Structure-Magnetism Relationships in α-Nitronyl Nitroxide Radicals: Pitfalls and Lessons to be Learned

Rational design of persistent radicals with crystals having ferromagnetic ordering at high critical temperatures is an important challenge in materials science. This can only be achieved through the control of the crystal packaging of the radicals and a well founded structure–magnetism relationship. A statistical analysis is presented that shows that in α-nitronyl nitroxide crystals it is not possible to define the magnetic role of the NO ⃛ON or C—-H ⃛ON contacts just by looking at the local distance and geometry of one type of contacts; magneto-structural correlations in these crystals must be collective.