Magnetic properties of a new type of 1,5-diphenyl-6-oxo- and -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 follows the Curie-Weiss law with a positive and negative Weiss constant of +2.5 and −7.7 K, respectively. On the other hand, the susceptibility of TTV and p-CDpTV can be interpreted in terms of an alternating and nonalternating antiferromagnetic Heisenberg linear chain model with an exchange interaction of 2J1/k = −66.0 K (alternation parameter α = J2/J1 = 0.6) and 2J/k = −58.5 K, respectively.