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

## TL;DR

This paper studies how fluorination affects the structure, reactivity, and magnetic properties of stable radicals.

## Contribution

The study introduces a new supramolecular packing motif and reveals fluorination's impact on radical reactivity and magnetic behavior.

## Key findings

- Fluorination creates a novel zip-π-stack synthon in crystal structures.
- Fluorinated radicals show unique reactivity toward moisture and protic acids.
- Magnetic properties of fluorinated radicals differ from non-fluorinated ones, with lower thermal stability and altered bistability.

## Abstract

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.

Fluorination reduces solid‐state thermal stability of 1,3,2‐benzodithiazolyl radicals and modulates crystal structures (e.g., by means of a new supramolecular zip‐synthon) and reactivity, in the latter case toward transformations unknown in the hydrocarbon series but potentially general in the fluorocarbon one. Low fluorination is favorable and high fluorination is unfavorable for hysteretic magnetic bistability of the radicals around room temperature.© 2026 WILEY‐VCH GmbH