Strong Exchange Coupling in a Trimetallic Radical‐Bridged Cobalt(II)‐Hexaazatrinaphthylene Complex. Issue 18 (21st March 2016)

• Record Type: Journal Article
• Authors: Moilanen, Jani O.; Chilton, Nicholas F.; Day, Benjamin M.; Pugh, Thomas; Layfield, Richard A.
• Is Part Of: Angewandte Chemie international edition. Volume 55:Issue 18(2016)
• Page Start: 5521
• Page End: 5525
• Publication Date: 2016-03-21
• Subjects: cobalt -- hexaazatrinaphthylene -- magnetism -- non-innocent ligands -- radicals; Chemistry -- Periodicals; 540
• DOI: 10.1002/anie.201600694
• Languages: English
• ISSNs: 1433-7851

Abstract

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 [Co{N(SiMe3 )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. Abstract : The [HAN] .− radical anion (see scheme, left) is synthesized as a stable potassium salt and transferred intact to Co II . The resulting complex anion [{(HAN){Co(N′′)2 }3 ] − is a rare radical‐bridged trimetallic complex, with very strong antiferromagnetic exchange between the Co II ions and the non‐innocent ligand.