Parity and heteroatom effects on open-shell exchange interactions: Nitrenophenyl iminoylnitroxides

[GRAPHICS] Photolysis of pN3PhIN and mN3PhIN in frozen matrix yields pNPhIN and mNPhIN, respectively. pNPhIN gives a quartet state with nonlinear ESR intensity behavior (vertical bar D/hc vertical bar = 0.300 cm(-1), vertical bar E/hc vertical bar congruent to 0.0 cm(-1)); mNPhIN gives a thermally excited quartet state (vertical bar D/hc vertical bar = 0.336 cm(-1), vertical bar E/hc vertical bar = 0.006 cm(-1)) with inverse Curie behavior. Computations show little nitrene delocalization onto the radicals even for the para system. The NPhIN systems behave differently from analogous nitronylnitroxides due to asymmetric radical spin distribution.