Magnetic-properties of 1,4-dihydro-1,2,4-benzotriazin -4-yl radicals

Abstract

Magnetic susceptibilities of 1,4-dihydro-1,3-diphenyl-1,2,4-benzotriazin-4-yl (DDB 1), 3-tert-butyl-1,4-dihydro-1-phenyl-1,2,4- benzotriazin-4-yl (BDPB 2) and 1-(4-chlorophenyl)-1,4-dihydro-3-phenyl-1,2,4-benzotriazin-4-yl (CDPB 3) radicals have been measured in the temperature range of 4.2-300 K. The susceptibility of DDB 1 and BDPB 2 follows the Curie-Weiss law with a negative Weiss constant of −2.2 and −0.3 K, respectively. The magnetic susceptibility of CDPB 3, on the other hand, exhibits a broad maximum at 138 K. This susceptibility can be interpreted in terms of an alternating antiferromagnetic Heisenberg linear chain model with an exchange interaction of 2 J 1/ k=−220 K and an alternation parameter of α= J 2/ J 1=0.3. The results of the X-ray structure analysis of CDPB 3 support the above explanation.