Modulation of Through‐Space Magnetic Exchange in Cyclophane‐Bridged Benzotriazinyl Diradicals

Most research on organic magnetic materials focus on maximizing ferromagnetic interactions. However, systems with tunable antiferromagnetic exchange ( J < 0) have potential for applications where controllable singlet‐triplet gaps enable coherent manipulation. Although 1,2,4‐benzotriazinyl (Blatter) radicals are exceptionally stable, the model diradical studied here, 1‐meta , possesses negligible intramolecular exchange due to the disjoint nature of the SOMOs across its C(3)‐meta‐phenylene‐C(3′) connectivity. Here, we investigate a topological strategy to induce antiferromagnetic exchange by enforcing π‐stacking within cyclophane scaffolds. Using SA‐CASSCF/NEVPT2 and SF‐TD‐DFT, we show that linear meta‐phenylene‐bridged diradical has small singlet‐triplet gaps (|2 J | < 19 cm −1 ) due to insufficient orbital overlap. In contrast, cyclophane‐bridged diradicals display persistent through‐space coupling caused by direct SOMO overlap. By modulating the cyclophane linkage ( syn ‐ versus anti ‐ stacking), the coupling is tuned from −4 to −1674 cm −1 . This spans three distinct physical regimes: the weak‐coupling limit spectrally addressable with high‐field EPR, the intermediate coupling regime with potential for thermal switching and finally, the strong‐coupling limit of incipient covalent bonding. Therefore, although [2.2]paracyclophane scaffolds enforce antiferromagnetic ground states, the magnitude of the interaction is sensitive to the orbital overlap dictated by the conformation of the radical decks. Strategies to further lower 2 J to −1.8 cm −1 are discussed.