Reassignment of the infrared spectra of SnPh3Cl. An infrared method to characterize SnPh3Cl 1—1 adducts

The stretching vibrations of the SnC₃Cl group in the infrared spectrum of SnPh₃Cl have been reassigned on the basis of an SnC₃ group belonging to the C_3ν point group which is replaced by D_3h in SnPh₃Cl₂TMN (TMN = tetramethylammonium). The important shift (108 cm⁻¹) of ν_sSnC₃ from SnPh₃Cl to SnPh₃Cl₂ TMN is due to a “C_3ν point group inversion” (ν_sSnC₃ is higher in frequency than ν_asSnC₃ in the i.r. spectrum of SnPh₃Cl).     

Structural and physicochemical characterization of zinc(II) and cadmium(II) complexes with 1,4‐dimethy‐lhomopiperazine

In order to know the relationship between structures and physicochemical properties of Group 12 metal(II) ions, the complexes with ‘simple’ ligands, such as alkyl cyclic diamine ligand and halide ions, were synthesized by the reaction of 1,4‐dimethylhomopiperazine (hp′) with MX₂ as metal sources (M = Zn, Cd; X = Cl, Br, I). The five structural types, [ZnX₂(hp′)] (X = Cl ( 1 ), Br ( 2 ) and I ( 3 )), [ZnX₃(Hhp′)] (X = Cl ( 1′ ) and Br ( 2′ )), [CdCl₂(hp′)]_n ( 4 ), [{CdCl₂(Hhp′)}₂(µ‐Cl)₂] ( 4′ ) and [{CdX(hp′)}₂(µ‐X)₂] (X = Br ( 5 ), I ( 6 )), were determined by X‐ray analysis. The sizes of both metal(II) and halide ions and the difference in each other's polarizability influence each structure. All complexes were characterized by IR, far‐IR, Raman and UV–Vis absorption spectroscopies. In the far‐IR and Raman spectra, the typical ν(M N) and ν(M X) peaks clearly depend on the five structural types around 540–410 cm⁻¹ and 350–160 cm⁻¹ respectively. The UV–Vis absorption band energy around 204–250 nm also reflects each structural type. Copyright © 2005 John Wiley & Sons, Ltd.     

Study of the ν1, ν1 + ν3 and ν2 + ν3 infrared bands of ONCl

A type (ΔK_a = 0) rovibrational lines of the near-prolate asymmetric top ¹⁶O¹⁴N³⁵Cl have been assigned on high resolution Fourier transform spectra: 820 lines of the ν₁ band, centered around 1800 cm⁻¹, 435 lines of the ν₁ + ν₃ band, centered around 2131 cm⁻¹, and 257 lines of the ν₂ + ν₃ band, centered around 925 cm⁻¹. Least-squares calculations have been carried out over these lines, using the A reduced Watson's hamiltonian in I^r representation; r.m.s. standard deviations of 0.0016 cm⁻¹, 0.0016 cm⁻¹ and 0.006 cm⁻¹ have been respectively obtained, making it possible to measure molecular constants of the (001), (101) and (011) vibrational levels of ¹⁶O¹⁴N³⁵Cl.     

The infrared spectra (3500—150 cm-1) of aniline complexes of cobalt(II), nickel(II), copper(II) and zinc(II) halides

The IR spectra (3500—150 cm^?1) of the complexes [M(aniline)₂,X₂ (M = Co, Ni, Cu, Zn; X = Cl, Br), [Zn(aniline)₂I₂] are discussed. Assignments of the internal ligand vibrations are based on the band shifts which result from ¹⁵N-labelling of the amino group. The metal—ligand stretching frequencies, ν(M—N) and ν(M—X), are assigned on the basis of the band shifts which occur on ¹⁵N-labelling and metal ion and halogen substitution. Two bands within the range 350–450 cm^?1 are assigned to ν(M—N) while the ν(M—X) bands occur within the range 170–320 cm^?1. The effects of structure and coordination number on ν(M—N) and ν(M—X) are discussed. The spectra of two ethanol adducts, [M(aniline)₂-(ethanol)₂Cl₂] (M = Co, Ni) compared with those of the unsolvated species [M(aniline)₂-Cl₂], exhibit a unique band near 480 cm^?1 which is insensitive to ¹⁵N-labelling and is assigned to ν(M—O).     

Raman spectroscopy in liquid xenon solutions: Trifluorohalomethanes

Raman spectra of good quality were obtained for liquid xenon solutions of CF₃X, where X = Cl, Br or I. Full and reliable vibrational assignments were obtained for all three molecules, including the ν₆ modes, whose positions had hitherto been subject to some doubt. ν₆ for CF₃I, for example, is confirmed at 267 cm⁻¹.     

