Structure and exchange in silicon-linked tetraradicals.

The EPR spectroscopy, crystallography, and magnetic susceptibility of tetrakis(N-oxyl-2,2,6,6-tetramethylpiperidin-4-yl)silane and tetrakis(4-N-tert-butyl-N-aminoxylphenyl)silane show that silicon acts as a weak intramolecular exchange linker for polynitroxides, although both tetraradicals show onset of inter-spin exchange at reduced temperatures.