CO Stretch Vibration Research Articles

Raman spectral studies of ion association and solvation in solutions of LiAsF6–acetone

The structure of the solvated lithium cation in acetone solutions has been investigated using Raman spectroscopy. Two bands at 1220 and 1238 cm–1 have been assigned to two types of asymmetric carbon–carbon stretching vibration of acetone: the former is from the bulk solvent and the latter arises from acetone molecules solvating the lithium cation. Analogous assignments are made in the C—C stretch vibration region for two bands at 788 and 802 cm–1 and in the CO stretch vibration region for bands at 1706 and 1720 cm–1. From the measurement of changes in intensity of the two bands in the C—C stretching region of acetone with increasing salt concentration a solvation number of four for lithium cation in acetone has been inferred. Large changes in the Raman bands at ca.1720 cm–1 suggest that solvation occurs through the carbonyl group. Evidence for contact ion pairing between Li+ and AsF–6 is also presented.

Structure and adsorbate-adsorbate interactions of the compressed Ni(110)-(2 × 1)CO structure

Electron energy loss spectroscopy (EELS) with a resolution down to 15 cm −1 was used to study the vibrational modes of the Ni(110)-(2 × 1)CO surface. Besides the CO-stretch and the CO-metal stretch vibration we measured a CO-rotational mode, and a “frustrated translation” mode. The observation of only these CO modes over the entire Brillouin zone favours an (bent) on-top adsorption site for the CO molecule. For the CO stretch vibration we observed a Davydov splitting. The dispersion of the CO-stretch vibration can be described by a simple model of electrostatic dipole-dipole interactions and is sensitive to a structural parameter of CO adsorption, namely the lateral displacement from the on-top position along [001]. The dispersion of the “frustrated translation” mode is caused by strong direct CO-CO interactions.

Picosecond IR studies of the vibrational dynamics of CO/Pt(111)

The vibrational dynamics of chemisorbed CO on Pt(111) are investigated by picosecond IR transient saturation spectroscopy. An intense ps pump pulse excites the CO stretch vibration for CO/Pt(111) and the transient differential IR spectrum of the vibrationally excited adlayer is monitored with a second IR probe pulse. The transient spectrum exhibits a dispersive bandshape, with both bleach and absorption features. The transient spectrum appears prior to the pump pulse and decays within a few ps following the pump pulse. The results are interpreted by comparison with analogous measurements on metal carbonyl molecules, and model calculations including the effects of optical coherence.

An infrared emission study of the C=O stretch vibration of bridge-bonded CO on Pt(111)

We have studied the C=O stretch vibration of bridge-bonded CO on Pt(111) in the temperature range from 225 to 300 K. Our spectra are qualitatively different from those previously reported by Hayden and Bradshaw [Surface Sci. 125 (1983) 787] in that we do not observe the line near 1810 cm −1 that they attributed to three-fold bonded CO. We observe only a single line at 1849 cm −1 . As the coverage is increased beyond 0.5 monolayer, the linewidth decreases, reaching its minimum value near ϱ=0.54. Little change in the frequency or integrated intensity of the line is seen. These observations tend to support “fault line” models for the high coverage structure of CO on Pt(111). The minimum linewidth of the line is 11.5±0.6 cm −1 for temperatures below 275 K, rising rapidly to ≈ 34 cm −1 at 300 K. This temperature dependence cannot be explained by current models of homogeneous broadening. We attribute it to inhomogeneous broadening associated with an order-disorder transition in the overlayer.

An infrared emission study of the CO stretch vibration of bridge-bonded CO on Pt(111)

An infrared emission study of the CO stretch vibration of bridge-bonded CO on Pt(111)

Population relaxation of CO( v = 1 ) vibrations in solution phase metal carbonyl complexes

Picosecond infrared saturation-recovery experiments were performed to obtain measurements of the vibrational energy lifetimes ( T 1) of CO( v = 1) vibrations ( v≈ 1920-1985 cm −1) of carbonyl-containing metal complexes in dilute, room-temperature solutions. For relaxation of the F 1u CO-stretching vibration of W(CO) 6 in CCl 4, CHCl 3, n-hexane and benzene, T 1, was found to be T 1 = 800±200, 480±50, 140±15 and 60±6 ps, respectively, while the same mode of Cr(CO) 6, in these solvents gave T 1 = 440±70, 295±30, 145±25 and 59±6 ps. Monocarbonyl complexes with coordinated triphenylphosphine groups (TPP) have shorter CO( v = 1 ) lifetimes. These observations are rationalized in terms of molecular structure, intramolecular bonding, solvent interaction, and energy accepting vibrational modes.

