6,9-Di(tert-butyl)-1-methyltetrazolo[1,5-a]perimidine (1) has been synthesized from naphthalene in seven steps. The EPR spectra, recorded after irradiation of 1 in a butyronitrile matrix at 77 K (lambda = 351 nm) and in Ar and Xe matrixes at 4.6 K (lambda > or = 345 nm), showed a six-line, high-field signal (Delta m(S) = +/- 1), centered at 3350 G in butyronitrile, along with a half-field signal (Delta m(S) = +/- 2), which is characteristic for triplets. Simulation of the observed EPR spectra gave values for the zero-field splitting parameters of |D/hc|/cm(-1) = 0.0105, |E/hc|/cm(-1) = 0.0014 in butyronitrile and |D/hc|/cm(-1) = 0.0107, |E/hc|/cm(-1) = 0.0016 in Ar. These EPR parameters are consistent with the diradical 5,8-di(tert-butyl)-2-(N-methylimino)perimidine-1,3-diyl ((3)2) as source of the EPR spectra. Linearity of the Curie-Weiss plot and UB3LYP and (14/14)CASPT2 calculations of the singlet-triplet energy difference (DeltaE(ST) approximately 8-10 kcal/mol) indicate that the triplet is the ground state of 2, as predicted for such a nondisjoint diradical.

A Perimidine-Derived Non-Kekule Triplet DiradicalSignificance: A triazaTMM triplet diradical is synthesized and characterized by EPR, confirming theoretical calculations from the authors that diradicals of this type would be high-spin. They generated the compound in several cryogenic matrices by photochemically eliminating dinitrogen. Comment:Many examples of high-spin organic diradicals inspired by TMM have been generated and observed, though generally at low temperatures. In this example, the rigidity of the naphthalene framework forces the nitrogen atoms attached to it farther apart, therefore favoring the triplet state over the singlet state. In the future, diradicals of this type may be used to form organic magnets, though the stability of the diradicals to oxygen and heat will have to be improved. e r a t e d i n a b u t y r o n i t r i l e m a t r i x a t 7 7 K a n d i n A r a n d X e m a t r i c e s a t 4 . 6 K . t r i m e t h y l e n e m e t h a n e ( T M M ) N R R N N R t r i a z a T M M -N 2