Infrared studies of matrix isolated sodium and potassium chloride and cyanide dimers

The infrared spectra of matrix isolated sodium and potassium chlorides and cyanides in different inert gas matrices were examined over the range 4000 cm^?1 to 33 cm^?1. A study of the effect of superheating the vapor species on the spectra has been carried out. Temperature cycling experiments have been pursued in an attempt to differentiate between bands due to monomers, dimers, and higher polymers. Isotopic frequency shifts were measured for a carbon-13 enriched sample of sodium cyanide and carbon-13 and nitrogen-15 enriched samples of potassium cyanide in the CN region. Symmetry force constants were calculated assuming a cyclic rhombic structure for the dimers. In the case of the cyanide dimer, the CN group of the molecule was considered as a halide atom. Finally a comparison is given between the symmetry force constants of the dimers of the alkali metal fluorides, cyanides and chlorides.     

Far-infrared spectrum and dielectric function of KCN and NaCN in the disordered cubic phase

The far-infrared reflection spectrum of KCN and NaCN in their cubic disordered phases is measured between 20 and 400 cm^?1 with dispersive Fourier-spectroscopy and the complex dielectric function ε̂(ω) is evaluated. At 295 K KCN exhibits a well defined TO mode at 148 cm^?1. The LO mode is at 234 cm^?1. The dielectric function of NaCN between 295 and 363 K is more complicated. Below 150 cm^?1 it can be approximated by an overdamped oscillator at 120 cm^?1.     

Molecular beam electric resonance study of KCN,K13CN and KC15N

The microwave spectra of the isotopic species K¹³CN and KC¹⁵N have been investigated by molecular beam electric resonance spectroscopy, using the seeded beam technique. For both isotopic species about 20 rotational transitions originating in the ground vibrational state were observed in the frequency range 9–38 GHz. The observed transitions were fitted to an asymmetric rotor model to determine the three rotational, as well as the five quartic and three sextic centrifugal distortion constants. The hyperfine spectrum of KCN has been unravelled with the help of microwave-microwave double-resonance techniques. One hundred and forty hyperfine transitions in 11 rotational transitions have been assigned. The hyperfine structures of K¹³CN and KC¹⁵N were also studied. For all three isotopic species the quadrupole coupling constants and some spin-rotation coupling constants could be deduced. The rotational constants of the ¹³C and ¹⁵N isotopically substituted species of potassium cyanide, combined with those of the normal isotopic species (determined more accurately in this work), allowed an accurate and unambiguous evaluation of the structure, which was confirmed to be T shaped. Both the effective structure of the ground vibrational state and the substitution structure were evaluated. The results for the effective structural parameters are $\text{r}{}_{\mathrm{<mtext>CN</mtext>}}\text{= 1.169(3)}\text{A}\text{?}$, $\text{r}{}_{\mathrm{<mtext>KC</mtext>}}\text{= 2.716(9)}\text{A}\text{?}$, and $\text{r}{}_{\mathrm{<mtext>KN</mtext>}}\text{= 2.549(9)}\text{A}\text{?}$. The values obtained for the principal hyperfine coupling constant eQq_z(N), the angle between the CN axis and z_N, and the bond length r_CN indicate that in gaseous potassium cyanide the CN group can be considered as an almost unperturbed CN^? ion.     

Vibrational Assignment of 2-Benzoyl Pyridine and its 18O Labelled Isomer

Abstract

Vibrational spectra of 2-benzoyl pyridine and 2-benzoyl pyridine-¹⁸O have been recorded in the solid and molten state in the infrared (4000–100 cm^?1) and in the Raman (4000–50 cm^?1). Polarized Raman spectra in the molten state have also been measured. The assignment of the vibrational bands is performed using the group vibrational concept, isotopic shifts and polarization features of the normal modes.     

The Vibrational Spectra of 9-Fluorenone and Some of Its Isotopic Isomers

Abstract

Vibrational spectra of 9-Fluorenone, 9-Fluorenone-¹⁸O and 9-Fluorenone-d₈ have been recorded in the solid state and solutions in the infrared and (4000–100 cm^?1) and in the Raman (4000–50 cm^?1). Differential infrared linear dichroic spectra have also been measured. The assignment of the vibrational bands is performed using the group vibrational concept, isotopic shifts and polarization features of the normal modes.     

