Transforming Triplet Vinylnitrene into Triplet Alkylnitrene at Cryogenic Temperatures.

Photolysis of 2,3-diazidonaphthalene-1,4-dione (1) in methyltetrahydrofuran matrices forms 2-(λ1-azaneyl)-3-azidonaphthalene-1,4-dione (vinylnitrene 32), as confirmed by electron paramagnetic resonance spectroscopy. The zero-field splitting (zfs) parameters for 32 (D/hc = 0.5338 cm-1, and E/hc = 0.0038 cm-1) reveal significant 1,3-biradical character. Irradiating 32 yields 2-(λ1-azaneyl)-1,3-dioxo-2,3-dihydro-1H-indene-2-carbonitrile (alkylnitrene 33), which has zfs parameters typical of a cycloalkylnitrene (D/hc = 1.57 cm-1, and E/hc = 0.00071 cm-1). Photolysis of 1 in argon matrices verifies that 32 forms 33.