Stable 1,3,2‐Benzodithiazolyl Radicals: Modification of Reactivity, Crystal Packing, and Solid State Magnetic Properties by Fluorination

Impact of fluorination on crystal and molecular structure, heteroatom reactivity, and solid‐state magnetic properties of thermally‐stable π ‐radicals is studied experimentally and computationally with 1,3,2‐benzodithiazolyl 1 · and its 4,7‐difluoro, 4,5,6,7‐tetrafluoro, and 4,7‐difluoro‐5,6‐(hexafluoropropane‐1,3‐diyl) derivatives 2 · ‐ 4 · , respectively. Radicals 2 · ‐ 4 · are isolated by vacuum thermolysis of their unusual covalent 2:1 adducts with 7,7,8,8‐tetracyanoquinodimethane. The impact of fluorination on reactivity is evidenced by transformation of 2 · ‐ 4 · and 2 + ‐ 4 + into corresponding 2H‐1‐oxo‐1,3,2‐benzodithiazoles under the influence of air's or solvents’ moisture; back transformation into the cations under the action of protic acids; and formation of a paramagnetic molecular complex between 3 · and naphthalene, whereas 1 · and octafluoronaphthalene do not exhibit complexation. The crystal structures of 3 · and 4 · reveal a novel packing motif featuring radical pairs linked by four‐center interactions that stack into offset π ‐columns, forming a unique zip‐ π ‐stack synthon that incorporates head‐over‐tail π ‐pairs of radicals. Despite the formation of π ‐pairs, polycrystalline 3 · and 4 · display a nonzero effective magnetic moment that rises with temperature above 200 K, although the values remain significantly lower than those of the high‐temperature polymorphs of magnetically‐bistable 1 · and 2 · . This behavior can be rationalized by different magnetic topologies and values of spin exchange between the radicals.