Two possible pathways have been investigated for the cis—trans conversion in diimide N-oxide, viz. a rotation around the NN bond and an in-plane inversion. Calculations have been performed for the ground and lowest excited states by means of a Cl treatment including the configurations found to be the most important in large Cl calculations performed in a few points. It is shown that the rotational mechanism is favoured in the excited states and is probable also in the thermal reaction. Such investigation has been repeated in parallel by using other techniques of lower accuracy: (1) Cl limited to single excitations (EHP method); (2) rigid excitation to virtual orbitals; (3) the half electron methods. Deficiencies of such methods have been brought out and analyzed. In particular methods (2) and (3) lead to an erroneus interpretation of the actual mechanism of the photochemical conversion by rotation.
The cis- trans thermal and photochemical interconversion mechanism in the diimide N-oxide. A comparison of the results obtainable with different ab initio calculation techniques
CIMIRAGLIA, Renzo;
1977
Abstract
Two possible pathways have been investigated for the cis—trans conversion in diimide N-oxide, viz. a rotation around the NN bond and an in-plane inversion. Calculations have been performed for the ground and lowest excited states by means of a Cl treatment including the configurations found to be the most important in large Cl calculations performed in a few points. It is shown that the rotational mechanism is favoured in the excited states and is probable also in the thermal reaction. Such investigation has been repeated in parallel by using other techniques of lower accuracy: (1) Cl limited to single excitations (EHP method); (2) rigid excitation to virtual orbitals; (3) the half electron methods. Deficiencies of such methods have been brought out and analyzed. In particular methods (2) and (3) lead to an erroneus interpretation of the actual mechanism of the photochemical conversion by rotation.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
