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 Jintra/kB = −106 K, Jinter/kB = −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/kB = −106 K Jinter/kB = −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 (Jintra/kB > ±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.