Equilibrium structure of maleic anhydride from gas-phase electron diffraction (GED) and quantum-chemical studies

• Published in: Journal of molecular structure Vol. 978; no. 1; pp. 153 - 157
• Main Authors: Vogt, Natalja, Altova, Ekaterina P., Karasev, Nikolai M.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 20-08-2010
• Subjects: Anharmonic corrections to experimental bond lengths and rotational constants; Bonding; Constants; Electron diffraction; Gas-phase electron diffraction; Maleic anhydride; Mathematical analysis; Molecular structure; Quantum chemistry; Quantum-chemical calculations of structure and force field; Rotational; Thermal-average and equilibrium molecular structure; Gas-phase electron diffraction; Anharmonic corrections to experimental bond lengths and rotational constants; Thermal-average and equilibrium molecular structure; Quantum-chemical calculations of structure and force field; Maleic anhydride
• ISSN: 0022-2860; 1872-8014
• DOI: 10.1016/j.molstruc.2010.02.037

The molecular structure of maleic anhydride was reinvestigated by the gas-phase electron diffraction (GED) method because it was determined with large uncertainties in a previous study. To take into account vibrational effects, the corrections to the experimental bond lengths (
r
a
) were calculated using quadratic and cubic force constants from high-level ab initio calculations (MP2/aug-cc-pVTZ). The determined equilibrium structural parameters (
r
e(C–C)
=
1.485(1)
Å,
r
e(C
C)
=
1.332(1)
Å,
r
e(C–O)
=
1.386(1)
Å,
r
e(C
O)
=
1.192(1)
Å, ∠
e(C–C
C)
=
107.8(1)°, ∠
e(O
C–C)
=
129.2(2)°) are very close to the parameters of the
r
s
structure from a previous microwave spectroscopic (MW) study. Some aspects of the combined analysis of GED and MW data are discussed. The agreement of the experimental rotational constants,
B
0
(
i
)
(MW), corrected for anharmonic effects,
B
e
(
i
)
(MW), with the rotational constants derived from the determined equilibrium geometry, is better than with
B
e
(
i
)
values from quantum-chemical calculations.