted to Dunham expansion for v = 0–7, yielding the parameters: ωe = 1792.6654(18) cm−1Be = 1.7204176(75) cm−1, Y20, = −13.22968(54) cm−1, and D0 = 62086(30) cm−1. The rotational temperature of CF+ in the plasma is near 650 K and the vibrational temperature is approximately 5200 K.  相似文献   

5.
Crystals of [Mo(η5-C5H5)2(NH3)(SC6H5)][PF6] · (CH3)2CO solvate are monoclinic, space group P21/n, a 9.777(1), b 11.6343(2), c 19.656(4) Å, β 93.60(1)°, V 2231-46 Å3, ZDc 1.617 g cm−3, μ(Mo-Kα) 7.21 cm−1. The structure was solved by Patterson and difference Fourier electron density synthesis and refined to R (F)  0.047 and Rw(F)  0.057 for 3293 observed reflections. The molybdenum atom has the usual distorted tetrahedral geometry comprising the two MoCp (Cp  η5-C5H5) ring normals (MoCp 1.988(13), 1.989(15) Å), one Mo-NH3 (MoN 2.226(12) Å), and one MoSc6H5 (MoS 2.465(5) Å). Extended HMO and steric energy calculations were made in order to account for the geometry adopted by the thiolato ligand in this complex.  相似文献   

6.
The spectrum of the emission from the 1B1*-n+) state of 1,2-cyclobutanedione excited at 488.0 nm has been measured. Wavelengths and vibrational assignments are reported for 24 bands between 490 and 550 nm, 12 of which can be identified with hot bands in the absorption spectrum. Prominent bands in the emission spectrum are associated with excitation of V''8, the symmetric in-plane carbonyl bend (281 cm−1); v''12, the asymmetric carbonyl wag (488 cm−1); and v''7, a symmetric ring distortion (522 cm−1). Sequences in v13, the ring-twisting vibration, are also prominent; the initial excitation lies in the 1333 absorption band, while the emission shows intensity maxima for v'13 = 0 and 2, and a bimodal vibrational relaxation is suggested.  相似文献   

7.
The gas phase emission spectrum of 1, 3, 5-C6Cl3H+3 was obtained in a discharge tube. Vibronic analysis involving correlation of ion fundamental frequencies with those of parent molecules enables a detailed comparison to be made between the vibrational structure of the spectrum of the trichloro-ion and that of 1, 3, 5-C6F3H+3. Analogous Jahn—Teller effects are shown to take place in the ground state of the two ions. The same linear coupling model is used and two possible solutions for D6 and ω6 are obtained by fitting the first two intervals in the 60,0v12 progression in 1, 3, 5-C6Cl 3H+3: (i) D6 = 0.05 - 0.08, ω6 = 455 - 447 cm?1, (ii) D6 = 0.39 - 0.49, ω6 = 399 - 392 cm?1. Arguments based on previously established criteria, and applied here to the case of the 1, 3, 5-C6Cl3H+3 ion are given to select set (ii) as being far more satisfactory in interpreting the experimental data. Fitting to a larger number of bands gave D6 = 0.45, ω6 = 395 cm?1. The Jahn—Teller potential energy barrier EJT6 = 178 cm?1 is about three times greater than in the 1, 3, 5-trifluorobenzene ions, but sufficiently small for the dynamic Jahn—Teller effect to be operative in 1, 3, 5-C6Cl3H+3. Some remarks are made concerning assignments in the excitation spectrum and matrix fluorescence analyses.  相似文献   