Iron–ligand bonding properties of synthetic iron–porphyrin complexes with oxygen transporting ability in aqueous media

Mossbauer spectra, i.r. spectra (Fe–CO stretching), and photodissociation quantum yields of the oxygen and CO adducts were measured for synthetic iron–porphyrin complexes with oxygen transporting ability in aqueous media: the 5,10,15,20-tetra{α-o-[2′,2′-dimethyl-20′-(2″-trimethyl-ammonioethylphosphonatoxy)eicosanamido]phenyl}porphyrinatoiron(II)(lipid-heme) complex of 1-laurylimidazole (lauryl = dodecyl) or 1-lauryl-2-methylimidazole embedded in the bilayer of phospholipid liposome (abbreviated as liposome–lipid-heme) and the tetradecyl-substituted copper–iron(II)–diporphyrin (diheme) complex of 1-laurylimidazole solubilized in a surfactant micelle (micelle–diheme). The quadrupole splitting (ΔEQ) for the CO adduct of the diheme indicated a large electric-field gradient at the iron nucleus, probably due to steric hindrance of the diheme structure. Its CO-stretching vibration (νCO) and photodissociation quantum yield (Φ), obtained by flash photolysis, were similar to those of carboxy hemoproteins and suggested the distorted ligation of CO to Fe. Mossbauer parameters for the oxygen adducts of liposome–lipid-heme and micelle–diheme in aqueous media agreed with those for the oxy hemoproteins.

The adsorption, interconversion, and dissociation of CO on Fe(111)

Adsorption of CO and the coadsorption of CO with low coverages of K on Fe(111) at temperatures as low as 83 K have been studied with low energy electron diffraction (LEED), thermal desorption spectroscopy (TDS), and high resolution electron energy loss spectroscopy (HREELS). The results indicate that CO fills three different adsorption sites and is mobile enough to access all binding sites after striking the surface at 83 K. A previously unobserved, very low CO stretch vibration is reported at 1325 cm−1 on the unpromoted surface. In addition, a missing metal–CO vibration is reported for an unpromoted surface. The screening mechanism for the missing Fe–CO stretch vibration is discussed in relation to promoted metal surfaces and to other adsorbates which display similar behavior.

Integrated IR and Raman intensities of aliphatic alcohols in the liquid phase

Integrated molar IR intensities of normal aliphatic alchols, methanol to n-heptanol, are computed by integration of the Lorentz local field corrected function V·(ν·ε″) over the wavenumber interval covered by the absorption band. Raman intensities are measured with the divided cell technique and external standards and the corresponding local field corrections are applied before integration. Absolute values for the integrated IR intensities and relative values for the integrated Raman intensities are given of the OH-stretch and CO-stretch vibrations.

A finite cluster approach to the electron-hole pair damping of the adsorbate vibration: CO adsorbed on Cu(100)

A finite cluster method is applied to describe the energy transfer from the adsorbate vibrations to the electron-hole pair excitations. For CO stretch vibration on Cu(100) surface a value of 0.5 meV is found for the consequent damping (corresponding to the lifetime of 1.3·10 −12- s) in an agreement with a recently measured vibrational line width. The mechanism behind the electron-hole pair excitations is found to be charge oscillations between the molecular 2π ★ resonance and the substrate, caused by the molecular vibration. Cluster size effects have been found to be negligible.

Structural and spectroscopic properties of [(CO) 5MM′ (CO) 3(R-DAB)] (M,M′=Mn,Re; R-DAB=1,4-diaza-1,3-butadiene complexes. X-ray structure of [(CO) 5ReMn(CO) 3-(i-Pr-DAB)] and infrared and resonance Raman spectra of [(CO) 5MM′(CO) 3(R-DAB)

The X-ray structure of the title compound has been determined by the heavy-atom method and refined by means of block-diagonal least-squares calculations from 2116 independent reflections. The crystals are monoclinic, space group P2 Vc with unit cell dimensions a = 18.494(3), b = 7.502(2), c = 16.52(2) Å, β = 113.760(6)° and Z = 4. The final R value was 0.037. The complex has an octahedral geometry and the CO ligands of the Re(CO) 3 and Mn(CO) 3(i-Pr-DAB) moieties are in staggered positions. The Mn-Re bond length is 3.012(2) Å and the MnN bond lengths are 1.994(9) and 2.003(9) Å. The infrared and resonance Raman (RR) spectra obtained by excitation into the lowest electronic absorption band, are reported. A tentative assignment for the CO-stretching vibrations is presented based on their solvent and temperature dependence. The RR spectra of (CO) 3MM′(CO) 3(i-Pr-DAB) (M,M′=Mn, Re) taken from N 2-matrices at 10 K are very weak, which means that the equilibrium conformation of these complexes hardly changes upon going from the ground state to the excited state. These RR spectra are discussed considering the electronic structure of these complexes.

“Chemical effects” of vibrational lifetime and frequency of CO ON Ag

The Raman band of the stretch vibration of CO adsorbed on cold deposited silver films shifts to lower frequency and broadens with increasing coverage. Isotopic mixture experiments show that this is not caused by dipolar interactions. A possible explanation of this pure “chemical effect” based on a finite density of the CO 2π ∗ resonance at the Fermi energy is proposed and critically discussed.

Screening properties of a metal surface at low frequencies and finite wave vectors.

