MAGNETISM IN ORGANIC MATERIALS

Tailoring magnetic interactions of organic solids is currently an area of intense research activity. We show that the quasi-one dimensional antiferromagnetic exchange coupling of the well-known organic free rad ical triphenylverdazyl (TPV) can be increased by a factor of 3 by syst ematic molecular modifications (i.e. J(1d)/k(B) = -16 K for 1,3,5,6-te traphenylverdazyl). 1,3,5-tri-6'-(1,3,5-triphenylverdazyl)-benzene as a representative of covalently bound multiradical molecules was analyz ed as solid and in solution. The energetic spin-doublet-quartet separa tion and intermolecular exchange interaction were estimated. Cooperati ve magnetic behaviour with ordering temperature of about 40K and well- defined hysteresis loops (H-c(5 K) approximate to 40 Oe) has been achi eved by the chelation of transition metals (e.g. Mn) in appropriate or ganic materials. NMR, ESR, static magnetic susceptibility, in part als o a.c. susceptibility, specific heat and x-ray structural analysis wer e used to characterize these new organic magnetic materials.