Rotational spectra of isotopic furan-(argon)n, n = 1,2, complexes and their vibrationally averaged structures

Self Cite

Section: Structure Of the Complexmentioning

confidence: 99%

Pure rotational spectrum, quadrupole coupling constants and structure of the dimer of pyrrole

Columberg¹,

Bauder²

1997

Self Cite

“…Although isomerization along the ring should not be ruled out, this could also be due to further complexation of the 1:1 complex with one or more Ar atoms. 12 Subject to computational confirmation, one may speculate that the preferred Ar complexation site in the C-docking isomer is opposite to the methanol coordination at the furan ring, where it competes for electron density, thus explaining a spectral upshift of the OH stretching band. However, this new kind of assignment aid requires future computational support to become useful for structural assignment.…”

Section: Resultsmentioning

confidence: 96%

“…10 Otherwise, they might provide information about the docking site from the shift of the electronic spectrum upon complexation. Microwave spectroscopy would be very attractive as it can provide direct structural evidence for the docking site and prove the coexistence of C-/O-docking in a supersonic jet, [11][12][13][14][15] but a quantification of the relative abundance is more challenging. Raman spectroscopy in supersonic jets could provide a higher relative sensitivity for the C-bonded complex and better spatial resolution of the concentration evolution, 16 but the computed scattering cross sections may be somewhat less reliable than IR absorption cross sections.…”

Section: Introductionmentioning

confidence: 99%

The furan microsolvation blind challenge for quantum chemical methods: First steps

Gottschalk

Poblotzki

Suhm

et al. 2018

Herein we present the results of a blind challenge to quantum chemical methods in the calculation of dimerization preferences in the low temperature gas phase. The target of study was the first step of the microsolvation of furan, 2-methylfuran and 2,5-dimethylfuran with methanol. The dimers were investigated through IR spectroscopy of a supersonic jet expansion. From the measured bands, it was possible to identify a persistent hydrogen bonding OH–O motif in the predominant species. From the presence of another band, which can be attributed to an OH-π interaction, we were able to assert that the energy gap between the two types of dimers should be less than or close to 1 kJ/mol across the series. These values served as a first evaluation ruler for the 12 entries featured in the challenge. A tentative stricter evaluation of the challenge results is also carried out, combining theoretical and experimental results in order to define a smaller error bar. The process was carried out in a double-blind fashion, with both theory and experimental groups unaware of the results on the other side, with the exception of the 2,5-dimethylfuran system which was featured in an earlier publication.

“…33 However, this was not observed to be the case for pyridine-Ar 0,1,2 or furan-Ar 0,1,2 comparisons. 33,34,36 For pyridine-Ar, P y is 0.8% smaller than P y for pyridine, while for furan-Ar the reduction is 1.1%. In our case, P y for FB-Ar is 1.5% smaller than that for FB.…”

Section: A Fb-ar S 1 Rotational Constants and Geometrymentioning

confidence: 99%

“…33,34,36 To account for this, the moments of inertia for the monomer must be replaced by "vibrationally averaged," effective values when it is in the complex. From here on the term "effective moment of inertia," I eff , will be used to describe the vibrationally averaged moments of inertia associated with the monomer in the complex.…”

Section: A Fb-ar S 1 Rotational Constants and Geometrymentioning

confidence: 99%

Two-dimensional laser induced fluorescence spectroscopy of van der Waals complexes: Fluorobenzene-Arn (n = 1,2)

Gascooke

Alexander

Lawrance

2012

The technique of two-dimensional laser induced fluorescence (2D-LIF) spectroscopy has been used to observe the van der Waals complexes fluorobenzene-Ar and fluorobenzene-Ar2 in the region of their S1-S0 electronic origins. The 2D-LIF spectral images reveal a number of features assigned to the van der Waals vibrations in S0 and S1. An advantage of 2D-LIF spectroscopy is that the LIF spectrum associated with a particular species may be extracted from an image. This is illustrated for fluorobenzene-Ar. The S1 van der Waals modes observed in this spectrum are consistent with previous observations using mass resolved resonance enhanced multiphoton ionisation techniques. For S0, the two bending modes previously observed using a Raman technique were observed along with three new levels. These agree exceptionally well with ab initio calculations. The Fermi resonance between the stretch and bend overtone has been analysed in both the S0 and S1 states, revealing that the coupling is stronger in S0 than in S1. For fluorobenzene-Ar2 the 2D-LIF spectral image reveals the S0 symmetric stretch van der Waals vibration to be 35.0 cm−1, closely matching the value predicted based on the fluorobenzene-Ar van der Waals stretch frequency. Rotational band contour analysis has been performed on the fluorobenzene-Ar $\overline {0_0^0 }$000¯ transition to yield a set of S1 rotational constants A′ = 0.05871 ± 0.00014 cm−1, B′ = 0.03803 ± 0.00010 cm−1, and C′ = 0.03103 ± 0.00003 cm−1. The rotational constants imply that in the S1 00 level the Ar is on average 3.488 Å from the fluorobenzene centre of mass and displaced from it towards the centre of the ring at an angle of ∼6° to the normal. The rotational contour for fluorobenzene-Ar2 was predicted using rotational constants calculated on the basis of the fluorobenzene-Ar geometry and compared with the experimental contour. The comparison is poor which, while due in part to expected saturation effects, suggests the presence of another band lying beneath the contour.