The local-density scheme is used to calculate the self-consistent electron density of a semi-infinite metal in the presence of a static external field of finite wave vector ${\mathbf{q}}_{\mathrm{\ensuremath{\parallel}}}$. The total electrostatic potential is used to determine the rate of exciting electron-hole pairs at low frequencies. The lifetime of the CO stretch vibration on Cu is calculated and the intensity of inelastically scattered electrons is predicted for finite momentum transfers.

Observation and assignment of torsional transitions in FIR emission from optically pumped CH3OH

Using output coupling by reststrahlen reflection from NaCl we have observed 14 new FIR lines in the wavelength range between 30 μm and 60 μm. Two of them have been identified as torsional n=1→0 transitions in the CO stretch vibration. Together with lines previously reported in the literature they are the basis for an identification of 41 FIR lines associated with torsionally excited states.

Ureadiid-Derivate von Mangan(I)-und Rhemum(I)-carbonylen / Ureadiide Derivatives of Manganese (I) and Rhenium (I) Carbonyls

The synthesis of the ureadiido compounds M′[M(CO)nL] (1-5; M′ = Li, K; M = Mn, Re; n = 5,4), in which the ureadiide ions act as monodentate and bidentate ligands, resp., is described. The force constants of the CO-stretching vibrations are calculated and the σ-donor and π-acceptor properties of ureadiide ligands are discussed.

Carbon monoxide adsorbed on Cu(100) Studied by infrared spectroscopy

The stretch vibration of CO adsorbed on Cu(100) has been studied by infrared spectroscopy. Measurements on isotopic mixtures show that the molecules constitute a strongly coupled vibrational system. The results are successfully interpreted in terms of a dipole-dipole interaction between the adsorbed molecules. The vibrational polarizability deduced from the measurements on the isotopic mixtures is in fair agreement with what is obtained from the total absorptance. The frequency shift for one isotope from zero to full coverage is 9cm −1, whereas the dipole-dipole interaction would give a shift of about 40 cm −1. It is suggested that the negative shift of ca. 30 cm −1 is due both to changes in the chemisorption bond and to the fact that the molecules are tilted for low coverages but forced to orient their axes normal to the surface as the coverages increase. For the compressed phase the results are consistent with a model with 75% of the molecules in ontop position and 25% bridge-bonded. The intrinsic peak width, the vibrational frequency dependence of the damping, and additional peak broadening caused by different sorts of disorder are also studied and compared with existing theories.

Molecular complexes of bismuth(III)-chloride and -bromide with benzophenone, 4-chloro-, 4-bromo- and 4-methyl-benzophenone

The 1:1 molecular complexes of bismuth(III) chloride and bromide with benzophenone and 4-R-benzophenone (RCl, Br, Me) have been prepared and spectrochemically studied. The small — Δν(CO) shifts (5–15 cm −1) of the i.r. CO-stretching vibration exclude an intermolecular bonding through the carbonylic group. A charge-transfer band is identified in the 300–350 nm region in the electronic spectra of the dichloromethane solutions of the components in various ratios and concentrations. By using the Benesi—Hildebrand method it is demonstrated that for BiCl 3 the 1:1 complexes are also formed in solution and that the stability constants K determined with this method are linearly proportional to the dipole moments of the ligands and also depend from the dipole moment of the metal trihalide. BiBr 3 forms in DCM solution two Ph 2CO-complexes each other in equilibrium.

Substituent effects in π-(tricarbonylchromium)arenes : III. an ir study of the co-stretching vibrations in substituted methyl π-(Tricarbonylchromium)benzoates

The preparation and the IR spectra (2050–1650 cm -1) of some forty substituted methyl π-(tricarbonylchromium)benzoates and the corresponding free aromatic ligands are reported. The ester carbonyl wavenumbers of the tricarbonylchromium complexes correlate only poorly with electronic substituent parameters, whereas a fair correlation is obtained for the free aromatic ligands. This is explained in terms of conformational preference. The metal carbonyl stretching frequencies were assigned on the basis of local C 3 v symmetry (A 1 + E). The force constants, obtained from the metal CO-modes, correlate satisfactorily with substituent constants in terms of the Yukawa-Tsuno equation. Mono- and bi-nuclear tricarbonylchromium complexes of some biphenyl systems have been prepared. The data for these complexes permit computation of the σ meta and σ para constants for the π-(Cr(CO) 3)phenyl group as a substituent.

Vibrational spectra of iron carbonyl complexes

The experiment described here distinguishes between cis and trans-isomers of Mo(CO)4L2 complexes on the basis of the observed infrared bands in the CO-stretching region and the expected number of infrared active CO-stretching vibrations as derived from group theoretical considerations.

Integralabsorption der CO-Valenzschwingungen unverzweigter homologer Aldehyde, Monocarbonsäuren und Monocarbonsäuremethylester

The integral absorption of the CO-stretching vibration has been estimated for several unbranched aldehydes, fattic acids and methylesters of fattic acids. By plotting the integral absorption against the Taft-constant of the alkyl groups, straight line were obtained. The slopes depend strongly on the nature of the second substituent. In the case of the esters it is shown that a single correlation exists between the integral absorption and the hydrolysis constant.