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.

Electronic Transitions in Different Redox States of Trinuclear 5,6,11,12,17,18‐Hexaazatrinaphthylene‐Bridged Titanium Complexes: Spectroelectrochemistry and Quantum Chemistry

“…In the literature, a large electron affinity of the HATN ligand is reported. [14] This can also be shown in first approximation by a PBE0/Def2-SVP/RIJCOSX calculation of the charged species (À 1, À 2 and À 3. From those data, the electron affinities E af in Table 2 were obtained by [Eq.…”

“…[10] HAT and its derivatives also belong to the family of redoxactive ligands, often used as non-innocent ligands. [14] One of the fundamental properties of these ligands is their ability to act as electron reservoirs, which allows the metal to store electrons on the ligand and/or accept electrons from the ligands. [15] This property is of interest for the design of homogeneous catalysts because many important transformations involve the transfer of multiple electrons between the catalyst and the activated substrate.…”

“…HAT and its derivatives also belong to the family of redox‐active ligands, often used as non‐innocent ligands [14] . One of the fundamental properties of these ligands is their ability to act as electron reservoirs, which allows the metal to store electrons on the ligand and/or accept electrons from the ligands [15] .…”

Coordination‐Induced Spin‐State Switching of an Aminyl‐Radical‐Bridged Nickel(II) Porphyrin Dimer between Doublet and Sextet States

“…[2][3][4] As one of advantageous characteristics of the metal-radical complexes is that the interaction between the metal centers can be tuned by utilizing the ligand'sn on-innocent properties. [5] Fore xample, bis (2,6-dimethylphenyl)-N-indigo-bridged dinuclear Co II complex 1 showed weak antiferromagnetic interaction between the quartet (S = 3/2) Co II centers with J of À11.7 cm À1 through super-exchange interaction. Upon reduction of the bridging ligand, strong antiferromagnetic interaction (J = À138 cm À1 )b etween the Co II and ligand radical emerged to give an overall sextet ground state (2 in Figure 1a).…”

Coordination‐Induced Spin‐State Switching of an Aminyl‐Radical‐Bridged Nickel(II) Porphyrin Dimer between Doublet and Sextet States

“…[1] Strong exchange interactions between the ligand-centered radical and paramagnetic metal centers offers predictable and designable ways to functional magnetic materials. [5] Fore xample, bis (2,6-dimethylphenyl)-N-indigo-bridged dinuclear Co II complex 1 showed weak antiferromagnetic interaction between the quartet (S = 3/2) Co II centers with J of À11.7 cm À1 through super-exchange interaction. [5] Fore xample, bis (2,6-dimethylphenyl)-N-indigo-bridged dinuclear Co II complex 1 showed weak antiferromagnetic interaction between the quartet (S = 3/2) Co II centers with J of À11.7 cm À1 through super-exchange interaction.…”