Reversible Redox, Spin Crossover, and Superexchange Coupling in 3d Transition‐Metal Complexes of Bis‐azinyl Analogues of 2,2′:6′,2′′‐Terpyridine

Reversible Redox, Spin Crossover, and Superexchange Coupling in 3d Transition‐Metal Complexes... The terpyridine‐inspired tridentate ligand, 2,6‐bis(5,6‐dialkyl‐1,2,4‐triazin‐3‐yl)‐pyridine (BTP), was synthesized and utilized to isolate five [MII(BTP)2]2+ (M = Fe and Co) transition‐metal complexes of various anions (BF4–, ClO4–, and NCS–). Notably, when metal‐halide precursors are employed, 1:1 M/L products [Co2II(µ‐X)2(BTP)2X2] (X = Cl or Br) are obtained, exhibiting µ‐halide bridges. All complexes were structurally characterized through single‐crystal X‐ray diffraction and their electrochemical and magnetic properties were investigated. Electrochemical studies reveal that the free BTP ligand has a single irreversible reduction, however; upon coordination to a metal center, stabilization of the reduced BTP ligand occurs and up to four reductive processes associated with the molecule are observed within the solvent window. The metal‐centered redox processes were either reversible or partially reversible, and fall within the range of 0.13 < E1/2 < 0.90 V vs. Fc/Fc+. Although there was minimal effect on the redox properties of the metal centers, there is strong dependence on the spin state. SQUID magnetometry elucidated a low spin state for the FeII complexes at room temperature, revealing a diamagnetic electronic structure. On the other hand, the cobalt monometallic complexes, [CoII(BTP)2]2+, showed gradual spin crossover properties between 1.8–370 K, displaying a minor dependence on the spin crossover behavior based on the respective anion. Additionally, ferromagnetic exchange interactions of J = +2.57 and +2.98 cm–1 were obtained using the –2J formalism for the dinuclear CoII complexes, [Co2II(µ‐X)2(BTP)2X2] for X = Cl and Br, respectively. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png European Journal of Inorganic Chemistry Wiley

Reversible Redox, Spin Crossover, and Superexchange Coupling in 3d Transition‐Metal Complexes of Bis‐azinyl Analogues of 2,2′:6′,2′′‐Terpyridine

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Publisher
Wiley Subscription Services, Inc., A Wiley Company
Copyright
© 2018 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim
ISSN
1434-1948
eISSN
1099-0682
D.O.I.
10.1002/ejic.201800065
Publisher site
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Abstract

The terpyridine‐inspired tridentate ligand, 2,6‐bis(5,6‐dialkyl‐1,2,4‐triazin‐3‐yl)‐pyridine (BTP), was synthesized and utilized to isolate five [MII(BTP)2]2+ (M = Fe and Co) transition‐metal complexes of various anions (BF4–, ClO4–, and NCS–). Notably, when metal‐halide precursors are employed, 1:1 M/L products [Co2II(µ‐X)2(BTP)2X2] (X = Cl or Br) are obtained, exhibiting µ‐halide bridges. All complexes were structurally characterized through single‐crystal X‐ray diffraction and their electrochemical and magnetic properties were investigated. Electrochemical studies reveal that the free BTP ligand has a single irreversible reduction, however; upon coordination to a metal center, stabilization of the reduced BTP ligand occurs and up to four reductive processes associated with the molecule are observed within the solvent window. The metal‐centered redox processes were either reversible or partially reversible, and fall within the range of 0.13 < E1/2 < 0.90 V vs. Fc/Fc+. Although there was minimal effect on the redox properties of the metal centers, there is strong dependence on the spin state. SQUID magnetometry elucidated a low spin state for the FeII complexes at room temperature, revealing a diamagnetic electronic structure. On the other hand, the cobalt monometallic complexes, [CoII(BTP)2]2+, showed gradual spin crossover properties between 1.8–370 K, displaying a minor dependence on the spin crossover behavior based on the respective anion. Additionally, ferromagnetic exchange interactions of J = +2.57 and +2.98 cm–1 were obtained using the –2J formalism for the dinuclear CoII complexes, [Co2II(µ‐X)2(BTP)2X2] for X = Cl and Br, respectively.

Journal

European Journal of Inorganic ChemistryWiley

Published: Jan 14, 2018

Keywords: ; ; ; ;

References

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