8.
The far i.r. (400-50 cm−1) spectra of gaseous and solid furfural (2-furancarboxaldehyde), c-C4H3O (CHO), have been recorded. Additionally, the Raman (3500-20 cm−1) spectra of the gas and liquid have been obtained at variable temperatures and the spectrum of the solid at 25 K. These data have been interpreted on the basis that the molecule exists in two different conformations in the fluid states and that the conformation which has the two oxygen atoms oriented in a trans configuration, OO-trans, is most stable (ΔH ⩽ 1 kcal/mol) in the gas; however, the conformation which has the two oxygen atoms oriented cis, OO-cis, is preferred in the liquid (ΔH = 1.07 ± 0.03 kcal/mol) and is the only rotamer present in the spectra of the solid. The asymmetric torsional fundamental for the OO-trans rotamer has been observed at 146.25 cm−1 in the far i.r. spectrum of the vapor and has five accompanying “hot bands”. The corresponding fundamental for the OO-cis rotamer has been observed at 127.86 cm−1 along with a “hot band” which occurs at 127.46 cm−1. From these data a cosine-based potential function governing internal rotation of the CHO top has been determined and the potential coefficients have values of V1 = 173 ± 2, V2 = 3112 ± 20, V3 = 113 ± 2 and V4 = −198 ± 6 cm−1. This potential is consistent with an enthalpy difference between the more stable OO-trans and high energy OO-cis conformers being 286 ± 24 cm−1 (818 ± 67 cal/mol) and a trans to cis barrier height of 3255 ± 20 cm−1 (9.31 ± 0.06 kcal/mol). These results are compared to the corresponding quantities obtained previously from microwave spectroscopy and theoretical methods.  相似文献   

9.
《Chemical physics letters》1987,139(2):159-164
A three-dimensional fit of ab initio MRD CI potential data has been made for the lowest two electronic states of the HNC1 molecule (X̃ 2A″ and à 2A'), and the corresponding vibrational frequencies and rotational energies have been computed using the non-rigid bender Hamiltonian. For the ground state the vibrational frequencies obtained are ν1 = 2942 cm−1, ν2 = 1232 cm−1, and ν3 = 549 cm−1, while the corresponding values for the first excited state are 3524,947 and 836 cm−1 respectively. We calculate Tc2A') 16200 cm−1, To2A') = 16400 cm−1, and the Franck-Condon maximum, Ã(0,3,1)-X̃(0,0.0), is calculate at 19200 cm−1(5200 Å).  相似文献   

10.
《Chemical physics letters》1987,134(5):497-501
Polarized absorption spectra of neat single-crystal [Ru(bpy)3](PF6)2 at 300 and 5 K are presented. The spectra show pronounced vibronic structure and it is possible to assign the vibrations to known Raman frequencies. Furthermore, the different electronic states corresponding to the vibronic transitions are identified and assigned. The assignment of the lowest excited states - observed in absorption - agrees with an earlier classification of the emitting states. In particular, the Ec-polarized transition A'1 ⇌ 2E' (classified in D'3), at 17816 cm−1, is found at the same energy (experimental error: ± 1 cm−1) in emission and absorption and represents a zero-phonon, zero-vibron transition. The low-energy part of the E¦¦c-polarized spectrum (below ≈ 24000 cm−1) is not dominated by a series of different electronic states but by a 1600 cm−1 progression with zero-vibron transition at 18770 cm−1.  相似文献   

11.
《Chemical physics letters》1986,132(2):103-107
The torsional data for CF3NO have been rein vest igated. A model with a single degree of freedom and three adjustable parameters is sufficient to fit data to v = 8 in the electronic ground state. For CF3NO we obtain Fo = 1.9822(42) cm−1, V3 = 238.4(1.6) cm−1 and V6 = −5.8(1.6) cm−1 or Fo = 1.9894(66) cm−1,F3= −0.194(55) cm−1 and V3 = 239.3(1.9) cm−1. A similar treatment for CF3CHO gives Fo = 1.97(14) cm−1, V3 = 305(25) cm−1 and V6 = −8.7(1.2) cm−1. A need for a re-examination of the torsional fundamental is indicated for CF3CHO. These studies support the general conclusion that for a heavy internal top the internal rotation constant, Fo, required to fit a range of torsional splittings is different from that calculated from structural considerations alone. The difference indicates a large change in F with torsional averaging.  相似文献   

12.
The deactivation of I(2P½) by R-OH compounds (R = H, CnH2n+1) was studied using time-resolved atomic absorption at 206.2 nm. The second-order quenching rate constants determined for H2O, CH3OH, C2H5OH, n-C3H7OH, i-C3H7OH, n-C4H9OH, i-C4H9OH, s-C4H9OH, t-C4H9OH, are respectively, 2.4 ± 0.3 × 10−12, 5.5 ± 0.8 × 10−12, 8 ± 1 × 10−12, 10 ± 1 × 10−12, 10 ± 1 × 10−12, 11.1 ± 0.9 × 10−12, 9.8 ± 0.9 × 10−12, 7.1 ± 0.7 × 10−12, and 4.1 ± 0.4× 10−12 cm3 molec−1 s−1 at room temperature. It is believed that a quasi-resonant electronic to vibrational energy transfer mechanism accounts for most of the features of the quenching process. The influence of the alkyl group and its role in the total quenching rate is also discussed. © 1997 John Wiley & Sons, Inc.  相似文献   

