Effective exchange coupling in alternating-chains of a π-extended 1,2,4-benzotriazin-4-yl

Abstract

Air stable 1,3,7-triphenyl-1,4-dihydrothiazolo[5′,4′:4,5]benzo[1,2-e][1,2,4]triazin-4-yl packs in 1D π stacks made of radical pairs with alternate short and long interplanar distances. The magnetic susceptibility exhibits a broad maximum at 73 ± 5 K and is interpreted in terms of an alternating antiferromagnetic Heisenberg linear chain model with an average exchange interaction of J = −43.8 cm⁻¹ and an alternation parameter α = 0.3 (g_solid = 2.0028). The enhanced overlap between the π-extended SOMO orbitals leads to strong antiferromagnetic interactions along the chains (J₁ = −87.6 cm⁻¹ and J₂ = −26.3 cm⁻¹).