A theoretical investigation of the vibrational states of HCO2? and its isotopomers

Abstract

Making use of the coupled cluster variant CCSD(T) and the aug-cc-pVQZ basis set a six-dimensional (6D) potential energy surface has been calculated for HCO2-, a fundamental organic anion. Therefrom, a variety of vibrational term energies and wavefunctions has been obtained by means of the discrete variable representation in an approach termed DVR(6). Calculated wavenumbers of the fundamentals of HCO2- and DCO2- agree with recent experimental values from neon matrix isolation IR spectroscopy within 15 cm(-1). The out-of-plane bending vibrations v4 are predicted at 1030 and 894 cm(-1). Moderately strong Fermi resonance interaction is calculated between vibrational states v1 and 2v4 of DCO2-. Excellent agreement with experiment (differences less than 0.7 cm(-1) is observed for the 13C and 18O isotopic shifts. Accurate ground-state rotational constants are predicted for eight different isotopomers of the formate ion and the dissociation process HCO2- --> H- + CO2 is investigated in some detail, with the dissociation energy D0 predicted to be 216 kJ mol(-1).

Vibrational Spectroscopy of Fluoroformate, FCO2–, Trapped in Helium Nanodroplets

“…The vibrational spectra of formate and fluoroformate collected utilizing the helium nanodroplet method are shown in Figures a and b, respectively. The excellent agreement between the vibrational transitions of formate observed utilizing the helium nanodroplet technique and those reported in preceding experimental and theoretical studies (within 5 cm –1 , Table S3) provides validation of the experimental methodology. − In the spectrum of both formate and fluoroformate, the spectral lines are narrow, exhibiting full width at half-maximum (fwhm) values of between 2 and 6 cm –1 . In many cases, the measured spectral line width is narrower than the bandwidth of the laser (typical fwhm of ∼0.5% of the photon energy).…”

UV/Vis Spectroscopy of Copper Formate Clusters: Insight into Metal‐Ligand Photochemistry

“…LargerC u II formate anions have been found to fragment in ac ascadet owards clusters with one or two copperc enters, upon which redox reactions can be observed, followed by decarboxylation towards Cu I hydrides as the predominant process. [33] The formate anion in variouse nvironments has been investigated, in detail,b y means of infrared spectroscopy and theoryd ue to anomalies within the vibrational spectrum with intense anharmonicities, [34][35][36][37][38] and its electronic structure has been studied in solution. [39] In the catalytically relevant case of formate ligated copper, structurald ata on coppers urfaces can be found, [40][41][42] whereas data on the electronic structure is still sparse.…”

Unraveling the Anomalous Solvatochromic Response of the Formate Ion Vibrational Spectrum: An Infrared, Ar-Tagging Study of the HCO2¯, DCO2¯, and HCO2¯·H2O Ions

“…The formate ion, HCO 2 ¯ , is ubiquitous in aqueous chemistry and biology, and its structural properties have been extensively catalogued over many decades using a wide variety of spectroscopic techniques. − There is renewed interest, however, in this ion’s intrinsic behavior due to its increasingly important role in the chain of events leading to activation of CO 2 to transportable fuels, for example, by reductive addition of hydride. , The electronic and vibrational level structures of the isolated ion were accurately calculated in 2007 by Botschwina and co-workers, and two aspects of the potential curve describing CH dissociation are nonintuitive. First, the ∼18700 cm –1 bond dissociation energy ,, is much lower than is typical for CH bonds of closed-shell singlets (e.g., 43370 cm –1 for HCN) and second, the shape of the CH potential does not conform to a Morse form, instead exhibiting a sharp change in slope around a bond length of 2 Å where it flattens toward the low dissociation asymptote.…”

“…Figure compares the Ar predissociation spectra for HCO 2 ¯ ·Ar (1b) and DCO 2 ¯ ·Ar (1d) with the harmonic (MP2 aug-cc-pVTZ, upward gray traces in traces a and c) and anharmonic (downward red arrows in traces b and d) predictions. Note that the anharmonic values capture the observed transition energies very accurately, including the large correction to the harmonic CH stretching value relative to that required for the CO stretches.…”