Spin Exchange Interaction through Phenylene-Ethynylene Bridge
in Diradicals Based on Iminonitroxide and Nitronylnitroxide
Radical Derivatives. 1. Experimental Investigation of the
Through-Bond Spin Exchange Coupling
posted on 2003-09-19, 00:00authored byPascale Wautelet, Jacques Le Moigne, Vladimira Videva, Philippe Turek
A series of bis-iminonitroxide diradical derivatives of different lengths and geometry have been
prepared that incorporate a conjugated phenylene-ethynylene bridge as a rigid spacer. This paper
describes the synthesis of these new components and their main characterizations. An unexpected
singlet ground state and substituent effects on the singlet−triplet gap have been found for
substituted “m-phenylene”-based diradicals. The effects of the π-conjugation on the intramolecular
through-bond spin coupling have been investigated by changing the length of the spacer within
linear derivatives. The EPR studies demonstrate the intramolecular magnetic coupling between
the radical spins within all compounds. This result is very attractive and unusual, given the large
distance between the radicals from 15 Å in the dimer to 36 Å in the pentamer.