Low frequency Raman scattering from ammonium ions is sodium beta-alumina

Based on isotopic frequency shifts and model calculations, bands observed near the region of 155 cm^-1 in Raman spectra of sodium beta-alumina containing ammonium ions have been assigned to translational modes of NH₄⁺. The spectra of a crystal containing 61% NH₄⁺ ions show a pair of bands at 165 and 145 cm^-1 (11 K). Possible origins of these bands are discussed.     

Infrared Spectra of the Anion-Radicals of Benzophenone and Some of Its Isotopic Isomers

Abstract

Band assignment of the infrared spectra of the anion-radicals of benzophenone-d_O, -d₁₀ and ¹⁸O has been given on the basis of isotopic shifts. The frequency of the ν_C=O band decreases by ca. 270 cm^?1 with the transformation of neutral keton into anion-radical, due to the strong electron-withdrawing character of the carbonyl group; frequencies of the other modes decrease slightly, down to 30 cm^?1.     

Vibrational Spectra of 2,2′-Pyridil and 2,2′-Pyridil-18O and Assignment of Infrared and Raman Bands

Abstract

Vibrational spectra of 2,2′-pyridil and 2,2′-pyridil-¹⁸O in the solid state and in solutions have been measured in the Raman (4000–50 cm^?1) and infrared (4000–100 cm^?1). The assignment of the bands observed is performed using the group vibrational concept and isotopic shifts data of the normal modes. The presence of synand anti-phase vibrations of both pyridyl rings is discussed. The results are compared to the corresponding data for some similar molecules.     

Temperature and pressure derivatives of the elastic constants of cubic rubidium cyanide

The temperature and pressure derivatives of all elastic constants of rubidium cyanide have been measured from 133 to 380 K respectively from 0 to 1500 × 10⁵ Nm^-2 by ultrasonic methods. The thermoelastic behaviour resembles that of KCN and NaCN. A strong softening of the shear resistance c₄₄ approaching the transition temperature from higher temperatures is observed. The pressure derivatives are also quite similar to those of KCN and NaCN, but fully different from those of normal alkali halides of rocksalt-type. This behaviour confirms a rule already observed in other isotypic crystal groups: the quasi-invariant pressure derivatives are shifted in a characteristic way for a certain structure type, if rare-gas-like ions are replaced by asymmetric ions. The nonlinear elastic behaviour is qualitatively interpreted by interactions of volume-conserving type as existing in fluids.     

Matrix reactions of Zn,Cd and Mg atoms with NO2. Infrared spectra of M+NO2− species

Matrix reactions of Mg, Zn and Cd atoms and NO₂ have been performed. Infrared absorptions in the 1220 cm^?1 range show isotopic shifts appropriate for M⁺NO₂^? species. Bands near 950 cm^?1 in the zinc experiments are attributed to a different ion-pair structural isomer.     

Submillimeter wave spectrum and molecular constants of N2O

The submillimeter wave spectrum of the N₂O molecule has been investigated within the 375–565 GHz frequency range with a sensitivity better than 10^?8 cm^?1. The measured frequencies include 161 lines with intensities γ ? 10^?6 cm^?1 belonging to 22 spectroscopically different species of the molecule (specifically, the ground and some excited vibrational states of the five most abundant isotopic species of the molecule in natural abundance) with a statisticall and systematic error of the order of magnitude 10^?8. Rotational and two centrifugal stretching constants could be determined for each spectroscopic species. For each isotopic species observed, we have made a general analysis of the spectrum in different vibrational states bearing in mind resonance effects. The total number of the rotational and rovibrational constants obtained exceeds 40.     

Vibrational Assignment of N-Phenylphthalimide and 15N-Phenylphthalimide

Abstract

The i.r. spectra of N-phenylphthalimide and ¹⁵N-phenylphthalimide have been measured in 4000–100 cm^?1 frequency range as KBr and polyethylene pellets and as chloroform solutions. The Raman spectra (4000–50) cm^?1 of microcrystalline powder of the of the same compounds have also been investigated.

A detailed assignment of most of the observed frequencies has been proposed on the basis of the group vibrational concept, isotopic shift data and analogies with the spectra of related molecules. Some literature data have been discussed and some frequencies are reassigned.     

