Antiferromagnetic Interactions in 1D Heisenberg Linear Chains of 7-(4-Fluorophenyl) and 7-Phenyl-Substituted 1,3-Diphenyl-1,4-dihydro-1,2,4-benzotriazin-4-yl Radicals

7-(4-Fluorophenyl) and 7-phenyl-substituted 1,3-diphenyl-1,4-dihydro-1,2,4-benzotriazin-4-yl radicals were characterized by X-ray diffraction analysis and variable-temperature magnetic susceptibility studies. The radicals pack in 1D pi stacks of equally spaced slipped radicals with interplanar distances of 3.59 and 3.67 angstrom and longitudinal angles of 40.97 and 43.47 degrees, respectively. Magnetic-susceptibility studies showed that both radicals exhibit antiferromagnetic interactions. Fitting the magnetic data revealed that the behavior is consistent with 1D regular linear antiferromagnetic chain with J=-12.9 cm-1, zJ '=-0.4 cm-1, g=2.0069 and J=-11.8 cm-1, zJ '=-6.5 cm-1, g=2.0071, respectively. Magnetic-exchange interactions in benzotriazinyl radicals are sensitive to the degree of slippage, and inter-radical separation and subtle changes in structure alter the fine balance between ferro- and antiferromagnetic interactions.