Rational Design of a Photomagnetic Chain: Bridging Single-Molecule Magnets with a Spin-Crossover Complex

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• 作者：Rodica Ababei ; C茅line Pichon ; Olivier Roubeau ; Yang-Guang Li ; Nicolas Br茅fuel ; Lionel Buisson ; Philippe Guionneau ; Corine Mathoni猫re ; Rodolphe Cl茅rac
• 刊名：Journal of the American Chemical Society
• 出版年：2013
• 出版时间：October 2, 2013
• 年：2013
• 卷：135
• 期：39
• 页码：14840-14853
• 全文大小：614K
• 年卷期：v.135,no.39(October 2, 2013)
• ISSN：1520-5126

文摘

The spin-crossover complex [Fe(LN₅)(CN)₂]路H₂O (1, LN₅ = 2,13-dimethyl-3,6,9-12,18-pentaazabicyclo[12.3.1]octadeca-1(18),2,12,14,16-pentaene), reported previously by Nelson et al. in 1986, was reinvestigated, and its structure determined by single crystal X-ray diffraction for the first time. The reaction between [Mn^III(saltmen)(H₂O)]⁺ and this photomagnetic linker yielded the trinuclear molecular complex [{Mn(saltmen)}₂Fe_HS(LN₅)(CN)₂](ClO₄)₂路0.5CH₃OH (2) and the one-dimensional compound [{Mn(saltmen)}₂Fe_LS(LN₅)(CN)₂](ClO₄)₂路0.5C₄H₁₀O路0.5H₂O (3) depending on the addition order of the reagents (HS: High-Spin; LS: Low-Spin). Compound 3 exhibits a wave-shaped chain structure built from the assembly of the trinuclear [Mn^III-NC-Fe^II] motif found in 2. Static magnetic measurements revealed the existence of antiferromagnetic Mn^III路路路Fe^II (Fe^II HS, S = 2) interactions in the trinuclear entity of 2 via the cyanido bridge leading to an S_T = 2 ground state. In the case of 3, concomitant ferromagnetic and antiferromagnetic exchange interactions are found along the chain due to the presence of two crystallographically independent {Mn₂(saltmen)₂} units, which behave differently as shown by the magnetic susceptibility analysis, while the Fe^II (LS, S = 0) cyanido-bridging moiety is isolating these dinuclear Mn^III units. ac susceptibility experiments indicated slow relaxation of the magnetization arising from the ferromagnetically coupled [Mn₂] units (蟿₀ = 1.1 脳 10^鈥? s and 螖_eff/k_B = 13.9 K). Optical reflectivity and photomagnetic properties of 1 and 3 have been investigated in detail. These studies reveal that the photomagnetic properties of 1 are kept after its coordination to the acceptor Mn^III/saltmen complexes, allowing in 3 to switch 鈥渙n鈥?and 鈥渙ff鈥?the magnetic interaction between the photoinduced Fe^II HS unit (S = 2) and the Mn(III) ions. To the best of our knowledge, the compound 3 represents the first example of a coordination network of single-molecule magnets linked by spin-crossover units inducing thermally and photoreversible magnetic and optical properties.