13.
The reactions of the cyclic molecules C6H6 (benzene), c-C3H6 (cyclopropane) and c-C6H12 (cyclohexane) with ArH+ (ArD+), H3+, N2H+, CH5+, HCO+, OCSH+, C2H3+, CS2H+ and H3O+ have been studied at 300 K using a SIFT apparatus. All the reactions except those of C2H3+ proceed via proton transfer and all are fast except the H3O+ and CS2H+ reactions with c-C6H12 which are endothermic and which establish that the proton affinity of c-C6H12 is 160 ± 1 kcal mol−1, which is considerably lower than the published value. In the c-C3H6 and the c-C6H12 reactions multiple products are observed and hence “breakdown curves” for the protonated molecules are constructed and the appearance energies of the various ion products are consistent with available thermochemical data. The reactions of C2H3+ with these cyclic molecules are atypical within this series of reactions in that they appear to proceed largely via hydride ion transfer. The implications of the results of this study to interstellar chemistry are alluded to.  相似文献   

14.
The Raman (3100–10 cm−1) and infrared (3100–30 cm−1) spectra of difluoroacetyl chloride, CHF2CClO, in the gas and solid phases have been recorded. Additionally, the Raman spectrum of the liquid with qualitative depolarization ratios has been obtained. From these data, a trans/gauche equilibrium is proposed in the gas and liquid phases, with the trans conformer (hydrogen atom eclipsing the oxygen atom and trans to the chlorine atom) the more stable form in the gas, but the gauche rotamer is more stable in the liquid and is the only form present in the annealed solid. From the study of the Raman spectrum of the gas at different temperatures, a value of 272 ± 115 cm−1 (778 ± 329 cal mol−1) was determined for ΔH, with the trans conformer the more stable form. Similar studies were carried out on the liquid and a value of 109 ± 9 cm−1 (312 ± 26 cal mol−1) was obtained for ΔH, but now the gauche conformer is the more stable form. A potential function for the conformational interchange has been determined with the following potential constants: V1 = 397 ± 23, V2 = −101 ± 5, V3 = 474 ± 3, V4 = −50 ± 3, and V6 = 10 ± 2 cm−1. This potential has the trans rotamer more stable by 179 ± 31 cm−1 (512 ± 89 cal mol−1) than the gauche conformer. A complete vibrational assignment is proposed for both conformers based on infrared band contours, Raman depolarization data, group frequencies and normal coordinate calculations. The experimental conformational stability, barriers to internal rotation, and fundamental vibrational frequencies are compared with those obtained from ab initio Hartree-Fock gradient calculations employing both the RHF/3-21G* and RHF/6-31G* basis sets, and to the corresponding quantities obtained for some similar molecules.  相似文献   

15.
From the infrared spectra of gaseous carbonyl fluoride-18O(F122C18O) the six fundamental vibrational frequencies (in cm−1) are: (a1) 1895.2 (average of Fermi resonance doublet), 947.3, 576.5; (b1) 1242.3, 604.9; (b2) 770.0. These unambiguous assignments are consistent with the less certain assignments for this isotopic species that Mallinson, McKean, Holloway and Oxton, Spectrochim. Acta 31A, 143 (1975) derived from an argon-matrix spectrum of 4% F122 C18O in a mixture of four isotopomers.  相似文献   

16.
F---F steric interaction between the two 6,6′-fluorines of the C6F4 rings in C12F8Ge(C6H5)2 cause quite distortions in the molecule as these two fluorine atoms are forced to within 2.419 Å of each other (Van der Waals distance ⋍ 2.7 Å). Crystal data: C12F8Ge(C6H5)2, Mr 522.89, C2/c, a 29.065(2), b 8.066(2), c 23.000(3) Å, β 129.85°, U 4139.63 Å3, Z = 8, Dx 1.678 Mg m−3, Mo-Kα, λ 0.7107 Å, μ 15.58 cm−1, F(000) = 2064, T 293 K, R = 0.044 for 2264 reflections with I > 3σ(I); Δϱ ± 0.5 e  相似文献   

