ESR study of high-spin nitrenes with s-triazine skeleton

Electronic and molecular structures of mononitrene 1 and bisnitrene 2 deriv ed from 2,4,6-triazide-s-triazine 4 by photolysis have been studied by powd er-pattern and single-crystal ESR spectroscopy. The experimentally determin ed fine-structure parameters D and E were 1.402 and 0.011 cm(-1) for 1 (S = 1), and 0.280 and 0.058 cm(-1) for 2 (S = 2), respectively. These values a re much larger than those of phenylnitrenes (S = 1) and m-phenylenebisnitre nes (S = 2). The fine-structure parameters of bisnitrene 2 were interpreted by a semiempirical model considering dominant one-center spin-spin interac tions at the monovalent nitrogen atoms, indicating that the pi-electron spi ns are more localized on the monovalent nitrogen atoms and that the K-deloc alization effect is hampered by introducing heteroatoms into the pi-conjuga tion system.