Ab initio studies of the CO2–HF and N2O–HF complexes

Abstract

Ab initio calculations are used to confirm the geometries found experimentally by Klemperer et al. for the CO2–HF and N2O–HF complexes.

Theoretical study of reaction channels for the weakly bound complex systems created with HF, CO2, and various amines

“…The s-fluoroformic acid or s-fluoroformic acid plus NH 3 or amine conformers are more stable than the related a-fluoroformic acid or a-fluoroformic acid plus NH 3 or amine conformers, due to the methylation and polarization effects, the syn-form molecular complexes are more strong intermolecular hydrogen bond than anti-form molecular complexes for second to fifth reaction channels, in which the distances decreased gradually from 1.6861 to 1.5728 Å for L 3 (n) , and 1.6632-1.5573 Å for L 2 (n) molecular complexes. Transition state distances ranges also decreased from 1.643 to 1.3192 Å for T 23 (n) molecular complexes, whenever n increased from 2 to 5, as shown in Figures 5-7.…”

“…In addition, experimental study of microwave and radiofrequency spectroscopy [21] and calculation-based studies [22,23] of the weakly bound CO 2 . .…”

“…, n ϭ 1-5) and the combined molecular systems (CO 2 ϩ HF and CO 2 ϩ NHR 3 F, RAH or CH 3 ) are optimized with all positive real vibration frequencies, and with one imaginary frequency in each transition state, and all the transition states (T 23 (n) and T 13 (n) , n ϭ 1-5) in the five reaction channels are the first-order saddle points in the related potential barrier of the reaction paths. For L 1 (n) weakly bound complex systems of n ϭ 1-5, CO 2 , n ϭ 1-5.…”

“…. NR 3 (RAH, CH 3 ) systems with D ϭ 180°3 internal rotation [transition state systems with closed to Ϫ90°(T 23 ) and relatively lower activation energy (31. .36 kJ/ mol)] 3 the anti-FCO 2 H .…”

Weakly Bonded Systems

“…The former is utilized if no BSSE correction is applied to CI or M#ller-Plesset perturbation theory results for van der Waals 33.1 80,200,222 moleculesl 6,93,112,[232][233][234][235][236][237][238][239][240][241][242][243] Such a cancellation of errors may occur for certain special basis sets, but it can never be ~o m p l e t e '~~,~~~, since the geometrical dependence of the BSSE may not beexpected to be similar to that oft he missing interaction energy,e.g. The latter is implicitly assumed if the geometry of a van der Waals complex is optimized within the Hartree-Fock framework'6~108*224-230 or when uncorrected small-basis SCF results are preferred based on a comparison with experimental data1s7,231.…”