Vibrational (i.r. and Raman) spectra and conformational studies of 1-formyl-3-thiosemicarbazide

The i.r. and Raman spectra (30–4000 cm⁻¹) of 1-formyl-3-thiosemicarbazide (FTSC) and deuterated ftsc-d₄, have been studied. Most of the vibration modes reveal pairs of bands and show strong temperature dependence. A band group {ν(NNH₂)} at ∼ 1100 cm⁻¹ exhibits well resolved doublet (1095 and 1112 cm⁻¹) structure below 100 k. The intensity in the 11 12 cm⁻¹ band decreases regularly (band disappears at 150 K) with the rise in temperature. Two new bands at 955 and 1070 cm⁻¹ appear while measured above 400 K. The system eventually exists in several conformers in simultaneous equilibria. Moreover, a few bands {e.g. ν(CO), ν(CS) and ν(CH)} that show strong intensifies in i.r. exhibit weak (or zero) intensifies in the Raman and vice-versa. The features (characteristic of u and g vibration species) could be explained by a C_2h pseudo symmetry space group proposed for the system. Both the FTSC and FTSC-d₄ represent strong molecular associations. This favours the maximum abundance in the dimer stabilized conformers.     

Study of the spectrum of CH379Br between 1520 and 1700 cm−1: The ν3 + ν6 and the ν5 rovibrational bands

The ν₃ + ν₆ band of CH₃ ⁷⁹Br has been directly analyzed for the first time, and an r.m.s. standard deviation of 0.0035 cm⁻¹ was obtained over 394 lines of K″ΔK = 2 up to 12, through a least-squares calculation using an unperturbed model. Nevertheless discrepancies occur on sub-bands with K″ ⩾ 9, which remain not yet understood. In particular it seems difficult to explain them by a Fermi resonance with the ν₅ band, since it has been possible to fit properly around 580 lines of this band, belonging to sub-bands K″ΔK = 7 up to 16, taking only into account the Coriolis resonance with the ν₂ band and the l(2,2) resonance of ν₅.     

Vibrational anharmonicity and Fermi resonances in CHF2Cl

The infrared spectrum of CHF₂Cl has been recorded between 15 000 and 350 cm⁻¹. The Fermi resonance between levels involving ν₄ and 2ν₆ is analysed in bands extending from 800 cm⁻¹ to 7000 cm⁻¹ leading to a best value of k₄₆₆ = ± 14.98 cm⁻¹. In conjunction with the recent results of Amrein, Dubal and Quack, Molec. Phys. 56,727 (1985); estimates are reported for 38 out of 45 possible x_ij constants. A variation in the relative intensity of the two Q branches associated with ν₁, on cooling the gas cell, indicates that a hot band contributes to the upper branch at 3024.55 cm⁻¹. However, other evidence suggests that the latter arises also from the combination ν₂ + ν₇ + ν₉, in a very weak, close resonance with ν₁ at 3021.27 cm⁻. A number of anomalous band contours are reported.     

A single crystal and polycrystalline study of potassium hydrogen malonate using inelastic neutron scattering

The incoherent ineleastic neutron scattering spectra of single and polycrystal samples of potassium hydrogen (deuterium) malonate have been obtained. These spectra have been assigned in concordance with optical spectra except for the location of the antisymmetric hydrogen bond stretch ν_as(OHO) which we observe at 470 cm⁻¹. The corresponding band in the spectrum of the deuterated sample occurs at 411 cm⁻¹. The CO₂ scissoring mode was also observed with significant intensity. These results are interpreted as a mixing of the two modes. This explains the rotation of ν_as(OHO) displacement vector. This vector lies, not along an O ⋯ O direction, but along a C ⋯ C direction.     

A re-examination of the infrared and ultraviolet spectroscopy of trifluoroacetyl fluoride and trifluoroacetyl chloride: An experimental and theoretical study

The fundamental IR vibrational modes of trifluoroacetyl fluoride CF₃C(O)F and trifluoroacetyl chloride CF₃C(O)Cl have been re-examined by ab initio molecular orbital calculations and compared with literature assignments. Several bands of the IR spectrum are reassigned. The Q-branch and integrated absorption cross-sections have been measured for ν₁, ν₃, ν₄ and ν₁₁ fundamental bands for both pressurized and unpressurized samples on each molecule. The UV absorption spectra of CF₃C(O)F and CF₃C(O)Cl show a structureless continuum with a maximum at 21Onm (σ_max=3.20±0.02 × 10⁻²⁰ cm² molecule⁻¹) and 255 nm (σ_max=7.66±0.26 × 10⁻²⁰ cm² molecule⁻¹), respectively. The nature of the electronic transition giving rise to the UV absorption spectrum for CF₃C(O)F and CF₃C(O)Cl has been examined by ab initio molecular orbital calculations. It is attributed to the A¹A″←X¹A′ electronic transition.     

