2,3,5,6‐Tetrafluoro‐1,4‐phenylenedinitrene: A dinitrene with near degenerate singlet and triplet states

• Published in: Journal of physical organic chemistry 2023-09, Vol.36 (9), p.n/a
• Main Authors: Portela‐Gonzalez, Adrian, Mendez‐Vega, Enrique, Sander, Wolfram
• Format: Article
• Language: English
• Subjects: Alkenes; Atomic energy levels; Cryogenic temperature; diradical; Electronic structure; EPR spectroscopy; matrix isolation; nitrene; Photolysis; singlet triplet gap
• ISSN: 0894-3230; 1099-1395
• DOI: 10.1002/poc.4544

The dinitrene 2,3,5,6‐tetrafluoro‐1,4‐phenylenedinitrene was synthesized by photolysis of matrix‐isolated 1,4‐diazido‐2,3,5,6‐tetrafluorobenzene at 365 or 405 nm in high yields at cryogenic temperatures and characterized by FT‐IR, UV‐Vis, and EPR spectroscopy. The electronic structure of the dinitrene is described best as a quinoidal diradical with an open‐shell singlet ground state and a triplet state laying only 650 ± 5 cal/mol higher in energy. Irradiation with λ = 254 nm results in fragmentation of the dinitrene into FCCF and several olefins which on prolonged photolysis fragment into FCCCN, FCCNC, and FCN. 2,3,5,6‐Tetrafluoro‐1,4‐phenylenedinitrene was generated in high yields and spectroscopically characterized at cryogenic temperatures. This dinitrene exhibits nearly degenerate singlet and triplet states and, upon short‐wavelength UV irradiation, undergoes extensive fragmentation leading to FCCF, FCCCN, FCCNC, and FCN.