A series of tetraazalene radical-bridged M2(M = CrIII, MnII, FeII, CoII) complexes with strong magnetic exchange coupling

DeGayner, Jordan A.; Jeon, Ie‐Rang; Harris, T. David

doi:10.1039/c5sc02725j

Cited by 72 publications

(58 citation statements)

References 113 publications

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“…This can be accomplished by using radical ligands. [29][30][31] We were interested to see if complexes 2 and 3 displayed SMM characteristics,h owever measurements of the in-phase and out-of-phase AC magnetic susceptibility as functions of temperature did not reveal any slow relaxation in fields of H dc = 0-1500 Oe.T he absence of SMM behaviour-despite the appreciable anisotropy-can be explained by the nonzero rhombicity of the Co II centres in 2 and 3,w ith the irregular 4-coordinate geometry also contributing.S imilar observations on as trongly coupled, radical-bridged dicobalt species were described recently. [32] In conclusion, [HAN]C À (1)was synthesized as the [K(18c-6)] + salt and shown to be an S = 1/2 radical with spin density distributed across the aromatic system.…”

Section: Angewandte Chemiementioning

confidence: 99%

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

et al. 2016

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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.

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Section: Angewandte Chemiementioning

confidence: 99%

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

et al. 2016

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“…An ultrafast k ET (S 1 ) value is extracted for the 1 Bodipy*→porphyrin (from one distant branch to the other) demonstrating with the help of a comparison of literature examples, a particularly efficient Dexter process. These results stress the ability of the uncycled azophenine core to act as an excellent electronic communicator between its branches, in line with the conclusion drawn by electron spin resonance, and a valuable fluorescent chromophore indicating that this dye is not photophysically silent as previously believed.…”

Section: Introductionmentioning

confidence: 99%

Azophenine as Central Core for Efficient Light Harvesting Devices

Karsenti

Harvey

2018

ChemPhysChem

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The notoriously non-luminescent uncycled azophenine (Q) was harnessed with Bodipy and zinc(II)porphyrin antennas to probe its fluorescence properties, its ability to act as a singlet excited state energy acceptor and to mediate the transfer. Two near-IR emissions are depicted from time-resolved fluorescence spectroscopy, which are most likely due to the presence of tautomers of very similar calculated total energies (350 cm ; DFT; B3LYP). The rates for energy transfer, k (S ), for Bodipy*→Q are in the order of 10 -10 s and are surprisingly fast when considering the low absorptivity properties of the lowest energy charge transfer excited state of azophenine. The rational is provided by the calculated frontier molecular orbitals (MOs) which show atomic contributions in the C H C≡CC H arms, thus favoring the double electron exchange mechanism. In the mixed-antenna Bodipy-porphyrin star molecule, the rate for Bodipy*→porphyrin has also been evaluated (≈16×10 s ) and is among the fastest rates reported for Bodipy-zinc(II)porphyrin pairs. This astonishing result is again explained from the atomic contributions of the C H C≡CC H and C≡CC H arms thus favouring the Dexter process. Here, for the first time, this process is found to be sensitively temperature-dependent. The azophenine turns out to be excellent for electronic communication.

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“…Redox-active ligands share an important trait in common with transition metal ions-the ability to exist in multiple charge and spin configurations and as a result RALs are often found to be in paramagnetic oxidation states when coordinated to transition metal ions. This aspect of RAL chemistry has been exploited to produce transition metal complexes with very strong intramolecular magnetic exchange couplings leading to interesting properties, including single molecule magnet behavior [9][10][11]. Recently we synthesized a ditopic bridging ligand baqp 1 ( Figure 1) that when uncoordinated provides an unusual example of a stable phenoxyl radical [12].…”

Section: Introductionmentioning

confidence: 99%

Synthesis, Characterization and Copper(2+) Coordination Chemistry of a Polytopic Paramagnetic Ligand

et al. 2017

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Abstract:We describe the synthesis of a new tetratopic phenoxyl radical ligand based on the previously reported ditopic "baqp" radical. The tetratopic ligand is prepared in five steps from 4-tert-butylphenol. Coordination of the ligand with Cu(OAc) 2 produced a tetranuclear complex with an S = 1 2 ground state featuring a coordinated hexa-anion radical with very strong intramolecular antiferromagnetic exchange coupling.

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A series of tetraazalene radical-bridged M₂(M = Cr^III, Mn^II, Fe^II, Co^II) complexes with strong magnetic exchange coupling

Abstract: The ability of tetraazalene radical bridging ligands to mediate exceptionally strong magnetic exchange coupling across a range of transition metal complexes is demonstrated.

Cited by 72 publications

References 113 publications

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

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

Azophenine as Central Core for Efficient Light Harvesting Devices

Synthesis, Characterization and Copper(2+) Coordination Chemistry of a Polytopic Paramagnetic Ligand

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