MAGNETIC-PROPERTIES OF A NEW-TYPE OF 1,5-DIPHENYL-6-OXO-VERDAZYL AND 1,5-DIPHENYL-6-THIOXO-VERDAZYL RADICALS

The magnetic susceptibilities of the 3-(4-chlorophenyl)-1,5-diphenyl-6 -oxoverdazyl (p-CDpOV), 3-(4-bromophenyl)1,5-diphenyl-6-oxoverdazyl (p -BDpOV), 1,3,5-triphenyl-6-thioxoverdazyl (TTV), and 3-(4-chlorophenyl )- 1,5-diphenyl-6-thioxoverdazyl (p-CDpTV) radicals have been measured between 4.4 and 300 K. The susceptibility of p-CDpOV and p-BDpOV foll ows the Curie-Weiss law with a positive and negative Weiss constant of + 2.5 and - 7.7 K, respectively. On the other hand, the susceptibilit y of TTV and p-CDpTV can be interpreted in terms of an alternating and nonalternating antiferromagnetic Heisenberg linear chain model with a n exchange interaction of 2J(1)/k = - 66.0 K (alternation parameter a = J(2)/J(1) = 0.6) and 2J/k = - 58.5 K, respectively.