Intra- and inter-molecular exchange on symmetrical hydrazine diradical dications and comparison of the magnetic exchange with ET parameters derived from their optical spectra

Abstract

The spin alignment in a charged molecular field is important research issue in the molecular magnetism. In order to clarify the interrelation between spin alignment and the charged molecular field, we have investigated intra- and inter-molecular exchanges on some Hydrazine diradical dictations 1–3 shown in Scheme 1 (see texts) by ESR and magnetic susceptibility measurement. The magnetic behavior of the dication salt 1 has been well analyzed using the alternating linear chain models with J_(intra)/k_B = −106 K, J_(inter_/k_B = −49 K and an alternating parameter α=0.46. The magnetic property of 3 has been also fitted to the alternating chain model with J/k_B = −106 K J_(inter)/k_B = −42 K (α=0.40). On the other hand, 2 gives a robust triplet ground state with larger energy separation from other spin states. The energy separation has been estimated to be larger than 300 cm−1 (J_(intra)/k_B > ±190 K) from the temperature dependence of the ESR signal intensity. These findings indicate that the sign of the intramolecular exchange depends on the linking position (m- or p-) of the hydrazine cation group, i.e. the topology of the π orbital network even in the cationic molecular field. The magneto-optical correlation is also discussed based on the intramolecular electron transfer (ET) parameters.

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