Low-lying Excited States of some Three Membered Antiaromatic Systems

What is it about?

The low-lying excited states of three membered ring systems are investigated by Configuration Interaction calculations using SINDO1 method. Though the ground state is moderately or highly antiaromatic in cyclopropenyl anion, azirene, oxirene and thiirene, the species exhibit moderate aromaticity in the excited states. The excited states of nonaromatic silirenyl anion and phosphirene are found to be antiaromatic.

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Why is it important?

In this work, we investigated the degree of aromaticity in the low-lying excited states of three-membered ring systems which are expected to be versatile synthons through ring opening and ring expansion. Oxirene and thiirene are highly antiaromatic in the ground state while are moderately aromatic in the excited states.. However, the excited states of nonaromatic silirenyl anion and phosphirene are found to be antiaromatic.