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

• Published in: Journal of molecular structure 2010-08, Vol.978 (1), p.153-157
• Main Authors: Vogt, Natalja, Altova, Ekaterina P., Karasev, Nikolai M.
• Format: Article
• Language: English
• 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
• 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.