MAGNETIC-PROPERTIES OF 1,4-DIHYDRO-1,2,4-BENZOTRIAZIN-4-YL RADICALS

Magnetic susceptibilities of 1,4-dihydro-1,3-diphenyl-1,2,4-benzotriaz in-4-yl (DDB 1), -butyl-1,4-diydro-1-phenyl-1,2,4-benzotriazin-4-yl (B DPB 2) and enyl)-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. Th e 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 magnet ic susceptibility of CDPB 3, on the other hand, exhibits a broad maxim um at 13 8 K. This susceptibility can be interpreted in terms of an al ternating antiferromagnetic Heisenberg linear chain model with an exch ange interaction of 2J1/k=-220 K and an alternation parameter of alpha =J2/J1=0.3. The results of the X-ray structure analysis of CDPB 3 supp ort the above explanation.