Darstellung und spektroskopische Charakterisierung der Nona-halogenodiiridate(III), [Ir2X9]3−, X = Cl,Br

Preparation and Spectroscopic Characterization of Nonahalogenodiiridates(III), [Ir₂X₉]^3?, X = Cl, Br The pure nonahalogenodiiridates(III), A₃[Ir₂X₉] (A = K, Cs, tetraalkylammonium; X = Cl, Br) have been prepared. They are formed from the monomer hexahalogenoiridates(III) which are bridged to confacial bioctahedral complexes by ligand abstraction in less polar organic solvents. The IR and Raman spectra exhibit bands in three characteristic regions; at high wavenumbers stretching vibrations with terminal ligands ν(Ir?Cl_t): 360?300, ν(Ir?Br_t): 250?220; in a middle region with bridging ligands ν(Ir?Cl_b): 290?235, ν(Ir?Br_b): 205?190 cm^?1; the deformation bands are observed at distinct lower frequencies. The distance between ν(Ir?X_t) and ν(Ir?X_b) increases with decreasing size of the cations. The electronic spectra measured at thin films of the pure complex salts at 10 K show some intensive charge transfer transitions in the UV and one or two weak d? d bands in the visible region.     

Diode laser i.r. spectrum and rovibrational analysis of CF3Br in the ν2 + ν3 region

The gas phase i.r. spectrum of CF₃Br, with natural isotopic abundance, has been investigated in the ν₂+ ν₃ region near 1120 cm⁻¹ using a tunable diode laser spectrometer. The measurements have been carried out at low temperature (⋍ 200 K) to minimize the effects due to the “hot” band absorptions. The K structure of many P(J) and R(J) manifolds has been resolved and analyzed: the maximum J value reached for individual lines was 62 and 70 for CF₃⁷⁹Br and CF₃⁸¹Br, respectively. The identified transitions have been used in a least-squares fit to the energy expression up to the quartic terms and molecular parameters for the ν₂ + ν₃ combination have been obtained. Residual weak features due to “hot” bands of ν₃ and ν₆ have been assigned; the J structure has been analyzed by means of a polynomial procedure and spectroscopic constants for both the isotopomers have been derived.     

Vibrational spectra of potassium hydrogen 2,3-furandicarboxylate and intramolecular H-bond

Infrared and Raman spectra of KHFur 2,3 and KDFur 2,3 are presented. An assignment of the bands is given which is in good agreement with previous results concerning acid salts possessing intramolecular hydrogen bonds. The ν_as OHO participation was observed at 670 and 520 cm⁻¹, absorption bands of medium intensity. The absence of a more pronounced broadening might be explained by assuming an anharmonic coupling between the ν_as OHO and the ν_s OHO modes, resulting in a combination band at 1000 cm⁻¹.     

Near infrared absorption spectrum of perfluoro-t-butanol/acetonitrile complexes at low temperatures: Fermi resonances and simultaneous transitions

Interactions between perfluoro-t-butanol (PFTB) and acetonitrile-d₃ (AN) in a mixture of freons are studied between 298 and 88 K in liquid or vitreous states. In the conditions of the experiment, a mean 1:2 stoichiometry [PFTB⋯(AN)₂] is inferred from previous matrix measurements. A ν_OH shift of about 160 cm⁻¹ is observed in this temperature range: it is mainly ascribed to solvent effects on the complex. In fact, the dν_OH/dT coefficient increases at low temperature on account of specific solvation of the complex by the freon Br atoms. The ν_OH + τ_OH combination wavenumber is little dependent on the state of PFTB, near 3900 cm⁻¹. A comparatively strong simultaneous transition involving the PFTB ν_OH mode and a ν_CN mode of neighbouring AN molecules is observed. Weaker bands could also be explained by such transitions involving a combination level of PFTB and a ν_CN vibration. Strong Fermi resonances are displayed in the 2ν_OH region when the ν_OH band is located around 3100 cm⁻¹, either in pure AN or in freons at low temperature. The levels interacting with 2ν_OH are ternary combinations and quaternary overtones mainly involving the COH bend and the CO stretch. These resonances are favoured by a strong increase of the OH stretching vibration anharmonicity.     

The analysis of high-resolution spectra of the ν2 and ν5 bands of CH335Cl and CH337Cl

The ν₂ and ν₅ bands of CH³₃⁵Cl and CH³₃⁷Cl between 1300 and 1600 cm⁻¹ have been analysed using a Fourier transform spectrum with 0.006 cm⁻¹ resolution. For CH³₃⁵Cl, the microwave data and 1200 lines from the IR spectrum with J⩽ 50 were fitted with an overall r.m.s. error of 0.00079 cm⁻¹ using the method of predicative observations. A similar fit for 900 lines of CH³₃⁷Cl gave an overall r.m.s. error of 0.00055 cm⁻¹, providing erroneous microwave data on the ν₅ level are omitted. Improved molecular constants are reported for both isotopic species. As expected, the values for ν₂ and ν₅ are little affected by chlorine isotopic substitution.     

