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Intramolecular Long Range Electronic Spin Exchange Coupling in Diradicals: A New Magnetic Coupling Unit

1995; Volume: 272; Issue: 1 Linguagem: Inglês

10.1080/10587259508055277

1058-725X

Philippe Turek, Pascale Wautelet, J. Le Moigne, Jean-Louis Stanger, Jean‐Jacques André, A. Bieber, Paul Rey, André De Cian, Jean Fischer,

Advanced Chemical Physics Studies

Abstract A phenyl diethynyl bridge is used as a magnetic coupling unit (MCU) between two iminonitroxide π-radicals. The ethynyl moiety is attached to the central phenyl ring either in the para or in the meta position. The magnetic properties of the resulting bis-imino nitroxide diradicals (p-BIN and m-BIN) are investigated both at the molecular scale and in the condensed phases. An intramolecular through bond spin coupling is observed at an unusual long distance (about 20 ÅS) in both derivatives. However, the ground state is found to be a singlet spin state in both compounds. The results suggest an interplay between the spin polarization and the spin delocalization (π-conjugation). An intermolecular weak antiferromagnetic spin coupling is occuring in both compounds.