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 (CHCl2CHO) in the lowest excited singlet state was calculated by the nonempirical multiconfigurational self-consistent field method. The electron transition of CHCl2CHO from the ground to lowest excited singlet state is accompanied by rotation of the CHCl2 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.