PHENAZIN-5(10H)-YLS .4. 10-ETHYLPHENAZIN-5(10H)-YL-CENTER-DOT-H2O - CRYSTAL-STRUCTURE, MAGNETIC-SUSCEPTIBILITY AND INTERMOLECULAR PI-PI INTERACTIONS (PIMERIZATION)

The unit cell of 10-ethylphenazin-5(10H)yl . H2O consists of eight phe nazin-5(10H)-yls that are arranged in four independent radical pairs A -D. All pairs show close interplanar distances (3.28-3.36 Angstrom). F urthermore, A, B, and D are characterized by short intermolecular cont acts between atoms with significant spin populations. This is not vali d for the pair C with the closest interplanar distance of 3.28 Angstro m. Magnetic susceptibility measurements as a function of temperature i ndicate complete spin pairing (''pimerization'') between 20 and 100 K. Therefore, the radical pair C provides evidence that unspecific close interplanar contacts together with a reasonable overlap of the pi sys tems are sufficient to lead to pimerization.