1. Influence of Pseudo-Jahn-Teller Activity on the Singlet-Triplet Gap of Azaphenalenes
- Author
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Majumdar, Atreyee, Jindal, Komal, Das, Surajit, and Ramakrishnan, Raghunathan
- Subjects
Physics - Chemical Physics - Abstract
We probe the sensitivity of the singlet-triplet energy gap of selected azaphenalenes to symmetry lowering induced by Jahn-Teller interactions. While cyclazine in its characteristic $D_{\rm 3h}$ structure defies Hund's rule, CCSD(T)-level modeling suggests its structure corresponds to two equivalent minima of $C_{\rm 3h}$ symmetry undergoing rapid automerization. The combined effect of symmetry reduction and high-level corrections indicates a negligible singlet-triplet gap in cyclazine. Notably, pentazine and heptazine prefer symmetric structures exhibiting negative gaps in accord with experiments. Azaphenalenes containing nitrogen atoms at electron-deficient sites exhibit stronger in-plane structural distortion; in their low-symmetry energy minima, they adhere to Hund's rule., Comment: first version
- Published
- 2024