Stable Mono-, Di-, and Triradicals as Constituent Molecules for Organic Ferrimagnets

Abstract

In order to realize organic ferrimagnets, we have prepared stable organic radicals, mono-, di-, trinitronyl nitroxides (1∼3) with different spin multiplicities. Among them, intramolecular ferromagnetic couplings in tri- and diradicals (3 and 2a), which are hidden by antiferromagnetic intermolecular interaction in the neat sample, were elucidated by using mixed crystals of 3 and 2a and trinitrobenzene (2a:TNB =1:1, 3:TNB =1:1). An X-ray crystallographic analysis of the mixed crystals revealed that 3 or 2a and TNB are stacked alternately in a one-dimensional column along the c axis. Ferromagnetic coupling in 3 was determined to be J/k_B=23 K by applying a triangular cluster model, and that for 2a (J/k_B=23K) was consistent with the above results.