(Nitronyl nitroxide)-substituted trioxytriphenylamine radical cation tetrachlorogallate salt: A 2p-electron-based weak ferromagnet composed of a triplet diradical cation

Abstract

The synthesis and the solid state magnetic properties of (nitronyl nitroxide)-substituted trioxytriphenylamine radical cation tetrachlorogallate, NNTOT +·GaCl 4-, are reported. In the temperature region between 300 and 3 K, the magnetic behavior is characterized by the strong intramolecular ferromagnetic interaction (J/k B=+400 K) between the radical (NN) and the radical cation (TOT +) and the weak intermolecular antiferromagnetic interaction (J/k B=-1.9 K) between NNTOT + ions. Below 3 K, a 3D-type long-range magnetic ordering into a weak ferromagnet was observed (T N=2.65 K). The magnetic entropy (S mag=8.97 J K -1 mol -1) obtained by the heat capacity measurement is in good agreement with the theoretical value of R ln3=9.13 J K -1 mol -1 based on the S=1 state. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.