Formation of a One-Dimensional Stacking Structure of π-Conjugated Nitroxyl Radical Bearing a 1,2,5-Thiadiazole Ring and Its Magnetic Property

A novel stable organic radical, 7,7-diphenyl-6,7-dihydro[1,2,5]thiadiazolo[3,4-f]quinoline-6-oxyl (1), forms a
one-dimensional columnar structure consisting of slipped π-stacks, which is in contrast to dimer formation of the isoelectronic
benzologue, 3,3-diphenyl-3,4-dihydrobenzo[f]quinoline-4-oxyl (2). Magnetic susceptibility of 1 obeyed an antiferromagnetic
chain model with J = −47 cm-1, while 2 behaved as an isolated doublet spin state even in the dimer.