Toward a Systematics for the Lowest Excited States of Heteroaromatics Enabled via Cyclic π-Conjugated Carbenes and Heteroelement Analogues.

ABSTRACT: The photochemistry of heteroaromatic compounds depends on the character of their lowest electronically excited states, which are of either n,π* or π,π* type. For species with 4n + 2 π-electrons, the latter type of states can be antiaromatic to various extents according to Baird's rule and, thus, highly reactive. The n,π* type of states, on the other hand, will have an odd number of π-electrons leading to an unclear character, spanning from aromatic to antiaromatic. Six-membered ring (6-MR) heteroaromatics with in-plane lone-pair orbitals (n_σ, herein n) have either n,π* or π,π* states as their lowest vertically excited states, but regular five-membered ring (5-MR) heteroaromatics with one or two N, O, and/or S atoms never have n,π*

SUBMITTER: Proos Vedin N 

PROVIDER: S-EPMC12281578 | biostudies-literature | 2025 Jul

REPOSITORIES: biostudies-literature