Preparation and spectroscopic studies of some cyclic urea adducts of triphenyl-tin and -lead halides

1,3-Dimethyl-2-imidazolidinone (dimethylethylene urea, DMEU) and 1,3-di- methyl-3,4,5,6-tetrahydro-2(IH)-pyrimidinone (dimethylpropylene urea, DMPU) adducts of the type Ph₃SnX·L (X = Cl, Br and I), Ph₃PbX·L (X = Br, I), 3Ph₃PbCl·2DMEU and 2Ph₃PbCl · DMPU have been prepared and characterized. Assignments are made for ν(CO) and ν(CN) frequencies in the IR, and for skeletal frequencies observed in both the IR and Raman spectra in the range 400 to 100 cm^?1 Infrared measurements show that the adducts are bound through the carbonyl oxygen, and are highly dissociated in dichloromethane solution. ¹H and ¹¹⁹Sn or ²⁰⁷Pb NMR measurements reveal that ligand exchange, fast on the NMR time scale, occurs in solution. Coordination of the ligand causes a large upfield shift in the ¹¹⁹Sn or ²⁰⁷Pb resonances, but Ph₃MI · L have shifts similar to those for the parent iodides, indicating almost complete dissociation. Thermodynamic parameters are reported for the dissociation of Ph₃SnX · DMPU (X = Cl, Br) in CH₂Cl₂ solution.     

FTIR spectra of the 2ν4, ν4 + ν6 and 2ν6 bands of formaldehyde

High resolution IR spectra of the overtones and the combination band of the ν₄ and ν₆ modes of formaldehyde (2ν₄, ν₄ + ν₆ and 2ν₆) were measured in the region of 2200–2650 cm⁻¹ using FTIR. The combination band ν₄ + ν₆, whose dipole transition is forbidden from molecular symmetry, was observed due to the intensity borrowed from the other bands. The observed frequencies were analysed by a Hamiltonian in which A-type Coriolis interactions and Darling—Dennison interaction were taken into account. The ratio and the relative signs of the transition dipole moments of the overtone bands, μ_2ν4 and μ_2ν6, have been determined by analysing the intensity distribution of the vibration—rotation lines.     

A Raman spectroscopic study of the effect of ion-pairing on the structure of the triiodide and tribromide ions

The changes in the Raman spectra of aqueous solutions of I₂ in HI (1:1 mole ratio) with changing concentration, have been shown to be a result of ion-pairing: H⁺ + I⁻₃ = H⁺I⁻₃.The anomalous high frequency stretching band of the solute at 172 cm⁻¹ for these solutions arises mainly from stretching of the stronger II bond in the H⁺I⁻₃ ion-pair and not from vibrational modes of I₂ or I⁻₅. Ion-pair dissociation constants estimated from the Fuoss equation, combined with the known I⁻₃ ion-pair and not from vibrational modes of I₂ or I⁻₅. Ion-pair dissociation constants estimated from the Fuoss equation, combined with the known I⁻₃ and I⁻₅ formation constants, account for the intensity changes of the stretching bands. The spectra of solutions of Br₂/HBr at 1:1 mole ratio may be interpreted in the same way but other Br species are present. The spectra of the isolated X⁻₃ ions in solution exhibit a shoulder to high frequency of the symmetric stretching band, ν₁. In the spectrum of the I⁻₃ ion, this peak is assigned to one of the two frequencies, resulting from Fermi resonance between ν₁ and 2ν₂ but, in the case of the Br⁻₃ ion, this peak may be due to ν₃, which becomes Raman active as a result of disymmetric solvation. The consequences of such ion-pairing for the nature of I₂ dissolved in polymers are discussed.     

The ab initio calculation of the band origin and vibrational frequencies of the Ã-X̃ system of HNCl using the non-rigid bender hamiltonian

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 T_c(à ²A') 16200 cm⁻¹, T_o(òA') = 16400 cm⁻¹, and the Franck-Condon maximum, Ã(0,3,1)-X̃(0,0.0), is calculate at 19200 cm⁻¹(5200 Å).     

Vibrational spectra of potassium hydrogen 3,4 furandicarboxylate and intramolecular H-bond

I.r. and Raman spectra of potassium hydrogen 3,4 furandicarboxylate are presented. An assignment of the band is proposed and the details of the hydrogen bond bonds are discussed by analogy with potassium hydrogen maleate. Anharmonic coupling between ν_as, OHO and ν_s OHO is found in the combination band at about 1000 cm⁻¹.