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 [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 CoII 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.

A Trinuclear Radical‐Bridged Lanthanide Single‐Molecule Magnet

“…Indeed, HAN −. was recently employed as a central bridging ligand in the assembly of [((Me 3 Si) 2 N) 6 Co 3 (μ 3 ‐HAN)] − , a complex that exhibits strong antiferromagnetic exchange coupling . While this complex did not show single‐molecule magnet behavior, the utilization of HAN as a radical bridging ligand for aligning the moments of three highly anisotropic lanthanide centers remained to be tested.…”

Conductive Metal–Organic Frameworks with Extra Metallic Sites as an Efficient Electrocatalyst for the Hydrogen Evolution Reaction

“…The bidentate tertamine of HATN can coordinate various metal ions to form M 3 ∙HATN with a two‐coordinated (M–N 2 ) moiety. [ 23 ] This structure can expose unoccupied positions of metal atom in a high content (≈14 at%), which are regarded as an efficient single‐atom center for catalysis. [ 24,25 ] HATN structure is also propitious to stabilize metallic ion with valence variation, which can serve as a key active intermediate for the electrocatalytic reaction.…”

Single-ion anisotropy and exchange coupling in cobalt(ii)-radical complexes: insights from magnetic and ab initio studies

“…69 Most oen multi-congurational techniques are used to dene the metal electronic state only in the absence of the radical. 2,34,63,64,[70][71][72][73][74] A multi-technique experimental approach combined with a multicongurational ab initio study is thus required to clarify the nature and the magnitude of the interactions in anisotropic metal-radical coupled systems and the way they can be varied to design improved bistable materials. Advances in computational methods and in magnetic and spectroscopic data analysis now allow us to resolve this issue for Co(II)-semiquinonate complexes, which we propose as a case study to demonstrate the advantages of this approach and the many pitfalls to be avoided.…”