61st OSU International Symposium on Molecular Spectroscopy RI12 Rotational spectrum, electric dipole moment and structure of salicyl aldehyde Zbigniew Kisiel, Orest Dorosh, Lech Pszczółkowski Institute of Physics, Polish Academy of Sciences Warszawa, Poland Marianna Kańska, Tadeusz M. Krygowski Department of Chemistry, University of Warsaw, Warszawa, Poland

Desyatnyk et. al.. PCCP 7, 1708 (2005) Benzaldehyde:Anisole:

1.76(1) Å Jones and Curl: Jones and Curl: J.Mol.Spectrosc. 42, 65 (1972) “…Structure of the Hydrogen Bond” Only  a, R-type transitions measured at GHz + rigid rotor analysis Some background on salicyl aldehyde:

MMW spectrum (Warsaw broadband spectrometer): analysed to determine accurate spectroscopic constants of the parent isotomers Ab initio: calculated force field scaled using experimental values for the parent and used to calculate quartic for the isotopomers FTMW spectrum (Warsaw jet spectrometer): ground state measurements made on at least 7 selected transitions to determine A, B, C Molecular structure: least-squares r m geometry fitted with program STRFIT from the website STRFITSTRFIT Steps in this investigation:

AABS = Assignment and Analysis of Broadband Spectra

bRbR aRaR b R + a R

GAMESSGAMESS FCONVFCONV VIBCAVIBCA } 1.5 % 541 transitions in fit Deviation of fit = 51.5 kHz a R, b R, a Q, b Q transitions measured Results for the ground state of parent salicyl aldehyde

All 15 singly substituted isotopomers: Heavy nuclei in natural abundance DO substitution with D 2 O, other D from three different reactions to substitute at C 7 (DCO), C 3 +C 5, and C 4 +C 6 } Number Type 1parent 2 18 O 7 13 C 6 d 1 5 d 2 1 d 3 1 d 4 1 d C,D _____  26 } Additional isotopomers obtained as a by- product or by deuterating other samples further with D 2 O Isotopomers used for structure determination

Desyatnyk et. al.. PCCP 7, 1708 (2005) Anisole: 100% Ar 100% He Use of He/Ar gas mixture to increase line intensity

Ground state Measured Equilibrium Calculated Vibration-rotation contribution: = harmonic + anharmonic,  = a, b, c Moments of inertia

a s /Å b s /Å C (6) (3) C i 0.818(2) C (1) 1.271(1) C (1) 0.345(4) C (1) (2) C (2) (1) C (1) (1) O (1) (5) O (2) 1.734(1) H (1) 1.260(1) H (1) 2.337(1) H (1) 0.706(2) H (1) (1) H (3) (1) H (1) (1) Kraitchman coordinates for salicyl aldehyde

r m (1)  c  r m (2)  c  d  J.Mol.Spectrosc. 196, 102 (1999) r m (L)    r m (1L)  c    Watson’s modified r m method

STRFITSTRFIT = STRucture FITting program : Flexible declaration using internal coordinates Fitting to moments of inertia, provision for various degenerate coordinates r 0, r z, r m (1), r m (2), r m (1L), r m (2L) (many worked examples) Any number of isotopomers, any combination of constants Structural declaration the same as used by PMIFST allowing direct visualisation PMIFSTPMIFST

Fit to 78 moments of inertia Deviation of fit = u Å 2 c a =0.067(11), c b =0.079(12), c c =0.099(13) u 1/2 Å [  H =0.01Å] 1.783(2) Å 145.1(1) o The r m (1L) geometry of salicyl aldehyde

electron diffraction Ab initio, 6-31G(d,p) this work previous rotational 1.783(2) Å 1.76(1) Å 1.74(2) Å 2.9(3) o 0.6(2) o 0.5(10) o 1.3(9) o DFT -0.6 o MP2 0.5 o DFT 1.3 o MP2 2.2 o 6o6o OO=2.645 Å OO=2.65 Å

Electrodes: 28x28 cm, 27cm apart Electric field:  500 V/cm IFPAN Stark electrodes for uniform field distribution Kisiel et. al.. CPL 325, 523 (2000)

Stark measurements for salicyl aldehyde

 a = 2.343(2)  b = 1.811(1)  tot = 2.961(2)  a = 2.906(2)  b = 1.188(1)  tot = 3.140(2) Dipole moment comparison between benzaldehyde and salicyl aldehyde 32.4 o 56.9 o

Resolved deuterium hyperfine structure in DO-salicyl aldehyde Information on the intramolecular hydrogen bond ?