Assignment of Vibrational Spectra of 1,10-Phenanthroline by Comparison with Frequencies and Raman Intensities from Density Functional Calculations

Abstract

NIR−FT-Raman spectra of 1,10-phenanthroline were recorded of crystalline material and three different solutions (CD3OD, CHCl3, and CS2) in the wavenumber range 100−1800 cm-1. FT-IR spectra of the solid material were obtained for the range 400−1800 cm-1. A complete assignment of the experimental vibrational spectra (IR and Raman) of 1,10-phenanthroline is given on the basis of calculated frequencies and Raman intensities obtained from the DFT(BP86) harmonic force field. A satisfactory agreement of the harmonic BP86 wavenumbers with the fundamental experimental ones is found. This good agreement is due to a systematic error compensation for BP86 harmonic force fields. Raman intensities were calculated within the double harmonic approximation with different basis sets in order to investigate whether moderately sized triple-ζ basis sets with comparatively few polarization functions can properly describe nonresonant Raman scattering. A satisfactory agreement with experimental data for all in-plane vibrations is already obtained with a standard valence triple-ζ basis plus polarization functions. However, for out-of-plane modes, we found a pronounced dependence of frequencies and intensities on the basis set size, which can be well understood by comparison with the results obtained with a larger basis set. The Sadlej basis set, which is recommended for the calculation of electrical properties, leads to deviations of up to 90 cm-1 for out-of-plane vibrations. Since 1,10-phenanthroline is hygroscopic and can hardly be obtained in water-free form, particular attention is paid to the influence of bound solvent molecules, like water and methanol, on the vibrational spectrum. Model systems with single solvent molecules attached to the isolated phenanthroline molecule were studied. It was found that the wavenumber shifts induced are generally small.

Targeting Intermediates of [FeFe]-Hydrogenase by CO and CN Vibrational Signatures

“…[34,[44][45][46]) as well as harmonic vibrational frequencies (see, e.g., Refs. [34][35][36]). The latter is due to a fortunate error compensation [35] that allows us to directly compare harmonic BP86 frequencies with experimental fundamental ones.…”

“…[23,31], and hence the uncertainty of the prediction might be too large. Therefore, we attempt to re-calibrate calculated vibrational frequencies employing a different density functional, namely BP86 [32,33], and a larger triple-zeta basis set, which are known to produce quite accurate vibrational frequencies [34][35][36][37]. Still, it needs to be shown whether the scatter of the calculated frequencies around their experimental references and, in particular, the scatter of the scaled frequencies can be reduced.…”

Raman spectra from ab initio molecular dynamics and its application to liquid S-methyloxirane

“…KS-DFT was used as the electronic structure method in the framework of the Gaussian and plane waves formalism. We tested three different density functionals: BP86, 48,49 that has been found to perform well in static frequency calculations within the doubleharmonic approximation, [50][51][52][53][54][55][56][57][58][59][60][61][62][63] 73,74 for comparing purposes. BLYP-Goedecker-Teter-Hutter (GTH) (in case of PBE the PBE-GTH) pseudopotentials [75][76][77] and the TZVP-GTH and DZVP-GTH basis sets were applied.…”

MOVIPAC: Vibrational spectroscopy with a robust meta‐program for massively parallel standard and inverse calculations

“…We should state here that the (unscaled) harmonic frequencies obtained with the BP86 functional are generally found to be in good agreement with measured fundamental ones, which is due to some kind of error cancellation. [14,16,23] Therefore, this functional is very well suited for vibrational analyses. In special cases, when weak interactions between noncovalently bound molecular moieties cannot be neglected, one can straightforwardly apply empirical dispersion corrections, such as the ones by Grimme and coworkers (see, e.g., Refs.…”

“…[15] Often one observes a very good agreement of calculated harmonic frequencies and measured fundamental ones (see, e.g., Refs. [16][17][18][19]), which is due to a fortunate error compensation of some density-functional approximations and sufficiently large basis sets. [14] If this is not the case, scaling factors may be used; note that the so-called scaled quantum mechanical force fields are one particular ' 'flavor' ' of these techniques.…”