Ferromagnetic Interactions in a 1D Alternating Linear Chain of p-Stacked 1,3-Diphenyl-7-(thien-2-yl)-1,4-dihydro-1,2,4-benzotriazin-4-yl Radicals

X-ray studies show that 1,3-diphenyl-7-(thien-2-yl)-1,4-dihydro-1,2,4-benzotriazin-4-yl (6) adopts a distorted, slipped p-stacked structure of centrosymmetric dimers with alternate short and long interplanar distances (3.48 and 3.52 angstrom). Cyclic voltammograms of 7-(thien-2-yl)benzotriazin-4-yl 6 show two fully reversible waves that correspond to the -1/0 and 0/+1 processes. EPR and DFT studies on radical 6 indicate that the spin density is mainly delocalized over the triazinyl fragment. Magnetic susceptibility measurements show that radical 6 obeys CurieWeiss behavior in the 5300 K region with C=0.378 emu?K?mol-1 and ?=+4.72 K, which is consistent with ferromagnetic interactions between S=1/2 radicals. Fitting the magnetic susceptibility revealed the behavior is consistent with an alternating ferromagnetic chain (g=2.0071, J1=+7.12 cm-1, J2=+1.28 cm-1).