Strong ferromagnetic exchange in 2-(4,5,6,7-tetrafluorobenzimidazol-2-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl

The strong ferromagnetic exchange in 2-(4,5,6,7-tetrafluorobenzimidazol-3- yl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl was investigated. The compound was synthesized to investigate effects of extensive aryl fluorination on the magnetism of BImNN variants. The data were analyzed using a literature model for ferromagnetic exchange coupled one-dimensional Heisenberg chain of S=1/2 spin units with a variable exchange constant. Comparison to theoretical Brillioun functions show that the data correspond to an effective spin quantum number in the range S=8-14 at 1.8K. It is shown to be possible that F4BImNN has other exchange interactions that become more manifest at lower temperatures.