Vibrational Spectra of 4-Benzoylpiridine and the 18O Substituted Derivative

Abstract

Infrared and Raman spectra of 4-benzoylpiridine (4BP) and its ¹⁸O substituted derivative have been recorded in the solid and in the molten state. Polarized Raman spectra in the molten state have also been measured. The assignment of the vibrational bands is performed on the basis of isotopic shifts, group vibrational concept and polarization features of the normal modes. The previous assignment of the in- and out-of-plane deformations of the carbonyl group and the fundamentals below 700 cm^?1 are questioned and corrected.     

The harmonic force field of methanol

A 28-parameter harmonic force field for methanol is calculated from the matrix frequencies and frequency shifts of ten isotopic species of methanol determined by Barnes and Hallam; Mallinson and McKean; and Serrallach, Meyer, and Günthard. This present force field reproduces the observed harmonic frequencies and frequency shifts far better than either of the two most recent force fields. The presence of a 20 cm^?1 Fermi resonance shift on the lower A′ CH₃ stretching mode deduced in an earlier work is confirmed here.     

Formate anion: The physical force field

Unequivocal assignments for all of the vibrational modes of the formate ion have been made from isotopic shifts measured in the Fourier transform infrared and Raman spectra of polycrystalline samples of the sodium salts of HCO₂^?, H¹³CO₂^?, DCO₂^?, and D¹³CO₂^?. Literature frequencies for DCO¹⁸O^? and DC¹⁸O₂^? have been added to the above results for the unique determination of the 10 force constants in the general harmonic force field. Product rule relations among the harmonic frequencies are shown to interfere seriously with the determination of the physical force field by the standard normal coordinate computation. The least-squares refinement is found to be particularly sensitive to identified types of anharmonic error in the frequencies. Refinements characterized as Φ^aH and Φ^aD improve reliability by elimination of the deuterium isotopic shift for νCH. The physical force field is interpreted in terms of the geometric and electronic structure.     

Water absorption line, 931–961 nm: selected intensities,N2-collision-broadening coefficients,self-broadening coefficients,and pressure shifts in air

Intensities were measured for 97 lines of H₂O vapor between 932 and 961 nm. The lines were selected for their potential usefulness for remote laser measurements of H₂O vapor in the earth's atmosphere. The spectra were obtained with several different H₂O vapor abundances and N₂ broadening gas pressure; the spectral resolution was 0.046 cm^?1 FWHM. Measured H₂O line intensities range from 7 × 10^?25 to 7 × 10^?22 cm^?1/molecules/cm². H₂O self-broadening coefficients were measured for 13 of these strongest lines; the mean value was 0.5 cm^?1/atm. N₂-collision-broadening coefficients were measured for 73 lines, and the average was 0.11 cm^?1/atm HWHM. Pressure shifts in air were determined for a sample of six lines between 948 and 950 nm; these lines shift to lower frequency by an amount comparable to 0.1 of the collision-broadened widths measured in air or N₂. The measured intensities of mainly lines of the 300-000 band are much larger than expected from prior computations, in some cases by over ab order if magnitude. Coriolis interactions with the stronger 201-000 band appear to be the primary cause of the enhancement of these line intensities.     

Isotope shifts in the spectra of LiLuF<Subscript>4</Subscript>:Ho<Superscript>3+</Superscript> crystals due to the isotopic disorder in the lithium sublattice

The isotope shifts of lines in the spectra of the LiLuF₄:Ho³⁺ crystal in the range of the transitions ⁵ I ₈→⁵ I ₇, ⁵ I ₆, and ⁵ I ₅ caused by the isotopic disorder with respect to lithium are measured. The shifts of different lines amount to 0.01–0.036 cm^?1. A comparison with the previously measured isotope shifts in the spectra of the LiYF₄:Ho³⁺ crystal is made.     

