Nonempirical Quantum-Chemical Calculations of the Structure and Conformations of the 2,2-Dichloroethanal Molecule in the Lowest Excited Singlet State

The structure of the 2,2-dichloroethanal molecule (CHC_l2CHO) in the lowest excited singlet state was calculated by the nonempirical multiconfigurational self-consistent field method. The electron transition of CHC_l2CHO from the ground to lowest excited singlet state is accompanied by rotation of the CHC₁₂ group, and the carbonyl fragment becomes nonplanar. The potential energy surface for the excited CHCl₂CHO molecule contains six minima corresponding to three pairs of enantiomers. This surface was used to solve torsion and inversion motion problems in the one-dimensional approximation and also two-dimensional torsion-inversion problem. Comparison of the results showed a relation between torsion and inversion motions.