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

Abstract

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 3.52Å). 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 5-300K region with C=0.378emuKmol -1 and Î̧=+4.72K, 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, J 1=+7.12cm -1, J 2=+1.28cm -1). © 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.