Ferromagnetic Interactions in a 1D Alternating Linear Chain of π-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 π‐stacked structure of centrosymmetric dimers with alternate short and long interplanar distances (3.48 and 3.52 Å). 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 Curie–Weiss behavior in the 5–300 K region with C=0.378 emu K mol−1 and θ=+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). Slippery characters: The 7‐(thien‐2‐yl)benzotriazinyl radical packs in 1D columns with alternate short and long interplanar distances. Slippage of radicals along the stacking direction causes the near orthogonality of their singly occupied molecular orbitals and therefore leads to ferromagnetic interactions between them (see figure).