The molecular and crystal structures of 4 amino 2,6 diazido 3,5 dichloropyridine and 6 amino 2,4 diazido 1,3,5 triazine, as well as the paramagnetic photolysis products of their crystals at 77 K, were studied using X ray diffraction analysis and ESR spectroscopy. Triplet nitrenes generated during the photolysis of diazidopyridine form triplet-triplet nitrene pairs, whose ESR spectrum corre sponds to the quintet spin state. The high spin state (S = 2) results from the exchange interaction between two triplet molecules with the zero field splitting parameters |D| = 1.0280 cm -1 and |E| = 0.0038 cm -1 and the θ angle between two С-N nitrene bonds equal to 133°. This angle is close to an angle of 136.2° between the С-N bonds of two adjacent molecules in the crystal structure. No formation of the triplet-triplet nitrene pairs is observed during the photolysis of crystalline diazidotriazine, whose molecules lie in the parallel planes.

An EPR spectrum of solid Ar isolated quintet 4 amino 3,5 dichloropyridin 2,6 diyldini trene that formed by the photolysis of 4 amino 2,6 diazido 3,5 dichloropyridine at 15 K was recorded. Using computer simulation based on numerical diagonalization of the quintet spin Hamiltonian matrices, it was established that this EPR spectrum corresponds to a quintet spin state with the magnetic parameters g = 2.0023, |D q | = 0.2100 cm -1 , and |E q | = 0.0560 cm -1 . Owing to high resolution of the experimental spectrum, the zero field splitting parameters of the quintet intermediate were determined to an accuracy of at least 5•10 -4 cm -1 . Calculations of the fine structure energy levels in external magnetic field and the dependences of the EPR signal positions and intensities of the quintet dinitrene on the direction of external magnetic field were performed for the first time. This allowed unambiguous assignment of all EPR lines of quintet molecules having both in principal axis and off principal axis orientations.