Synthesis, microwave spectra, x-ray structure and high-level theoretical calculations for formamidinium formate
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An efficient synthesis of formamidinium formate is described. The experimental x-ray structure shows both internal and external H-bonding to surrounding molecules. However, in the gas phase this compound occurs as a doubly hydrogen bonded dimer. This doubly hydrogen-bonded structure is quite different from the solid state structure. Microwave spectra were measured in the 6-14 GHz range using a pulsed-beam Fourier transform microwave spectrometer. The two nonequivalent N-atoms exhibit distinct quadrupole coupling. The rotational, centrifugal distortion and quadrupole coupling constants determined from the spectra have values: A = 5880.05(2), B = 2148.7710(2), C = 1575.23473(13), 1.5 χaa (N1) =1.715( 3), 0.5(χbb- χcc)(N1) = -1.333(4), 1.5χaa (N2) = 0.381(2), 0.25(χbb- χcc)(N2) = -0.0324(2), and DJ = 0.002145(5) MHz. The experimental inertial defect, Δ = -0.243 amu Å2, is consistent with a planar structure. Accurate and precise rotational constants (A, B and C), obtained from the microwave (MW) measurements, were closely reproduced, within 1-2% of the measured values, with the M11 DFT functional theoretical calculations. Detailed comparison of the measured and calculated A, B and C rotational constants confirm the planar doubly hydrogen bonded structure. the nitrogen quadrupole coupling strengths of the monomer are quite different from either of the two nitrogen sites of the dimer. The poor agreement between measured and calculated quadrupole coupling strengths show that the dimer is not locked in the equilibrium structure, but is likely undergoing large amplitude vibrational motion of the hydrogen atoms moving between the N and O atoms involved in the hydrogen bonding.
Zhou , Z , Aitken , R A , Cardinaud , C , Slawin , A M Z , Wang , H , Daly , A , Palmer , M & Kukolich , S 2019 , ' Synthesis, microwave spectra, x-ray structure and high-level theoretical calculations for formamidinium formate ' , The Journal of Chemical Physics , vol. 150 , 094305 . https://doi.org/10.1063/1.5081683
The Journal of Chemical Physics
Copyright © 2019 The Author(s), published by AIP Publishing. This work has been made available online in accordance with the publisher’s policies. This is the author created, accepted version manuscript following peer review and may differ slightly from the final published version. The final published version of this work is available at https://aip.scitation.org/journal/jcp
DescriptionThis material is based upon work supported by the National Science Foundation under Grant No. CHE-1057796 at the University of Arizona.
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