17.
The conformational stability, barriers to internal rotation, and fundamental vibrational frequencies of cyclopropylmethyl ketone, c-C3H5C(CH3)O, have been obtained from Hartree—Fock ab initio calculations with the RHF/3-21G and RHF/6-31G* basis sets, as well as the 6-31G* basis set with electron correlation at the MP2 level, and the results are compared to those obtained from experiment. The data are consistent with the predominant rotamer having the cis conformation (carbonyl bond cis to the ring). A second form, having a “near” trans structure, is calculated to have a larger total dipole moment than the cis form, which accounts for its increased abundance in the liquid compared to that in the gas. A complete vibrational assignment is proposed based on experimental data and normal coordinate results from the ab initio calculations. The asymmetric torsional barrier has been calculated to be approximately 2000 cm−1 and this result along with others is compared to the corresponding data obtained from both experiment and theory for the cyclopropylcarbonyl halides.  相似文献   

18.
《Chemical physics letters》1987,141(6):493-498
A useful graphical method for the assignment and analysis of the effects of Fermi resonance in rotational spectra has been devised and applied to vibrational satellites in the microwave spectrum of H12C14N…H19F. The analysis leads to a value of 7.4 cm−1 for the cubic potential constant kσββ.  相似文献   

19.
Here we show that cyclic trimetric perfluoro-o-phenylenemercury (o-C6F4Hg)3 is capable of forming complexes with [PPh4]+Br, [PPh3Me]+I and [PPh4]+Cl of the composition [(o-C6F4Hg)3X] [PR3R′]+ (X = Br, R = R′ = Ph; X = I, R = Ph, R′ = Me) or {[(o-C6F4Hg)3X2}2−[PR3R′]+2 (X = Cl, R = R′ = Ph). An X-ray study of the complex with [PPh4]+Br revealed that it has the unusual structure of the polydecker bent sandwich wherein each Br anion is coordinated with six mercury atoms of two neighbouring molecules of (o-C6F4Hg)3.  相似文献   

20.
The infrared (3500-20 cm−1) and Raman (3200-10 cm−1) spectra have been recorded for gaseous and solid fluoroacetone (1-fluoro-2-propanone), CH2FC(O)CH3. Additionally, the Raman spectrum of the liquid has been recorded and qualitative depolarization values have been obtained. These data have been interpreted on the basis that the molecule exists predominantly in the cis (fluorine atom oriented cis to the methyl group) conformation in the vapor but for the liquid a second conformer having a trans orientation (fluorine atom oriented trans to the methyl group) is present. From a study of the Raman spectrum of the liquid at variable temperatures the trans conformation has been determined to be more stable than the cis form by 416 ± 54 cm−1 (1.19 ± 0.15 kcal mol−1) and is the only conformation present in the spectrum of the annealed solid. The asymmetric torsional fundamental for the more stable cis conformer has been observed in the far infrared spectrum of the gas at 69.6 cm−1 with six accompanying hot band transitions proceeding to lower frequency. The corresponding mode for the high energy trans conformer is extensively overlapped but is distinguishable at ∼65 cm−1. From these data the asymmetric torsional potential function governing internal rotation about the CC bond has been determined and the potential coefficients are: V1 = 675 ± 2, V2 = 991 ± 5, V3 = 74 ± 1 and V4 = 54 ± 2 cm−1. The cis to trans and trans to cis barriers are 1332 ± 5 and 731 ± 5 cm−1, respectively, with an enthalpy difference of 601 ± 8 cm−1 (1.72 ± 0.02 kcal mol−1). From ab initio calculations at the 3-21G and 6-31G* basis set levels optimized geometries for both the cis and trans conformers have been obtained and the potential surface governing internal rotation of the asymmetric top determined. The observed vibrational frequencies with their assignments for both the cis and trans conformers are compared to those from the ab initio calculations. All of these results are compared to the corresponding quantities for some similar molecules.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号