Matrix reactions of alkaline earth metal atoms with ozone : Infrared spectra of the metal ozonide and metal oxide molecules

The 15°K deposition of alkaline earth metal atoms and ozone molecules at high dilution in argon yielded intense bands near 800 cm⁻¹ and in the region, 450–650 cm⁻¹. The bands near 800 cm⁻¹ showed the appropriate oxygen isotopic shifts for assignment to ν₃ of the ozonide ion; the use of scrambled isotopic ozones indicated that the metal cation is symmetrically bound to the ozonide anion which contains three oxygen atoms with two equivalent oxygens. For the case of Ca and Ba atoms and ozone, infrared absorptions appeared between 450–650 cm⁻¹ which showed appropriate oxygen isotopic shifts for vibrational assignment to several metal oxide species. In the calcium experiments, bands at 635.7 and 575.5 cm⁻¹ which showed diatomic oxygen-18 isotopic shifts were tentatively identified as (CaO)₂ species; a pair of bands at 593.0 and 592.2 cm⁻¹ were tentatively assigned to CaO₂. For the barium reactions, bands at 634.7, 571.3, and 460.0 showed appropriate oxygen-18 frequency shifts for assignment to BaO, BaO₂, and (BaO)₂, respectively. The BaO assignment was confirmed by the N₂O-nitrogen matrix reaction which yielded a nitrogen matrix counterpart for BaO at 612.4 cm⁻¹.     

Fourier Transform Infrared Spectroscopic Investigation of the Binary and Ternary Cyanide Adducts of the Oxidized Horseradish Peroxidase: Identification of a Second Stretching Mode for the Carbon-Nitrogen Bond of the Bound Cyanide Ion

The binary and ternary cyanide adducts of the ferric horseradish peroxidase were investigated by Fourier transform infrared spectroscopy. The carbon-nitrogen bond of the bound cyanide ion in the binary ferric cyanohorseradish peroxidase exhibits two stretching vibrations at 2130 cm^?1 and 2127 cm^?1 with the latter mode being observed in this work for the first time. This finding supports the results of the resonance Raman study of cyanohorseradish peroxidase, which identified two iron-carbon-nitrogen bending vibrations and two iron-carbon stretching vibrations, proving the existence of two conformational states. The identification of the latter carbon-nitrogen stretching frequency allowed the assignment of all of the vibrational modes of the iron-carbon-nitrogen groups of the two conformational states of the ferric cyanohorseradish peroxidase. The first conformer is characterized by a carbon-nitrogen stretch at 2130 cm^?1, an iron-carbon stretch at 453 cm^?1, and an iron-carbon-nitrogen bending mode at 405 cm^?1. The second state has a carbon-nitrogen stretch at 2127 cm^?1, an iron-carbon stretch at 360 cm^?1, and an iron-carbon-nitrogen bending mode at 422 cm^?1. The iron-carbon stretching band is weakly sensitive to pH changes, but it is sensitive to H₂O/D₂O substitution, indicating that the bound cyanide ion in cyanohorseradish peroxidase is hydrogen bonded to the surrounding protein. The two states were attributed to variation in the extent of hydrogen bonding of the iron-carbon-nitrogen groups in the two states. The carbon-nitrogen stretching vibrations of the ternary complexes of cyanohorseradish peroxidase with ferulic acid, benzamide, and benzhydroxamic acid have been investigated for the first time. The binding of the substrate to cyanohorseradish peroxidase does not always lead to the vanishing of one of the conformational states as in the carbon monoxide adducts of the ferrous horseradish peroxidase, but can cause shifts in the νC-N frequency and in the relative population of both conformational states.     

Infrared Spectra of the Square Planar Rhodium(I) Complexes cis-[Rh(CO)2(pyridine) (X)] (X = Cl,Br): Isotopic Labelling Studies and Normal Coordinate Analysis

Abstract

The infrared spectra (4000 - 50 cm^?1) of the square planar rhodium(I) complexes cis-[Rh(CO)₂ (pyridine) (X)] (X = Cl, Br) and their isotopomers with pyridine-d ₅ and ¹³CO have been determined. Assignments are based on earlier studies on pyridine and its complexes and on the shifts in infrared bands which are caused by the isotopic substitutions employed. Normal coordinate analysis following the procedure of Becher and Mattes has been used to confirm the empirical assignments. The two v(RhC) bands are observed near 490 and 450 cm^?1. v(RhN) is found near 210 cm^?1 and v(RhX) occurs at 310 (X = Cl) and 235 (X = Br) cm^?1. At frequencies below 200 cm^?1, the bands are assigned to bending modes in the following sequence: δ (RhN) > δ (CRhC) > δ (RhCl) > γ (RhCl) > γ (RhN).