The complete molecular geometry of salicyl aldehyde from rotational spectroscopy Orest Dorosh, Ewa Białkowska-Jaworska, Zbigniew Kisiel , Lech Pszczółkowski, Institute of Physics, Polish Academy of Sciences, Warszawa, Poland Marianna Kańska, Tadeusz M.Krygowski Department of Chemistry, University of Warsaw, Warszawa, Poland Heinrich Mäder Institut für Physikalische Chemie, Christian Albrechts Universität zu Kiel, Germany 68th OSU International Symposium on Molecular Spectroscopy MH09
Transcript
The complete molecular geometry of salicyl aldehyde from rotational spectroscopy
Orest Dorosh, Ewa Białkowska-Jaworska, Zbigniew Kisiel, Lech Pszczółkowski,
Institute of Physics, Polish Academy of Sciences, Warszawa, Poland
Marianna Kańska, Tadeusz M.Krygowski
Department of Chemistry, University of Warsaw, Warszawa, Poland
Heinrich Mäder
Institut für Physikalische Chemie, Christian Albrechts Universität zu Kiel, Germany
68th OSU International Symposium on Molecular Spectroscopy MH0968th OSU International Symposium on Molecular Spectroscopy MH09
1.76(1) Å
Jones and Curl: J.Mol.Spectrosc. 42, 65 (1972)
“Microwave spectrum of salicyl aldehyde: Structure of the Hydrogen Bond”
Only ma , R-type transitions measured at 26.5-40 GHz + rigid rotor analysis
Some background on salicyl aldehyde:
Overview of our salicyl aldehyde work:
As already reported, RI12 OSU2006: The room temperature MMW spectrum and supersonic expansion FTMW spectra were used to determine precise values of spectroscopic constants for the parent species
Calculated force field was scaled to reproduce the quartics and then used to calculate quartics for the isotopic species
Multiple isotopic species were measured with supersonic exp. FTMW, either in natural abundance or in synthethic samples
Electric dipole moment also measured
Problem: considerable variation in structural parameters between rs, r0, rm
(1) geometries in the region of the central C(1)-C(2) bond
Current solution: Another spectrometer (waveguide FTMW) brought in to measure excited vibrational states in order to calibrate ab initio Bv-B0 calculations
The preferred reSE geometry evaluated
Substitution coordinates (Å) for salicyl aldehyde:
Ground state
Measured
Equilibrium Vibration-rotation contribution consisting of harmonic andanharmonic terms
, a = a, b, c
Structural analysis options:
Ignore є0: rs, r0
Treat є0 as a parameter of fit: rm(1)...
Precalculate є0 from anharmonic ab initio force field: reSE
Program STRFIT from the PROSPE site was used for the analysis (allows r0, rm
(1), rm(1L) , rm
(2) , reSE fits)
The band nature of the MMW spectrum of salicyl aldehyde:
v39v37
v38g.s.
J”=104
The bands are of type-II and consist of overlaps of aR- and bR- transitions for different J. Band appearance is critically dependent on the inertial defect.
Obs.
Calc.
Lowest vibrational energy levels in salicyl aldehyde:
The 8-18GHz waveguide FTMW spectrometer with auto scanning:
Only the two lowest excited vibrational states unperturbed
MMW transitions in the next three states carry various signatures of mutual perturbations
While testing the newly relocated waveguide FTMW spectrometer it was found that the lower J and Ka transitions accessible to it are largely free from the effects of perturbation
The 8-18GHz waveguide FTMW spectrometer :
12m waveguide cell
Salicyl aldehyde sample
Sample cell and LO line of the waveguide FTMW spectrometer:
Detector station
Wall passage
The region of the aR-branch 53,343,2 transition:
Obs.
Calc.v39
v27
v37v38 2v39
g.s.
**
*
*
* *
Synthetic spectrum made with VKIEL, PROSPE website
The region of the bQ-branch 134,9133,10 transition:
Obs.
Calc.v39
v27
v37
v38 2v39
g.s.
*
*
*
* *
*
Calibration of anharmonic Bv-B0 calculations:
Results for the two lowest excited vibrational states for which the MMW rotational transitions are unperturbed
Calculations made with CFOUR at the MP2/DZP level (165 basis functions, 12 days on an i7 computer)
Inertial defect, -0.090865(13) uÅ2 for the ground state
Calibration of anharmonic Bv-B0 calculations:
Results for the next three vibrational states for which the MMW rotational transitions are known to be mutually perturbed
Number Type
1 parent
2 18O7 13C6 d1
5 d2
1 d3
1 d4
1 d5
2 13C,D _____ = 26
Isotopologues used for structure determination:
Also additional isotopologues obtained as a by-product or by deuterating other samples further with D2O
All 15 singly substituted isotopologues:
Heavy nuclei in natural abundance
DO substitution with D2O, other D from three different reactions to substitute at C7 (DCO), C3+C5, and C4+C6
The complete reSE geometry of salicyl aldehyde:
Comparison of salicyl aldehyde bond lengths:
6-311++G(d,p)
Comparison of salicyl aldehyde angles:
6-311++G(d,p)
Previous MMW and supersonic expansion cavity FTMW measurements were augmented with room-temperature waveguide FTMW data to determine perturbation free spectroscopic constants for the five lowest excited vibrational states
The excited state rotational constants served to calibrate the ab initio anharmonic calculation of Bv-B0 values (made with CFOUR) and the MP2/DZP level proved to be cost effective for this molecule
The complete reSE geometry was determined and it seems to be in best agreement
with electron diffraction and computed data, while rs and rm(1) seem to be
susceptible to artefacts resulting from several small inertial coordinates
Room-temperature FTMW rotational spectroscopy currently seems to be the main alternative/replacement technique to Stark spectroscopy for complementing MMW and supersonic-expansion FTMW measurements
