MAGNETIC-PROPERTIES OF 1,3,5,6-TETRAPHENYL-VERDAZYLS AND RELATED VERDAZYLS

The magnetic properties of 1,3,5,6-tetraphenyl-verdazyl and related ve rdazyls were characterized by static magnetic susceptibility measureme nts (1.8K less-than-or-equal-to T less-than-or-equal-to 300K, H less-t han-or-equal-to 55 kOe), ESR (10 GHz, solid and solution) and proton N MR (360 MHz, dilute solution). Concentration of radical spins, asympto tic Curie temperature, 1d-exchange integral, ESR linewidth (and thus t he strength of exchange narrowing) and spm densities (from proton para magnetic shifts) were derived. The onedimensional antiferromagnetic ex change interaction is increased by a factor larger than 3 if one addit ional phenyl unit is added to 1,3,5-triphenyl-verdazyl (TPV). The unsy mmetrical substitution of TPV by 3-trifluoromethylphenyl reduces the 1 d antiferromagnetic exchange drastically, in contrast to the symmetric al substitution by 4-trifluoromethylphenyl.