Strong Exchange Coupling in a Trimetallic Radical‐Bridged Cobalt(II)‐Hexaazatrinaphthylene Complex

Abstract Reducing hexaazatrinaphthylene (HAN) with potassium in the presence of 18‐c‐6 produces [K(18‐c‐6)HAN], which contains the S=1/2 radical [HAN] .− . The [HAN] .− radical can be transferred to the cobalt(II) amide [CoN(SiMe 3 ) 2 2 ], forming [K(18‐c‐6)][(HAN)Co(N′′) 2 3 ]; magnetic measurements on this compound reveal an S=4 spin system with strong cobalt–ligand antiferromagnetic exchange and J≈−290 cm −1 (−2 J formalism). In contrast, the Co II centres in the unreduced analogue [(HAN)Co(N′′) 2 3 ] are weakly coupled (J≈−4.4 cm −1 ). The finding that [HAN] .− can be synthesized as a stable salt and transferred to cobalt introduces potential new routes to magnetic materials based on strongly coupled, triangular HAN building blocks.